|
Hi all!
I am going to try to describe an issue here that is not very easy to describe....
In my recent attempts to automatize variable star observations, I have run into an issue about side-of-pier on the G11, Gemini 2. THe issue is this:
If I slew from Southwest to Northwest, the mount crosses the Az line of 270 degrees. The mount essentially shifts side-of-pier in a very simple physical sense, and the Gemini seems to report this as a change of side-of-pier. I use Ekos/Indi, and here it is clearly reported as a shift of side-of-pier. Now, however, shift of side-of-pier is interpreted by PHD2 as a meridian flip, and thus RA direction is reversed (contrary to my first understanding). But I have not done a meridian flip, just slewed a rather short distance (in my case from RR Tau to GM Cam at around 10 pm). So PHD2 stars a run away chase, creating images with loooong star trails and nothing else.
Point very much in need of stressing: this is NOT a meridian flip.
Now, it seems that Ekos/Indi utilise the side-of-pier reported by Gemini, thus depending on how Gemini itself interprets the sitation. So to correct this issue, there would need to be a change in Gemini code, says people at the Indi forum (see here: )
So my question to you folks: can you with a Gemini 2 confirm this behavior - shift-of-pier shifts when slewing from SW to NW (which in one sense makes sense, but it is NOT a meridian flip)?
If this is really the way Gemini 2 handles side-of-pier - any ideas on how to handle my kind of problem on the Gemini side?
(there are 3 systems involved here: Gemini2, Ekos/Indi, and PHD2 - they all seem to point me in the direction of one another....)
For a far more extensive discussion including Bruce Waddingtons wonderful explanation of why RA signals must change direction after a meridian flip, see here:
!topic/open-phd-guiding/s2TVIS3_K_Y
Magnus
|
Hi Magnus!
What you are describing is, to me, an anomaly in PHD2 itself, for my lack of a better way to describe it.
What I learned to do (this was with my old mount) was to close PHD2. And I mean just slam the door on it.
Then open it again to a fresh unadjusted program, and start it up again after the change. Let it automatically select a guide star, and give it time to settle in and stabilize.
After that, it would go on guiding.
It was another of my "Sonny's Work Rounds" to keep me in this crazy way of connecting my yard with outer space.
Some things I do make no sense to others, but they work.
--
SonnyE
(I suggest viewed in full screen)
|
Hi Sonny!!
Well, I could easily "fix" it by re-calibrating in PHD2. But that
is not a good solution, as this problem happens several times in
the midst of my 20-25 jobs schedule, as the mount works through
lower altitudes to higher, in the process slewing hither and
dither... And: automated... I cannot have it recalibrate after
every slew, as that would almost double the time for the whole
process.
Thing seems to be, that side-of-pier is reported by Gemini
whenever the side-of-pier shifts, physically. But that messes
things up and causes this issue. PHD2 cannot differentiate between
a side-of-pier-shift because of a meridian flip and just slewing
from SW to NW.... But the Gemini can differentiate these between
these cases. And, as I understand it, should ONLY report
side-of-pier when it is a meridian flip case. As I understand it
from the PHD and Indo fora. But I might be wrong - it has happened
before....
I don't know how other mounts manage this, and I am way out of my
depth when we talk about what the codes the Gemini sends to my
Indi-server really are (serial commands....). But that seems to be
where this happens.
And: what would really be helpful, is if someone else can verify
the behavior. To see if there is something with just my mount, or
really in the Gemini code.
Best,
Magnus
Den 2020-04-18 kl. 18:00, skrev Sonny
Edmonds:
toggle quoted message
Show quoted text
Hi Magnus!
What you are describing is, to me, an anomaly in PHD2 itself, for
my lack of a better way to describe it.
What I learned to do (this was with my old mount) was to close
PHD2. And I mean just slam the door on it.
Then open it again to a fresh unadjusted program, and start it up
again after the change. Let it automatically select a guide star,
and give it time to settle in and stabilize.
After that, it would go on guiding.
It was another of my "Sonny's Work Rounds" to keep me in this
crazy way of connecting my yard with outer space.
Some things I do make no sense to others, but they work.
--
SonnyE
(I suggest viewed in full screen)
|
Magnus
can you clarify what exactly is the test you want to verify?
I've been following your PHD thread and looked at the indi thread. I'm not convinced it's a gemini firmware issue, since i've really never heard this before, but i'm willing to test it out
On Sat, Apr 18, 2020 at 10:35 AM Magnus Larsson < magnus@...> wrote:
Hi Sonny!!
Well, I could easily "fix" it by re-calibrating in PHD2. But that
is not a good solution, as this problem happens several times in
the midst of my 20-25 jobs schedule, as the mount works through
lower altitudes to higher, in the process slewing hither and
dither... And: automated... I cannot have it recalibrate after
every slew, as that would almost double the time for the whole
process.
Thing seems to be, that side-of-pier is reported by Gemini
whenever the side-of-pier shifts, physically. But that messes
things up and causes this issue. PHD2 cannot differentiate between
a side-of-pier-shift because of a meridian flip and just slewing
from SW to NW.... But the Gemini can differentiate these between
these cases. And, as I understand it, should ONLY report
side-of-pier when it is a meridian flip case. As I understand it
from the PHD and Indo fora. But I might be wrong - it has happened
before....
I don't know how other mounts manage this, and I am way out of my
depth when we talk about what the codes the Gemini sends to my
Indi-server really are (serial commands....). But that seems to be
where this happens.
And: what would really be helpful, is if someone else can verify
the behavior. To see if there is something with just my mount, or
really in the Gemini code.
Best,
Magnus
Den 2020-04-18 kl. 18:00, skrev Sonny
Edmonds:
Hi Magnus!
What you are describing is, to me, an anomaly in PHD2 itself, for
my lack of a better way to describe it.
What I learned to do (this was with my old mount) was to close
PHD2. And I mean just slam the door on it.
Then open it again to a fresh unadjusted program, and start it up
again after the change. Let it automatically select a guide star,
and give it time to settle in and stabilize.
After that, it would go on guiding.
It was another of my "Sonny's Work Rounds" to keep me in this
crazy way of connecting my yard with outer space.
Some things I do make no sense to others, but they work.
--
SonnyE
(I suggest viewed in full screen)
-- Brian?
Brian Valente portfolio
|
Hi!
It might be that there is no issue, and I have messed things up.
But it might also be that my use case is somewhat rare, which is a
reason this has not been surfaced before. THe thinking around this
is really a bit above my paygrade. I can follow the logic but not
assess it. So my understanding is: There are two cases when
side-of-pier really shifts: in a meridian flip, that is, shifting
side of pier for an object traversing the meridian. Or, as in my
case, when slewing from SW to NW or the other way around. These
cases are very different in a guiding sense. For the meridian
flip, RA should be reversed. For the second case, nothing should
happen.
So: what I think would be good is to hear if other's G2s also
report a shift in side-of-pier when slewing from SW to NW and
back, and from SE to NE and back. For instance, following this
sequence:
1. South
2. SW
3. NW
4. SW
5. NW
6. N (meridian flip)
7. NE
8. SE
9 NE
10. SE
11. S (meridian flip)
In this sequence, a "wrong" side-of-pier shift should be reported
in step 2-3, 3-4, 4-5, 7-8, 8-9, 9-10, and a "correct"
side-of-pier shift in steps 5-6 and 10-11.
Does that make sense?
Magnus
Den 2020-04-19 kl. 01:15, skrev Brian
Valente:
toggle quoted message
Show quoted text
Magnus
can you clarify what exactly is the test you want to
verify?
I've been following your PHD thread and looked at the indi
thread. I'm not convinced it's a gemini firmware issue, since
i've really never heard this before, but i'm willing to test
it out
On Sat, Apr 18, 2020 at 10:35
AM Magnus Larsson < magnus@...> wrote:
Hi Sonny!!
Well, I could easily "fix" it by re-calibrating in PHD2.
But that is not a good solution, as this problem happens
several times in the midst of my 20-25 jobs schedule, as
the mount works through lower altitudes to higher, in the
process slewing hither and dither... And: automated... I
cannot have it recalibrate after every slew, as that would
almost double the time for the whole process.
Thing seems to be, that side-of-pier is reported by
Gemini whenever the side-of-pier shifts, physically. But
that messes things up and causes this issue. PHD2 cannot
differentiate between a side-of-pier-shift because of a
meridian flip and just slewing from SW to NW.... But the
Gemini can differentiate these between these cases. And,
as I understand it, should ONLY report side-of-pier when
it is a meridian flip case. As I understand it from the
PHD and Indo fora. But I might be wrong - it has happened
before....
I don't know how other mounts manage this, and I am way
out of my depth when we talk about what the codes the
Gemini sends to my Indi-server really are (serial
commands....). But that seems to be where this happens.
And: what would really be helpful, is if someone else can
verify the behavior. To see if there is something with
just my mount, or really in the Gemini code.
Best,
Magnus
Den 2020-04-18 kl. 18:00, skrev Sonny Edmonds:
Hi Magnus!
What you are describing is, to me, an anomaly in PHD2
itself, for my lack of a better way to describe it.
What I learned to do (this was with my old mount) was to
close PHD2. And I mean just slam the door on it.
Then open it again to a fresh unadjusted program, and
start it up again after the change. Let it automatically
select a guide star, and give it time to settle in and
stabilize.
After that, it would go on guiding.
It was another of my "Sonny's Work Rounds" to keep me in
this crazy way of connecting my yard with outer space.
Some things I do make no sense to others, but they work.
--
SonnyE
(I suggest viewed in full screen)
--
Brian?
Brian Valente
portfolio
|
Hi Magnus!
I'm afraid this is not only above my pay grade as you put it, but probably above my present intellect.
However, I wanted you to know I am following this in the hope I can see it to a solution.
It's in my blood to be a troubleshooter, so I take a keen view. But I wanted to let you know I'm watching this.
Just setting on the sidelines, in case it crops up for me someday.
--
SonnyE
(I suggest viewed in full screen)
|
Hi Magnus
No, it doesn't really make sense to me.? if i go from NE to SE, this is just a DEC move, i'm not crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is guiding impacted, correct?
So i would assume you need some guiding to take place in this situation to see how it impacts.
|
Hi!
No, it is a slew in RA - I'm doing it with the same declination,
just slewing in RA, to test. And right, no crossing the meridian.
But physically, crossing the 90 degree azimuth line, the
counterweight bar crosses to the other side of the mount - hence
shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of
side-of-pier, PHD2 swaps direction of RA guiding. But since no
direction of the guidecam or otherwise in the mount has happended,
this means that RA now escalates errors, rather than works against
them - hence escalating run away scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian
flip. But this is not the only case when it occurs nor when the G2
reports it.
It took me quite a while to see this... And I guess this is not
what would be problematic in regular AP, when you find a target,
maybe calibrate, and then track for hours. Then there is a
meridian flip, RA shifts, and back to tracking. It happens here
because I slew from target to target, imaging 20-25 different
targets with just one or two subs of each, but I need guiding
because I do some 5 mins exposures and I get too much drift if no
guiding. I have my complex sequence set up so it goes from lower
altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more (manually
sorted). It means that it will start out on the west side, going
in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U
Gem and so on.
Do you see it now? Or what can I send or describe that makes it
more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian
Valente:
toggle quoted message
Show quoted text
Hi Magnus
No, it doesn't really make sense to me.? if i go from NE to SE,
this is just a DEC move, i'm not crossing the meridian. So why
would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is
guiding impacted, correct?
So i would assume you need some guiding to take place in this
situation to see how it impacts.
|
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew in DEC for me. you're saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson < magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination,
just slewing in RA, to test. And right, no crossing the meridian.
But physically, crossing the 90 degree azimuth line, the
counterweight bar crosses to the other side of the mount - hence
shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of
side-of-pier, PHD2 swaps direction of RA guiding. But since no
direction of the guidecam or otherwise in the mount has happended,
this means that RA now escalates errors, rather than works against
them - hence escalating run away scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian
flip. But this is not the only case when it occurs nor when the G2
reports it.
It took me quite a while to see this... And I guess this is not
what would be problematic in regular AP, when you find a target,
maybe calibrate, and then track for hours. Then there is a
meridian flip, RA shifts, and back to tracking. It happens here
because I slew from target to target, imaging 20-25 different
targets with just one or two subs of each, but I need guiding
because I do some 5 mins exposures and I get too much drift if no
guiding. I have my complex sequence set up so it goes from lower
altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more (manually
sorted). It means that it will start out on the west side, going
in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U
Gem and so on.
Do you see it now? Or what can I send or describe that makes it
more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian
Valente:
Hi Magnus
No, it doesn't really make sense to me.? if i go from NE to SE,
this is just a DEC move, i'm not crossing the meridian. So why
would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is
guiding impacted, correct?
So i would assume you need some guiding to take place in this
situation to see how it impacts.
-- Brian?
Brian Valente portfolio
|
Hi!
Let me take SW to NW as an example instead:
I slew from RR Tau to GM Cam. This is from:
05 39 30.51??? +26 22 27.0
To:
03 59 10.08??? +58 01 07.7
At around 10pm (at my location, but that should be same for you,
shouldn't it?), that means slewing from somewhere roughly SW to
more NW - and in doing this slew, the mount shifts side-of-pier -
roughly as it crosses 270 degrees azimuth.
Roughly, I stay at an altitude of around 30 degree, and slew on
the western side of the sky. Then the slew is both in RA and Dec.
Does that help?
Simulate on for instance CdC, and I think you will see what I
mean. And I'm at latitude 55 degrees North.
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian
Valente:
toggle quoted message
Show quoted text
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE
to SE, that is a slew in DEC for me. you're saying slew in RA,
and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19
AM Magnus Larsson < magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same
declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90
degree azimuth line, the counterweight bar crosses to the
other side of the mount - hence shift of side-of-pier, in
a very literal sense.
Yes, it impacts my guiding since when the mount reports
shift of side-of-pier, PHD2 swaps direction of RA guiding.
But since no direction of the guidecam or otherwise in the
mount has happended, this means that RA now escalates
errors, rather than works against them - hence escalating
run away scope.
In essence, PHD2 interprets shift of side-of-pier as a
meridian flip. But this is not the only case when it
occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this
is not what would be problematic in regular AP, when you
find a target, maybe calibrate, and then track for hours.
Then there is a meridian flip, RA shifts, and back to
tracking. It happens here because I slew from target to
target, imaging 20-25 different targets with just one or
two subs of each, but I need guiding because I do some 5
mins exposures and I get too much drift if no guiding. I
have my complex sequence set up so it goes from lower
altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more
(manually sorted). It means that it will start out on the
west side, going in sort of zig-zag motion from RR Tau to
GM Cam, to YY Aur, to U Gem and so on.
Do you see it now? Or what can I send or describe that
makes it more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me.? if i go from NE
to SE, this is just a DEC move, i'm not crossing the
meridian. So why would it report side of pier change?
confused abou tthis
i can slew back and forth, but it sounds like your issue
is how is guiding impacted, correct?
So i would assume you need some guiding to take place in
this situation to see how it impacts.
--
Brian?
Brian Valente
portfolio
|
Hi!
How's it going with this? Makes any more sense? On the
indi-forum, it is spoken about in terms of hour angle, maybe
better way. My test shows that between -3 and -9 hours, the
side-of-pier shifts (approximately at -6) and the same happens
between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there
should not be a meridian flip (and none is initiated).
See the indi-forum thread here:
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian
Valente:
toggle quoted message
Show quoted text
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE
to SE, that is a slew in DEC for me. you're saying slew in RA,
and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19
AM Magnus Larsson < magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same
declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90
degree azimuth line, the counterweight bar crosses to the
other side of the mount - hence shift of side-of-pier, in
a very literal sense.
Yes, it impacts my guiding since when the mount reports
shift of side-of-pier, PHD2 swaps direction of RA guiding.
But since no direction of the guidecam or otherwise in the
mount has happended, this means that RA now escalates
errors, rather than works against them - hence escalating
run away scope.
In essence, PHD2 interprets shift of side-of-pier as a
meridian flip. But this is not the only case when it
occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this
is not what would be problematic in regular AP, when you
find a target, maybe calibrate, and then track for hours.
Then there is a meridian flip, RA shifts, and back to
tracking. It happens here because I slew from target to
target, imaging 20-25 different targets with just one or
two subs of each, but I need guiding because I do some 5
mins exposures and I get too much drift if no guiding. I
have my complex sequence set up so it goes from lower
altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more
(manually sorted). It means that it will start out on the
west side, going in sort of zig-zag motion from RR Tau to
GM Cam, to YY Aur, to U Gem and so on.
Do you see it now? Or what can I send or describe that
makes it more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me.? if i go from NE
to SE, this is just a DEC move, i'm not crossing the
meridian. So why would it report side of pier change?
confused abou tthis
i can slew back and forth, but it sounds like your issue
is how is guiding impacted, correct?
So i would assume you need some guiding to take place in
this situation to see how it impacts.
--
Brian?
Brian Valente
portfolio
|
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis position alone. It is not affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't provide enough information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90 degrees (or -90 degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note that when doing that the actual pier side change occurs when the declination axis passes the celestial pole to the other side.
-Ray Gralak
Author of PEMPro V3:
toggle quoted message
Show quoted text
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts (approximately at -6) and the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian flip (and none is initiated).
See the indi-forum thread here:
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the counterweight bar crosses to the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has happended, this means that
RA now escalates errors, rather than works against them - hence escalating run away scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25 different targets with just one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get too much drift if no guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more (manually sorted). It means that it will start out on the west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and so on.
Do you see it now? Or what can I send or describe that makes it more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is guiding impacted, correct?
So i would assume you need some guiding to take place in this situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
|
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I find this to be a difficult issue to describe and understand. I think the hour angle description was the clearest so far, for me...But, I don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My side-of-pier shifts when I slew in RA, not in DEC (don't know how to do that). Of course my DEC axis moves, since it rotates around the RA axis. But it is the slew in RA that causes a shift in side-of-pier, as the counterweight bar (to describe it physically) moves across the meridian. I guess that is what you mean by "note that when doing that the actual pier side change occurs when the declination axis passes the celestial pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in side-of-pier - maybe I describe it in totally wrong words. But: my PHD2 reacts to a shift in side-of-pier when I slew from some variables to certain others - without any meridian flip nor a need for any - because both stars are on either west or east side of the mount. This is my problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very real.... so how can we describe it in a reasonable way, and maybe find a way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
toggle quoted message
Show quoted text
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis position alone. It is not affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't provide enough information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90 degrees (or -90 degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note that when doing that the actual pier side change occurs when the declination axis passes the celestial pole to the other side.
-Ray Gralak
Author of PEMPro V3:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts (approximately at -6) and the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian flip (and none is initiated).
See the indi-forum thread here:
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the counterweight bar crosses to the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has happended, this means that
RA now escalates errors, rather than works against them - hence escalating run away scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25 different targets with just one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get too much drift if no guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more (manually sorted). It means that it will start out on the west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and so on.
Do you see it now? Or what can I send or describe that makes it more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is guiding impacted, correct?
So i would assume you need some guiding to take place in this situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
|
Hi!
Here is a post from indilib forum, with a film posted by another guy that exactly describes the situation I am in. Look at the first of the two videos.
Magnus
Den 2020-04-21 kl. 15:29, skrev Magnus Larsson:
toggle quoted message
Show quoted text
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I find this to be a difficult issue to describe and understand. I think the hour angle description was the clearest so far, for me...But, I don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My side-of-pier shifts when I slew in RA, not in DEC (don't know how to do that). Of course my DEC axis moves, since it rotates around the RA axis. But it is the slew in RA that causes a shift in side-of-pier, as the counterweight bar (to describe it physically) moves across the meridian. I guess that is what you mean by "note that when doing that the actual pier side change occurs when the declination axis passes the celestial pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in side-of-pier - maybe I describe it in totally wrong words. But: my PHD2 reacts to a shift in side-of-pier when I slew from some variables to certain others - without any meridian flip nor a need for any - because both stars are on either west or east side of the mount. This is my problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very real.... so how can we describe it in a reasonable way, and maybe find a way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis position alone. It is not affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't provide enough information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90 degrees (or -90 degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note that when doing that the actual pier side change occurs when the declination axis passes the celestial pole to the other side.
-Ray Gralak
Author of PEMPro V3:?
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts (approximately at -6) and the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian flip (and none is initiated).
See the indi-forum thread here:
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
????I generally understand your somewhat unusual case
????What i don't understand is this: when I want to go from NE to SE, that is a slew in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
????On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...> wrote:
??????? Hi!
??????? No, it is a slew in RA - I'm doing it with the same declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the counterweight bar crosses to the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
??????? Yes, it impacts my guiding since when the mount reports shift of side-of-pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has happended, this means that
RA now escalates errors, rather than works against them - hence escalating run away scope.
??????? In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But this is not the only case when
it occurs nor when the G2 reports it.
??????? It took me quite a while to see this... And I guess this is not what would be problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25 different targets with just one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get too much drift if no guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking stars before they are too low,
basically, and then waiting for some to rise some more (manually sorted). It means that it will start out on the west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and so on.
??????? Do you see it now? Or what can I send or describe that makes it more clear?
??????? Best,
??????? Magnus
??????? Den 2020-04-19 kl. 17:48, skrev Brian Valente:
??????????? Hi Magnus
??????????? No, it doesn't really make sense to me.? if i go from NE to SE, this is just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
??????????? i can slew back and forth, but it sounds like your issue is how is guiding impacted, correct?
??????????? So i would assume you need some guiding to take place in this situation to see how it
impacts.
????--
????Brian
????Brian Valente
????portfolio brianvalentephotography.com <>
|
Magnus,
Take a look at this link for a detailed explanation:
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
toggle quoted message
Show quoted text
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 6:29 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I
find this to be a difficult issue to describe and understand. I think
the hour angle description was the clearest so far, for me...But, I
don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My
side-of-pier shifts when I slew in RA, not in DEC (don't know how to do
that). Of course my DEC axis moves, since it rotates around the RA axis.
But it is the slew in RA that causes a shift in side-of-pier, as the
counterweight bar (to describe it physically) moves across the meridian.
I guess that is what you mean by "note that when doing that the actual
pier side change occurs when the declination axis passes the celestial
pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in
side-of-pier - maybe I describe it in totally wrong words. But: my PHD2
reacts to a shift in side-of-pier when I slew from some variables to
certain others - without any meridian flip nor a need for any - because
both stars are on either west or east side of the mount. This is my
problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very
real.... so how can we describe it in a reasonable way, and maybe find a
way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis position alone. It is not affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't provide enough
information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90 degrees (or -90
degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note that when doing
that the actual pier side change occurs when the declination axis passes the celestial pole to the other side.
-Ray Gralak
Author of PEMPro V3:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts (approximately at -6) and
the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian flip (and none is initiated).
See the indi-forum thread here:
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the counterweight bar crosses to
the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has happended, this means
that
RA now escalates errors, rather than works against them - hence escalating run away scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25 different targets with just
one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get too much drift if no
guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking stars before they are too
low,
basically, and then waiting for some to rise some more (manually sorted). It means that it will start out on the
west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and so on.
Do you see it now? Or what can I send or describe that makes it more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is guiding impacted, correct?
So i would assume you need some guiding to take place in this situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
|
Hi!
OK, I see what you mean by declination axis. Just to understand,
though:
"Mechanical zero HA/Dec will be one of the two ways of
pointing at the intersection of the celestial equator and the
local meridian. In order to support Dome slaving, where it is
important to know which side of the pier the mount is actually on,
ASCOM has adopted the convention that the Normal pointing state
will be the state where a German Equatorial mount is on the East
side of the pier, looking West, with the counterweights below the
optical assembly and that??will
represent this pointing state."
If I place my mount in this position, it will point
straight to the south, right? Where the celestial equator
intersects the local meridian - south, in my case ca 25 degrees
altitude (I'm at 55 degrees North). So that is zero mechanical Dec
and HA?
If so, how should I understand this?
| Normal () |
Where the mechanical Dec is in the
range -90 deg to +90 deg |
If I move the scope to - 90 degrees Dec, it will point
straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator....
So if I in this position, without moving the RA/HA-axis,
move the dec to somewhere north - that would be beyond +90 degrees
- then I should have a shift of side-of-pier?
Magnus
Den 2020-04-21 kl. 15:51, skrev Ray Gralak:
toggle quoted message
Show quoted text
Magnus,
Take a look at this link for a detailed explanation:
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 6:29 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I
find this to be a difficult issue to describe and understand. I think
the hour angle description was the clearest so far, for me...But, I
don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My
side-of-pier shifts when I slew in RA, not in DEC (don't know how to do
that). Of course my DEC axis moves, since it rotates around the RA axis.
But it is the slew in RA that causes a shift in side-of-pier, as the
counterweight bar (to describe it physically) moves across the meridian.
I guess that is what you mean by "note that when doing that the actual
pier side change occurs when the declination axis passes the celestial
pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in
side-of-pier - maybe I describe it in totally wrong words. But: my PHD2
reacts to a shift in side-of-pier when I slew from some variables to
certain others - without any meridian flip nor a need for any - because
both stars are on either west or east side of the mount. This is my
problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very
real.... so how can we describe it in a reasonable way, and maybe find a
way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis position alone. It is not
affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't provide enough
information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90 degrees (or -90
degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note that when doing
that the actual pier side change occurs when the declination axis passes the celestial pole to the other side.
-Ray Gralak
Author of PEMPro V3:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts (approximately at -6) and
the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian flip (and none is initiated).
See the indi-forum thread here:
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the counterweight bar crosses to
the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has happended, this means
that
RA now escalates errors, rather than works against them - hence escalating run away scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25 different targets with just
one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get too much drift if no
guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking stars before they are too
low,
basically, and then waiting for some to rise some more (manually sorted). It means that it will start out on the
west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and so on.
Do you see it now? Or what can I send or describe that makes it more clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is guiding impacted, correct?
So i would assume you need some guiding to take place in this situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com
|
Magnus, If I move the scope to - 90 degrees Dec, it will point straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator.... Dec = -90 is not straight at the ground unless you are at the north pole. :-) For example, if your latitude is 40 degrees then the north celestial pole is 40 degrees above the horizon. The horizon at due south is -50 degrees latitude, and south celestial pole 40 degrees below the southern point of the horizon (not 90 degrees south of it). -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro V3: Author of Astro-Physics V2 ASCOM Driver: -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 7:19 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
OK, I see what you mean by declination axis. Just to understand, though:
"Mechanical zero HA/Dec will be one of the two ways of pointing at the intersection of the celestial equator and
the local meridian. In order to support Dome slaving, where it is important to know which side of the pier the mount
is actually on, ASCOM has adopted the convention that the Normal pointing state will be the state where a
German Equatorial mount is on the East side of the pier, looking West, with the counterweights below the optical
assembly and that pierEast <
standards.org/Help/Platform/html/T_ASCOM_DeviceInterface_PierSide.htm> will represent this pointing state."
If I place my mount in this position, it will point straight to the south, right? Where the celestial equator intersects
the local meridian - south, in my case ca 25 degrees altitude (I'm at 55 degrees North). So that is zero mechanical
Dec and HA?
If so, how should I understand this?
Normal (pierEast <> )
Where the mechanical Dec is in the range -90 deg to +90 deg
If I move the scope to - 90 degrees Dec, it will point straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator....
So if I in this position, without moving the RA/HA-axis, move the dec to somewhere north - that would be beyond
+90 degrees - then I should have a shift of side-of-pier?
Magnus
Den 2020-04-21 kl. 15:51, skrev Ray Gralak:
Magnus,
Take a look at this link for a detailed explanation:
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus
Larsson
Sent: Tuesday, April 21, 2020 6:29 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I
find this to be a difficult issue to describe and understand. I think
the hour angle description was the clearest so far, for me...But, I
don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My
side-of-pier shifts when I slew in RA, not in DEC (don't know how to do
that). Of course my DEC axis moves, since it rotates around the RA axis.
But it is the slew in RA that causes a shift in side-of-pier, as the
counterweight bar (to describe it physically) moves across the meridian.
I guess that is what you mean by "note that when doing that the actual
pier side change occurs when the declination axis passes the celestial
pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in
side-of-pier - maybe I describe it in totally wrong words. But: my PHD2
reacts to a shift in side-of-pier when I slew from some variables to
certain others - without any meridian flip nor a need for any - because
both stars are on either west or east side of the mount. This is my
problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very
real.... so how can we describe it in a reasonable way, and maybe find a
way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis
position alone. It is not
affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't
provide enough
information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90
degrees (or -90
degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note
that when doing
that the actual pier side change occurs when the declination axis passes the celestial pole to the
other side.
-Ray Gralak
Author of PEMPro V3:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about
in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts
(approximately at -6) and
the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian
flip (and none is initiated).
See the indi-forum thread here:
problem-bug.html
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew
in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...>
<mailto:magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing
in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the
counterweight bar crosses to
the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-
pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has
happended, this means
that
RA now escalates errors, rather than works against them - hence escalating run away
scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But
this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be
problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a
meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25
different targets with just
one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get
too much drift if no
guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking
stars before they are too
low,
basically, and then waiting for some to rise some more (manually sorted). It means that
it will start out on the
west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and
so on.
Do you see it now? Or what can I send or describe that makes it more
clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is
just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is
guiding impacted, correct?
So i would assume you need some guiding to take place in this
situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
<>
|
Hi!
You are a star, Ray! For the first time, I feel like I understand it better! (Sorry for the "straight into the ground" - I only got half of my thinking there. Of course not straight, but somewhat down into the ground....)
Now, I have made a bunch of screenshots, here in a shared Dropbox-folder:
To be viewed in this sequence:
Start.png
DEC_65.png
DEC_102.png
DEC_132.png
SV.png
NV.png
What I did was to place the mount in zero mechanical Dec/HA (roughly). That is Start.png (I apologize for everything being in Swedish). You see the mount on the star map, and the side of pier in the window to the lower right, where "?st" means East. THe coordinates are given in the window top right - "Dek" is declination, "ELEV" is altitude.
Now I move the mount in Dec only, up past the pole. DEC_65.png is in the way up. Still side-of-pier is East (?st) as it should be. THen I cross the pole to DEC_102.png (I had to cross the meridian too, to avoid a flip). Still it is East (?st) - but now it should be West, right? But it is still East! Further down on the north side to DEC_132.png, and still East.
The way I interpret it, this is not consistent with how side of pier is defined in that ASCOM document you linked to, Ray. Or do I misinterpret?
The last two is where it DOES shift side of pier. THat is pointing in what I call south west (SV.png), then slewing to north west (NV.png). THis is a slew in RA, mainly. And not much shift in Dec, at least not going beyond ¡À 90 degrees. But here it shifts.
Is this correctly understood now?
Best,
Magnus
Den 2020-04-21 kl. 16:27, skrev Ray Gralak:
toggle quoted message
Show quoted text
Magnus,
If I move the scope to - 90 degrees Dec, it will point straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator.... Dec = -90 is not straight at the ground unless you are at the north pole. :-)
For example, if your latitude is 40 degrees then the north celestial pole is 40 degrees above the horizon. The horizon at due south is -50 degrees latitude, and south celestial pole 40 degrees below the southern point of the horizon (not 90 degrees south of it).
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 7:19 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
OK, I see what you mean by declination axis. Just to understand, though:
"Mechanical zero HA/Dec will be one of the two ways of pointing at the intersection of the celestial equator and
the local meridian. In order to support Dome slaving, where it is important to know which side of the pier the mount
is actually on, ASCOM has adopted the convention that the Normal pointing state will be the state where a
German Equatorial mount is on the East side of the pier, looking West, with the counterweights below the optical
assembly and that pierEast <
standards.org/Help/Platform/html/T_ASCOM_DeviceInterface_PierSide.htm> will represent this pointing state."
If I place my mount in this position, it will point straight to the south, right? Where the celestial equator intersects
the local meridian - south, in my case ca 25 degrees altitude (I'm at 55 degrees North). So that is zero mechanical
Dec and HA?
If so, how should I understand this?
Normal (pierEast <> )
Where the mechanical Dec is in the range -90 deg to +90 deg
If I move the scope to - 90 degrees Dec, it will point straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator....
So if I in this position, without moving the RA/HA-axis, move the dec to somewhere north - that would be beyond
+90 degrees - then I should have a shift of side-of-pier?
Magnus
Den 2020-04-21 kl. 15:51, skrev Ray Gralak:
Magnus,
Take a look at this link for a detailed explanation:
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus
Larsson
Sent: Tuesday, April 21, 2020 6:29 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I
find this to be a difficult issue to describe and understand. I think
the hour angle description was the clearest so far, for me...But, I
don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My
side-of-pier shifts when I slew in RA, not in DEC (don't know how to do
that). Of course my DEC axis moves, since it rotates around the RA axis.
But it is the slew in RA that causes a shift in side-of-pier, as the
counterweight bar (to describe it physically) moves across the meridian.
I guess that is what you mean by "note that when doing that the actual
pier side change occurs when the declination axis passes the celestial
pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in
side-of-pier - maybe I describe it in totally wrong words. But: my PHD2
reacts to a shift in side-of-pier when I slew from some variables to
certain others - without any meridian flip nor a need for any - because
both stars are on either west or east side of the mount. This is my
problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very
real.... so how can we describe it in a reasonable way, and maybe find a
way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis
position alone. It is not
affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't
provide enough
information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90
degrees (or -90
degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note
that when doing
that the actual pier side change occurs when the declination axis passes the celestial pole to the
other side.
-Ray Gralak
Author of PEMPro V3:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about
in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts
(approximately at -6) and
the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian
flip (and none is initiated).
See the indi-forum thread here:
problem-bug.html
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew
in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...>
<mailto:magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing
in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the
counterweight bar crosses to
the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-
pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has
happended, this means
that
RA now escalates errors, rather than works against them - hence escalating run away
scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But
this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be
problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a
meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25
different targets with just
one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get
too much drift if no
guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking
stars before they are too
low,
basically, and then waiting for some to rise some more (manually sorted). It means that
it will start out on the
west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and
so on.
Do you see it now? Or what can I send or describe that makes it more
clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is
just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is
guiding impacted, correct?
So i would assume you need some guiding to take place in this
situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
<>
|
Hi all!
This is a follow up on my potentially confusing issue about odd side of pier reporting by the Gemini 2. I think the issue is solved.
Here is my understanding:
Gemini 2 on the G11 reports the physical side of pier of the mount. This is not consistent with the ASCOM standard, only relying on Dec - and this not really being "side of pier" (thanks Ray for clarifying this!!!)
PHD2 needs the ASCOM standard to adjust direction of RA after a meridian flip. But the report of the physical as opposed to the ASCOM standard, produces precisely the behavior that I observed - at around HA 6h, side of pier shifts and suddenly PHD2 guides in the wong direction in RA. Now, this behavior is only observed if one hunts objects around the sky, like I do with variables. Tracking an object for hours across the meridian, doing a flip, and more tracking (as in deep sky imaging) would be less likely to produce this erratic behavior.
Further: how come no one else seems to recognize this? Well, because it seems that this non-standard reporting of side of pier was handled by ASCOM some 6 years ago - so that ASCOM computes the correct state of the side of pier. So all you guys who use ASCOM already have a solution.
However, I do not use ASCOM. I use Indi/Ekos. And here the driver just forwarded the state observed by the mount. It took some work to isolate the details of this... So for me, using Indi/Ekos, this produced a problem.
Now, being open source and full of very helpful people, the Losmandy driver in Indi has now been updated with code that handles this situation (as of last night). It seems to work nicely, although it of course needs more testing.
So, all in all: The mount clearly reports side of pier in a way that is somewhat problematic (there might be a good reason, although at present unknown). This is handled on the driver side - in ASCOM since several years, in Indi since yesterday.
Problem essentially solved. One happy variable star observer produced :)
Magnus
Den 2020-04-21 kl. 16:27, skrev Ray Gralak:
toggle quoted message
Show quoted text
Magnus,
If I move the scope to - 90 degrees Dec, it will point straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator.... Dec = -90 is not straight at the ground unless you are at the north pole. :-)
For example, if your latitude is 40 degrees then the north celestial pole is 40 degrees above the horizon. The horizon at due south is -50 degrees latitude, and south celestial pole 40 degrees below the southern point of the horizon (not 90 degrees south of it).
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: Tuesday, April 21, 2020 7:19 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
OK, I see what you mean by declination axis. Just to understand, though:
"Mechanical zero HA/Dec will be one of the two ways of pointing at the intersection of the celestial equator and
the local meridian. In order to support Dome slaving, where it is important to know which side of the pier the mount
is actually on, ASCOM has adopted the convention that the Normal pointing state will be the state where a
German Equatorial mount is on the East side of the pier, looking West, with the counterweights below the optical
assembly and that pierEast <
standards.org/Help/Platform/html/T_ASCOM_DeviceInterface_PierSide.htm> will represent this pointing state."
If I place my mount in this position, it will point straight to the south, right? Where the celestial equator intersects
the local meridian - south, in my case ca 25 degrees altitude (I'm at 55 degrees North). So that is zero mechanical
Dec and HA?
If so, how should I understand this?
Normal (pierEast <> )
Where the mechanical Dec is in the range -90 deg to +90 deg
If I move the scope to - 90 degrees Dec, it will point straight into the ground, wouldn't it? TO the south celestial
pole.... And I could to that if I lived on the equator....
So if I in this position, without moving the RA/HA-axis, move the dec to somewhere north - that would be beyond
+90 degrees - then I should have a shift of side-of-pier?
Magnus
Den 2020-04-21 kl. 15:51, skrev Ray Gralak:
Magnus,
Take a look at this link for a detailed explanation:
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro V3:
Author of Astro-Physics V2 ASCOM Driver:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus
Larsson
Sent: Tuesday, April 21, 2020 6:29 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
Thanks for your reply!
However, I am not sure I understand - which is not surprising because I
find this to be a difficult issue to describe and understand. I think
the hour angle description was the clearest so far, for me...But, I
don't know what Gemini uses to detect a shift of side-of-pier.
I don't follow what you mean by declination and RA-axis position. My
side-of-pier shifts when I slew in RA, not in DEC (don't know how to do
that). Of course my DEC axis moves, since it rotates around the RA axis.
But it is the slew in RA that causes a shift in side-of-pier, as the
counterweight bar (to describe it physically) moves across the meridian.
I guess that is what you mean by "note that when doing that the actual
pier side change occurs when the declination axis passes the celestial
pole to the other side"?
Either way - whichever axis moves and whatever causes the shift in
side-of-pier - maybe I describe it in totally wrong words. But: my PHD2
reacts to a shift in side-of-pier when I slew from some variables to
certain others - without any meridian flip nor a need for any - because
both stars are on either west or east side of the mount. This is my
problem, and it seriously messes up my variable sequences.
Maybe I describe it in odd ways - but the unusable images are very
real.... so how can we describe it in a reasonable way, and maybe find a
way to handle it?
Best,
Magnus
Den 2020-04-21 kl. 14:17, skrev Ray Gralak:
Hi Magnus,
I'm not sure if this has been said before, but "pier side" is determined by declination axis
position alone. It is not
affected by the right ascension axis position, so slewing the mount to "N", "NW", "S", etc. doesn't
provide enough
information to determine side of pier.
Specifically, pier side changes at the celestial pole when the Dec axis passes through 90
degrees (or -90
degrees).
A change in pier side often is associated with the mount "flipping" to the other side but note
that when doing
that the actual pier side change occurs when the declination axis passes the celestial pole to the
other side.
-Ray Gralak
Author of PEMPro V3:
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Magnus Larsson
Sent: Tuesday, April 21, 2020 2:57 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Side-of-pier issue
Hi!
How's it going with this? Makes any more sense? On the indi-forum, it is spoken about
in terms of hour angle,
maybe better way. My test shows that between -3 and -9 hours, the side-of-pier shifts
(approximately at -6) and
the
same happens between 3 and 9 hours.
So these are shifts of side-of-pier in situations where there should not be a meridian
flip (and none is initiated).
See the indi-forum thread here:
problem-bug.html
Best,
Magnus
Den 2020-04-19 kl. 18:28, skrev Brian Valente:
I generally understand your somewhat unusual case
What i don't understand is this: when I want to go from NE to SE, that is a slew
in DEC for me. you're
saying slew in RA, and I don't see how i would get to SE just by moving RA?
On Sun, Apr 19, 2020 at 9:19 AM Magnus Larsson <magnus@...>
<mailto:magnus@...> wrote:
Hi!
No, it is a slew in RA - I'm doing it with the same declination, just slewing
in RA, to test. And right, no
crossing the meridian. But physically, crossing the 90 degree azimuth line, the
counterweight bar crosses to
the
other side of the mount - hence shift of side-of-pier, in a very literal sense.
Yes, it impacts my guiding since when the mount reports shift of side-of-
pier, PHD2 swaps direction
of RA guiding. But since no direction of the guidecam or otherwise in the mount has
happended, this means
that
RA now escalates errors, rather than works against them - hence escalating run away
scope.
In essence, PHD2 interprets shift of side-of-pier as a meridian flip. But
this is not the only case when
it occurs nor when the G2 reports it.
It took me quite a while to see this... And I guess this is not what would be
problematic in regular AP,
when you find a target, maybe calibrate, and then track for hours. Then there is a
meridian flip, RA shifts, and
back to tracking. It happens here because I slew from target to target, imaging 20-25
different targets with just
one
or two subs of each, but I need guiding because I do some 5 mins exposures and I get
too much drift if no
guiding.
I have my complex sequence set up so it goes from lower altitude to higher, picking
stars before they are too
low,
basically, and then waiting for some to rise some more (manually sorted). It means that
it will start out on the
west
side, going in sort of zig-zag motion from RR Tau to GM Cam, to YY Aur, to U Gem and
so on.
Do you see it now? Or what can I send or describe that makes it more
clear?
Best,
Magnus
Den 2020-04-19 kl. 17:48, skrev Brian Valente:
Hi Magnus
No, it doesn't really make sense to me. if i go from NE to SE, this is
just a DEC move, i'm not
crossing the meridian. So why would it report side of pier change? confused abou tthis
i can slew back and forth, but it sounds like your issue is how is
guiding impacted, correct?
So i would assume you need some guiding to take place in this
situation to see how it
impacts.
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
<>
|
