Re: Still some DEC issues
A good puzzle, Alan.
Your mount has spring loaded RA and DEC.? The RA is the G11 type drive and the DEC is the GM8 type.
The RA and DEC are orthogonal.? The only way a vibration from.DEC could affect RA is if a jolt from DEC somehow shook the whole mount.
So: a few questions...
1. What is your tripod type?? If it is lightweight perhaps it could vibrate?
2. Last few emails, it seemed the view was to lock down the worm blocks (as they used to be before the spring loaded mechanism was introduced).? Did you bolt down the RA and DEC worm blocks?? If you didn't I'd suggest you bolt them down tightly on both axes, and skip the looser spring loaded operation to see the effect.??
3. When we spoke, you wanted to keep the same worm to ring gear lube as the factory installed.? It was a semitransparent and lightly red or pink color....I think that's what I saw.? ?I think this is the? ? ? ? Jet-Lube Arctic low temp grease ? that Brian has suggested.? You did not want to take a chance on the CRC brake and caliper grease that I offered.? I wonder if you were to try the thicker CRC lube if it could eliminate the vibration.??
Anyway, that's my suggestion for experiments to try.? ?
Best of luck, Michael
Hello folks,
I have the latest GM811.? A few weeks back, I posted about adjusting the screw to get the backlash as low as possible, mechanically.? When using the mount for long-exposure imaging, there are still some DEC issues that ruin a frame here and there.? I have the clutch pressure set very low.
0) First, I should mention that sometimes when the seeing is good, the guiding is good too at < 0.6 rms and the DEC axis just gives gentle nudges back and forth to the axis and everything is fine.
1) Sometimes a large DEC pulse (when changing direction) will cause a corresponding spike in RA also.? See attached picture.? Here only the northward pulses (approx 1 second worth, if I remember + TVC 10) cause a spike in RA.? (BTW, I also had these spikes with TVC 0) I noticed when running the backlash test in Guiding assistant that the guide star also moves a little in RA when changing DEC direction from N to S.
2) a dither move in DEC seems to "unsettle" the axis, and it seems to misbehave for maybe the next 30 seconds or more.? It's like the axis builds up "sticktion" and then releases it at some random time later.? In the picture, the sticktion amount is about 3 arc-sec.? After several minutes, this sticktion drops down to about 2 arc-s, and maybe if the seeing is good for a long time and I don't do any dithers in DEC, it gets even lower.? It's like the worm needs to move back and forth a few times before settling down for best performance.
So at this moment dither in DEC is unreliable because the later movement will mess up a frame.? I've resorted to dither RA only and then "manual DEC dither" after a sequence of images.
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Re: Editing posts - please don't
I have only ever used groups.io as a forum.? Just about the last thing I want is more emails. The way I use groups.io, each separate forum is its own channel.??
I make the occasional spellnig erraz when typing.? Sometimes, say a dropped s when I meant to use a plural, it can completely change a sentence's meaning.? If I do not catch this prior to posting, I need to edit.
Editing is a part of today's computerized life and has been since the mid-1980s.
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Brian, I just watched the wavy washer video.? Two things:
1. I expected to see workers from a laundry greeting me by raising their arms in greeting (wavy washers...).
2.? I had no idea the wavy washer went where it does.? I thought it went between the (on order) spacer/slip ring and the rear bearing thrust washer.
Thanks for pointing me in the right direction.
Pete
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With the wavy washers and the spacer/slip rings ordered, I shall rebuild my mount and see how well it works in its existing worm and bearing configuration before making changes.? Change one variable at a time and watch its effect.? This will be my motto until I understand this mount.??
I'll upgrade the Gemini-1 firmware to the latest available and see how that goes with ASCOM and indi.? Later I may wish to upgrade to Gemini 2.? I have read good and not so good reports of various features of Gemini 2.? Since I mainly use either ASCOM and more recently indi/KStars//Ekos, I honestly wonder if this particular upgrade is warranted for my installation.? For me a major advantage of Gemini 2 is that it has an RJ45 Ethernet connection and this is my preferred method of connection wherever possible.
Pete
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Thanks, Derek for the suggestion. It works great in keep the declination motor cable from fouling with the clutch knobs. The yogurt tub has been retired from service.
Russ
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Re: Gemini-2 momentarily went haywire
Thanks for your thoughts, Michael. I'm hoping the board is bit less than you are quoting. Desoldering the old encoder chip and soldering in a few dozen 0.5mm(?) connectors sounds like an extreme challenge. Even under a magnifying lens using a super small soldering iron, this will required quite a steady hand. If only I had one of those manufacturing robots :). Just wondering if the old board can be connected to some sort of analyzer to check what this chip is really doing.
Regards,
John
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Hi gang,
The wavy style washers, and the cup-shaped Belleville spring washers, are used commonly in mechanical systems.? Their purpose is to provide a rather constant axial force, vs a force that would change very abruptly and dramatically when temperature changes.? And temperature certainly does change in our outdoor usage.
The cup-shaped Belleville spring can be used in any situation where you want a rather uniform force on the outer circumference on one side of the spring, and a corresponding force in the inner edge of the spring on the other side.
When you want to keep the constant force on the worm bearings, that keeps the balls on their races for lowest bearing rumble, you want to use the Belleville cup shape (R4 sized spring for the R4ZZ bearing size).??
If you want a force that is somewhat uniform on the thrust bearing, you first of all should use a thick spacer on the thrust washer thin race washer.? After the thick spacer disk which is flat you can use either a wavy or a Belleville cup shape washer.? Losmandy used a cup shaped Belleville spring in the CG11 Celestron G11 ...that's what came in my unit.? Later they switched to a wavy style washer.? Once you have the thick aluminum flat spacer on the thin thrust washer race disk, the type of spring washer on the other side cannot matter.
If you were to put the spring right on the thin thrust washer race disk, as the factory prefers, you'd be better off with the wavy washer.? But I can't support that assembly sequence.? I prefer the way Mark Crossley described in his website
Anyway, there are "bigger fish to fry" in the optimization of the performance.? In this case, the used mount was purchased missing a key part.? You just need to buy the part and you will be fine.? You can use the existing cup shaped Belleville or the wavy equivalent.? You want find any difference in practice.
The CG11 came with steel worms.? It came with two separate worm blocks.? If you replace the steel worm on RA with a new brass worm, new R4ZZ ABEC-7 bearings like these? ?
and if you add on an OPW, you will get better RA PE.??
You can have fun all along the way.? The mount is very strong and can support a 12 inch SCT.??
Have fun!
Michael
@Les Niles,??
My mount currently does not have "wavy washers."? It has true Belleville washers which Brian says are not supported by Losmandy.? I have therefore ordered a pair of Losmandy wavy washers?
They were so cheap that it was silly not to buy them.? Thanks for your input.? It swung my decision.
Pete
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Hey P.
That sounds good. Please make sure to check out our wavy washer video on our YouTube channel as well
@Les Niles,??
My mount currently does not have "wavy washers."? It has true Belleville washers which Brian says are not supported by Losmandy.? I have therefore ordered a pair of Losmandy wavy washers?
They were so cheap that it was silly not to buy them.? Thanks for your input.? It swung my decision.
Pete
-- Brian?
Brian Valente portfolio
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@Les Niles,??
My mount currently does not have "wavy washers."? It has true Belleville washers which Brian says are not supported by Losmandy.? I have therefore ordered a pair of Losmandy wavy washers?
They were so cheap that it was silly not to buy them.? Thanks for your input.? It swung my decision.
Pete
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Re: Gemini-2 momentarily went haywire
David,
Thanks for the info. Please see attached photo with board label. The chip you mentioned seems like it has a few dozen pins. I am capable on doing some fine soldering, but that many connections so close together would probably be beyond my skill level. Still I might risk it since the other alternative would be buying the whole board. Would you know the chip price offhand?
I have corresponded with Michael before on this and I don't think he does this with the G-2. I have previously checked all the cable socket connections to the PC board and they are solid.
Any further suggestions would be appreciated.
Thanks,
John
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Re: RA spikes towards west
Hej :)
Good to hear!
Best,
Magnus
Den 2021-05-04 kl. 17:03, skrev Carl
Bj?rk:
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Hej Magnus!
OMG I had issues since two weeks I couldn't figure out. I
encountered 9" spikes while guiding out of nowhere. Also it was
impossible to polar align using a plate solving solution near
Polaris (Ekos in my case), changes were somehow random sometimes
undercorrecting, sometimes overcorrecting, sometimes moving at the
opposite of the correction
Like you went into tuning and re-tuning, but I thought it was
good.
Long story short I read your post and realized I had reset the
mount two weeks ago at which point PEC got activated (with a very
bad PE recording on the SD Card).?I can't wait to try it but am
very confident this was it.
Thank you so much! See, you even solved my issue :-D
Also many thanks to Michael and Sonny, and obviously Brian which
is helping me a lot too.
Cheers,
Carl
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Re: RA spikes towards west
Nice Carl!
A Bad PEC is worse than no PEC at all
Hej Magnus!
OMG I had issues since two weeks I couldn't figure out. I encountered 9" spikes while guiding out of nowhere. Also it was impossible to polar align using a plate solving solution near Polaris (Ekos in my case), changes were somehow random sometimes undercorrecting, sometimes overcorrecting, sometimes moving at the opposite of the correction
Like you went into tuning and re-tuning, but I thought it was good.
Long story short I read your post and realized I had reset the mount two weeks ago at which point PEC got activated (with a very bad PE recording on the SD Card).?I can't wait to try it but am very confident this was it.
Thank you so much! See, you even solved my issue :-D
Also many thanks to Michael and Sonny, and obviously Brian which is helping me a lot too.
Cheers,
Carl
-- Brian?
Brian Valente portfolio
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Re: Gemini-2 momentarily went haywire
>>>
We already know the major cause of damage is a rotated DIN connector insertion.??
Keys were added to the Gemini 2 nearly a decade ago, so this is not an issue with Gemini 2
John,
The Gemini-1 are generally repairable.? The unit has a board that was designed in the day when the chips were larger and their leads were spaced out so a skilled person could de-solder the old chip and re-solder a new chip.? If your unit shows trouble, I can attempt a repair.? Bren Smith in Australia and David Partridge in UK are experts in G1 and G2 repairs.??
The Gemini-2 is modern.? It's small board has fewer, faster chips with tiny lead spaces.? Brendan Smith in Australia is most expert at these repairs.? However I've never encountered any G-2 needing repair.??
As I said, the first step when you do encounter trouble is to use the ability of the Gemini system to swap RA and DEC parts: the cables, the motors, to assess what is truly damaged.? Then replace or try a repair.??
Certainly contact the factory so they can track what components are failing most of the time.? In a later design someone can engineer a way to protect the parts from major damage.? That would have to be inside the Gemini unit to protect it's optical sensor detector chip.? That's the $1000 value unit.
A motor is $225.? Also expensive and needs the optical encoder protected from anything over 5.2 volts probably.? That can be done too inside on the motor board.??
Can a protection mechanism be designed to be in the cable?? That is a good engineering challenge.? ?We already know the major cause of damage is a rotated DIN connector insertion.? Some electronics in the cable might save the day ... or ...?
A great homework problem for electronics experts!
As I mentioned, an ounce of prevention (label the cable ends for pennies) is worth a pound of cure ($1000 Gemini replacement)
Stay well, all.??
Michael
Thanks, Michael.
?
In my case it is the Gemini 2 output, but I don't suppose the encoder detector is something that could be replaced. I don't have the G-2 open right now but I kind of remember all the chips are flush mounted on the board and micro-soldered. So it's replace the whole board or nothing I assume. I'll have to see what HGM has to say.
Best regards,
John
-- Brian?
Brian Valente portfolio
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Re: RA spikes towards west
Hej Magnus!
OMG I had issues since two weeks I couldn't figure out. I encountered 9" spikes while guiding out of nowhere. Also it was impossible to polar align using a plate solving solution near Polaris (Ekos in my case), changes were somehow random sometimes undercorrecting, sometimes overcorrecting, sometimes moving at the opposite of the correction
Like you went into tuning and re-tuning, but I thought it was good.
Long story short I read your post and realized I had reset the mount two weeks ago at which point PEC got activated (with a very bad PE recording on the SD Card).?I can't wait to try it but am very confident this was it.
Thank you so much! See, you even solved my issue :-D
Also many thanks to Michael and Sonny, and obviously Brian which is helping me a lot too.
Cheers,
Carl
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Re: Gemini-2 momentarily went haywire
John,
The Gemini-1 are generally repairable.? The unit has a board that was designed in the day when the chips were larger and their leads were spaced out so a skilled person could de-solder the old chip and re-solder a new chip.? If your unit shows trouble, I can attempt a repair.? Bren Smith in Australia and David Partridge in UK are experts in G1 and G2 repairs.??
The Gemini-2 is modern.? It's small board has fewer, faster chips with tiny lead spaces.? Brendan Smith in Australia is most expert at these repairs.? However I've never encountered any G-2 needing repair.??
As I said, the first step when you do encounter trouble is to use the ability of the Gemini system to swap RA and DEC parts: the cables, the motors, to assess what is truly damaged.? Then replace or try a repair.??
Certainly contact the factory so they can track what components are failing most of the time.? In a later design someone can engineer a way to protect the parts from major damage.? That would have to be inside the Gemini unit to protect it's optical sensor detector chip.? That's the $1000 value unit.
A motor is $225.? Also expensive and needs the optical encoder protected from anything over 5.2 volts probably.? That can be done too inside on the motor board.??
Can a protection mechanism be designed to be in the cable?? That is a good engineering challenge.? ?We already know the major cause of damage is a rotated DIN connector insertion.? Some electronics in the cable might save the day ... or ...?
A great homework problem for electronics experts!
As I mentioned, an ounce of prevention (label the cable ends for pennies) is worth a pound of cure ($1000 Gemini replacement)
Stay well, all.??
Michael
Thanks, Michael.
?
In my case it is the Gemini 2 output, but I don't suppose the encoder detector is something that could be replaced. I don't have the G-2 open right now but I kind of remember all the chips are flush mounted on the board and micro-soldered. So it's replace the whole board or nothing I assume. I'll have to see what HGM has to say.
Best regards,
John
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Re: Getting great alignment
On Mon, May 3, 2021 at 07:53 PM, Brian Valente wrote:
Hi George
?
assuming you have Gemini 2 and are building a model for the first time (cold start) you use Align
?
1 Polar align as best I can using Losmandy polar scope.? Set mount at CWD.
2 Do a Quick or cold start. Either tosses any previous alignment, model, whatever and I can start fresh.?
3 Enter all the parameters correctly and boot up.
4 Do polar align assist if I think I need to BEFORE I 'build a model'
5 GOTO bright star.? Carefully center the star.
6 Select 'Align' ??? or? 'Synchronize' ??? Which?? ALIGN
7 Select and goto another bright star. Prefer >4HA from first.
8 Center and align or sync this star. Which?? ALIGN
9 Continue this until I think I'm done. 3 STARS ON EACH SIDE OF MERIDIAN IS PLENTY
Test?
Hi George, ? ? ?I generally follow Brian's work flow here. ? In my case I use Polemaster to do a polar alignment. ? I always do a cold start when I go out. ?Generally, 3 stars in the model, two on one side, 1 on the other is good enough to put a target on my 4/3 sensor at 2000 mm. ? I usually do 4 or 5 and add stars as the night progresses. ?Originally, I would center each star in the eyepiece as Brian describes, then put my camera in after building a quick model. ? Since I learned to do plate solving, I use THAT to do the centering as I build the model. ?Once I get 4 or 5 stars centered and included in the model, ?I am usually good for the night and do not have to plate solve or add stars etc... ? Good polar alignment is of course critical to all of this. ?If I am doing visual work, and I have good polar alignment, Generally my target star will be in the FOV of my 53 mm plossl at 1000 mm on the first go. ? I find Gemini II to be quite accurate compared to other mounts I have used, and once you get a feel for the work flow, it is actually faster, since I have less hunting around to do. ?Lots of ways to do this and with practice you will find the flow that works for you. Good Luck! JMD?
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Re: Meridian flip sanity check please?
On Tue, May 4, 2021 at 08:07 AM, Paul Goelz wrote:
I had a look in Gemini.net and two questions came up....
1. When I check the "nudge" checkbox, I get a warning that I am
disabling the Gemini built in slew disabling mechanism and do I want to
do that. Does that mean that when the box is checked, after the western
safety limit is reached a slew to an object past the western safety
limit will now slew PAST the western safety limit if that box is
checked? Or is the western safety limit a hard limit and only slews to
the east will function?
2. I note that the in the safety limit settings section of the
Gemini.net driver, the western GOTO limit is described as "degrees from
CWD". Is that actually how the western GOTO limit is set in the driver?
I have always understood the western GOTO limit to be degrees EAST of
the western safety limit.
1: That warning is telling you that you're overriding the default behavior of Gemini once stopped at the safety limit. It doesn't override the safety limit. It will never slew past the safety limit. 2: That's a copy/paste error in the Goto limit label. I'll fix it :) Regards, ? ? ?-Paul
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Re: Meridian flip sanity check please?
On 5/4/2021 7:27 AM, Paul Kanevsky wrote: Alignment is not lost after safety limit stop. You can use the HC buttons at centering or slew speeds to back the mount out of the safety limit stop. In Gemini.NET driver you can also ask the driver to do this for you, automatically. Set near the bottom of safety limit configuration screen: I had a look in Gemini.net and two questions came up.... 1. When I check the "nudge" checkbox, I get a warning that I am disabling the Gemini built in slew disabling mechanism and do I want to do that. Does that mean that when the box is checked, after the western safety limit is reached a slew to an object past the western safety limit will now slew PAST the western safety limit if that box is checked? Or is the western safety limit a hard limit and only slews to the east will function? 2. I note that the in the safety limit settings section of the Gemini.net driver, the western GOTO limit is described as "degrees from CWD". Is that actually how the western GOTO limit is set in the driver? I have always understood the western GOTO limit to be degrees EAST of the western safety limit. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Re: Meridian flip sanity check please?
Try Centering speed to nudge the mount out. I forget, but it's likely that slew speed isn't supported when stopped at the safety limit.
Yes, when nudge option is turned on, Gemini.NET will simulate you pressing the HC buttons at centering speed to nudge the mount out of the safety limit, and then will issue the Goto command that you requested.?
Regards,
? ? ?-Paul
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On Tue, May 4, 2021 at 07:45 AM, Paul Goelz wrote:
Thanks for the explanation of the "nudge" checkbox. I assume with that
checked, a slew will function normally even if the mount has hit the
safety limit? So if I track an object until the western safety limit is
reached and the mount stops, a subsequent slew to the same object will
cause a flip and complete normally?
But FWIW, the last time I tracked into the safety limit after a failed
NINA meridian flip, the HC buttons DID NOT work at slew speed. The only
way I could get the mount responsive again was to initiate a PARK and
then abort it after the mount started slewing. Did I miss something?
Paul
--
Paul Goelz
Rochester Hills, MI USA
pgoelz@...
www.pgoelz.com
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Re: Meridian flip sanity check please?
On 5/4/2021 7:27 AM, Paul Kanevsky wrote: On Mon, May 3, 2021 at 05:01 PM, Paul Goelz wrote:
I've asked before and I forget the answer.... if I track into the
western limit and the mount stops, what is the easiest way to wake it
back up so that it is responsive to slew commands and buttons without
losing alignment? Or is alignment lost when tracking stops?
Alignment is not lost after safety limit stop. You can use the HC buttons at centering or slew speeds to back the mount out of the safety limit stop. In Gemini.NET driver you can also ask the driver to do this for you, automatically. Set near the bottom of safety limit configuration screen: Thanks for the explanation of the "nudge" checkbox. I assume with that checked, a slew will function normally even if the mount has hit the safety limit? So if I track an object until the western safety limit is reached and the mount stops, a subsequent slew to the same object will cause a flip and complete normally? But FWIW, the last time I tracked into the safety limit after a failed NINA meridian flip, the HC buttons DID NOT work at slew speed. The only way I could get the mount responsive again was to initiate a PARK and then abort it after the mount started slewing. Did I miss something? Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Michael Herman
Pete
Russell Milton
Paul Kanevsky