Re: Help with DEC backlash/jumpy guiding
Ray,
A quick question for you. Is there set yet for Pempro 3?
Rob
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From: Losmandy_users@... on behalf of 'Ray Gralak (Groups)' groups3@... [Losmandy_users]
Sent: Sunday, November 26, 2017 1:37:59 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
?
?
Michael,
> This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
> 4¡Á60sec =240 sec, right?
I know you are just trying to help, but Brian's mount is not a G11. It is a G11GT, as both Brian and Paul have already confirmed in their recent posts.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma
> -----Original Message-----
> From: Losmandy_users@... [mailto:Losmandy_users@...]
> Sent: Sunday, November 26, 2017 1:18 PM
> To: Losmandy_users@...
> Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
>
>
>
> Ray,
>
> This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
> 4¡Á60sec =240 sec, right?
>
> Here is the text, from the Losmandy website:
>
> http://www.losmandy.com/g-11-manual.html
>
>
> Periodic Error Correction (PEC)
>
> Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is
> designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a
> slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is
> equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope
> drives will have some periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC
> function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered
> on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It
> takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes.
> The second step is to play back the corrections you made during the recording phase. The microcomputer
> inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that
> this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC
> function most effectively.
>
>
>
> On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]"
> wrote:
>
>
>
>
>
>
> > That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
> eliminated
> > mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
> sounds
>
>
> Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about
> 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over
> a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm
> gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds
> peak-peak.
>
> Best regards,
>
> -Ray Gralak
> Author of APCC (Astro-Physics Command Center): http://www.astro-
> physics.com/index.htm?products/accessories/software/apcc/apcc
> physics.com/index.htm?products/accessories/software/apcc/apcc>
> Author of PEMPro: http://www.ccdware.com
> Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
> Author of PulseGuide: http://www.pulseguide.com
> Author of Sigma: http://www.gralak.com/sigma
>
>
> > -----Original Message-----
> > From: Losmandy_users@... [mailto:Losmandy_users@...
> ]
> > Sent: Sunday, November 26, 2017 10:43 AM
> > To: Losmandy_users@...
> > Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
> >
> >
> >
> > I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the
> EQMOD
> > group who made up PECprep to add to their G11 list.
> >
> > How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as
> high as
> > that one?
> > (Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in my
> > PECprep.exe program to see its FFT.)
> >
> >
> > That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
> eliminated
> > mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
> sounds
> > to me like a design problem...
> >
> > Best,
> > Michael
> >
> >
> >
> > On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
> > > wrote:
> >
> >
> >
> >
> >
> > Michael
> >
> >
> > I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
> > introduce new gearing ratios (probably true for G11G as well).
> >
> > This has also been confirmed by Ray with PemPro
> >
> >
> > B
> >
> >
> >
> >
> >
> >
> >
>
> > --
> >
> > Michael Herman
> > mobile: 408 421-1239
> > email: mherman346@...
> >
> >
> >
>
>
>
>
>
|
Re: Help with DEC backlash/jumpy guiding
Michael, This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
4¡Á60sec =240 sec, right? I know you are just trying to help, but Brian's mount is not a G11. It is a G11GT, as both Brian and Paul have already confirmed in their recent posts. Best regards, -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro: Author of Astro-Physics V2 ASCOM Driver: Author of PulseGuide: Author of Sigma: -----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Sunday, November 26, 2017 1:18 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)
Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is
designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a
slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is
equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope
drives will have some periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC
function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered
on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It
takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes.
The second step is to play back the corrections you made during the recording phase. The microcomputer
inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that
this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC
function most effectively.
On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]"
<Losmandy_users@...> wrote:
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
sounds
Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about
319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over
a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm
gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds
peak-peak.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
physics.com/index.htm?products/accessories/software/apcc/apcc <
physics.com/index.htm?products/accessories/software/apcc/apcc>
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
> -----Original Message-----
> From: Losmandy_users@... [mailto:Losmandy_users@...
<mailto:Losmandy_users@...> ]
> Sent: Sunday, November 26, 2017 10:43 AM
> To: Losmandy_users@...
> Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
>
>
>
> I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the
EQMOD
> group who made up PECprep to add to their G11 list.
>
> How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as
high as
> that one?
> (Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in my
> PECprep.exe program to see its FFT.)
>
>
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
sounds
> to me like a design problem...
>
> Best,
> Michael
>
>
>
> On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
> <Losmandy_users@... <mailto:Losmandy_users@...> > wrote:
>
>
>
>
>
> Michael
>
>
> I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
> introduce new gearing ratios (probably true for G11G as well).
>
> This has also been confirmed by Ray with PemPro
>
>
> B
>
>
>
>
>
>
>
> --
>
> Michael Herman
> mobile: 408 421-1239 <tel:(408)%20421-1239>
> email: mherman346@...
>
>
>
|
Re: Help with DEC backlash/jumpy guiding
Michael we're talking a G11GT - the 'T' is for the titan RA portion which is the 319 worm
also I don't know about the regular G11 with tucked in gears, but i wouldn't be surprised if those added some periodic error somewhere as well
B
On Sun, Nov 26, 2017 at 1:18 PM, Michael Herman mherman346@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes = 4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope drives will have?some?periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes. The second step is to play back the corrections you made during the recording phase. The microcomputer inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC function most effectively.
-- Brian?
Brian Valente portfolio
|
Re: Help with DEC backlash/jumpy guiding
Michael,?
Brian has a G11GT mount, which has a Titan-based RA and a G11-based DEC assembly. RA has a 270 tooth wheel, which translates into just under 320 seconds worm cycle.
Regards,
? ? -Paul
|
Re: Help with DEC backlash/jumpy guiding
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes = 4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope drives will have?some?periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes. The second step is to play back the corrections you made during the recording phase. The microcomputer inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC function most effectively.
On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]" < Losmandy_users@...> wrote:
?
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds
Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds peak-peak.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
> -----Original Message-----
> From: Losmandy_users@... [mailto: Losmandy_users@yahoogroups.com]
> Sent: Sunday, November 26, 2017 10:43 AM
> To: Losmandy_users@...
> Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
>
>
>
> I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD
> group who made up PECprep to add to their G11 list.
>
> How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as high as
> that one?
> (Or better for me: send me [ mherman346@...] your raw PHD2 log file and I can run it in my
> PECprep.exe program to see its FFT.)
>
>
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds
> to me like a design problem...
>
> Best,
> Michael
>
>
>
> On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
> < Losmandy_users@yahoogroups.com> wrote:
>
>
>
>
>
> Michael
>
>
> I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
> introduce new gearing ratios (probably true for G11G as well).
>
> This has also been confirmed by Ray with PemPro
>
>
> B
>
>
>
>
>
>
>
> --
>
> Michael Herman
> mobile: 408 421-1239
> email: mherman346@...
>
>
>
|
Re: Help with DEC backlash/jumpy guiding
That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds peak-peak. Best regards, -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro: Author of Astro-Physics V2 ASCOM Driver: Author of PulseGuide: Author of Sigma: -----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Sunday, November 26, 2017 10:43 AM
To: Losmandy_users@...
Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD
group who made up PECprep to add to their G11 list.
How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as high as
that one?
(Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in my
PECprep.exe program to see its FFT.)
That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds
to me like a design problem...
Best,
Michael
On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
<Losmandy_users@...> wrote:
Michael
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
--
Michael Herman
mobile: 408 421-1239
email: mherman346@...
|
Hi!
Great, thanks!! Will play with this next clear night.... next year or so, I guess... :)
Best,
Magnus
|
Re: Help with DEC backlash/jumpy guiding
I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD group who made up PECprep to add to their G11 list.??
How does that 42 sec peak compare in size to the Worm peak at 239.4 sec.? Is it anywhere near as high as that one? (Or better for me: send me [ mherman346@...] your raw PHD2 log file and I can run it in my PECprep.exe program to see its FFT.)
That 239.4/42 = 5.7.? That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds to me like a design problem...? ?
Best,? Michael
On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Michael?
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
|
Re: Help with DEC backlash/jumpy guiding
Michael?
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
|
Re: Help with DEC backlash/jumpy guiding
Unknown on the new G11G system...? but you have to understand the contributors to noise in the PE and PE error itself.
It was thought that only the worm mattered, and that of course rotates in ~239.4 sec on the G11 (double that time on the GM8).? The idea of PEC is that the rotational speed can be "corrected" by speeding up or slowing down the worm to make it "perfect".??
But there are other factors that come in... some of them do not spin at the same period as the worm so are not correctable by PEC, (But we hope are correctable mechanically).??
The worm bearings have tiny balls in them and these rotate on the inner race and outer race and there can be noise there (called "rumble").? Using higher quality bearings have lower rumble and so expected to have better PE and less noisy PE.? ?(We have no measure of "noise" in the PE... )
The Oldham coupler may also contribute on the original striaght line design.? That coupler has some sliding parts that... if they don't slide easily but have noise could cause glitches.? Also any angle between the gearbox axle and the worm axle will give a periodic error of about period/4 (my calculations... may be wrong?) .? The best bet is to keep all those Oldham parts pressed together and line up the left and right side so the coupler never has to slide/move except to rotate.??
Also the bearings are not "up to spec" unless they are under compressive force, called "preloading".? For that, I found (and Ovision already knew) that at Belleville spriing washer is useful to keep those worm bearings uinder constant force.? Some people wrap a weighted cord around the RA axis for that purpose... I only use a Belleville washer for that but the far worm bearing must be able so slide so the spring can push it into the worm.
Aside from the last item:? getting the worm engaged in the Ring gear teeth.. that you have to adjust by hand, and can monitor the separation with car feeler gauges.? Keep compressing that until the axis "stalls" with the motor drive, then back off slightly ( season to taste, shall we say).
The new system has the motor drive wrapped down so it does not interfere with full rotation of the axis.? I don't know the components of that drive system, gears or belts... lots of ways to kill a cat.? But the ideas above are a guide to what to watch out for.
-------- Off-topic....?
There was an earlier question (if in another thread...sorry!) about a 42 second period (not a integral fraction of a worm period so not amenable to PEC correction).? The nice program PECPrep (from the EQMOD group) has many periods for the G11 mount shown.? But no 42 second contributor shown.? These frequencies can be whacked out if you have a lot of DEC drift, so if the main contributor is not the Worm/1 period of 239.4 sec, you likely have some bad PE data and should retake it.??
That program lists these: Worm 239.4 sec Worm bearing ball spin 109.4 Worm 2nd harmonic 118.7 Worm 3rd harmonic 79.8 Worm bearing ball passes outer race 76.2 Worm 4th harmonic 59.8 Worm bearing ball passes inner race 49.2 Worm 5th harmonic 47.9 Worm 6th harmonic 39.9 Worm 7th harmonic 34.2 Worm spur gear 31.9 Worm 8th harmonic 29.9 Servo spur gear? 9.6 Transfer/worm spur gear mesh 3.2 sec
That's the list of known frequencies for the G11? (for GM8 double those) ---------------------------
All the best,
Michael
On Sun, Nov 26, 2017 at 9:42 AM, steamdiesel@... [Losmandy_users] <Losmandy_users@...> wrote:
?
I have the same issues with both axes of my new-design G-11G. I am still going through the trouble shooting process but expect I eventually will have to do the bearing/washer mod. How much does this modification improve performance?
Glenn?
|
Re: Help with DEC backlash/jumpy guiding
I have the same issues with both axes of my new-design G-11G. I am still going through the trouble shooting process but expect I eventually will have to do the bearing/washer mod. How much does this modification improve performance?
Glenn?
|
Comments...
1. You don't need any PC connection, per se, to run the Gemini PEC recorder.? You could use an autoguider camera and the ST4 port to do it I suppose.
2. If you are looking at PHD2 on your PC,? and you can use its Manual guide to move your mount (remember Gemini must be set to Guide mode or easiest to select "G" on the Gemini.net applet) then your mount is getting pulse commands from the Ascom system. (You had to install ASCOM first and the Gemini.net driver).??
In that Gemini.net driver, I think is how you either select the Serial port, or ethernet connection method.
Anyway... play around and you will find a way. ...!
Have fun, Michael?
On Nov 26, 2017 8:26 AM, " yh@... [Losmandy_users]" < Losmandy_users@...> wrote:
?
>?I think the big question is what is PEC for? It is my view that it is there to get you better unguided exposures.
I know this is a frequent subject for debates, but proper PEC programming does help prevent tracking errors before they happen. This results in better guided or unguided performance. An autoguider can only correct errors after they have occurred, PEC can correct them so they never happen.
If you want to compare PEC to PPEC, there may still be benefits, although these may be fewer - For one thing, PEC operates internally to Gemini. The corrections are not only precise, they are instantaneous, not subject to communications delays and PC timing like the corrections from PPEC
- Gemini keeps track of the worm index position through encoders, allowing existing PEC to be used immediately after slews and goto's -- PPEC has to be relearned after a slew
- PEC software allows many cycles to be used and programmed, filtering out a lot of the random errors that PPEC might not. Since PEC doesn't have to be relearned after each slew, dedicating an hour or two to training PEC can pay off big dividends over many months of imaging
- Some PEC software (f.i., PemPro) has built-in knowledge about various gears and error cycles particular to each mount type. This allows PEC curve to be fine-tuned very easily to fix issues specific to a mount. PPEC doesn't do that. I believe an upcoming version of PemPro will even correct errors that occur over multiple worm cycles.?
PPEC is a great tool, but generally it's not better than PEC for both, guided or unguided exposures. In fact, PHD2 team recommends to train PEC before using PPEC if your mount allows it. Perhaps that's the best of both worlds: PEC correcting most of the errors, and PPEC picking up any small uncorrected errors that remain.
Regards,
? ? -Paul
|
>?I think the big question is what is PEC for? It is my view that it is there to get you better unguided exposures.
I know this is a frequent subject for debates, but proper PEC programming does help prevent tracking errors before they happen. This results in better guided or unguided performance. An autoguider can only correct errors after they have occurred, PEC can correct them so they never happen.
If you want to compare PEC to PPEC, there may still be benefits, although these may be fewer - For one thing, PEC operates internally to Gemini. The corrections are not only precise, they are instantaneous, not subject to communications delays and PC timing like the corrections from PPEC
- Gemini keeps track of the worm index position through encoders, allowing existing PEC to be used immediately after slews and goto's -- PPEC has to be relearned after a slew
- PEC software allows many cycles to be used and programmed, filtering out a lot of the random errors that PPEC might not. Since PEC doesn't have to be relearned after each slew, dedicating an hour or two to training PEC can pay off big dividends over many months of imaging
- Some PEC software (f.i., PemPro) has built-in knowledge about various gears and error cycles particular to each mount type. This allows PEC curve to be fine-tuned very easily to fix issues specific to a mount. PPEC doesn't do that. I believe an upcoming version of PemPro will even correct errors that occur over multiple worm cycles.?
PPEC is a great tool, but generally it's not better than PEC for both, guided or unguided exposures. In fact, PHD2 team recommends to train PEC before using PPEC if your mount allows it. Perhaps that's the best of both worlds: PEC correcting most of the errors, and PPEC picking up any small uncorrected errors that remain.
Regards,
? ? -Paul
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PE correction helps for both guided and unguided imaging. Some errors cannot be easily guided out, and PEC helps smooth things out so the guiding is better
My G11GT has a nasty 42 second recurring error that i see on my PHD guiding, which none of the algorithms including PPEC can effectively address.?
I'm waiting on pempro to have the two worm cycle error correction to address this
B
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Do you have to use an Ethernet connection to do all the pec runs, or can you use just USB connection?? ?I only use USB and can't get Gemini.net, right.? I have a new G811G with gemini-2.? No pempro yet.
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Magnus,
You are correct : you can use your autoguider with the Gemini's built in PEC recorder /corrector.? You skip using the old hand controller method.? The correction signals from the autoguider work just fine.
That is not clearly explained in the Gemini 1 manual.??
You want to start by a precise polar drift align,? using a star near meridian and the celestial equator.
That is important because the PEC you want to correct is the RA's error, and even though the software says it can subtract out DEC drift, you want that as near zero as possible.
After drift alignment is clean and DEC drift is near zero over 8+ minutes, test that your autoguider is working correctly.? Remember to put the Gemini.net into G for Guide mode, else the Gemini will not accept any autoguide signals. Take a 10 minute? autoguide image.? ?Are the stars correctly round...no glitches?? If the stars are proper and no glitches, you can start a PEC recording.
Again select a new star near meridian and equator, perhaps point the scope to the west, then slew to a star just east of the meridian that will pass to through meridian over time.? You do that because you want to run about 3 PEC recordings and "add" and "average" them in the Gemini system.
The first PEC recoding will last exactly 8 minutes. Before that begins, the Gemini will transfer it's existing PEC data to its SRAM backup register, but that is all 0s.
? ?The system knows from its optical encoder where the starting position is (relatively, not exactly).? When the first run ends, the Gemini puts that data into its primary PEC register (in SRAM).??
When you start the next run, the Gemini will first transfer it's PEC data to the SRAM, then wait for the worm to get back to its same starting rotation.? That could take up to 7.99 more minutes.? Then the run itself will take 8 minutes.? At the end of that ND run, the 2nd PEC data is in the "top" PEC register.? You can tell the Gemini to "average" the 2nd run with the backup data.? That averaged data is now in the topmost PEC register in SRAM.??
You should use Gemini.net to save that data into your PC in a file.??
You can redo the steps of the 2nd run.? It is not clear to me how averaging the 3rd run works.? It might actually have (in another register) a counter so it knows this is the 3rd run, so all 3 runs are equally weighted.? ?Or it may be just takes 1/2 of run 3 and adds it to 1/2 of (the PEC backup data).? Only the person with the source code can say for sure.??
There are commands to smooth the PEC data, and other things.? I used those commands also.??
Save the resulting PEC to your PC in a new filename.? When you are done, test the PEC by taking a 10 minute image.? If you had a glitch you PEC data will have recorded the glitch and your PEC image could be worse than one plain autoguided.? If the PEC has a glitch, you can upload one of the earlier PEC files to the Gemini and see if it is correct.??
And:
You must park your mount before shutting off power.? That puts the worm in a known (in SRAM) rotation.? (It is said that even if the power goes out, the Gemini knows the last worm position, but on other mounts like the Atlas, you must always park.)
On power up, the Gemini always defaults to "PEC OFF".? Be sure to turn that on in the hand controller.? There is a checkbox in Gemini.net to automatically turn on PEC when it connects.? You could ensure your PEC is on using that.??
Epilogue:
PEC did work well for me, but I no longer use the PEC...I was lucky to get my PE without PEC down to ~1arcsec, so regular autoguiding gives me round stars.? Thats,all written up in the PDF "Improving the PE of the G11" in our group files section.??
(I will send you some Belleville worm washers,? Magnus.)
All the best, and hope these comments help you.
Michael?
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Hi!
I'm trying to get my head around how I can train PEC in a good way. I understand that I can do it manually, that is with an eyepiece and manually issuing guide commands.
But: If I can do that manually, could I not use PHD2 to do the same? Use the RA guide commands to train PEC, instead of me sitting there trying to guide? That is: manually engaging the "Train PEC", then start the gudiing only in RA, and let it run. Take a number of runs, then average and smooth them. Would that work?
Thirdly, Pecprep seems to be a utility that can produce a "PEC file". Can I use that and someway upload to the Gemini 1? I understand Pecprep to be part of th EQMOD project, and that does not include Gemini, but is it doable anyway?
Finally, I can use Pempro. However, somewhat costly.... is that worth the money?
Magnus
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I think the big question is what is PEC for? It is my view that it is there to get you better unguided exposures.
I believe that if you taking guided exposures, then you don¡¯t need PEC (at least not traditional PEC) but just rely on PHD2 (with possible use of PPEC). I¡¯ve never heard of anyone actually doing a proper double blind test to see which is the better approach.
And in answer to your question about using guiding s/w to train PEC, yes that¡¯s what I do: Set up PHD2 with the guide camera in the imaging scope, calibrate it and start guiding. The start the PEC training.
Dave
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: 26 November 2017 14:09
To: Losmandy_users@...
Subject: [Losmandy_users] How to train PEC
Hi!
I'm trying to get my head around how I can train PEC in a good way. I understand that I can do it manually, that is with an eyepiece and manually issuing guide commands.
But: If I can do that manually, could I not use PHD2 to do the same? Use the RA guide commands to train PEC, instead of me sitting there trying to guide? That is: manually engaging the "Train PEC", then start the gudiing only in RA, and let it run. Take a number of runs, then average and smooth them. Would that work?
Thirdly, Pecprep seems to be a utility that can produce a "PEC file". Can I use that and someway upload to the Gemini 1? I understand Pecprep to be part of th EQMOD project, and that does not include Gemini, but is it doable anyway?
Finally, I can use Pempro. However, somewhat costly.... is that worth the money?
Magnus
|
Hi! I'm trying to get my head around how I can train PEC in a good way. I understand that I can do it manually, that is with an eyepiece and manually issuing guide commands. But: If I can do that manually, could I not use PHD2 to do the same? Use the RA guide commands to train PEC, instead of me sitting there trying to guide? That is: manually engaging the "Train PEC", then start the gudiing only in RA, and let it run. Take a number of runs, then average and smooth them. Would that work? Thirdly, Pecprep seems to be a utility that can produce a "PEC file". Can I use that and someway upload to the Gemini 1? I understand Pecprep to be part of th EQMOD project, and that does not include Gemini, but is it doable anyway? Finally, I can use Pempro. However, somewhat costly.... is that worth the money? Magnus
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Re: Help with DEC backlash/jumpy guiding
Hi!
Thanks a lot! Yes, I'd be very happy to buy a bunch (3 might be enough :)) belville washers from you, and see what difference that makes!! Can you email me off the list? magnus @ vista . se.
I've been experimenting with it tonight as well (it's just past midnight here now) and I'm not getting wiser. I'm thinking of taking the mount apart and clean and regrease it too. There might be some stiction playing into it too.... maybe.
Magnus
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Re: G11 Guding PHD2 rms number High G1
Used not sure how old......
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Paul Kanevsky
Michael Herman
Mearl Balmer
David C. Partridge