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Re: [Losmandy_users] PEC and autoguider


Sep 8, 2015

 


----------------------------

#56150 Sep 8, 2015

Hi guys,

��i have to solve my lacks on PEC usage on Losmandy G11 Gemini1 system, and i confess that after almost 10 year of using Losmandy�� doing imaging i never studied this area.Sorry, my fault.

From last readings on the web i "discovered" (we say in Italy that�� "i discovered the hot water".....you can imaging what does it means) that i can enable PEC during auto-guiding.

Now i come with some questions to see if i understood well : I can enable it when guiding

The learning will come to 240sec PEC will stop automatically the learning after the above 240secs I can then start to shoot the object

Now i have some further questions if the above are ok: during PEC learning i should guide to let Gemini to understand corrections, correct ?

Any change on the guiding setup when PEC is enabled ? i use MAximDL and always keeping the default values on 0.1 secs for Delay after correction.



I thank you very much if someone can help.

Just a share ,here my astronomy collections www.flickr.com/photos/fabioh2o/collections/72157631874618638/��

Almost all DSO shot using G11, SXVF-M25C and Lodestar v1, other info on the image pages





Best Regards

Fabiowww.flickr.com/photos/fabioh2o/



----------------------------

#56152 Sep 8, 2015

Hi Fabio,

While I can't answer you questions, at one point I was wondering if there were any advantages to using PEC while auto-guiding. I found the following link interesting.

eq-mod.sourceforge.net/docs/PEC_and_guiding.pdf

If you do try PEC and autoguiding, I would be interested to note if you find any improvements in your images.

Alan.



----------------------------

#56154 Sep 8, 2015

Hi Alan,

> While I can't answer you questions, at one point I was wondering if there were any

> advantages to using PEC while auto-guiding. I found the following link interesting.

>

> eq-mod.sourceforge.net/docs/PEC_and_guiding.pdf



I believe that was written by a person with experience with a single mount type (EQ-6) so you should not use it as a reference for mounts outside of Synta mounts. Some of that information in that link is wrong for mounts in general and some of the assumptions are even wrong for the specific mount for which it was written. Virtually every mount that implements PEC does so in a different way, so generic assumptions should not be applied to every mount.



That said, properly programmed PEC pre-emptively corrects some mechanical errors, leaving the autoguider to correct uncorrected mechanical errors and drift. Autoguiding provides closed loop correction after residual tracking errors are seen. In most modern mount implementations there is no conflict between autoguiding and PEC.



Two reasons why PEC + autoguiding got a bad reputation:



1) Some older mounts had non-functioning PEC implementations, so they hurt more than helped autoguiding.

2) Users recorded PEC curves using autoguiding. The recorded moves sometimes included spurious spikes from bad seeing that resulted in a bad PEC curve. Every rotation of the worm where spikes had been recorded would cause jumps that the autoguider had to correct afterwards (but the damage had already been done)

.

In general, if the autoguider has to make a move the image has already been damaged, so pre-emptively correcting periodic error (assuming the PEC implementation is good) helps produce sharper images. Using PEC won't correct every tracking error but it usually helps.



-Ray Gralak

Author of PEMPro: www.ccdware.com

Author of Astro-Physics V2 ASCOM Driver: www.gralak.com/apdriver

Author of PulseGuide: www.pulseguide.com

Author of Sigma: www.gralak.com/sigma



> -----Original Message-----

> From: Losmandy_users@yahoogroups.com

> [mailto:Losmandy_users@yahoogroups.com]

> Sent: Tuesday, September 08, 2015 6:15 AM

> To: Losmandy_users@yahoogroups.com

> Subject: Re: [Losmandy_users] PEC and autoguider

>

>

>

> Hi Fabio,

>

> While I can't answer you questions, at one point I was wondering if there were any

> advantages to using PEC while auto-guiding. I found the following link interesting.

>

> eq-mod.sourceforge.net/docs/PEC_and_guiding.pdf

>

> If you do try PEC and autoguiding, I would be interested to note if you find any

> improvements in your images.

>

> Alan

>

> On Tue, Sep 8, 2015 at 8:48 AM, Fabio Acquarone fabio_acquarone@...

> [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:

>

>

>

>

>

>

>

> .Hi guys,

>

> . i have to solve my lacks on PEC usage on Losmandy G11 Gemini1 system,

> and i confess that after almost 10 year of using Losmandy doing imaging i never

> studied this area.

> .Sorry, my fault.

>

> .From last readings on the web i "discovered" (we say in Italy that "i

> discovered the hot water".....you can imaging what does it means) that i can enable

> PEC during auto-guiding.

>

> .Now i come with some questions to see if i understood well :

>

> .1..I can enable it when guiding

>

> .2..The learning will come to 240sec

> .3..PEC will stop automatically the learning after the above 240secs

> .4..I can then start to shoot the object

>

> .Now i have some further questions if the above are ok:

>

> .1..during PEC learning i should guide to let Gemini to understand

> corrections, correct ?

>

> .2..Any change on the guiding setup when PEC is enabled ? i use

> MAximDL and always keeping the default values on 0.1 secs for Delay after

> correction.

>

>

>

>

> .I thank you very much if someone can help.

>

> .Just a share ,here my astronomy collections

> www.flickr.com/photos/fabioh2o/collections/72157631874618638/

>

> .Almost all DSO shot using G11, SXVF-M25C and Lodestar v1, other info on

> the image pages

>

>

>

>

> .Best Regards

>

> .Fabio

> .www.flickr.com/photos/fabioh2o/

>

>

>

>

>







----------------------------

#56155 Sep 8, 2015

I asked essentially the same question on one of the Gemini users yahoo groups, and Ray's answer is the basic response I got.. I had not previously used PEC with autoguiding, however I now have a longer focal length and heavier scope on the mount.. I have found that using Gemini-2's built in PEC recording process and using PEC with autoguiding has resulted in a better guiding and imaging experience.. I believe that Ray's assertion that modern mounts see no conflict between autotuiding and PEC is correct and PEC should be used.joel

On Tue, Sep 8, 2015 at 10:02 AM, 'Ray Gralak (Groups)' groups3@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:

.Hi Alan,



> While I can't answer you questions, at one point I was wondering if there were any

> advantages to using PEC while auto-guiding. I found the following link interesting.

>

> eq-mod.sourceforge.net/docs/PEC_and_guiding.pdf



I believe that was written by a person with experience with a single mount type (EQ-6) so you should not use it as a reference for mounts outside of Synta mounts. Some of that information in that link is wrong for mounts in general and some of the assumptions are even wrong for the specific mount for which it was written. Virtually every mount that implements PEC does so in a different way, so generic assumptions should not be applied to every mount.



That said, properly programmed PEC pre-emptively corrects some mechanical errors, leaving the autoguider to correct uncorrected mechanical errors and drift. Autoguiding provides closed loop correction after residual tracking errors are seen. In most modern mount implementations there is no conflict between autoguiding and PEC.



Two reasons why PEC + autoguiding got a bad reputation:



1) Some older mounts had non-functioning PEC implementations, so they hurt more than helped autoguiding.

2) Users recorded PEC curves using autoguiding. The recorded moves sometimes included spurious spikes from bad seeing that resulted in a bad PEC curve. Every rotation of the worm where spikes had been recorded would cause jumps that the autoguider had to correct afterwards (but the damage had already been done)

.

In general, if the autoguider has to make a move the image has already been damaged, so pre-emptively correcting periodic error (assuming the PEC implementation is good) helps produce sharper images. Using PEC won't correct every tracking error but it usually helps.



-Ray Gralak

Author of PEMPro: www.ccdware.com

Author of Astro-Physics V2 ASCOM Driver: www.gralak.com/apdriver

Author of PulseGuide: www.pulseguide.com

Author of Sigma: www.gralak.com/sigma



----------------------------

#56156 Sep 8, 2015

Thanks to all for the replies.

Is it correct my assumption that during PEC learning the auto guider should be working ?

Otherwise i do not see how the gemini can learn...but i suppose that it is providing bad learning if guider is no working fine and it should be always done every time....

��Fabiowww.flickr.com/photos/fabioh2o/



----------------------------

#56157 Sep 8, 2015

All good comments...thanks all.The original post mentioned using a Gemini1, so let me comment on that.The Gemini1 has the built in capability to take a first PEC during autoguiding, then you can smooth that data, or add and automatically average additional PEC training... See the Gemini1 manual for those instructions, sections 4.3.2.6 for instructions on smoothing, and 4.3.2.7 for instructions on averaging.. Averaging multiple runs divides the effect of any glitches in any single run.

I have run these procedures on my CG11 mount with Gemini1 and had no troubles.. You must do a drift alignment first to get as close to polar alignment as you can, so the autoguide corrections will be primarily RA worm corrections.. If your polar alignment is off, the PEC system will try to subtract out the DEC drift, but its better to make that error as small as you can..The PEC captures are 240 sec each, as was stated in the first email.. After the first PEC run, the Gemini1 system will automatically start it's next PEC runs at the right phase (time) matched to the first PEC run, for the 2nd and later PEC runs, so at worst that can take up to an additional 240 sec on each run after the first.. It's all automatic...easy to do.. You just press Average Data after each 2nd, 3rd, etc runs..In long duration deep sky imaging,. I run Ascom pulse guiding using PHD2, with good results, on a variety of scopes.. I suggest you start with trying those built in PEC capabilities of the Gemini1, and see how your imaging goes..Best of luck,

Michael

On Sep 8, 2015 8:21 AM, "Joel Short buckeyestargazer@... [Losmandy_users]" Losmandy_users@yahoogroups.com> wrote:

.I asked essentially the same question on one of the Gemini users yahoo groups, and Ray's answer is the basic response I got.. I had not previously used PEC with autoguiding, however I now have a longer focal length and heavier scope on the mount.. I have found that using Gemini-2's built in PEC recording process and using PEC with autoguiding has resulted in a better guiding and imaging experience.. I believe that Ray's assertion that modern mounts see no conflict between autotuiding and PEC is correct and PEC should be used.joel

On Tue, Sep 8, 2015 at 10:02 AM, 'Ray Gralak (Groups)' groups3@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:

.Hi Alan,



> While I can't answer you questions, at one point I was wondering if there were any

> advantages to using PEC while auto-guiding. I found the following link interesting.

>

> eq-mod.sourceforge.net/docs/PEC_and_guiding.pdf



I believe that was written by a person with experience with a single mount type (EQ-6) so you should not use it as a reference for mounts outside of Synta mounts. Some of that information in that link is wrong for mounts in general and some of the assumptions are even wrong for the specific mount for which it was written. Virtually every mount that implements PEC does so in a different way, so generic assumptions should not be applied to every mount.



That said, properly programmed PEC pre-emptively corrects some mechanical errors, leaving the autoguider to correct uncorrected mechanical errors and drift. Autoguiding provides closed loop correction after residual tracking errors are seen. In most modern mount implementations there is no conflict between autoguiding and PEC.



Two reasons why PEC + autoguiding got a bad reputation:



1) Some older mounts had non-functioning PEC implementations, so they hurt more than helped autoguiding.

2) Users recorded PEC curves using autoguiding. The recorded moves sometimes included spurious spikes from bad seeing that resulted in a bad PEC curve. Every rotation of the worm where spikes had been recorded would cause jumps that the autoguider had to correct afterwards (but the damage had already been done)

.

In general, if the autoguider has to make a move the image has already been damaged, so pre-emptively correcting periodic error (assuming the PEC implementation is good) helps produce sharper images. Using PEC won't correct every tracking error but it usually helps.



-Ray Gralak

Author of PEMPro: www.ccdware.com

Author of Astro-Physics V2 ASCOM Driver: www.gralak.com/apdriver

Author of PulseGuide: www.pulseguide.com

Author of Sigma: www.gralak.com/sigma







----------------------------

#56159 Sep 8, 2015

Hi Fabio,

That's correct. Something must send corrections to the mount while PEC training is going on. This can be an autoguider, or it could be you manually guiding using Gemini hand controller, or it could also be some other software sending corrections, such as PemPro.

I must also agree with Ray and state that I've found PEC to be very useful on my G11 and Titan mounts using Gemini even while guiding. As Ray says, the autoguider can't correct errors that have not happened yet, but once the error has happened, it's already too late to fix it.��

PEC can prevent most of the periodic errors before they happen, which means the quality of guiding will improve.

Regards,

�� �� -Paul



----------------------------

#56160 Sep 8, 2015

Thank you very much to all for the support!!I'll elaborate all suggestions and instructions and i'll apply next time i'll go in the dark. I hope soon.

I'll post my results when availableThanks again to all of you !



Best Regards

Fabiowww.flickr.com/photos/fabioh2o/



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