--

Stuart
http://www.astrofoto.ca/stuartheggie/

i'm an old guy who, after 25 years absence, (now at N 59.5 degrees) wants to watch the sky again. can you help me find a book/course/tutorial that would update me on modern amateur astrophotography? i am building a new dome, and have an old meade 12" lx200. electronics are eff-ed, but ota is just fine. i'm looking for a solid equatorial mount and the requisite "go-to" and tracking software.

dick fast
atlin bc canada

Ray, I did an experiment to understand the source of issue.  When I run APCC and nothing else, including not having the ASCOM V2 I immediately get the -15.04056 vs the 4.48 in Tracking Correction.  I don’t know of where I could introduce an offset.  Open to suggestions of the source and how to resolve.

I did a 25 point Point Model Solve as I just purchased software (just got the software and doing a small model first).  I was able to get Pointing to work effectively but the tracking is not working.  When I turn on Tracking Correction, I see the stars streak.  My AP1600GTO polar alignment and PEC was just completed recently with Pempro and tracks less than 1.5 arcsec of drift in 5min.  I have the latest software for APCC, 1.8.1.1, ASCOM and drivers, MaximDL Pro, and TheSkyX Pro.  Appreciate help on this matter.

Some screen captures:

5sec image without guiding with Point Correction On and Tracking Correction Off

5sec image without guiding with Point Correction On and Tracking Correction On

 

 

OK, after pulling the imaging computer out and looking at the PHD2 settings I see that under the Algorithms/Mount Guide Algorithms/Right Ascension settings I am not using Predictive PEC.
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Dean Jacobsen
http://astrophoto.net/wp/ 
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I’m confused now.  What are you guys talking about?  I guide my mount with PHD2 and with the mount’s on board PEC/PEM turned on.
--
Dean Jacobsen
http://astrophoto.net/wp/ 
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Bryan,

You wrote:

Did you mean PPEC algorithm? There is no PHD2 algorithm in PHD2.

Yes, the PPEC algorithm is in PHD2, so I consider it a "PHD2 algorithm".

My intent was not to 'hype' PPEC, but to answer the OP's original question about PEC and guiding. I extracted
info from the PHD2 Help that discusses that question and it happens to fall in the PPEC portion of the manual.

Understood! I was just pointing out that using that PHD2 algorithm should not provide any benefit over using AP's PEC (aka PEM). In fact, if it falsely identified frequencies it may be detrimental.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Worsel via groups.io
Sent: Sunday, May 3, 2020 2:18 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] PHD 2 Guiding "Good Enough"

Ray

You wrote
"I would not rely on the PHD2 algorithm for most AP mounts. It will not be able to accurately predict any residual
periodic error that could already be taken out by AP's PEC mechanism. It may be useful if there is periodic error
not correctable by PEC because it doesn't repeat in phase every worm cycle, but there are very few cases where
that might happen. "

Did you mean PPEC algorithm? There is no PHD2 algorithm in PHD2.

My intent was not to 'hype' PPEC, but to answer the OP's original question about PEC and guiding. I extracted
info from the PHD2 Help that discusses that question and it happens to fall in the PPEC portion of the manual.

Bryan

Ray

You wrote
"I would not rely on the PHD2 algorithm for most AP mounts. It will not be able to accurately predict any residual periodic error that could already be taken out by AP's PEC mechanism. It may be useful if there is periodic error not correctable by PEC because it doesn't repeat in phase every worm cycle, but there are very few cases where that might happen. "

Did you mean PPEC algorithm?  There is no PHD2 algorithm in PHD2.

My intent was not to 'hype' PPEC, but to answer the OP's original question about PEC and guiding.  I extracted info from the PHD2 Help that discusses that question and it happens to fall in the PPEC portion of the manual.

Bryan

Hi Bryan,

That said, PEC in the mount is never perfect, and you will often see residual repetitive errors even when PEC is
active. These often arise when the tracking errors occur with a frequency that is not a harmonic (integer fraction)
of the mount’s worm period – most PEC implementations can’t deal with those. You can also get residual
periodic errors if they are dependent on the mechanical loading of the mount or if the mount’s behavior has
changed since the PEC was programmed..

I would not rely on the PHD2 algorithm for most AP mounts. It will not be able to accurately predict any residual periodic error that could already be taken out by AP's PEC mechanism. It may be useful if there is periodic error not correctable by PEC because it doesn't repeat in phase every worm cycle, but there are very few cases where that might happen.

Even then, It may not be very effective unless the residual error is truly periodic and you can wait for multiple periods for the phase and amplitude to be determined to reasonable accuracy. For example, the result may inaccurate because portions of continuous timeline tracking data may be missing while image downloading or dithering operations. Just check your PE every few months and update it if necessary. This will provide better overall results. (And a more advanced solution is coming. :-)

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Worsel via groups.io
Sent: Sunday, May 3, 2020 11:59 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] PHD 2 Guiding "Good Enough"

Charles

See Slide 14 in Best Practices for PHD2 <https://openphdguiding.org/PHD2_BestPractices_2019-12.pdf>

Also. from the Help file discussing the PPEC algorithm in PHD2 (note that PPEC guiding algorithm is NOT the
same as PEC in the mount)

·Short-term: for high-frequency errors such as those caused by gear roughness or seeing

·Medium-term: for residual periodic errors, typically occurring at intervals less than or equal to the worm period

·Longer-term: for steady drift and for lower frequency (longer time interval) harmonics that can be caused by the
interaction of multiple gears in the drive train

The short-term behavior is used to identify the unpredictable noise in the system, which is essentially filtered out
in order to identify components that are predictable. For most mounts, the medium-term component is likely to
be the most important. If you’re following best practices, you will have programmed periodic error correction in
your mount (assuming that feature is available to you). Doing this reduces the amount of work that needs to be
done by PHD2, and the PEC correction in the mount is normally saved permanently. This approach is preferable
to having to measure and infer the periodic error behavior every time you set up your equipment.

That said, PEC in the mount is never perfect, and you will often see residual repetitive errors even when PEC is
active. These often arise when the tracking errors occur with a frequency that is not a harmonic (integer fraction)
of the mount’s worm period – most PEC implementations can’t deal with those. You can also get residual
periodic errors if they are dependent on the mechanical loading of the mount or if the mount’s behavior has
changed since the PEC was programmed..

Bryan

Charles

See Slide 14 in Best Practices for PHD2

Also. from the Help file discussing the PPEC algorithm in PHD2 (note that PPEC guiding algorithm is NOT the same as PEC in the mount)

·Short-term: for high-frequency errors such as those caused by gear roughness or seeing

·Medium-term: for residual periodic errors, typically occurring at intervals less than or equal to the worm period

·Longer-term: for steady drift and for lower frequency (longer time interval) harmonics that can be caused by the interaction of multiple gears in the drive train

The short-term behavior is used to identify the unpredictable noise in the system, which is essentially filtered out in order to identify components that are predictable.  For most mounts, the medium-term component is likely to be the most important.  If you’re following best practices, you will have programmed periodic error correction in your mount (assuming that feature is available to you).  Doing this reduces the amount of work that needs to be done by PHD2, and the PEC correction in the mount is normally saved permanently.  This approach is preferable to having to measure and infer the periodic error behavior every time you set up your equipment. 

That said, PEC in the mount is never perfect, and you will often see residual repetitive errors even when PEC is active.  These often arise when the tracking errors occur with a frequency that is not a harmonic (integer fraction) of the mount’s worm period – most PEC implementations can’t deal with those.  You can also get residual periodic errors if they are dependent on the mechanical loading of the mount or if the mount’s behavior has changed since the PEC was programmed..

Bryan

Thanks Mike.....

Good advice on the re-mesh of the gears. Thanks for all your comments. I will be at my remote site ( about 120 miles away in the Bradshaw Mountains ) in 2 weeks. I will give you an update .

Clear Sky's

Thank you for the responses to my "Guiding-Good enough" post. Yes. I have run PEMPro, loaded the "model" to the CP4 controller and Enabled PEC on the mount. However, it has been a while (>1 yr) so a new run at it would probably be beneficial. I will make that my first priority. I would like to reduce the RA error.

I have two AP mounts in the observatory , an AP 1100 and an AP 1600. The AP 1100 has encoders. I plan to add encoders to the AP 1600 this summer. I agree that it is easy to get drawn into "perfection" on this topic. However, when you ( all of us) make a big investment in the best equipment ( Astro Physics) you like to get full value. That's my excuse and I am sticking to it.

On Sat, May 2, 2020 at 12:19 PM, Charles Thompson wrote:

Can you run PEC while guiding with PhD2?

Yes.
 
--
Dean Jacobsen
http://astrophoto.net/wp/ 
Image Gallery - http://astrophoto.net/wp/image-gallery/
Astrobin - https://www.astrobin.com/users/deanjacobsen/ 

Yes, one can certainly get sucked down the guiding perfection black hole.  As Brian has said, how do your stars look?  Are you happy with the stacked images?

However, as Roland noted, there is some room for improvement that really doesn't take a lot of time.  Use PEM Pro to evaluate your native periodic error and then have the software create a new solution.  You will be amazed at the difference when you run the PE analysis again in PemPro with the new PE solution running.
--
Dean Jacobsen
http://astrophoto.net/wp/ 
Image Gallery - http://astrophoto.net/wp/image-gallery/
Astrobin - https://www.astrobin.com/users/deanjacobsen/