With the moon up, I decided to tweak my G11G mount and completed a new PEC curve with PEMPRO and uploaded it to the mount. Tracking via PHD2 looks good (apologizes I don't have the numbers) and prior to PEC I also nailed my polar alignment to be spot.

My question is that although my PHD2 tracking looks good I did notice there were a lot of RA corrections being made and I was curious if this was normal?? I would assume if PEC was on and working there really should be too many RA adjustments showing up in PHD2 graph, but these adjustments were being made it appears every 2.5 sec guide capture.

Russ,

The RA is constantly running/turning, so any tiny imperfection in the drive will show up. If your polar alignment is good you'll only see the atmosphere on DEC.
So it is normal, with good polar alignment, to see a lot more RA corrections than DEC.

PEC, notionally, only removes larger errors that follow the rotational period of the worm (and even then only 50 to 70% of the magnitude, with a lot depending on the magnitude of the periodic error vs that of non-periodic errors). Hence, all PEC can address are errors that occur with the worm rotation period.

Anything else (main shaft bearing rumble, imperfections in the worm wheel, grit, and so on) will still be there, including the atmosphere.

PEC is not a silver bullet.

But all that matters is (relative to your imaging requirements) the final, guided, performance. Everything else is academic.

Mark C.

I have personally found that it helps to compare the RA/DEC fluctuations during the Guiding Assistant run (corrections off) with the PEC ON guiding RA/DEC corrections.?

If the Guiding Assistant displays gentle drift without huge fluctuations/spikes and my actual guiding does have spikes, I interpret that as my aggressiveness being too high. Generally speaking with good PEC data, my RA/DEC aggressiveness are around/below 35-40. I don’t mind my RA and DEC not correcting back perfectly/immediately to zero as long as they are “flat” for the duration of my sub exposure. YMMV

Ryan

Appreciate the feedback gents. Will do some more testing tonight. I completed a few PEMPRO runs and uploaded those results to my G11G. Since Moon is high I decided to play with my guiding (made it worse). Think I had PPEC (PHD2) and mount PEC both turned on for past few weeks and guiding seem to be fine. I turned off PEC and only allowed PPEC on and then I started noticing some problems. Will start over tonight and try to dial all this in again.?

Also, I believe aggressiveness numbers are very high, on the order of 75-80 at 3 sec guide exposures. May lower these to 35-40 and see what happens.

Ryan; could you please a screenshot of your settings (various numbers at bottom of PHD2; aggressivness....etc)?

BTW: my DEC is almost a flat line, the RA is what has been all over the place.

开云体育

Adjusted PHD2 to the recommend settings and found leaving PEC on the mount on and having PPEC on PHD2 gave me good tracking. I also reduced my guidescope exposure to 1 sec and changed the worm cycle in PHD2 to 76 secs. Now getting tracking in RA to 0.3

Whoa. Nice work!

On Tue, Jun 18, 2024 at 08:01 PM, Russ wrote:

Adjusted PHD2 to the recommend settings and found leaving PEC on the mount on and having PPEC on PHD2 gave me good tracking. I also reduced my guidescope exposure to 1 sec and changed the worm cycle in PHD2 to 76 secs. Now getting tracking in RA to 0.3

Why did you change your worm cycle to 76 seconds? The G11 has a 240 second worm cycle.

--

Chip Louie Chief Daydreamer Imagination Hardware?

Astrospheric Forecast - South Pasadena, CA?

Experiment based on YouTube video about PHD2. They showed by changing it to the period issue will provide good tracking.

A 76sec error is common with a pinched worm or one misaligned with Oldham coupler or the worm-wheel. Because 76 sec isn't periodic with G11 worm cycle, it can't be corrected by Gemini PEC. So, even with the best possible PEC programming, the 76 sec error will remain uncorrected.

But, PHD2 PPEC can be told to correct errors periodic with any desired cycle, which doesn't have to be the actual worm cycle. When done this way, Gemini PEC can correct for all the worm-related periodic errors (periodic with 240s cycle), while PHD2 PPEC can correct for any remaining large error that is periodic with the 76sec cycle. I've seen this work before, and recommend this when the 76sec error is reasonably large. As it was here, for example: /g/Losmandy_users/message/82559

Regards,

? ?-Paul

On Wed, Jun 19, 2024 at 03:58 PM, Paul Kanevsky wrote:

A 76sec error is common with a pinched worm or one misaligned with Oldham coupler or the worm-wheel. Because 76 sec isn't periodic with G11 worm cycle, it can't be corrected by Gemini PEC. So, even with the best possible PEC programming, the 76 sec error will remain uncorrected.

But, PHD2 PPEC can be told to correct errors periodic with any desired cycle, which doesn't have to be the actual worm cycle. When done this way, Gemini PEC can correct for all the worm-related periodic errors (periodic with 240s cycle), while PHD2 PPEC can correct for any remaining large error that is periodic with the 76sec cycle. I've seen this work before, and recommend this when the 76sec error is reasonably large. As it was here, for example: /g/Losmandy_users/message/82559

Regards,

? ?-Paul

So you use the Gemini's PEC for the standard 240 second worm period and let PHD2 PPEC filter out the rest actively? Can some combination of this be manipulated in PEMPro and then used with ASIAIR users? I have not bothered to play with this as my G11G/ASIAIR Pro guides very well.??
?
--

Chip Louie Chief Daydreamer Imagination Hardware?

Astrospheric Forecast - South Pasadena, CA?

On Thu, Jun 20, 2024 at 12:32 PM, Chip Louie wrote:

So you use the Gemini's PEC for the standard 240 second worm period and let PHD2 PPEC filter out the rest actively? Can some combination of this be manipulated in PEMPro and then used with ASIAIR users? I have not bothered to play with this as my G11G/ASIAIR Pro guides very well.??

Right. Unless you have excessive 76-sec error, I wouldn't bother with 76s PPEC and just use Gemini built-in PEC to correct for all worm-related (240s) errors. Especially if you're auto-guiding. Mechanical adjustments are a better way to correct the 76s error in any case, as PPEC can take some time for PHD2 to measure and to start correcting, and may not be able to correct for it fully.

I don't believe that the current version of PEMPro can correct for errors that are non-periodic with 1 or 2 worm cycles of the mount, which means it can't correct the 76s error. I believe Ray has a new design in mind that could potentially correct for other, non-worm-periodic errors, but he'd have to comment on any future plans related to this.

Based on my settings above and guiding for about 20 minutes. Significant improvements with guiding on PHD2.

Yeah that's well below your image scale so should be great for your sub frames.??

I've just set up a miniPC with NINA and PHD2, have yet to try it.? I have struggled to get good guiding that other people get with their G11Gs using the ASI Air algorithms, which is a stripped down PHD2.? ?I have had success at 0.8arc-s/px image scale with my 130mm refractor, but the images do often require deconvolution to get round stars.? ? My guiding is roughly right on top of my image scale, and RA about 2x that of DEC so I get a little eggy in some of the subs.?

Brian