I don't know what "down" is. So I will have to guess. When doing unguided imaging with modeling, it's not just the RA axis that has to track accurately. Dec has to also track, although at a much

Oh yeah I don't think PE is related, just something to add to the checklist when prepping a system for unguided. If the drift is in declination then yeah PA could be related.

Ray, Here is that zip file: https://www.dropbox.com/s/ko57c8licscbhs8/ApccZip-R-2021-08-20-135422.zip?dl=0

Model values

Bill, Yes unguided with APCC corrections. I doubt its PE as the image is consistently drifting in 1 direction. PE would cycle (sine wave like) around a certain point I believe. It is neutral fine

Ray, I had it pointing at zenith (85 degrees) so having the mirror almost flat on the cell and the focuser hanging downwards. Tightened each and every bolt in the setup too. The mirror is bonded to

Roland, I'm not entirely sure. The target moves "down" mostly with a 90 degree camera angle. I have solved the 1st and last image of the session. First image Observation start time ... 2021-08-20

This is unguided imaging right? If so as a best practice I dial in my PA as close as I can with SharpCap before I build the model. When I was not using encoders I would ensure my PEC curve was solid

It's not a flex problem, Ray. Roland

It's good that it is consistent, but it is possible that it is unmodeled flexure. The pointing terms best model a solid object with consistent flexure characteristics. When you have a large mirror on

If you can answer my question I could probably tell you what's happening. Roland

Also, I suspect polar alignment isn't perfect. Could that be the cause. The model can correct for that right? To what degree. Is that polar az and polar Alt values in the model?

On Fri, 20 Aug 2021 at 22:17, Rouz <rbidshahri@...> wrote: Ray, Ah, so I shouldn't use "hour angle", I can try that. I tried pointing corrections on and Dec Arc off, seemed better. It looked like Dec

You didn't answer my question. Which axis is showing the error? Roland

Ray, Ah, so I shouldn't use "hour angle", I can try that. I tried pointing corrections on and Dec Arc off, seemed better. It looked like Dec arc made it worse but the object still moves. Some subs

Here is another blink clip of the previous nights tracking with a model with less points. I believe its not a flex problem as its very

Can you tell me which way the image drifts, RA or Dec? Roland

Rouz, Unfortunately, I think the "Hour Angle" point ordering strategy may be the problem. Because the points are not collected in a declination-arc it is way more likely to be subject to random

Hi Roland, My camera orientation is 90 degrees and the image downwards mostly but at a slight diagonal. I have made a short video clip in the

Hi Ray, Yes I used "Hour Angle" with APPM. I closed APCC, I'll open it again and see if I can create that zip file now. Thanks, Rouz