Imaging Session --did my scope move?

Description

I had SGP set to take 100 exposures of a target, but it looks like the scope moved between frame 22 and frame 23, since the actual target is no longer in the frame from frame 23 to 100. Is there a way to tell what happened and to prevent this from happening again?
Thanks,
Alan

Aprox time of issue: Unsure

Link to Logs

Useful Info

OS: Microsoft Windows 10 Pro
Ver: 3.1.0.479
.NET: 4.8

Nothing in the SGP log about moving between those two frames and it also doesn’t seem like PHD2 was hunting or lost the guide star. The only slews I see are at the beginning and end of the log. After frame 23 there was a dither and it seems like it took a while to get back on track. Maybe the large dither caused things to move out of frame?

There are no slews coming from SGP though.

Jared

It does say “lost guide star” after frame 22 though. Maybe it was too large of a dither? I wonder if there’s a way to plate solve after recovering from a “lost guide star” event to make sure we are still where we should be. What do you think? Good idea, bad idea?
Thanks,
Alan

Ah, yes, I had missed that. If you have recovery enabled SGP will plate solve and get back on track when the guide star is lost. Otherwise we wait for a bit in hopes that it was just a passing cloud and eventually will give up.

Jared

I figured you’d already thought of that !
I’m sure I can find it myself, but can you tell me where to enable this option?
Thanks again!
Alan

There are a couple of different modes. More info can be found here:
https://mainsequencesoftware.com/Content/SGPHelp/SequenceRecovery.html

Jared

Makes sense, thanks. One question though, reading through the documentation, I see the recovery mode gets cancelled after a meridian flip. Does this mean that if anything bad happens after a meridian flip you’re out of luck? Just wondering why it doesn’t get re-enabled.
Alan

Actually, I just looked at my settings and I do have recovery mode on for this sequence (I thought I did). So what do you think went wrong?

Maybe that’s just bad wording. It does not get cancelled after a meridian flip…what happens is that if you encounter the flip time while you’re in recovery mode that will cause the sequence to shutdown rather than flip and continue to attempt recovery.

Guessing since PHD lost the star between images that recovery wasn’t triggered since it reacquired the guide star (or some guide star) fairly quickly.

Jared

That makes sense, but if it recovered a guide star so quickly, I would think the target would still be in the frame somewhere, no?

Apparently not? A lot of that probably depends on your FOV but at higher magnifications it doesn’t take long to move out of view. Based on the logs it’s difficult to know exactly what transpired. You can look at the FITs headers to see how much the telescope things the image moved from one frame to the next.

Jared

Just a thought. If you have a Cass, any chance the mirror flopped? That would move the FOV some and happen very quickly. I imagine you’ve got it locked up though.

Kent

Hi,
Could also be differential flexure is your not using an OAG. I tried piggybacking a refractor as a guidescope on my CDK. The stars were all short lines, and my imaged marched, frame by frame across the FOV through the night (with a reset at flip time). This I am putting down to differential flexure of the refractor vs the reflector. The guidestar was never lost, but the refractor was tracking at a greater rate than the reflector due to the bending of the upper D plate on the refractor that the reflector was mounted to… My lesson was to go back to using an OAG, use a side by side configuration, or a lighter refractor.
Not sure if this was your situation, but it was puzzling at first.
Dave