beta issue with rotator?

Hi Guys,

I ran into an issue testing I have a sequence with a target that I was imaging tonight, and in the target settings the option “On target start rotate to” is unchecked. When it came time for a meridian flip, SGP moved the rotator approx 180 degrees. I was not expecting that to happen since I had the rotate option un-checked. Is this a bug, or am I missing some other setting to prevent SGP from moving the rotator for this target?

Log file: http://adgsoftware.com/ap/misc/sg_log_rotator_moved.zip


Looks like you asked SGPro to rotate 180 degrees after flip. This setting is independent of a target’s settings.

Ah yes, I see it now in the Meridian Flip options. Sorry for the trouble.

I’m wondering if this would be better as a per-target setting? In a star-rich field it’s easy to get a guide star after the flip without moving the rotator, and this has the benefit of only requiring one set of flats. In a sparse field moving the rotator allows me to guide on the same star after the flip, but it also means I have to produce a second set of flats.


Sure. Seems reasonable. The one issue I see is that the option, as it is now, belongs to the equipment profile. Moving it to the target removes the it from profiles and pushes it into sequence data. Given that “Sequence Profiles” are not in the super near future, what is more important?

I guess my preference would be removing it from the profile and moving it to the target. I think the default setting should probably be un-checked (no rotation at meridian flip.)


I thought about this for a while. I wanted to present this is a way that is intuitive (and mostly hidden since most users will not care about it).

This is what the target settings dialog looks like now:

This is very close to what is used to be so it shouldn’t cause any confusion. For people that are interested in using it, it looks like this:

I’ll avoid explaining this to see if you (or anyone else interested) finds it intuitive.

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That is brilliant. Not invasive at all, very simple and yet takes care of the requirement. Well done.

Let’s see if I got it right… for my two scenarios:

  1. If I want to rotate both initially and after the pier flip, I select “Always”. This allows me to use the same guide star after the flip.

  2. If I only want to rotate initially, I select “On West” (ASCOM convention: pier side West is before the meridian flip, with the scope on the West side of the pier pointing (usually) East). This would be the one to choose if I don’t mind getting a different guide star after the flip, but I only need a single set of flats. If I started imaging on the East side (after the meridian) SGP would still rotate for me when the target started.

Did I get it right?


… just read your release notes for I guess I got it wrong (opposite), so I think I do need it spelled out. :confused:

If the options are “move the rotator at target start” / “move the rotator at target start and at meridian flip”, then Always means “only move the rotator at target start” and “On West” means “move the rotator both at target start and at meridian flip”. Right?


No… I just crossed the selections in the boxes. Your first description is accurate (despite the bug I just released in It was a hasty implementation… I’ll fix it up shortly.

Sorry… a bit tired. I think the implementation might actually be correct in, and I just borked my description. Either way, I’ll check it out this weekend… or you are free to double check it as well.

A quick inspection of the code shows that should work fine for flips (the way you stated), but for center here operations that cross the meridian, SGPro needs a different set of logic for checking Camera PA as it will still accept PA + 180 as “good” and not attempt to move the rotator (even if the the option is “Always”). In this case it should not accept 212 as OK and rotate back to 32. Choosing On West would continue to allow any combination of 32 / 212 as valid.

As such, the release notes should say that if you want to continue using the angle as before, you should choose “On West”. I will also add a better description on the line below for choosing “Always”. It is possible that there are better “words” to use here, but I could not think of any. One option keeps your angle, the other accepts pos or pos + 180 as valid.

ok, got it. thanks.

OK… Refactored this a bit today. Here is what I hope will be the final implementation…

When you do not want to rotate the camera after a flip:

SGPro does not care if you start at 15 or 195. It will also not care after a flip since both are acceptable.


In this case the camera will ALWAYS rotate to 15. After a flip (or possible transition of targets across the meridian), the camera will report 195 and the sequence will rotate in order to keep 15 (and the same guide star if that’s important).

Seem reasonable?

yup, works for me