I’m not seeing it, if so. If it’s not, how can I tell what side of the pier the mount was on? I need to apply different flats to pre- and post-flip lights. (Apologies if this is obvious. Pier flips are still brand new to me.)
Kevin
No, but Angle should be which is likely what is causing the need to apply new flats. Although if you’re rotating between pier side then your angle would be the same (and I’m honestly not sure how you’d handle that).
Thanks,
Jared
you should be able to tell from the angles if new flats are needed…
on one side of the meridian the sky angle will be X and the rotator angle Y. if you don’t rotate the camera, then post flip, the sky angle will be X+180 but the rotator angle will be the same. in this case no new flats are needed because the camera angle did not change.
if you do rotate the camera after a flip, then the sky angle will be the same pre- and post- flip, but the rotator mechanical angles will be 180 degrees different.
i write both angles to the filename so i can keep this all straight. i guess that you can’t necessarily know what the pier side was unless you have images of the same object pre and post meridian to compare the angles. on the other hand the pier side is not really the salient info for whether or not you need different flats - it’s the rotator mechanical angle which is important. in the worst case the date/time and RA will tell you what side of the pier the OTA was on, but that takes a little work to compute.
are both the rotator mechanical angle and sky angle written to the FITS header??
rob
I can write the actual rotator angle to the file name? I never knew that, but that solves two problems. Now I can see which side of the pier each image was on, and know exactly what angle to set the rotator when taking flats, without even needing to dig into the FITS headers. Thanks for pointing that out, Rob.
Kevin
sure NP.
when you do flats, are you able to set a rotator angle without a solve/sync? i have a flat panel and i can set the park position so that SGP points the telescope to the flat panel, but so far i’ve been stuck with the rotator angle of the target that ran just prior to the flats target.
rob
I’m not sure. We talked about this a few months back and Ken seemed to think it could be done in the SGP control panel, which would be a lot better than using the Optec interface. Maybe when you first fire up SGP - ie, before any platesolve and sync - any angle you input gets read directly from the rotator. But if you’re trying to do it automatically at the end of the night, I think SGP will be synced to the sky angle, so the angle you input won’t be what you’re expecting.
But I haven’t actually tried it yet I just got my observatory done last week, and got two nights of imaging in before the rain came along. I’ll try to figure out flats next.
Kevin
yes, that’s what i remember as well. i guess that the rotator stuff kind of needs a bit of an overhaul in SGP.