Quote:
Originally Posted by Slawomir
Thanks for the link to the thread Lee - will check it this evening.
Yes, my OAG is fixed relative to the main camera, and to date I never had to rotate it due to the lack of suitable guide stars. After meridian flip I would select a different star because the camera is "upside-down" relative to its orientation prior to the flip, thus the OAG points at a different area near the main target.
I have a motorised rotator though - it is very convenient (and fun to use!) for planning the photograph and precisely orientating the camera  |
Wow, that'd be nice. I've actually only just started doing flips recently, I can count the number I've done on one hand. But yeah, at 840mm with a QHY5L-II, I usually have to rotate to find a guidestar, and I don't currently have a motorised rotator.
Quote:
Originally Posted by rally
The existing solution works ! - you have a rotator that is positioned in front of the OAG/guide camera and the main camera and with ASCOM and the appropriate image acquisition software, after a meridian flip the software automatically rotates the whole system 180 degrees for you.
This way you keep using the same guidestar and there is no change in position.
SBIG cameras have a fixed position internal guide chip and its rare not to be able to get a good guide star, so the same should apply to any setup if the mount is stable and accurate then you simply keep exposing for longer to improve the SNR of the guide image
Usually >20 SNR is what you want, but on a Paramount for example you can still use a guide star around 10 SNR.
Having a chilled guide camera with a shutter so you can take darks and have them applied automatically during the guiding process is also something that really helps improve the SNR.
Rally
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Yep, fair point Rally. The reason I was thinking one such that I described would be useful is for those of us who have to rotate to find a guide star. How would you do that remotely? With existing solutions either you don't rotate and you need to have a sensitive enough cam (or big enough FOV) to get stars wherever you land, or your composition is entirely dependent on guide star availability (because you rotate the whole train to find a star).
Increasing exposure length isn't always an option; fine if you have a premium mount that only needs to correct low-frequency, smooth errors, but for the majority running on workhorses like the EQ6...
So while the existing solution works, it's not without its issues.