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Hi Ray,
I just wanted to say that I finally got around to having a go with this last night.
I was using my FSQ-106N at f/8 (with the Extender-Q 1.6x) on an STL-11000M.
I took a ten second dark, and, my background (bias) was reading around the 830 mark.
The read noise for the camera is 13 electrons RMS and the gain is 0.8 electrons/ADU. Plugging those values in:
830 + ((10 * 13 * 13 )/ 0.8) = ~2943
I was trying to shoot through clouds, so, couldn't nail down the appropriate exposure time correctly, but, from my experimentation, pointed at Antares (near zenith) using the luminance filter, somewhere between 6 and 12 minutes would give me the appropriate background of ~2950 (after dark calibration). I then turned to M8, and using the hydrogen alpha filter, I got a reading of 650-odd after a ten minute exposure (again, dark-calibrated). This leads me to believe that I should be able to go for around an hour per sub-exposure. That's crazy considering guiding, clouds, and, whatever else throws itself our way. So, maybe 30-minutes might be a compromise.
The 6-12 minute guideline isn't bad, considering the Moon was out. Living on the coast (I've moved up from Canberra/Queanbeyan, where the sky was quite nice for the most part), there's nothing further east of here, so, it gets reasonably dark. I'm quite happy with this!
Thanks, again!
H
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