Best Pixel Size on CCD for New England
Posted 26 March 2014 - 06:08 AM
I will be receiving an AP 130 EDF GT at some point here, and will be graduating from dslr to ccd photography. I am aware that poorer skies make high resolution CCD AP more difficult. Given the more unstable skies here in New England, I was wondering what pixel size I should choose on a CCD camera. Any experiences that you are willing to share would be great. I am also aware that binning of smaller pixels has its advantages, but again, I figured it could hurt to inquire.
Posted 26 March 2014 - 02:33 PM
If you're interested in high resolution work, say 1 second per pixel your imaging time will be rather long at that aperture. For such imaging aperture pretty much controls the time needed to take an image. At 1" per pixel (good for 3 to 3.5 second seeing) you'd need 12.5 hours to capture the same number of photons I do in 1.67 hours. Another reason I'd use that scope for as wide a field as your can afford. Unfortunately prices of cameras rise exponentially with chip size. A camera using a KAI-4022 or KAF-8300 would be the minimum sized chip I'd want on that scope. Note the 8300 often blooms sideways when binned though I'd not want to bin either of these chips on that scope. You might however consider the reducer with these smaller chips. The scope can support the largest chips made. With larger chips the flattener would be required. Might even with the 4022 or 8300. If someone wants to send me such a scope I'd be happy to find out!
Posted 26 March 2014 - 06:00 PM
Given the more unstable skies here in New England, I was wondering what pixel size I should choose on a CCD camera. Any experiences that you are willing to share would be great.
I'm not sure where you are in New England - but even though the area isn't famous for good seeing - it has a range of seeing conditions that include very good - and sub 2" fwhm are obtainable with well guided, long focal length imaging and small pixels. If you are using a relatively short focal length and small aperture refractor - compared to a large SCT or Cassegrain - it will be harder to obtain sub 2" fwhm even with small pixels. But the limitation won't be seeing.
I have imaged from many areas of the U.S. but mostly just north of NYC, and I have nights of good seeing that coincide with what others experience just across the border in Canada to the north, and to New Jersey in the south. This makes me think deep sky work in the area is largely limited by the jet stream.
Other examples of good imaging in the area are from Clay Center observatory near Boston, and imagers in Connecticut.
So I wouldn't give up on good seeing in the area and instead I would look at what you want to do and what optics you will use. The AP is nice but even in good seeing and guiding I don't think that resolution is its strength - so I would focus on the field of view you can get and what objects you want to image. If you are able to obtain 2" fwhm then 0.5" pixels would be fine and help you reach that level, while 1" would be undersampled. I think there is very little penalty from oversampling as long as the field is big enough for your target - and at f/6.3 the optics are still fast enough that your exposure won't have to be too long - compared to f/8 or f/10 for example.
Posted 27 March 2014 - 06:21 AM