Jump to content


Photo

Best Pixel Size on CCD for New England

  • Please log in to reply
3 replies to this topic

#1 bb4

bb4

    Vostok 1

  • -----
  • Posts: 135
  • Joined: 16 Apr 2007

Posted 26 March 2014 - 06:08 AM

Hi All -
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.

Thanks everyone.

#2 Rick J

Rick J

    Fly Me to the Moon

  • *****
  • Posts: 5658
  • Joined: 01 Mar 2008
  • Loc: Mantrap Lake, MN

Posted 26 March 2014 - 02:33 PM

Given unstable skies going for a wide field of view to capture those many large faint nebulae, dark and light, would be your best use of that scope. Thus chip size rather than pixel size would be more important to me in that situation. Note many fantastic wide field images have been taken with 9 micron 35 film size or larger chips on even shorter focal length scopes than yours. The image may be undersampled but the wide view makes for a fantastic picture anyway, many an APOD has been taken this way.

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!

Rick

#3 freestar8n

freestar8n

    Soyuz

  • *****
  • Posts: 3886
  • Joined: 12 Oct 2007

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.



Hi-

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.

Frank

#4 bb4

bb4

    Vostok 1

  • -----
  • Posts: 135
  • Joined: 16 Apr 2007

Posted 27 March 2014 - 06:21 AM

Thanks to you both for your answers. They both made perfect sense. Maybe I was overthinking pixel size, given the FL of my telescope. I must confess the 11000 chip does hold some appeal, as I would like to work on mosaics of the night sky.

Thanks again!






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics