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Hi, I like to experiment with different OTAs for Astrophotography. Initially, I had Sky-watcher 6 inch & 10 inch Dobsonian through which I have done some Planetary & Lunar surface imaging. Later I sold it away for getting the DSO imaging setup. I currently have the following setup. iOptron iEQ45-PRO mount Sky-watcher 130 PDS (Newtonian) Sharpstar 60ED APO (Refractor) GSO 6 RC (Ritchey-Chretien) I have seen many people with backyard observatories using either large Newtonian 10/12 inch or 5 inch Refractor as their primary telescope. Want to know which telescope should I opt for the long term DSO imaging. Note that my sky is limited because of high rise buildings in surroundings so my view of the sky is limited to around 2-3 hours for any target. Should I consider 8-10 inch F4 fast Newtonian or get a quality Double/Triplet Refractor? Thanks! |
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Hi Abhijit First question should be like: Which one of my telescopes I like the most? You have a Newt a RC and a Refractor... For me it was clearly the newton. Because: -Temperature stability -Aperture -Focal Ratio -Price One of the biggest advantages over a refractor was (for me) Temperature stability. I need to focus once per night (per filter) and i am done. Your apo might have an carbon tube which looks nice, but your lenses are the problem. The focus point changes with or without carbon tube. I have no idea about the RC because I do not have one  But I think it should nearly behave the same as the newton. But the big contra for me is the low f- ratio.Hopefully, I could help a bit with your decision Greetings from switzerland |
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Hard to go wrong with an APO refractor. So easy to use. Spend 2 minutes focusing every fourth 5 minute frame and you are probably good even in the worst conditions. Take it anywhere. No messing with collimation! CS Bob |
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With only a 2 to 3 hour imaging window you need to focus on imaging efficiency . Imaging efficiency is measured by a parameter called E'tendue which is the actual photographic field of view, image width times height, in arc seconds squared, times the collecting area (objective area corrected for obstruction). Optimizing E'tendue alone will lead you to a wide-field scope with somewhat low resolution so you have to decide what resolution you want, then select the scope and camera you can afford that gives the desired resolution and the best E'tendue. Or you can just buy a RASA , Hyperstar or Takahashi Epsilon ($$$) with the largest camera that works with the selected telescope. Factoring in other parameters may change the answer, but with such a small imaging window imaging efficiency should remain high on the list of factors to consider. E'tendue= FOV*CO where FOV is the actual camera FOV and CO is the corrected objective area. |
