Quote:
Originally Posted by Andrew_Campbell
Cheers. That leads to my next question:
Is there a resource that will show me what I can capture at a given focal length? I've been looking, but can't seem to find what I'm looking for. Sort of a "At 1500mm Focal Length, this is your field of view for THESE DSO, here they are at 2000, here they are at 500" etc.
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Starry night Pro Plus(SNPP) has a camera field function. Pro plus is the most expensive version - full price $250USD but they sometimes have end of version promotions around this time of year - I purchased my version of pro plus January 2 years ago for USD$99.
I am not sure if the cheaper versions of starry night have this field of view function for eyepieces and cameras. SNPP uses stitched photographic images of the sky for a photorealistic view. Attached is a screen shot of the function display. I have selected to display the DSLR field around eta carina with 3 different lenses.
I think Stellarium is free so you might want to try that first.
You can of course calculate it yourself using the image size formula
angular size(degrees) = I(mm) x 57.3 ÷ f(mm)
where
I is image size (in this case the dimensions of the DSLR sensor)
f is the focal length of the lens or telescope
There are online lists of the angular size of deep sky objects
http://en.wikipedia.org/wiki/User:Ia...y_angular_size
Best of luck
Joe