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Andy,
The article by Craig Stark that Geoff linked explains how binning works more eloquently than I could. Binning does effectively give you larger pixels and the ability to trade off reduced resolution for increased SNR. The article also reinforces what I've been trying to say - pixel size is very important in imaging and is directly relevant to exposure time.
OK, so we are talking about basically the same thing. Your arcmin/mm is calculated using exactly the same formula as my arcsec/pixel. The angular size corresponding to a distance on the focal plane is derived through basic trigonometry:
angular size = 2 * arctan(d/2F) radians [multiply by 3438 for arcmin or 206265 for arcsec]
The angular size depends on two things: d, which is 1mm for you and the pixel size for me, and F which is the focal length. You'll notice that it does not depend on the focal ratio! So I say again (for the last time in this thread, I hope) image scale does not depend on focal ratio.
Cheers,
Rick.
Last edited by iceman; 23-01-2014 at 05:52 AM.
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