Quote:
Originally Posted by LewisM
I know Clive, just hoping it can be done with reasonable results with a refractor of intermediate focal length. I am guessing mediocre is the word.
No matter, nebulae will do.
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even with only 100mm aperture, the resolution will mostly be determined by the atmosphere and will typically be about 2 arc seconds. To sample this properly, you need slightly smaller than 1 arcsec pixels, so you need to choose the focal length to do this (or use workarounds to get to the same sampling). If you do it right, the resolution will be almost as good as any other system.
However, the big disadvantage of a small aperture (as already pointed out) is that you have reduced sensitivity. For example, if you run your 100mm system at 1.2m fl, you will need to spend 9x as long getting data as you would if you had a 300mm aperture at 1.2m fl. Since galaxies are fairly dim, expect to spend maybe 100 hours to get the sorts of SNRs that Mike gets in 10 hours. In the end, it all comes down to how many photons get into the hole up front and there is no substitute for aperture.