Quote:
Your aperture is 130mm (not 130cm!  ), and dividing this into your focal length is about 7 which is where the f/7 f-ratio comes from. This is a measure of the lens/scope's light gathering capability. The wider the aperture, or hence smaller the f-ratio for the same focal length, the quicker it can gather the same amount of light, which is why they call them "faster".
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Considering some Newtonians/reflectors are in the f/4.5-f/5 range (without reducers/flatteners), and some SCT's and Maks etc are in the f/10 range (without barlows etc), I'd say your in the medium fast range?[/QUOTE]
Oops! I meant 130mm.
Thanks, troypiggo, for that explanation of the relationship between the aperture and the focal length making it fast or slow.
I'm beginning to see light at the end of the tunnel (or is that tube)
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It makes sense that on a scale of around f/4.5 to f/10 that f/7 is medium/fast.
Thanks everyone for your input, this technical stuff sure is a steep learning curve, at least for me.
Listening to a discussion like this, understanding begins to seep into my slow brain.
