Ok, I just had a bit more of a look at the specs and did some calculations. There was an error in my assumptions. The dimensions are 3"x3.5" (Diam x length). ie 75mm wide to outside of lens. That would make the lens aperture only 62.5mm (500/8). But is it really f8 (is an f10 sct really f10 if it doesn't have 200mm clear aperture for a 2000mm scope
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