01-15-2011, 06:25 PM
[quote name='genotypewriter' timestamp='1295094193' post='5531']
That's a scary thought... to add that many extension tubes![/quote]
It might not be that bad! I achieved my example with only the built in focusing, which went quite a lot closer than the manufacturer's spec claimed.
I should add the scope I tried is a mirror design, whereas the original post was more about refractors. In general, refractors are shorter focal lengths and should behave similarly to a photographic lens. For example the model mentioned is 300mm f/5. Not that exciting in photograph lens terms. I guess at astronomical distances you don't usually have to worry about bokeh... so I have no idea what they might do there.
I only did a few test shots on my mirror scope terrestrially. It wasn't practical in any way due to a combination of factors, not least that fixed f/13 is already softened by diffraction and in daytime the air was never that stable! Beyond a few hundred meters or so it gets quite wobbly.
That's a scary thought... to add that many extension tubes![/quote]
It might not be that bad! I achieved my example with only the built in focusing, which went quite a lot closer than the manufacturer's spec claimed.
Quote:Needless to say, they won't be optimised for the close distances but for the sorts of terrestrial distances one would use a 1300mm lens for shouldn't be that far from infinity, so any performance drops should be minimal. I'm of course, not referring to macro or close-ups... just things like long distance sceneries, etc.
However, I don't expect bokeh to be particularly smooth. Any comments from your experience?
I should add the scope I tried is a mirror design, whereas the original post was more about refractors. In general, refractors are shorter focal lengths and should behave similarly to a photographic lens. For example the model mentioned is 300mm f/5. Not that exciting in photograph lens terms. I guess at astronomical distances you don't usually have to worry about bokeh... so I have no idea what they might do there.
I only did a few test shots on my mirror scope terrestrially. It wasn't practical in any way due to a combination of factors, not least that fixed f/13 is already softened by diffraction and in daytime the air was never that stable! Beyond a few hundred meters or so it gets quite wobbly.
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