Quote:
Originally Posted by NQLD_Newby
If I am understanding correctly, the lower the f ratio of a scope, the less exposure time is needed for photography. If I am correct in this assumption, it stands to reason therefore, the faster a scope is the more detailed its views will be at a particular magnification when viewing at the ep. (more light in the same amount of time hitting your eye).
My question is, if the above statements are correct, then wouldn't the best viewing scope be the one that is fastest?  |
ok, my two cents worth:
Your assumption is false, as I take it - it is aperture that determines the resolution of the image, not the focal length. If you want a more detailed image you need to go for a wider mirror. While the people above have made some valid comments i.e. that a larger aperture can collect too much light on bright objects like Jupiter, for detail in low surface brightness objects such as nebulae and galaxies aperture is king.
When choosing focal length, you need to take into account what you are going to use the scope for the most. If it is imaging then shorter can be better. But if you going to image the planets or moon most of the time then a longer focal length may be better.
The rule of thumb I learnt was that if you are going to do comet searching or variable star observing or imaging then a short f-ratio/ wide field view is usually the way to go.
If you mainly want to do visual viewing somewhere inbetween would be good, say F/5 to f/8.
Unfortunately there is no perfect scope for both, you usually need to make a sacrifice somewhere (even if it's your wallet when you pay for two different scopes). It's horses for courses, as tempestwizz says!