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Old 05-12-2008, 06:57 AM
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OneOfOne (Trevor)
Meteor & fossil collector

OneOfOne is offline
Join Date: Jul 2005
Location: Bentleigh
Posts: 1,386
The F5 6" has a focal length of 30 inches whilst the F10 10" has a focal length of 100 inches. So the image scale of the 10 is about 3 times that of the 6 and so photographically the same target will appear about 3 times larger, as a result, the 6" would have a wider field of view of the same area (about 3 times in each direction, or about 9 times the area).

The 10" gathers around 3 times the amount of light (10 squared:6 squared) per unit area, but this is spread 9 times more than the 6" and so the larger image will appear duller (about 3 times) than the same object seen in the 6".

Visually, the same eyepiece in the 10" will give 3 times more magnification than in the 6".

Does this make sense? The figures are of course "ballpark".
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