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Re: [APML]: New Topic
> He claims f6 is f6...
> His contention is that you have to shoot the same time for both instruments..
It's a matter of image scale. The exposure time for a particular EXTENDED
image is the same no matter what the objective diameter, given a constant
f/ratio. What changes is HOW BIG the image is... there are a lot more photons
collected for a bigger diameter, but they're spread over a larger film area,
so the amount of light falling on any particular point on the film stays
the same.
However, this only applies to extended images. For a star image, all the
light is (theoretically) concentrated at one point, so a bigger diameter
means more light AT THAT POINT, and thus shorter times to achieve the
same exposure.
______________________________
| Bill Ezell |
| wje@sii-nh.com |
| http://www.duckpond.mv.com |
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The box said 'Win95, NT, or better', so I used Linux