Quote:
Originally Posted by OzEclipse
Andrew,
Sorry about that :
It is:-
max exposure time(s) = [14*N*P] / [FL*cos(d)]
I've edited the original post to reflect this.
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It seemed to make more sense that way than the other so I thought I check it.
Quote:
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The cos(d) term is 1 for a declination of 0 so you can leave it out all together if you want to calculate for stars on the celestial equator.
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To make use of that you need to know the image center and FOV to work out "d".
eg APS-C long axis 23.3mm. At 11mm -> 93° FOV so pointed at dec -45 with that axis aligned n/s some stars are on the equator.