Originally posted by Blaine91555
reply to post by obilesk
I suspect the problem to be lens size. I can shoot a clear shot of a car from about 1,000 yards with a 1,000mm lens and an exstention tube, but it
requires a lot of light and no motion on top of the extremely limiting size of the lens. To shoot in motion in low light and get any good results
would require a very large lens. My first guess is that is the issue.
They have a .195m lens for the narrow angle camera, basically the same size as my telescope. The thing is, it's f/3.59. Why? Well for one thing,
as you mentioned, they are in motion, so you need fast exposures to avoid blurring due to the satellite's orbital speed. That means the same size
'telescope' lens could be magnified more if it had more focal length with a slower f ratio (like my own f/10 telescope), but the images would be
blurred and useless or so fast in exposure that they'd be underexposed. Furthermore, the kind of resolution enhancement you'd get would be on par
with the kind they're going to get just by dropping into a lower final mission orbit; that kind of gain is unlikely to please those who aren't
already pleased.
Theoretically you
could orbit the moon with a much bigger telescope with the same F/ratio and have a camera with an insane amount of megapixels
(5,000 something pixels wide on a CCD like with LROC is already pushing the limit on what we have that's certified as radiation hardened I think),
but you're looking at a much bigger satellite at that point, more like a tradiational spy sat 14 times as massive as LRO, so you're basically
launching the same magnitude of mass to the moon as a manned mission anyway.
[edit on 17-7-2009 by ngchunter]