astrolucida
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Registered: Jan 07, 2005
Total Posts: 1472
Country: Finland
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 Re: Moon shooting... what equipment next? | |
VanIsle wrote:
a) buy an Xti for its extra reach. The downside here is that I wont be able to AF. Manual focus is fine, but I am concerned that the xti viewfinder is dim to begin with... so how will it be at f/8? Will I still be able to achieve *critical* focus (I say this, because of course I want to be able to catch as much crater detail as possible) by using manual focus and f/8? I am particularily concerned about shots where the moon is a very thin crescent.
I regularily use the 400f2.8L II + 2x + 1.4x + 1.4x on XTi. That combination means f11, wide open! However, manual focus works quite nicely, with Canon Angle finder C. Mostly this is because the Moon provides such a good contrast, so in your case of a very thin crescent, things might be a bit different. Though, I have found the angle finder to be just the tool for manual focusing.
VanIsle wrote:
b) buy a 2x converter. But again I lose AF. And though the 1D2 vf is quite bright, im sure f/11 won't be so much fun. Also, I know from experiece, that f/8 I am already strating to push my limites for a short enough shutter speed (particularily when a full moon rises at sunset, and is not very bright at all) at an acceptable ISO... going to f/11 , and then stopping down because the 2X will be a bit soft... I worry about shutter speeds.
Talking about shutter speed, a good rule of thumb is that when you take the hundreds (of mm) in focal length, you'll get the maximum exposure time as 1/(that value). I.e. for 400mm, 1/4 s, for 800mm, 1/8s etc.
However, when the Moon is very low, the atmospheric effects are largest (the Moon seems to "boil" in the viewfinder). Hence, a shorter exposure time can be better, at the expense of increasing the ISO. But you should also take a few dozen images and pick the sharpest. The atmosphere is changing constantly and occasionally it is calmer, producing a much sharper image.
As digital images cost nothing, take many and pick the best. Also refocus from time to time. You can pick the sharpest image by choosing the one with the biggest file size, though if the Moon is a small part of the image frame, this method may not be accurate enough.
Also, use a good tripod, mirror lock and a remote shutter or self-timer.
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