Re: Photographing the moon with 300D

Thanks. That have saved me quite some time with the calculations.

On 24 Aug, 15:17, "Roger N. Clark (change username to rnclark)"
<usern...@xxxxxxxxx> wrote:
Pete D wrote:
Mirror lockup certainly helps, moony 8 rule, 1.4 converter I find helpful as
well.

Try for at least 1/125 to freeze the fast moving moon. lowest ISO you can
set.

The moon, stars, planets, and the sun move about 15 arc-seconds per second
of time. Unless you have extreme magnification, one pixel covers
a few arc-seconds. At 300 mm on a 300D, each pixel is 7.4 microns,
which at 300 mm gives 7.4/(300mm*1000/206265) = 5 arc-seconds per
pixel. (The 1000 factor is microns/mm and the 206265 is the
number of arc-seconds/radian.)
It takes about 1/3 second for the moon to move one pixel
width. For sharp images, you want exposure times to be less than
1/3 pixel, so about 1/10 second would freeze the motion.
For longer focal lengths, 1/25 to 1/30 second is fine.
Only with very big telescope magnifications do you need
1/100 second. Of course, use mirror lock up, or 1/10 to 1/30
second exposures will likely show mirror bounce, so 1/100
helps insure against that.

I don't think that I have mirror lock up unless I use a firmware hack
that I have read about but not dared to attempt. However it sounds
like I can use much faster exposures than I expected so maybe this is
not such an issue. Also, if you read some of my other replies, you
will see that I won't always be using 300mm. That is my longest lens
so I feel I must try it on the moon but I also need some smaller
images at more modest focal lengths.

This might be of interest:

http://www.clarkvision.com/imagedetail/moon-test1

http://www.clarkvision.com/astro/moon_saturn_jupiter.d60.v1

Nice pictures Pete.

Thanks. I thought that I have seen some good articles in previous
browsing but I had forgotten where. I think that I have seen that
first one before. Certainly I have been to that site which is very
interesting.

--
Seán Ó Leathlóbhair

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