Alan C wrote:
I'm surprised there is virtually no lateral movement of the stars
visible with a 10 sec. exposure. I suppose the short focal length plays
a part. In 1965 I photographed the Ikeya-Seki comet using a Super Tak
135/3.5, ASA 1250, 5 sec and slight movement was visible.
20 seconds on the FA 31 is pushing the "rule of 600" that the exposure
time in seconds times the focal length of the lens needs to be under
600. Modified, of course, by the resolution of the sensor, how much you
crop it down etc.
In my case, when I'm stitching multiple exposures together then
downsizing for the web, my "effective focal length" for the rule of 600
is much shorter than 31. When pixel peeping, you can see the stellar
blur, or even some doubling up of stars from the stitching.
For example, this is one at 1440 wide, and if you look closely you can
see the blur
https://www.flickr.com/photos/ellarsee/26316993875/sizes/o
The "original" is stitched to 6844 wide, so printed big, the blur is a
lot more noticeable.
Note that 135 * 5 is 675, just slightly more than 31*20 (620), although
that can be effectively divided by 3 or 4 on some of the stitched shots.
--
Larry Colen [email protected] (postbox on min4est) http://red4est.com/lrc
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