[AZ-Observing] Re: Was Saturday Great or What???
- From: ketelsen@xxxxxxxxxxxxxx
- To: az-observing@xxxxxxxxxxxxx
- Date: Mon, 1 May 2006 15:29:26 -0700 (MST)
Brian-
I've not taken many wide field shots with digital cameras, but it seems
that the jpeg compression would really kill your resolution and limiting
magnitude. There are a bucketload of stars in that image, yet only a 1mb
file, so the star images are significantly undersampled, with blocky stars
and compression artifacts. Generally speaking, since he was shooting a
stop slower than I, but exposed a little over twice as long as my typical
single exposure, I'd expect a comparable limiting exposure, limited by the
above-mentioned resolution loss. Oh, I forgot Keith shot at an ISO of 400
and I was 2 stops faster at 1600... So what is the "secret" to moderate
resolution wide-field shots - 25mb Tiff images?
-Dean
> I was curious about Keith's image, given the very short focal length
> and what seemed to be near-zero processing. The nearly-equal pair
> on the southeast side of M11 are 43" apart, which appear as a single star.
> So I estimate that the angular resolution seems to be about an
> arcminute. The single star within Barnard 92, the oval dark cloud
> on the north side of the M24 starcloud, is HD 312872, which has a
> V magnitude close to 11.0, and this is faintly visible on the posted
> image, and sets a rough limit on how faint the picture goes---
> a flattering case, since the star has near-black surroundings whereas
> the typical star in this area would be crowded.
>
> \Brian
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