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"Astro" scope with smaller sensors? (1 Viewer)

Chris B.

Well-known member
I was just wondering if anyone has used an "astro" scope with smaller than an APS-C sensor (20D, 30D, 40D, 50D, 7D...). Like say perhaps with a Micro 4/3rds sensor as in a Panasonic G1? I would think that it would increase the magnification factor significantly given the increased angle of view... or do I have my math screwed up?
 
Paul C would probably be able to answer you, as i'm too much of a novice for this question, but i cant see why not, though i dont know anyone who has.

Its still a DSLR at the end of the day, so see no reason for problems, but someone with better experience will be able to say about pros and cons of this method
 
I don't know the exact link but there's some photos taken with a Panasonic G1 on the Borg telescope website. The bigger dsl'r tend to win on low noise at high iso, better resolution for capturing fine detail etc. You do get the cropping thing but then you could just crop the photo of a dslr and get the same result. I think in a year or two there may be a small mirrorless camera worth buying but there's nothing that catches my eye at the minute.

Paul.
 
Thanks, Paul! I figured if anyone would know you would! Personally, I'm looking forward to seeing the quality of images I get with the 7D through an astro scope. Images from my Canon "L" lenses have been nothing short of spectacular!
 
The Panasonic Lumix DMC-G1 has the same pixel pitch as the Canon 7D, if my calculations are correct:

22.3 mm / 5184 = 4.30 microns (Canon 7D)
17.3 mm / 4000 = 4.33 microns (Panasonic Lumix DMC-G1)

They should give the same resolving power with the same telescope, but the 7D would have a a wider frame. So assuming the 7D is as sharp or sharper than the G1, the 7D would win all-round. However... looking at the DPReview of the DMC-G1, its sharpness and low noise are impressive indeed. I'd love to see a comparison between it and the 7D using the same lens at the same physical focal length.
 
The G1 is ok for resolution but falls short by quite a bit in the noise tests. Even at ISO 100 the noise is clearly visible. I like to shoot at ISO800 pretty much all the time and on my 450D it's possible. The 450D at ISO800 looks better than the G1 at ISO 100 in the dpreview tests.

Paul.
 
The G1 is ok for resolution but falls short by quite a bit in the noise tests. Even at ISO 100 the noise is clearly visible. I like to shoot at ISO800 pretty much all the time and on my 450D it's possible. The 450D at ISO800 looks better than the G1 at ISO 100 in the dpreview tests.

Paul.

I retract what I said about the G1 being impressive in terms of noise performance. But looking again at the dpreview tests, I must say that I cannot draw any conclusion whatsoever. Unfortunately they don't show any RAW noise comparisons (except for a graph which is not very meaningful). Imaging Resource doesn't have any RAW comparisons either.

From looking at the JPEG comparisons I can see that the G1 does hardly any noise reduction in-camera. The noise in its JPEGs has a relatively natural look, rather than the clumpy look characteristic of NR. There was a time when I would have liked that... but these days, I always use RAW, so it doesn't matter to me how good a camera's JPEGs are (except for chimping).

The only really proper way to compare noise would be:

1. First compare sharpness at ISO 100. The softer a camera is, the more sharpening it will require, and sharpening increases noise.
2. Measure RAW sensitivity on all three color channels, in terms of quantum efficiency.
3. At each ISO, measure read noise (in electrons) and gain (in electrons per ADU).
4. Measure the amount of pattern noise in the bias frame (in modern cameras, there will be virtually no pattern, i.e. no banding)
5. Formulaically combine these numbers into four "noise performance indexes" for each ISO: indicating Chromatic Noise, Noise in Dark Areas, Banding in Dark Areas, and Noise in Midtones and Highlights.

This would give a truly objective means of measuring noise performance in digital cameras, meaningful to people who shoot in RAW, and yet AFAIK no review site does it.
 
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