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Old 06-11-2013, 02:23 PM
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Shiraz (Ray)
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binning with the ICX694 - software bin added

took two broadband images of the same piece of sky with equal exposures, using 2x2 binning on one and 1x1 binning on the other. tried to measure sky signal on exactly the same region with the following results:

bin1x1 SNR = 12.7 signal = 591

bin2x2 SNR = 25.9 signal = 2347

within the limits of experimental accuracy, the SX H694 implements a pure binning, with no fiddling with gain (there was a minor bias change) and no erosion of SNR. The increase of SNR is 2x and of signal is 4x, which is what would be expected if the binning was perfect.
Both exposures were long enough that read noise was swamped, so I have not investigated any change of read noise with binning - will need to do this with NB data.

The other issue of overload in saturated regions also appears to be a non-event. Stars do not show any obvious signs of blooming artefacts when they saturate in 2x2 binned mode.

I was astounded that the camera performed to the theoretical limit - this gives some confidence in using it as a 1.5mp high QE ABG camera on larger scopes, or in binned mode for gathering colour information when colour resolution is not a major issue.

Thanks for reading. regards Ray

Last edited by Shiraz; 07-11-2013 at 08:50 AM.
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Old 06-11-2013, 02:55 PM
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Good results, Ray. I'll be interested to see how it does with read noise. The recent Sony sensors perform very well on just about every measure except physical size!

Cheers,
Rick.
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Old 06-11-2013, 04:50 PM
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Quote:
Originally Posted by RickS View Post
Good results, Ray. I'll be interested to see how it does with read noise. The recent Sony sensors perform very well on just about every measure except physical size!

Cheers,
Rick.
yep, if only they would put this technology into something big and mono. Have yet to find any significant downsides apart from size.

just realised that this data allows the internal chip "gain" to be calculated - it is about 0.27, which agrees well with other evaluations, so read noise must have been pretty low for these 200sec images. regards Ray

Last edited by Shiraz; 06-11-2013 at 05:59 PM.
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Old 06-11-2013, 06:09 PM
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I got A Starlight Express Trius 694 the other day and did a first light image with it last night after getting everything working.

Its definitely an impressive little camera and it worked very well on the CDK. I intend to try using it with the CDK reducer shortly once I receive a better adapter than my temporary one (it works nicely but keeps the CCD another 19mm from the filter wheel which is not an issue normally but will be with the extremely limited backfocus of the reducer).

More data tonight although I was able to produce a nice result from 5 hours on a dim small galaxy.

Greg.

Last edited by gregbradley; 06-11-2013 at 06:31 PM.
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Old 07-11-2013, 08:57 AM
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looking forward to your results Greg

Since read noise was so low in the binning test, decided to try software binning to take the 1x1 result to 2x2 in Nebulosity. Ended up with an SNR of 24.7 which is practically identical to the hardware binning. Thinking about it, the main advantage of hardware binning is the possibility that the single read is less noisy than the combined read noise from four pixels merged in software - but if the read noise is well below the shot noise anyway, software binning produces the same result as hardware binning.

This ties in with comments on Greg's parallel thread where it is suggested by Rick and Rob that full resolution colour data could be gathered 1x1 and then software binned if required - looks like a good strategy if you have read noise well below the shot noise.
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Old 07-11-2013, 05:52 PM
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Sounds like another trick in the tool bag to help out when needed.

Its good to know.

Greg.
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Old 07-11-2013, 10:08 PM
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Maths aside, I tend to use 2x2 a lot, especially for galaxies - mainly as my imaging time is limited, and I get better results with 2x2, and the seeing here seems rarely better than 2" in any case.
I have just upgraded my Atik 420 to the 428EX which has the ICX674, so I'll be paying close attention to your posts Ray....
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