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nytecam

Ultrastar binning: image resolution v 'speed'

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Below is a preliminary result of progressively binning the SX Ultrastar 2x2, 3x3, 4x4 and 8x8 in identical exposures of 5sec via my Meade 30cm SCT @ f4 over a few minutes for consistancy. As the image is progressively binned [superpixel] it becomes more blurred but shows a 'speed' gain via a deeper image. Potentially a briefer exposure will attain similar stellar penetration. The biggest gain is 8x8 binning [x14 over 2x2 binning] but with very course image but ideal in 'finder mode' via say 1 second exposure for the faintest object.

The estimated 'speed' gain [in blue] done via photometry [star count - background sky 9px9p box] for marked m12.5 star east of M57. Used the native SX s/w for binning, exposures and photometry on the raw image but presented here processed with a non-linear stretch.

Top right is an 10s image at full res from 1392p x 1040p frame on a second evening. I need to repeat the unbinned 1x1/ binned 2x2 etc to add unbinned images to the 'speed' list. It will of course be the 'slowest' effective speed but with the highest resolution the ICX825 sensor is capable of.

Hope this is of interest ;-)

Nytecam

post-21003-0-94537100-1439654125.jpg

Edited by nytecam
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Hi Nytecam,

Very interesting and useful !

At 2x2 we are close to Lodestar resolution. But why are you saying exp.gain =x1? I understand that this is what you get but is still counterintuitive. Shouldn't photometry applied to a star rich area with more faint stars give a more accurate result?

At 4x4 we seem to be back at the square pixels of the bygone modded high-gains security camera days...

Clear Skies!

--Dom

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Hi Nytecam,

Very interesting and useful !

At 2x2 we are close to Lodestar resolution. But why are you saying exp.gain =x1? I understand that this is what you get but is still counterintuitive. Shouldn't photometry applied to a star rich area with more faint stars give a more accurate result?

At 4x4 we seem to be back at the square pixels of the bygone modded high-gains security camera days...

Clear Skies!

--Dom

My last paragraph Dom! It doesn't matter at what point value x1 is set relative to the remainder :-)

Nytecam

Edited by nytecam

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Very interesting test.  I am seeing triangular shaped stars on the large x1 and crop image, is this just a compression artefact on this forum or can it be seen on the original?

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I think the binning will only give good results with long focal length scopes. Also resolution is a function of focal length. A 60" fl scope using a X2 will have as about equal  resolution as a 48" fl using a 825.

Edited by f15p5

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Very interesting test.  I am seeing triangular shaped stars on the large x1 and crop image, is this just a compression artefact on this forum or can it be seen on the original?

Yes when enlarged it looks like a tracking error - should have used a better frame:-)

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I think the binning will only give good results with long focal length scopes. Also resolution is a function of focal length. A 60" fl scope using a X2 will have as about equal resolution as a 48" fl using a 825.

I regard sensitivity via binning invaluable particularly when resolution is less important:-)

Nytecam

Edited by nytecam

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I regard sensitivity via binning invaluable particularly when resolution is less important:-)

Nytecam

Absolutely.  For use in finder mode the 4x4 or 8x8 binning will be superb for locating and framing faint objects.  I'm not surprised, BTW, that your numbers pretty much line up with the theoretical expectation.  Given that you started with 2x2 as the baseline, I would have expected 2.25, 4.0, 16.0 for the remaining steps.  So we can expect the 8x8 to be ~64X as sensitive as the full resolution, which should make a world of difference in finding stuff.  

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I'm aiming to get binning in the next version of LL, if not then the one after...

As you say its perfect for quick target acquisition etc, especially if you star hop using the system..

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