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Old 15-12-2019, 08:19 AM
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Quote:
Originally Posted by Peter Ward View Post


Picked it in one.

Most commercial telescope optics deliver 10 micron (or larger) spot sizes in their central zones, and quickly bloat out to more than two or more times that figure.

Add seeing disturbances and 30 micron will be a good figure on most nights.

75Mp in a 35mm sensor might sound awesome, but the reality is: those 2 micron pixels are doing you no favors at all.

Your can over-sample blurred data as much as you like. It will still look blurred.

However an optical system that delivers say 5 micron spot sizes and superb mount (+AO) that does not smear the incoming starlight beyond what the optics can deliver is FAR more important than megapixels.



Yes Peter,
you own pictures prove that point.


cheers
Allan
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  #42  
Old 15-12-2019, 09:04 AM
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Apart from paying for theoretical resolution that is in most cases unusable, s there any great issue with binning these small pixel, high pixel count cameras?


Regards the sensors in mobile phones, more than the silly high mp count on a tiny sensor, my beef is the lens. As Allan wrote, the size of a pea (Or smaller) probably made of plastic and worth about half a cent.
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Old 15-12-2019, 10:33 AM
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Originally Posted by The_bluester View Post
Apart from paying for theoretical resolution that is in most cases unusable, s there any great issue with binning these small pixel, high pixel count cameras?


Regards the sensors in mobile phones, more than the silly high mp count on a tiny sensor, my beef is the lens. As Allan wrote, the size of a pea (Or smaller) probably made of plastic and worth about half a cent.

If this is true then there is no advantage to CMOS binning:


https://www.atik-cameras.com/news/bi...-cmos-and-ccd/


Quote:
To put it very basically, in both CCD and CMOS, “binning” is the technique of combining pixels in an image into a “super pixel”. It typically takes place in 2×2 or 3×3 blocks etc. In doing so, the signal in the individual pixels is combined into the super pixel. This helps improve the signal to noise ratio (SNR). However, it also lowers the resolution of your image as it contains fewer, but larger pixels. Where CMOS differs is that this process takes place in the software after the digitalisation of the pixels has been completed. This is very different to CCD where binning takes place in hardware, or “on-chip”.
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Old 15-12-2019, 12:21 PM
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I have seen it written that there is still an SNR advantage to be had in CMOS, but it is nothing like as large as for a CCD and it tapers off even more as your binning increases. What it would mean (I presume) is pixels small enough to have a well sampled image at short focal lengths with the ability to bin the output for long focal length scopes without a penalty to pay in terms of SNR, and the advantage of not producing bigger than necessary file sizes. With a cost penalty of course.
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Old 16-12-2019, 06:30 AM
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QHY600 and IMX455 binning

Quote:
Originally Posted by Atmos View Post
I guess one of the lines of thought is that with something like the QHY600, you can always capture and full resolution and then bin it before working on anything. Or even just bin during capture if that is easier, it's what I would do with my Mewlon but that's when 2x2 binned gets me to 0.62"/pixel

With that though I'd have a 15mp BSI mono FF sensor with a QE peaking at near 90% and 7.52 micron pixels. Although it doesn't get the same SNR improvement with binning as a CCD it also doesn't have the high near noise which was the purpose of hardware binning anyway.
I posted in another thread about this but with the QHY600 (and possibly other IMX455-based cameras), a 2x2 software bin does not have 4 times the read noise as a single pixel. It's not quite the same as a CCD but it is better than 4x read noise. The IMX455 does have a true hardware bin that works essentially the same as a CCD bin but only when operating at a lower bit-depth than 16-bit. The motivation for that mode is for higher-frame rates e.g., when shooting video. As far as I know, QHY have not enabled that mode in their drivers.
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