M81 with SharpCapPro and StarTools

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Re: M81 with SharpCapPro and StarTools

#11

Post by admin »

Hi Stewart,

in the days of CCD cameras, binning on the camera was important as it reduced the noise burden of the resulting image. Noise tends to be lower in modern CMOS sensors anyway, and the CMOS technology cannot take advantage of binning to get the same gains that CCD did. That means that for CMOS cameras like your 533 it doesn't really matter where you do the binning from an image quality point of view.

Binning in SharpCap can have some advantages - smaller files for instance, but that's about it.

cheers,

Robin
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Re: M81 with SharpCapPro and StarTools

#12

Post by teletraveler »

Good to know.

Many Thanks
Stewart
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Re: M81 with SharpCapPro and StarTools

#13

Post by oopfan »

Hi Stewart,

I recently wrote about the differences between hardware binning versus software binning. I'll recreate it here:

************************
In my opinion, user forums perpetuate the myth that there is no advantage to using software binning in CMOS cameras. That is just not true. Still, however, there are differences between software and hardware binning especially when you are at the limits of detection under dark skies, for example when imaging the Integrated Flux Nebula.

To demonstrate, I put together these two identical Projects under Bortle 2 skies. Everything is the same except that one Project uses hardware binning and the other, software. Notice the extremely short Exposure times. I did that to simulate the conditions that are encountered when imaging very faint nebulae like the IFN. I chose values that force the "Signal per sub" to be approximately equal to the Read Noise. Now, compare the Total SNR between hardware binning and software binning:
Hardware vs Software Binning.jpg
Hardware vs Software Binning.jpg (131.51 KiB) Viewed 781 times
As you would expect, the SNR difference rapidly decreases as you increase exposure.

In summary, don't shy away from Bin 2 with CMOS sensors. Use it when necessary to reduce Total Integration Time. Just know that if your target is the IFN then you will need to boost your integration time to compensate for the higher total Read Noise in a CMOS super-pixel versus a CCD.
*********************

As far as using post-processing tools to reduce noise, I like the de-noising algorithm in Affinity Photo (currently $25). I have used a product called "NEAT", but now I prefer Affinity. Two years ago, I used StarTools under some circumstances.

My recommendation is to do all you can at the telescope at capture time. Increase Total Integration Time and/or Exposure, so that now you need to rely less on post-processing wizardry.

Brian
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Re: M81 with SharpCapPro and StarTools

#14

Post by teletraveler »

Hi Brian

Thanks for the info. Hardware binning definitely something to think about with faint objects although I have to say I like the idea of doing it on the fly
with software binning. One of my scopes is a 80mm APO and that coupled with my ZWO 533 camera and a 073 FR makes the image significantly undersampled 4.43 arc sec/ pixel under OK seeing. One of these days I will do a comparison between binning 2x2 and 1x1 to see if the tradeoff for less
noise vs softer images is worthwhile. No doubt it will be object dependent.

Cheers
Stewart
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Re: M81 with SharpCapPro and StarTools

#15

Post by oopfan »

Hi Stewart,

Yeah, 4.43 arcsec/pixel is definitely under-sampled. I am running at 2.29 arcsec/pixel which is borderline. Bin 1 for you is like my Bin 2, stars are square. What about removing the focal reducer?

Brian
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Re: M81 with SharpCapPro and StarTools

#16

Post by turfpit »

Stewart

https://astronomy.tools/calculators/ccd_suitability

Will allow you to try binning & barlow/reducer combinations to see the effect on under/oversampling.

Dave
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Re: M81 with SharpCapPro and StarTools

#17

Post by teletraveler »

Sorry I meant to say my bin 2 is at 4.43 arc/pixel. Yeah I have been doing EAA which with an Alt Az which really means I need all the speed I can get hence the focal reducer. That said I just inherited a celestron AVX mount which should help. I like the FR for the wider field and speed . For this scope setup I will just stick to Bin 1 which gives me about 2.2 arc sec/pixel. Still undersampled but doable
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