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Old 12-07-2021, 09:52 PM
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The_bluester (Paul)
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Comparison of HA data shot with a mono sensor versus a bayer matix.

Some time back I commented that while I was pleased with how much NB filters extended the usefulness of an OSC camera, I was keen to make a comparison between NB data shot with the OSC versus the same target with my new mono version (ASI2600MC versus ASI2600MM, so quite a straight shootout)

I shot data on SH2-34 with the OSC camera as OSC, HA and Oiii data, and I was pretty happy with the result. Then my mono cam arrived, so I shot the target again with the mono cam and same NB filters, plus the RGB filters with the new cam.

Link to the semi finished RGB-HA-Oiii image with the new cam (I say semi finished, as my first mono cam image I will probably reprocess it again from scratch, Andy01 reckons a bit much cyan and I am inclined to agree with him) https://www.astrobin.com/full/oiilf5/0/

The real star of the show is a straight comparison between HA data shot with the OSC and debayered with the HA algo in Astro Pixel Processor, and HA data shot with the same filter over the new mono cam. I made an animated GIF of the results of two integrations, registered so they line up and cropped to match. Pretty obvious the difference between the two. Both sensors were cooled to -10, both are calibrated with a master bias and flats, both were at 1200 second exposures, but the OSC cam had an extra 5 exposures over the mono, and it is still grainy in comparo.

https://www.astrobin.com/full/dsafar/0/

My take on it is if you can afford to go mono, and have time and patience to shoot and process RGB-HA-Oiii-Sii/whatever else as separate filters (And skies dark enough to make the RGB sing) you won't regret the move. If I had some cash to burn I would sell my now "Second" cam (The 2600MC) and buy a second mono one so both scopes were set up the same way.

Last edited by The_bluester; 12-07-2021 at 10:10 PM.
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Old 12-07-2021, 10:08 PM
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That's a great comparison Paul and thanks for your efforts.

Given the OSC has 25% of the pixels available to respond to Hydrogen Alpha compared with the Mono camera, I think that's a very good result for the OSC, yes it has more noise, but the resolution/overall detail is still up there, more so than I would have clearly expected. Of course the mono wins, but the OSC is not disgraced. For those that may want to keep their setups and processing simple without going mono, throwing in a bit more exposure will help further bridge the gap somewhat. I'm a lot happier now knowing this as this is a comparison I've always wanted to do / seen done as I lean towards preferring a simpler setup.

Best
JA
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Old 13-07-2021, 07:16 AM
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I am surprised by the lack of difference. I would have thought it was a more one sided affair.

Also a testimony to how good these Sony CMOS sensors are. This wasn't the case in the past with one shot colour CCDs. More of a difference then.

Greg.
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Old 13-07-2021, 07:24 AM
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It would be interesting to compare an older sensor like the IMX294 now that there is a mono version available. But even then, while NB filters certainly made the 2600MC more useful, I am not keen to go back.

I will do the same comparison with the Oiii tonight as I have that from both cameras too.
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Old 13-07-2021, 07:30 AM
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The Sony CCDs are pretty sensitive to Ha, around 77% for the ICX 694.
So I imagine the differences, at least for that sensor, would be not that great again.

Greg.
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Old 13-07-2021, 08:08 AM
Startrek (Martin)
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Paul,
Excellent report and thanks for spending time on testing with both your great cameras
For the moment Iím sticking with my 2600MC and L Extreme as the images Iím producing under both sky conditions ( Sydney Bortle 8 and South Coast NSW Bortle 3 ) are very satisfying
Of course the Mono will always produce better images but the 2600MC does a tremendous job for simplicity
No doubt the Mono bug will bite me at some stage later on .......
Thanks for posting
Martin
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Old 13-07-2021, 12:17 PM
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The OSC certainly didn’t disgrace itself, but the comparison does show that interpolation is in the end not a match for the full resolution.

If anyone asked me if they can do some NB with a decent OSC sensor I would certainly tell them to go for it.
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Old 13-07-2021, 02:18 PM
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rustigsmed (Russell)
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yes i've done similar tests on a modified dslr the resolution loss is the main weakness especially on the clean astro sensors (not so much on a dslr).
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Old 13-07-2021, 04:22 PM
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Definitely a plus for the newer generation backlit Sony sensors. They are incredible. As a Canon shooter in terrestrial photography, I've always been envious of the backlit stuff from Sony, and was pleased to hear Canon getting involved with the R3.

That said, Mono is obviously king, and you can't argue with physics. If I had the space and time, I'd be going with Mono. As I don't have either, OSC for me. Maybe in future that will change.
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