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ZWO 2600MC Pro: a dream camera ?

Astrophotography CMOS DSLR DSO Filters
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#1 lpalbou

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Posted 18 May 2021 - 04:57 PM

Prelude: much ado about nothing

 

Ah California and the Bay area.. Nice winters without snow allowing you to image, but in summer time, Karl the Fog is as active as any child wanting to enjoy the sun.. Except Karl is egoist and steal all the sun from the common folks of the Bay Area (yep, LOTS music and I am indeed thinking of the Shire and Gandalf.. but that's a long story for another day).

 

Anyhow, I have  been intrigued, as a number of people, about the ZWO 533 / 2600 and its 6200 as expensive as amazing on paper. 533MC was really too small in terms of field of view for my scope and targets. 2600 on the other hand.. APS-C format is starting to be great and you have a few advantages (smaller files, quick processing, less demanding on optics, etc). So one morning, I put my Financial Adviser Moral in the closet and order the 2600MC from OptCorp. Why the MC ? Great question and I hesitated. Maybe it wasn't in stock or maybe I wanted to keep my workflow simple for now. Obviously, one can expect much better results from the monochrome camera, as you would with any camera.

 

Of course, Murphy's (law) and Karl are good friends, so I just got my first clear night after 10 days. Not a lot of data, but already something that intrigued me enough to decide to start this post.

 

The question: just how good is it ?

 

I have been imaging since 2015 and doing observations since I was a child (parent scientist & all). Passionate about photography, I admit I have or have tested just too many cameras. D800e, D850, Z6, Z7, a few canon too, and even more recently the A7RIV. I was actually curious to see how the A7RIV would perform vs the ZWO 2600MC since.. aside from the APS-C vs FF, they do share a number (if not most) characteristics. Hold your horses.. I haven't had time yet to do that comparison, but provided Karl gets a girlfriend or just decide to sleep.. I will be able to post that comparison as well. Now, what I have been able to do, is to compare 4h of exposure of the Sadr region with the IDAS NB1 on both my D850 (4h exposure, 5mn subs, ISO 400) and yesterday the new 2600MC Pro (1h51mn exposure, 5mn subs, gain 300 - yes it's not 100 but that's what was needed to have sufficient separation from the left side of the histogram). First impression, the result looks clean. Second impression.. boy, I really had to raise that gain to get a good exposure, I really was hoping to stay at unity gain. I tried longer exposures 7, 8mn but it wasn't enough, and decided for now just to use a gain of 300.

 

The image from the D850 was done on May 7 and on the ZWO 2600MC yesterday on May 18. Approximately at the same time interval to have similar air masses. And... without too much talk, here is the red channel I captured with both (only calibrated with flats, no bias, no darks).

 

Without commenting myself, I would first be curious to hear what you think about the performance of both camera. 

 

Preliminary results

 

For all 3 images:

- Left: ZWO 2600MC (1h51 exposure, gain 300) - 100%

- Right: D850 (4h exposure, ISO 400) - 115% (to roughly match different pixel size)

 

2600MC Pro Vs D850
 
2600MC Pro Vs D850 Im2
 
2600MC Pro Vs D850 Im3
 
 
The last one is to show the field of view difference between APS-C vs FF at 300mm (same lens, same settings).
Also note my D850 is not modified.

 

That's it.. What's your first impressions ?

 

 

PS: they were processed on two different days so it's not 100% the same processing, but I use a very similar workflow. The 2600MC is slightly more exposed in the highlight compared to the D850 for instance


Edited by lpalbou, 18 May 2021 - 05:14 PM.


#2 eyeoftexas

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Posted 18 May 2021 - 05:08 PM

Thanks for the comparison.  To my (untrained) eye, I see more detail and contrast in the 2600MC images, especially the middle set.



#3 bobzeq25

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Posted 18 May 2021 - 05:36 PM

Flat calibration does not work well without bias.  Math.



#4 Jim Waters

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Posted 18 May 2021 - 05:39 PM

Why are you settling the gain to 300?

#5 lpalbou

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Posted 18 May 2021 - 06:41 PM

@bobzeq25 I know the equations, it's in the Keller book of pixinsight. In terms of noise, you are right but in terms of removing dust and other issues in your optical train, it's a necessity. When I want to go quick, that's the only calibration frame I use. In addition, I would add that if you expose "enough" (long discussion) your sub so that your histogram is not just a peak at the far left, you don't need to over stretch 10 times and calibration frames become less relevant. That's also part of the reason why we use filters.

 

@Jim Waters as explained in the post, to get a sufficient exposure (histo detached from left-side), I either had to increase my exposure to 10mn+ or increase the gain. I would have preferred to stay at unity gain to maximize DR, thing I do with the D850 by staying at ISO 400. When I have more clear skies, I will of course try to image at unity gain with longer exposures but it was just too risky for such a small session.

 

@eyeoftexas thanks for the first impression ! Indeed the goal of that thread is not to get the perfect photo of the Sadr region (I already have 20h + all calibration frames for my final project). The goal is to see how these camera compare in real life, beyond the advertised specs and limitations (we think) we know. I am already starting to forge an opinion from what I saw but I would be interested to read people thoughts about how and why they think one camera is better than the other.


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#6 AgilityGuy

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Posted 18 May 2021 - 08:08 PM

Thanks for posting.  Looks like the fog is back to stay!  It's been down right brisk on the peninsula.  There might be differences but they are very slight.  I'd rather have the convenience of the D850.  You mentioned you also had a D800E at one time, all the images I've seen from the D850 look like it was a big improvement?  I'm looking to upgrade from my current full spectrum D800E 



#7 Jon Rista

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Posted 18 May 2021 - 08:14 PM

@Jim Waters as explained in the post, to get a sufficient exposure (histo detached from left-side), I either had to increase my exposure to 10mn+ or increase the gain. I would have preferred to stay at unity gain to maximize DR, thing I do with the D850 by staying at ISO 400. When I have more clear skies, I will of course try to image at unity gain with longer exposures but it was just too risky for such a small session.

You really don't need to do that histogram separation thing. That only really works with DSLRs when specifically observing the back of camera histogram display. The histogram separation stuff doesn't actually work in any other context, because of how the cameras CHANGE the data to compute that histogram.

 

Histogram separation doesn't apply with CCD/CMOS astro cameras. You can get away with SIGNIFICANTLY less "histogram separation" or "histogram shift" with these cameras, and still more than sufficiently swamp the read noise. My guess is you could still use exposures a couple minutes long and get plenty sufficient exposure at unity gain with the 2600. The benefit there then, should be much better DR with the CMOS astro camera than you have thus far experienced. 


Edited by Jon Rista, 18 May 2021 - 08:15 PM.

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#8 TelescopeGreg

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Posted 18 May 2021 - 10:36 PM

What Jon said.

 

I did the same thing as you - imaged at 300 gain initially - in order to get some separation on the left.  Previously, I was running my Nikon DSLR at ISO 6400 and taking 30 second subs, so it made me nervous to extend my subs out to 2-4 minutes and crank the gain up for a similar exposure.  I've since calmed down a bit, and am taking 5 minute subs at gain 100-150, depending on the background light pollution in that part of the sky.  There was a thread some weeks ago where a calculation was done on what ADU represented enough signal to swamp the noise, and it came out to something like 1,700.  I get just above that with these exposures.

 

But, I grew up in the Bay Area, and would think that your LP would be such that you'd need much shorter exposures and lower gain to not saturate your images.  What sort of telescope are you using?

 

I also love the camera, but the biggest reason I upgraded from the Nikon to the 2600MC was to fix the DSLR's insensitivity to the deep red of Hydrogen Alpha.  The Sadr region probably has a lot of that, so the astro camera will win over an unmodified DSLR any day.



#9 lpalbou

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Posted 19 May 2021 - 07:20 PM

@AgilityGuy I still have my D800e and I use it as a secondary imaging camera. The D850 is obviously a better camera.. but I would say more in terms of convenience and if you go high ISO. Which I never do (refer to https://www.astropho...y.app/nikon.php for recommended ISO). It's a question of selecting the best ISO where your noise gets low enough while not losing too much DR. For both the D850 and D800e, I find that ISO 400 works quite well. Out of the box, the D800e gets or boosts the red channel a bit more than the D850, which can be useful for capturing Ha targets (same for Z6 and Z7 actually). In terms of what you can get with a D800e, here is an example of Andromeda:

 

Andromeda Galaxy - Nikon D800e - LPS D2

Granted, I went crazy on that one (25h exposure), but it was done over multiple nights while imaging something else on my primary system, so I wasn't counting. I just wanted to get the best I could. So even a $600 camera like the D800e can do wonders IMO.

 

@Jon Rista @TelescopeGreg I admit I was perplex as an histogram is nothing else but a distribution of your pixel intensities (using APT for both DSLR & ZWO, so same transformation). However, there is something to be said about dark & highlight recovery which do differ from camera to camera.. and you still have to be careful not to lose faint details if you under expose. Still, as I was curious, I decided to do a test last night (very bad night, winds up to 30km, so tracking was not perfect; plus some clouds from time to time). To mitigate the effects of weather and air mass on both tests, I took multiple series of 5 shots at gain 101, then 5 shots gain 300, and over again. I still use the same exposure time (420s) for both. At g101 the histogram was at the far left (max values about 1/6th of the histogram) whereas at g300, the histogram was expanding up to 60% right. I just processed both images in the same way; initial stretch is slightly different as the input is not the same, but other steps are tthe same. Here is the result:

 

ZWO2600MC - Sadr region - g101 vs g300 - part2
 
ZWO2600MC - Sadr region - g101 vs g300

 

Left = gain 300, Right = gain 101.

 

Overall, I would say I captured the same nebulosity, including the faint ones. So the dark/shadow recovery of the 2600MC works quite well in that regard. Some richer Ha areas are also less saturated with g101, allowing for better gradients / DR (possibly fixed with custom processing). But more importantly (and as expected), indeed at g101, the noise is significantly lower. Note I only had 1h17 at g300 and 1h31 at g100, so with a bit more exposure, g300 would be slightly better, but the difference would still be there.

 

So to summarize this part: as the 2600MC has good dark/shadow recovery, I agree we should shoot at unity gain (100 or 101 - just in case), but I would still be considerate about not losing faint signals and expose enough. So my next comparisons will be done at g101. For the D850, I will continue to use ISO 400; the A7RIV same thing (I am quite curious of that test, possibly tonight) and the Z6 at ISO 800. I am not sure I will test the D800e even though I am curious.. but it does take some time. But considering I will stick with 1 or 2 cameras, I prefer to do those tests once and for all.

 

@AgilityGuy there is indeed something to be said about the convenience of DSLRs; I was indeed quite surprised the D850 captured nearly as much details as the 2600MC, albeit twice the exposure time and with a bit more noise. First impression is... I was expecting more from the 2600MC considering it's a dedicated camera and my D850 is unmodified. But this needs a bit more tests as on the paper the 2600MC is supposed indeed to be much better. Both processing were done at different times so I would probably like to redo those, just to be sure the noise difference comes from the camera and not a different processing. For now, I have saved my workflow, so that I can apply it to all the camera and avoid too many bias on that side. I will redo the D850 as well and ideally will post a gallery of the same region with all camera (I will really get bored on the Sadr region at some point... especially in APS-C as I can not frame/capture the Crescent Nebula at the same time.

 

@TelescopeGreg LP is high in the middle of SF but I am using the IDAS NB1 filter + I try to shoot only when a target is above 40°, otherwise the air mass really complicates things to capture faint details. At those short focal length, I am using the Nikon 300mm f2.8 @f4. It's a remarkable lens for FF I have been using for years. It's better in sharpness and aberrations control than the Orion 80T CF triplet or S.Explorer, but has slightly less good color rendition (a triplet is still a triplet). For higher focal length, I use my C8 edgehd.


Edited by lpalbou, 19 May 2021 - 07:37 PM.


#10 xonefs

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Posted 19 May 2021 - 10:15 PM

If you're comparing two modern sony sensor OSC cameras there won't be a huge difference. The cut off of the stock filter will be the biggest difference on a dslr/mirrorless, but modded I wouldn't expect really much difference since dark current is already so low on these sensors that cooling isn't going to make a big difference.

 

 

If you're spending that much money on a dedicated astro camera I don't really get why you wouldn't just go mono since that's where you will really see a huge performance difference over modded dslr/mirrorless, and you're already giving up the convenience factor of not needing any computer control.


Edited by xonefs, 19 May 2021 - 10:17 PM.


#11 birddog99

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Posted 20 May 2021 - 02:53 PM

Ipalbou stated >>> So to summarize this part: as the 2600MC has good dark/shadow recovery, I agree we should shoot at unity gain (100 or 101 - just in case)

 

 

If I'm not mistaken, unity gain is 0 on the 2600. I use gain 100 because that gives me the lowest readout noise.


Edited by birddog99, 20 May 2021 - 02:53 PM.


#12 gregbradley

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Posted 20 May 2021 - 04:10 PM

I am surprised they look so close in performance. I would have thought the biggest difference would have been Ha sensitivity.

Nikon though, has always been good at getting the best out of Sony's sensors. They seem more able to do so than Sony themselves.

 

Greg.



#13 Astrojedi

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Posted 20 May 2021 - 05:50 PM

I use the asi2600mc quite a bit and have used many DSLRs and other OSC astro cameras as well. I personally find the data produced by the 2600MC to be much better in all respects. The sensor is just very clean and the cooling also makes a huge impact as I can get the dark calibration perfectly matched.

 

Here are a few examples with my EdgeHD 8 @ F10 from my Bortle 8 backyard. These are the best results I have achieved with an OSC from my light polluted backyard in the 15+ years I have been imaging. All these images are less than 2 hours of total exposure time!

 

Whale Glx 57x120s

 

whale_galaxy_f10-mod-lpc-cbg-st-57x120s-

 

NGC5907 45x120s

 

 

ngc5907-mod-lpc-cbg-st-45x120s.jpg

 

M13 28 x 120s

 

m13-mod-lpc-cbg-st-denoiseai-denoise-28x


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#14 Astrojedi

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Posted 20 May 2021 - 06:01 PM

With regards to your post... I think you have 2x the exposure time with the D850 vs. the 2600MC (assuming you used the same optics and f-ratio). Being a less nosier camera I would expect the 2600MC to reach the same SNR in a shorter total exposure time. With sufficient exposure time you can typically overcome many shortcomings of a camera.

 

Another point. The Butterfly is a relatively bright object. If you match optics and exposure times especially on fainter objects the 2600 will significantly pull away vs. the D850 wrt to SNR.


Edited by Astrojedi, 20 May 2021 - 06:01 PM.


#15 Prudentis

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Posted 20 May 2021 - 07:55 PM

Man Astrojedi, how did you process the noise?

I mean, I like the cluster pic better overall, since I find killing all the noise leaves the images looking a bit unnatural. But I still like your galaxies.

It's all subjective, so no critique here. Those are really great images! Care to share your denoising routine? I would not go as aggressive, but I still would like to know, how you achieved this result.

I recently upgraded to a C9.25 and a ToupTek with the same IMX571 sensor, So my source data should be comparable.


Edited by Prudentis, 20 May 2021 - 07:56 PM.

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#16 Astrojedi

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Posted 20 May 2021 - 09:12 PM

Man Astrojedi, how did you process the noise?

I mean, I like the cluster pic better overall, since I find killing all the noise leaves the images looking a bit unnatural. But I still like your galaxies.

It's all subjective, so no critique here. Those are really great images! Care to share your denoising routine? I would not go as aggressive, but I still would like to know, how you achieved this result.

I recently upgraded to a C9.25 and a ToupTek with the same IMX571 sensor, So my source data should be comparable.

Thanks. I use Topaz Denoise AI... best thing since sliced bread... only half joking... smile.png

 

I did overcook the Whale slightly but only because it was shot in poor transparency which gives the background a blotchy look which really bugs me. Even with all this technology there are limits to what you can achieve from a Bortle 8 zone.


Edited by Astrojedi, 20 May 2021 - 09:15 PM.

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#17 lpalbou

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Posted 21 May 2021 - 02:13 AM

@birddog99 that's a good comment. I don't actually know what is the unity gain of the 2600MC even though there is a post about it: https://www.cloudyni...ro-or-100-gain/ . However, as commented on that post, just by looking at the charts of DR and noise, it's clear that in low light / using filters, a gain of 100 is a much better choice.

 

@xonefs that's indeed what I think. Note however this first comparison is with the D850, not so new but still a BSI sensor. With the A7RIV, I would expect a difference mostly in the gathering of Ha due to the filter indeed (I actually finished that, but I will post it a bit later). There is a noise difference between the 2600MC and the A7RIV if using the same exposure time, simply because you have to boost Ha a bit more.. But I will let you all see for yourself. As for the monochrome camera: I agree, my plan is more to continue to have my best DSLR/mirrorless for convenience "rapid shooting/processing" and a monochrome camera to grab the max resolution and have more freedom of balancing the various atomic emissions. I was curious however about the 2600MC as I read so many positive reviews, including from people in light polluted area, so I wanted to see how good it was. Plus, with dual band filters, you are not losing as much time as before compared to a monochrome camera.. but you do are losing some resolution. Anyhow, that's a long discussion to have with a beer smile.gif

 

@gregbradley I was surprised too. Note however the D850 was 4h exposure while the 2600MC was only 1h51. When I finish this review, I will use same exposure time so one can better appreciate the difference of noise. I know the Z6 and Z7 are more sensitive to Ha than the D850.. I don't have the Z7 anymore, but I still have a Z6, so we'll have a comparison of that too. The D850 have been my favorite camera of all time, robust, reliable, fast, great lenses, good pixel size (not too small, not too big). One way I could end this review could be : well actually I will keep my D850 lol.gif . But we are not there yet. And as a preliminary result, it's clear you can still image faster with the 2600MC, but I don't think 4x faster, more like 2x.

 

@Astrojedi I agree the sensor of the 2600MC is very clean.. but I also think it's nearly the same as the A7RIV, just smaller. It's also nice to be able to control the temperature on the 2600MC and have a single / simple dark library. And I believe your pictures is an illustration of something I will see too. It will partially be due to the camera ability to recover dark / highlight and not over expose, but possibly also from the camera color sensitivity. I do believe the 2600MC will have a better color rendition. I also have the C8 edgehd (love it btw, quite versatile with a 0.7x reducer too and not too heavy either). I have imaged both M13 and the Whale galaxy as you, from a Bortle 8 (SF) and my D850 and.. your colors pops up much more. Either you have better processing skills (totally possible), or indeed the 2600MC somehow capture better color gradients. Did you do by any chance M101 or M51 ? I would be curious of the comparison of what I got with my C8 and D850:

 

M51   8h 2000mm final DeNoiseAI Low light 3
 
M101   12h11   PS

 

> "If you match optics and exposure times especially on fainter objects the 2600 will significantly pull away vs. the D850 wrt to SNR."

 

Any proposal of target ? After those tests at 300mm, I was thinking to put back my C8 edgehd and image the Eagle nebula.. one of my favorite, also for sentimental issue.. But from memory, it's even brighter than the Sadr region. I think it's too late for the Bubble nebula too.. The Iris nebula is not Ha but could be a nice test to evaluate dark sensitivity, and I believe in late nights it's starting to rise again above 30°.

 

Anyhow, tomorrow I will be posting the results of the 2600MC vs A7RIV. There will definitely be a few pros and cons to both and at this level, I must say that all will be great performers.. To some extent, I still love my D800e for imaging but it does have more noise, especially if you go over ISO 400. Overall, I also feel like even unmodified camera will perform as good as astro cameras, but will just take longer to capture the same signal. If you are the kind of person to travel to a dark site... then you really want to maximize your time there and an astro cameras will be the way to go, especially if you want to do a marathon night with multiple targets (one of my best memory :) ). If you have a permanent setup... that's another story as you will be able to control the noise pretty well. What I am unsure however is about color rendition.. I get the feeling that astro cameras might be better, but I could be completely wrong. If you have opinions, feel free to share !


Edited by lpalbou, 21 May 2021 - 02:33 AM.


#18 erictheastrojunkie

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Posted 21 May 2021 - 02:06 PM

There quite literally is no point in shooting the ASI2600mc above Gain 100, you get nothing from it and the idea that you need some kind of histogram separation is a relic of the DSLR days. Set the camera to Gain 100 (for narrowband I do 100, for broadband I do 0), calculate your subframe exposure time needed to swamp read noise by a minimum of 3xRN^2 (handy calculator spreadsheet made by StevenBellavia: https://www.cloudyni...w-available/). 



#19 Hobby Astronomer

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Posted 22 May 2021 - 10:42 AM

I use the asi2600mc quite a bit and have used many DSLRs and other OSC astro cameras as well. I personally find the data produced by the 2600MC to be much better in all respects. The sensor is just very clean and the cooling also makes a huge impact as I can get the dark calibration perfectly matched.

 

Here are a few examples with my EdgeHD 8 @ F10 from my Bortle 8 backyard. These are the best results I have achieved with an OSC from my light polluted backyard in the 15+ years I have been imaging. All these images are less than 2 hours of total exposure time!

 

Whale Glx 57x120s

 

whale_galaxy_f10-mod-lpc-cbg-st-57x120s-

 

NGC5907 45x120s

 

 

ngc5907-mod-lpc-cbg-st-45x120s.jpg

 

M13 28 x 120s

 

m13-mod-lpc-cbg-st-denoiseai-denoise-28x

bow.gifbow.gifbow.gifbow.gifbow.gif 



#20 bobzeq25

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Posted 22 May 2021 - 11:27 AM

 I get the feeling that astro cameras might be better, but I could be completely wrong. If you have opinions, feel free to share !

Astro (one shot color) camera have two advantages.

 

The first is that thermostatically controlled cooling lets you do good darks.  Darks are chancy with DSLRs, because the sensor temperature is far from constant, no matter what.  So much so that it may be counterproductive to take darks with a DSLR.  One thing that means is that saving a few hundred dollars by buying an uncooled astro camera throws away much of the advantage of getting one.

 

The second is that quantum efficiencies of astro cameras are _usually_ significantly better than quantum efficiencies of DSLRs. Manufacturers of DSLRs have little motivation to design for quantum efficiency, the signal to noise ratio in terrestrial imaging is generally much greater.

 

Color is far more a matter of processing skill than type of camera.  The Bayer matrix filters on astro OSC cameras are just as bad as the ones on terrestrial cameras.   The device was designed to make cheap terrestrial cameras that will sell (hence the choice of 50% green pixels that slop over into red and blue.  People like green in their terrestrial photography, most astro specific processing programs have specific tools to reduce excess green from OSC cameras) .

 

I find mono with RGB filters makes color processing significantly easier.  Not saying it can't be done with OSC, just that it requires more skill and is harder.


Edited by bobzeq25, 22 May 2021 - 11:33 AM.



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