Combining OSC with Mono

It definitely works. I did it briefly in the past.

For narrowband work I would use a dual band filter, extract the HA and OIII using APP, then stack it with the HA and OIII from the mono camera.

For broadband work I would extract the RGB from the OSC data using APP and then stack with the mono RGB.

Ultimately I ended up ditching the OSC though because of the low efficiency.

This is a bit of a rabbit hole, but generally speaking there are spatial resolution losses because of the CFA array on OSC cameras. There's also quite noticeable losses in light gathering behind the CFA filters compared to the same colour filter on a mono camera (on a per pixel level with the same colour filter).

Then there's the fact that mono can capture across the entire spectrum on all pixels simultaneously with usage of a luminance filter. This is impossible with OSC.

I have done some direct comparisons between 533MC and 533MM myself (on the exact same telescope) with the same target and roughly similar sky conditions. The MM beats the SNR of the MC in 1/3 the exposure time.

So based on my experience it's almost always easier from a imaging logistics perspective and a processing complexity perspective to just sell the 533MC and buy LRGB filters. And I'm not even going to get into the difficulties in getting OSC colors to calibrate correctly without a green bias (it has consumed dozens of hours of my time attempting to get it look as good as mono without ever being completely satisfyingly).

Modern software (NINA and PixInsight) makes managing the extra filters trivial and completely automated.

It certainly can work (using OSC RGB and Mono Lum). However as I've alluded to, my experience proves practically that Mono RGB is always superior from an efficiency and image quality perspective.

If I remember to do so tomorrow, I will provided raw real-world examples that I have captured which demonstrates this point.

Wei-Hao Wang:
I can provide real word example of mono RGB vs OSC.  The mono is even cooled, and the OSC uncooled.

Take a look at the first post here without further reading down:
https://www.cloudynights.com/topic/858009-cooled-mono-astro-camera-vs-modified-dslrmirrorless/
And guess which one is OSC, which one is mono.  Same exposure time, same scope, same condition.

Did you guess right?

*** its compelling and i coudnt separate the two ***

I do it constantly. I started off with a OSC (QHY268C). However, I quickly realised the limitations using dual narrowband filters with OSC and bought a Mono as well (QHY268M). Now I use the OSC for my star colours, RGB imaging in general and the Mono for LUM and narrowband, or feeding my OSC with Ha etc. This works very well for me. However, I cannot make any statements of how much I "lose" not doing RGB with M as well (I am not having any RGB filters, so cannot test).

The advantage using OSC for me is, that at the end of a session, I have a set of data. My weather conditions are poor and I have very limited imaging time, so at least after one session I have some data to play around with (with M - I already have some projects sitting there waiting for next year to be continued…) . I have no calibration issues using OSC, PI does this for me, no rotation issues, NINA sorts this out and combining both works very well.
CS, Rob

Coolhandjo:

Wei-Hao Wang:
I can provide real word example of mono RGB vs OSC.  The mono is even cooled, and the OSC uncooled.

Take a look at the first post here without further reading down:
https://www.cloudynights.com/topic/858009-cooled-mono-astro-camera-vs-modified-dslrmirrorless/
And guess which one is OSC, which one is mono.  Same exposure time, same scope, same condition.

Did you guess right?

*** its compelling and i coudnt separate the two ***

Wei-Hao shared this on another thread on CN. It is definitely possible to guess which is which, if you understand the underlying characteristics of the kind of noise and signal profile each sensor.  I've spent a lot of time analyzing a lot of image data from a lot of people over the years, which gives some insight into what the data looks like from each kind of camera. CCD vs. CMOS, mono vs. OSC, etc. I was able to guess which was which (I will not provide the answer here) based on two key factors:

1. Noise characteristics
2. Color characteristics

OSC can do very well, and its efficiency depends on the Q.E. of the sensor, and the nature of the OSC filters. Not every OSC camera is the same from a filter standpoint. Some use richer color dyes in the CFA, some use weaker. The richer the dyes, the more narrow the bandpasses will usually be, and the more pure the color from each, while the weaker, the more bell-curve shaped and overlapped the filters will be, and how pure the colors in each will be. Filter transmission in OSC is lower than a lot of RGB filters used with monochrome cameras, however...most of the time those filters are interference filters, which provide just about 100% transmission but have hard-edged cutoffs for bandwidth. OSC filter bandpasses usually overlap, and the greater the degree of overlap, the wider the bandpasses, the more light passes through. OSC's lower CFA transmission is usually offset somewhat or wholly by passing more light per channel. 

OSC for RGB and mono for NB can certainly work great! My recommendation would in fact be to use Bayer Drizzle to integrate your OSC RGB data. That will distribute the OSC color data into a final integration in a manner that will produce a noise profile more similar to the NB mono data, which should produce a better noise profile in the end once you combine them. You do not necessarily need to increase the resolution while drizzling, its just that the way bayer drizzle works it distributes the information in such a way that produces a different kind of noise profile than normal debayering algorithms do. 

Now, all the above said, OSC under light polluted skies, is not necessarily the best option. If you have the ability to use dark skies, or better LIVE under dark skies, then OSC is great, especially bayer drizzled, and it will combine fine with mono NB data. However I've always found that OSC under light polluted skies ends up being more effort than its worth. The overlapping bandpasses can complicate LP issues, gradients are usually not just simple linear brighter to darker gradinets that are easy to remove, but instead often involve complex multi-scale structured complexity that makes them a real pain to remove. If you do live under light polluted skies, not because of any inherent inefficiency in "all" OSC cameras, but just because of the way their filters work and overlap, you might be better off selling the OSC camera, and replacing it with another mono camera and just doing RGB imaging with that, while you do NB imaging with the other (if you can image with both at the same time.) Mono channels will allow you to deal with gradients in each channel independently, which is often easier than trying to unravel them from all the overlapping channels of OSC.

Combining OSC and mono data definitely works (almost all my recent images are made like that, they are not IOTD , but are reasonable I think) Yes, the color resolution of OSC  is worse, yes mono is faster, but if you have two setups one with mono one with OSC, combination is possible. I am running 2setups in parallel imaging the same target. I get RGB images (stars) and dualband from OSC and for example narrowband from mono and combine dualband and narrowband. Would it be better if done on 2 mono cameras? Most likely, but I do not have 2 mono setups. The other way to combine is to do luminance on mono and RGB on OSC.  If you do not plan to use 2 cameras in parallel , than  it is perhaps the best to sell OSC and buy mono and filters, or do nothing as with your current camera you can make  nice images (takes a bit more time though)

Coolhandjo:
I am wondering if anyone would recommend combining OSC data with Mono data. in particular OSC for RGB and Mono for Narrowband Ha Oii Sii?

I have a 533mcpro and want to get a 533 mm pro. trying to do away with rgb filters for the MM and simply combine.

Anyone has any examples or techniques on how that would be good?

Joe, I am curious what your skies are like? Do you live under dark skies, or light polluted skies? 

Also, I'm curious what your ultimate goals are in the long run with combining OSC data with NB data. Depending on exactly what kind of skies you have, this can work exceptionally well, well, or it could be that low quality OSC data might not be worth the effort. 

Your images appear to be pretty good, and it looks like most were created with the MC camera. Based on that, and the IQ, I'm going to assume you at least live under reasonably dark skies, even if they are a little light polluted. Given that, I think OSC could work very well for you, unless I've just totally misjudged your skies. IMO, OSC can produce some of the best images around under dark skies, with a better diversity of color than your standard mono+LRGB or even mono+RGB (if they are standard square-cutoff interference filters). Mono might surpass, if you use a better set of filters, something that overlaps, like the J-C BVR filters or maybe Astronomik Type-2c.

With reasonably dark skies, I think you could do some amazing things with your MC for RGB and an MM+NB filters for the rest.

There's also quite noticeable losses in light gathering behind the CFA filters compared to the same colour filter on a mono camera (on a per pixel level with the same colour filter).

I don't think this is accurate. Remember that the transmission curves for the mono color filters have to be multiplied with the QE of the mono sensor. When you do this. and consider that the bandpasses of the RGB filters in the OSC have overlap and are wider than the sharp cutoffs you see in the mono color filters, at least some analyses show an efficiency advantage for OSC for RGB (note: not LRGB) imaging. See for example, John Upton's posts on CN from a few years ago. Obviously, it would depend on the specific OSC under consideration, but I think the Sony sensors do have significant spectal overlaps.

In answer to the OP's question, I have used the combinations both for LRGB ( L from Mono and RGB from OSC) and H-alpha from Mono and RGB from OSC, and have generally been satisfied with the results. The broader OSC bandpasses work against you if you are imaging from a light polluted site, so the best use for the OSC would be if you are imaging from or have access to a dark site.

Jon Rista:

Coolhandjo:
I am wondering if anyone would recommend combining OSC data with Mono data. in particular OSC for RGB and Mono for Narrowband Ha Oii Sii?

I have a 533mcpro and want to get a 533 mm pro. trying to do away with rgb filters for the MM and simply combine.

Anyone has any examples or techniques on how that would be good?

Joe, I am curious what your skies are like? Do you live under dark skies, or light polluted skies? 

Also, I'm curious what your ultimate goals are in the long run with combining OSC data with NB data. Depending on exactly what kind of skies you have, this can work exceptionally well, well, or it could be that low quality OSC data might not be worth the effort. 

Your images appear to be pretty good, and it looks like most were created with the MC camera. Based on that, and the IQ, I'm going to assume you at least live under reasonably dark skies, even if they are a little light polluted. Given that, I think OSC could work very well for you, unless I've just totally misjudged your skies. IMO, OSC can produce some of the best images around under dark skies, with a better diversity of color than your standard mono+LRGB or even mono+RGB (if they are standard square-cutoff interference filters). Mono might surpass, if you use a better set of filters, something that overlaps, like the J-C BVR filters or maybe Astronomik Type-2c.

With reasonably dark skies, I think you could do some amazing things with your MC for RGB and an MM+NB filters for the rest.

*** T
Thanks Jon. I live in Bortle 4 east Bortle 5 zenith Bortle 6 west becuase I live on the coast so i have fairly dark sky as you deduced! YOur rsponse helps a lot! ***

Coolhandjo:

Jon Rista:

Coolhandjo:
I am wondering if anyone would recommend combining OSC data with Mono data. in particular OSC for RGB and Mono for Narrowband Ha Oii Sii?

I have a 533mcpro and want to get a 533 mm pro. trying to do away with rgb filters for the MM and simply combine.

Anyone has any examples or techniques on how that would be good?

Joe, I am curious what your skies are like? Do you live under dark skies, or light polluted skies? 

Also, I'm curious what your ultimate goals are in the long run with combining OSC data with NB data. Depending on exactly what kind of skies you have, this can work exceptionally well, well, or it could be that low quality OSC data might not be worth the effort. 

Your images appear to be pretty good, and it looks like most were created with the MC camera. Based on that, and the IQ, I'm going to assume you at least live under reasonably dark skies, even if they are a little light polluted. Given that, I think OSC could work very well for you, unless I've just totally misjudged your skies. IMO, OSC can produce some of the best images around under dark skies, with a better diversity of color than your standard mono+LRGB or even mono+RGB (if they are standard square-cutoff interference filters). Mono might surpass, if you use a better set of filters, something that overlaps, like the J-C BVR filters or maybe Astronomik Type-2c.

With reasonably dark skies, I think you could do some amazing things with your MC for RGB and an MM+NB filters for the rest.

*** T
Thanks Jon. I live in Bortle 4 east Bortle 5 zenith Bortle 6 west becuase I live on the coast so i have fairly dark sky as you deduced! YOur rsponse helps a lot! ***

From the static viewpoint of a camera sensor, its really tough to get better than Bortle 4. That is my own dark site...unless I point due west into the Denver LP bubble. Due to variations in airglow, its pretty rare, at least as far as I've found tromping around the Colorado front range and plains for years, to get much darker than about 21.5mag/sq", even hundreds of miles from any big city. The difference of half a stellar mag, doesn't make a lot of difference to a camera sensor, and a full mag when you are already at a dark site, makes a minimal difference. You should be able to make the most of both cameras, IHMO.

Jon Rista (jrista)

Coolhandjo:

Jon Rista:

Coolhandjo:
I am wondering if anyone would recommend combining OSC data with Mono data. in particular OSC for RGB and Mono for Narrowband Ha Oii Sii?

I have a 533mcpro and want to get a 533 mm pro. trying to do away with rgb filters for the MM and simply combine.

Anyone has any examples or techniques on how that would be good?

Joe, I am curious what your skies are like? Do you live under dark skies, or light polluted skies? 

Also, I'm curious what your ultimate goals are in the long run with combining OSC data with NB data. Depending on exactly what kind of skies you have, this can work exceptionally well, well, or it could be that low quality OSC data might not be worth the effort. 

Your images appear to be pretty good, and it looks like most were created with the MC camera. Based on that, and the IQ, I'm going to assume you at least live under reasonably dark skies, even if they are a little light polluted. Given that, I think OSC could work very well for you, unless I've just totally misjudged your skies. IMO, OSC can produce some of the best images around under dark skies, with a better diversity of color than your standard mono+LRGB or even mono+RGB (if they are standard square-cutoff interference filters). Mono might surpass, if you use a better set of filters, something that overlaps, like the J-C BVR filters or maybe Astronomik Type-2c.

With reasonably dark skies, I think you could do some amazing things with your MC for RGB and an MM+NB filters for the rest.

*** T
Thanks Jon. I live in Bortle 4 east Bortle 5 zenith Bortle 6 west becuase I live on the coast so i have fairly dark sky as you deduced! YOur rsponse helps a lot! ***

From the static viewpoint of a camera sensor, its really tough to get better than Bortle 4. That is my own dark site...unless I point due west into the Denver LP bubble. Due to variations in airglow, its pretty rare, at least as far as I've found tromping around the Colorado front range and plains for years, to get much darker than about 21.5mag/sq", even hundreds of miles from any big city. The difference of half a stellar mag, doesn't make a lot of difference to a camera sensor, and a full mag when you are already at a dark site, makes a minimal difference. You should be able to make the most of both cameras, IHMO.

*** here is my sky showing the difference in Bortle***