I'm about to purchase the ASI2600MC Pro and I got to thinking, should I go mono now, or wait. I have been at this a year and have been shooting OSC with an ASI294MC Pro and I like the results, but I think I may want to step it up a notch, even though I still have much to learn. So, should I continue as is, or step it up? With any suggestions to step it up, please include your preferred LRGB filter set. Preferably something less than $1000, but don't let that stop you. Any good reasons to continue shooting OSC are welcome also, such as obtaining more skills before I move on.
To mono, or not to mono... That is the question.
Engaging
I recently got into that question. I mean quite a lot… I was just like you, about to get ASI2600MC. I eventually ended up holding my ASI2600MM yesterday. I checked every possible comparison that has been done and shared. The theoretical explanations are far away from the practical results, in general. Mono always makes a difference, but that difference is not always so pronounced. But minor differences at top levels make the difference. So I'll not say what has already been said many times.
I'm an astrophysicist and I'm interested in more than just nice pictures. Mono gives me that flexibility, so that was one reason. The other reason though is that, although it is not mentioned too much, mono gives you more flexibility in astrophotography as well. For example, I like shooting IFN structures or dark nebulae. Being able to shoot more L than RGB to reveal more of those structures, and get a better SNR is quite a deal. Thing are different on paper and there is a lot of discussion. But as a theoretical astrophysicist, I value what the actual results are. Because a theory should be consistent with the observations. For MONO vs OSC discussion, there is a big inconsistency. That is due to the fact that, details play a major role. So, I checked quite a lot of actual results. Go ahead and search for ASI2600MC and ASI2600MM on same objects with same conditions. You'll start noticing real differences. With OSC, you are more limited to what is built in. It is convenient for many users, I agree with that. But I always like to have the freedom to choose what I'll shoot. The only reason I'd choose OSC would be the cost.
For the filters, I chose Antlia LRGB-V Pro and Antlia NB Pro series. The problem with these is there is no standard and you may just end up with unlucky filters (low QE due to shift in the spectrum). But I have access to a spectrometer to measure what I get. If I was looking for a good quality, I'd go for Chroma NB and stick with Antlia LRGB.
I'm an astrophysicist and I'm interested in more than just nice pictures. Mono gives me that flexibility, so that was one reason. The other reason though is that, although it is not mentioned too much, mono gives you more flexibility in astrophotography as well. For example, I like shooting IFN structures or dark nebulae. Being able to shoot more L than RGB to reveal more of those structures, and get a better SNR is quite a deal. Thing are different on paper and there is a lot of discussion. But as a theoretical astrophysicist, I value what the actual results are. Because a theory should be consistent with the observations. For MONO vs OSC discussion, there is a big inconsistency. That is due to the fact that, details play a major role. So, I checked quite a lot of actual results. Go ahead and search for ASI2600MC and ASI2600MM on same objects with same conditions. You'll start noticing real differences. With OSC, you are more limited to what is built in. It is convenient for many users, I agree with that. But I always like to have the freedom to choose what I'll shoot. The only reason I'd choose OSC would be the cost.
For the filters, I chose Antlia LRGB-V Pro and Antlia NB Pro series. The problem with these is there is no standard and you may just end up with unlucky filters (low QE due to shift in the spectrum). But I have access to a spectrometer to measure what I get. If I was looking for a good quality, I'd go for Chroma NB and stick with Antlia LRGB.
If you have a lot of dark nights then maybe. If anything like me you won't or do it only sporadically.
Frankly the only advantage to OSC over mono is cost. Convenience is also another issue especially if you are using systems that can't incorporate an EFW, like a RASA / Hyperstar, where you have to manually change filters
Integration time for a mono system is not any more than an OSC for equivalent SNR. If anything you should achieve better results with Mono system for the same integration time as an OSC.
Integration time for a mono system is not any more than an OSC for equivalent SNR. If anything you should achieve better results with Mono system for the same integration time as an OSC.
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Ashraf AbuSara:
Integration time for a mono system is not any more than an OSC for equivalent SNR. If anything you should achieve better restuls with Mono system for the same integration time.
Only if you doing luminance and LRGB composition otherwise you won't. Assuming you are doing true colors, at any rate.
andrea tasselli:Ashraf AbuSara:
Integration time for a mono system is not any more than an OSC for equivalent SNR. If anything you should achieve better restuls with Mono system for the same integration time.
Only if you doing luminance and LRGB composition otherwise you won't. Assuming you are doing true colors, at any rate.
That's true. Only if you use LRGB. That's the primary advantage to mono.
If I had only two hours of clear skies for example, I would rather do 60 minutes of L, and 20 minutes of each RGB filter over two hours of OSC.
Ashraf AbuSara:
If I had only two hours of clear skies for example, I would rather do 60 minutes of L, and 20 minutes of each RGB filter over two hours of OSC.
I'm just the opposite but then I don't fancy LRGB for a number of reasons. To each his/her/their own I suppose...
andrea tasselli:
I'm just the opposite but then I don't fancy LRGB for a number of reasons. To each his/her/their own I suppose...
I agree to each their own. But I am just curious what other reasons? Just like to know the prespective.
This question, mono vs OSC, pops up here regularly 
Look at older threads. Mono gives you flexibility, OSC gives you convenience. For a broadband target there is no practical difference between RGB mono and OSC.
Of course you can shoot L with a mono camera in order to increase SNR. However an L image will include all chromatic aberrations of the scope and atmospheric dispersion leading to a lower resolution compared to RGB.
You should decide for yourself what you priorities are. This depends mostly on your preferred targets and desired result. If you plan to shoot emission nebulae then there is no way around mono.
I am happy with my OSC setup because I prefer to image galaxies and star clusters, i.e. broadband targets, and like to get fine details.
Look at older threads. Mono gives you flexibility, OSC gives you convenience. For a broadband target there is no practical difference between RGB mono and OSC.Of course you can shoot L with a mono camera in order to increase SNR. However an L image will include all chromatic aberrations of the scope and atmospheric dispersion leading to a lower resolution compared to RGB.
You should decide for yourself what you priorities are. This depends mostly on your preferred targets and desired result. If you plan to shoot emission nebulae then there is no way around mono.
I am happy with my OSC setup because I prefer to image galaxies and star clusters, i.e. broadband targets, and like to get fine details.
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We had a very extensive discussion about that here on AB few weeks ago, if you recall. My own take is that for a LRGB composition to have the same chromatic dynamic range than an equivalent RGB composition you essentially need to have the same dynamic range in all four channels at which point there is very little point in doing it for efficiency reasons. Anything less and you are already compromising, which might be all right (and I did and do it know for time/cost constraints) but I consider that less than ideal. And I also like the aesthetic purity of RGB or HOO compositions (bit less SHO) but you get my drift here. Let's face it, LRGB is a clutch devised in a time when CCDs and digital imagery was in its infancy and anything that saved time was readily accepted by the community so you traded spatial resolution for chromatic depth and call it a win.
A major point for me to add an OSC to my equipment, after shooting mono for quite a while, was the weather. A streak of clear nights has become extremely rare and so it frequently happened to me that I ended up with stories like: "I've got the L and R data, but only 50% of G that I wanted and none in B."… Nothing that allowed me to make an image out of it. The OSC gives me the convenience of just capturing and capturing and capturing and with higher probability, I end up with a (not so bad) image.
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The likelihood is high there would be less and less stable weather, at mid-latitudes at least, as the atmosphere and the oceans experience global warming. It might not end well…
Is there a reason why folks are not rotating through their filters during an imaging session plan? I typically set my sessions to rotate between each R/G/B filter every 30-60 minutes depending on the forcast. You can do it every 15 minutes if you like.
With parafocal filters and filter offsets refocusing should not be necessary and it only takes a few seconds to do this with an EFW. I rarely end up with an imaging session that does not have a relatively balanced set to work with.
With parafocal filters and filter offsets refocusing should not be necessary and it only takes a few seconds to do this with an EFW. I rarely end up with an imaging session that does not have a relatively balanced set to work with.
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Vitali:
Of course you can shoot L with a mono camera in order to increase SNR. However an L image will include all chromatic aberrations of the scope and atmospheric dispersion leading to a lower resolution compared to RGB.
Why would your OSC image not suffer from CA and atmospheric dispersion just as much as an L image?
Vitali:
Of course you can shoot L with a mono camera in order to increase SNR. However an L image will include all chromatic aberrations of the scope and atmospheric dispersion leading to a lower resolution compared to RGB.
I'm not sure if I can follow this argument. Do you mean OSC by saying RGB? Because OSC camera will also capture those chromatic aberrations and atmospheric dispersion as well. If this is a matter of how broad the spectrum is, some L filters are narrower than what OSC has as a built-in UV/IR, providing mono a better resolution than OSC. So again, mono has the flexibility advantage here. Am I missing something?
Engaging
Sound like me 18 months ago.
Bought an 2600mc, used it a bit, always had the feeling to miss out, sold it and bought a 2600mm.
Cs
andi
Bought an 2600mc, used it a bit, always had the feeling to miss out, sold it and bought a 2600mm.
Cs
andi
Kay Ogetay:
I'm not sure if I can follow this argument. Do you mean OSC by saying RGB? Because OSC camera will also capture those chromatic aberrations and atmospheric dispersion as well. If this is a matter of how broad the spectrum is, some L filters are narrower than what OSC has as a built-in UV/IR, providing mono a better resolution than OSC. So again, mono has the flexibility advantage here. Am I missing something?
First and foremost, some OSC cameras have built in UV/IR filter and some other don't. And do I really have to explain that the ~300 nm width of a typical L filter is much wider than the typical band-pass of the organic-dye filters in an OSC camera? As far as resolution is concerned you'll find that most of the high resolution planetary images out there are taken with OSC cameras so there you go.
Thanks for all the replies. Keep 'em coming. I'm almost over my urge, mono may be a nono… for now.
DavesView:
Thanks for all the replies. Keep 'em coming. I'm almost over my urge, mono may be a nono... for now.
Do it man! It's fun... just do it, switch!
Ashraf AbuSara:
Why would your OSC image not suffer from CA and atmospheric dispersion just as much as an L image?
Kay Ogetay:
Do you mean OSC by saying RGB? Because OSC camera will also capture those chromatic aberrations and atmospheric dispersion as well.
Andrea Tasselli already answered this. R, G and B filters, either built-in OSC or filters for mono, have narrower pass-band compared to an L filter. Therefore OSC and RGB suffer less from CA and dispersion
BTW, here is an useful article about atmospheric dispersion: https://www.damianpeach.com/images/articles/JBAA%20dispersion%20Peach.pdf
Jure Menart:DavesView:
Thanks for all the replies. Keep 'em coming. I'm almost over my urge, mono may be a nono... for now.
Do it man! It's fun... just do it, switch!
🤣 If I were to make my decision based on your finished products, I'd switch, no questions asked. Good stuff!
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Vitali:Ashraf AbuSara:
Why would your OSC image not suffer from CA and atmospheric dispersion just as much as an L image?Kay Ogetay:
Do you mean OSC by saying RGB? Because OSC camera will also capture those chromatic aberrations and atmospheric dispersion as well.
Andrea Tasselli already answered this. R, G and B filters, either built-in OSC or filters for mono, have narrower pass-band compared to an L filter. Therefore OSC and RGB suffer less from CA and dispersion
BTW, here is an useful article about atmospheric dispersion: https://www.damianpeach.com/images/articles/JBAA%20dispersion%20Peach.pdf
The paper in question is talking about planetary imaging and atmospheric dispersion. Which is interesting because even Damien Peach supports using monochrome system for Planetary imaging.
I would like to see more supportive practical evidence that an L image suffers from lower resolution than an OSC image for long exposure DSO photography. Theoretically, the Red / Blue images in your OSC camera are each using 25% of your sensor's pixels, while your green filter is using 50% of your sensor's pixels. Can't imagine the Bayer matrix configuration produces a higher resolution than a Luminance image for DSO photography.
I mean it is a really important point if OSC images are truly higher resolution than LRGB images. But need more evidence to it.
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I think you know that with CFA drizzle you regain most of the lost spatial resolution (if the appropriate technique is followed) at the price of a reduction of SNR. So, in that sense, L can potentially deliver better resolution at higher SNR than OSC and filtered (NB) imagery even better resolution at the price of loss in chroma information. RGB imagery with filters can potentially out-resolve CFA drizzle but not with equal integration times and thus SNR.
Atmospheric dispersion does play a role in loss of resolution as a function of altitude and this independently from whether you are shooting planetary or deep sky, it only depends on the image scale.
If you browse in the AB posts I think there were interesting contributions comparing LRGB and OSC results in equal terms.
Atmospheric dispersion does play a role in loss of resolution as a function of altitude and this independently from whether you are shooting planetary or deep sky, it only depends on the image scale.
If you browse in the AB posts I think there were interesting contributions comparing LRGB and OSC results in equal terms.
Ashraf AbuSara:
Theoretically, the Red / Blue images in your OSC camera are each using 25% of your sensor's pixels, while your green filter is using 50% of your sensor's pixels.
Right, this is why drizzle integration with scale 1x must be used for OSC frames in order to get the native resolution of the sensor.
For broadband, I would say mono gives a 20% better result when eveything clicks in just right. And needs maybe 80% more fuss overall to make it so.
Cheers,
Dimitris
Cheers,
Dimitris