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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 |
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The decision was simple for me when I started, and the budget was there. Mono all the way to isolate the desired signal with the appropriate filters without workarounds. The single disadvantage I found so far: A comet that is moving too fast. |
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I think, this discussion can provide an endless list of pro´s and con´s for each option - OSC or Mo I do both but due to the local weather conditions, I prefer to do OSC for galaxies and clusters. For nebulae and similar targets, I use my mono cameras. The main reason is, that where I live, clear nights are rather rare since about one year ago and using mono, I would be afraid not to get enough integration time for LRGB unless I concentrate on just one target for about two or three months. 240 minutes clear sky - at least in my personal opinion results in overall better results that 120minutes L plus 3x40 minutes RGB. Not to forget, that mono with filters means at least after filter change refocusing - that also takes some time away. But maybe I try it out - one target and same total time - one time with OSC and one time with monoLRGB - maybe I would say after seeing the results - sorry, I was wrong... And yes - with my RASA, I must say, I am not very happy to change filters during the night, often I use an OSC plus a two- or three wavelengths filter. Again - my personal view only. |
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I bought an ASI2600MC and have only shot OSC. I come from a photography background but since astrophotography is not my profession and I live in skies that experience a lot of fog, I decided to go OSC. For a professional astronomer who is doing research and real science, I can see why a mono camera is a little better for that. I see great images taken with mono and I see mediocre images taken with mono. Same with OSC, I see wonderfully sharp, detailed images and I see images that are out of focus, weird colors and generally low quality. Image quality, besides residing in the mount, sky conditions and optics, are also much determined by post-processing skills. I see images that appear to have excellent data, but someone cut corners in the post-processing and didn't pay attention to contrast. I think the worth of an opinion about astrophotographic tools and techniques can be be resolved by looking at the person's images who is sharing that opinion. If you think they're wonderful, pay attention and learn. If you think the images are not so great, seek advice elsewhere. I'm just emerging from being a complete beginner at astrophotography but am satisfied I am making good progress. The big question for me is whether I want to tackle remote imaging or whether I want to continue shooting from my backyard and a dark sky spot 3 hours away. |
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andrea tasselli: I think I found the thread you are referring to: https://www.astrobin.com/forum/c/astrophotography/deep-sky-processing-techniques/combining-osc-with-mono/?page=1 Seems like I missed it. I will read through it seems juicy. |
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Vitali:Ashraf AbuSara: Right, and that helps it recover the majority of the resolution back. But I honestly don't think I have ever seen the claim that you get finer details with an OSC over an LRGB mono image. People spend tons of $$$ to get even the slimmest advantage possible on maximizing their fine details, which makes me wonder why most folks who are posting broadband images using long focal length large and expensive OTAs under remote dark skies are not all using OSC sensors instead of Mono sensors. Just to be clear, I'd happily concede this if there is any direct comparison or evidence, not just theory. I am even tempted to get a 2600mc just to try to do an apples to apples comparison with my 2600mm with chroma filters. The only limit is I am working from light polluted backyard, and galaxy season has worse seeing conditions. P.S. Your galaxy images are truly stunning. Your colors are also fantastic. How are the seeing conditions from your remote site in spain? |
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To mono is not the question, it is the answer. All the arguments claiming to only go mono if you have alot of dark nights is wrong. Mono is more efficient, and don't let anyone tell you otherwise. It's a very old argument, and one that frankly I'm tired of trying to explain to folks only to be overrun by the die hard OSC fans. Advances in camera tech have made OSC alot better than it used to be, but it's still not the same. |
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Brian Puhl: I had an idea for a single word that explains die hard Mono fans: monomaniacs!!!!  probably very silly joke, idk... |
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| Lol, I'm fine with that. |
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Brian Puhl: Cool! Now let's go fish that boat of yours. |
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andrea tasselli:Kay Ogetay: First of all, you do not have to explain anything at all. Especially if a genuinely asked question bothers you. I'd not like to upset anyone for asking questions to learn. I'm sorry if it upset you. Second, I do not refer to a typical L filter. Take Astronomik L3 as an example. Isn't this narrow enough? What is the range of spectral response of ASI2600MC? When I check the cut window, I don't think this is any narrower than L3. Am I wrong? Because in that case, I'd wonder what stops us from manufacturing such L filters (or using the same UV/IR that OSC have). Let's take the discussion to a more scientific level. How much would be the difference (if it exists) and how much effect would it have (between narrow L filters and OSC)? I do not think it would be even pronounced in good optics that an ASI2600MM owner would have. And for Damian, I think @Ashraf AbuSara made my point. To add to the drizzle, I believe Tim Hawkes did a great job analyzing that and nothing more to add to the discussion here. This was the post that convinced me to buy mono: https://www.astrobin.com/forum/c/astrophotography/deep-sky/dual-narrowband-filterosc-vs-hao3-filtersmono-comparison/?page=5 I also have to say that the word "recover" for drizzle bothers me as it is still an interpolation of data. But for practicality, I think we can ignore my nit-picky semantics. |
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| I think a good test for anyone is to look at their recent work and check how many projects they have with more than 4-5 hours total integration. If the are none, stay with color, otherwise go mono. |
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Rafał Szwejkowski: I shan't think so. |
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Kay Ogetay: Very good read on the subject. I may have been swayed. Much to consider. |
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Rafał Szwejkowski: That makes sense to me. I live near the Pacific ocean and fog and wind are a given here. It's very hard for me to find even 2 consecutive nights where I can image. I'd love to have a permanent setup where I can take 10-20 hour images or longer, but I don't, so I am forced to stick to 3-6 hour images. |
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Rafał Szwejkowski: While Andrea doesn't agree and I think I know why (plenty of mono pics with little integration time, yet outstanding work), it made me think. So I looked at my average integration time and it is about 6 hours and growing. My int. time is increasing as I am not so quick to process after a year in the hobby and look to get as much time on a target as possible. When I first started, I was finalizing pictures with maybe 30 subs, some less. One partial to whole night and I was done. My last two were 17 hours and 11 hours. So your statement, albeit one of contention and not a primary reason for switching, is a valid point for me. |
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If you can afford it, keep the 294MC and buy a 2600MM. Then you have the option of both. If mono doesn't work out, sell both cameras and get a 2600MC.. |
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Dunk: I've decided. The MM takes the cost from $1499 with a 2600MC to approximately $2958. I'll put the 294MC, OSC filters and current filter wheel on my RedCat51 permanently (USC) and go mono on my FLT91. EDIT: I forgot a set of Ha/OIII/SII filters in my figure which adds another $700, or so. |
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| FWIW, I have a 294MM and 294MC and 2 rigs. Its great to have the option to do both... |
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Ashraf AbuSara:Vitali:Ashraf AbuSara: Mono always wins, all other things being equal. At the limit, with every conceivable extrapolation and whatnot, the best you can hope for with OSC is to approximate mono's resolution almost at 100% (but not quite). There is no question about that. However, it is possible that mono will do worse due to some things not being equal. An example that springs to mind is that in OSC all colors benefit equally from an interval with very good seeing and very good transparency, say an hour between 22:30 and 23:30. If you were doing RGB with an identical rig side by side with the OSC one, it could well be the case that all that hour is taken up by one colour, taxing the resolution and quality of the other two far more than the Bayer matrix does. |
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Ashraf AbuSara:Vitali:Ashraf AbuSara: Drizzle integration produces a full resolution image if frames are sufficiently dithered. There is no interpolation involved. Consider R pixels which occupy 25% of the sensor. In order to get a full resolution image we need 4 frames. We take one frame, then shift the sensor 1 pixel to the right and take the second frame, then shift the sensor 1 pixel down for the third frame, and then 1 pixel to the left for the forth. If these 4 frames are combined, the resulting frame is completely covered with red pixels. In practice the dithering will shift the sensor randomly in a hope that these red pixels will cover the entire frame and drizzle integration will be able to fill every master pixel with information about red channel intensity. I claimed that a RGB master light with aligned channels will have finer details compared to an LRGB master, because L resolution is lower than resolution of each separate channel. This comparison can be done with a mono camera. You could compare FWHM of a L master with a G master. Just make sure that sky conditions are the same (for example take the data as LLGGLLGG....) and that the pixel scale is small enough, less than 1" per pixel at least. OSC is practically equivalent to imaging RGB with 25% R, 50% G and 25% B frames. Difference will be caused by the fact that R, G an B filter pass bands are not equal to OSC filters. Of course it is necessary to use CFA drizzle for the master light. PixInsight has a correct OSC workflow which produces R, G and B masters using drizzle integration. Mono camera gives people flexibility to take for example 1/3R, 1/3G and 1/3B frames, use narrow bands filters, etc. OSC obviously does not give you that. I guess that is why people choose mono cameras for their $$$ observatories. Taking L in such case means that you can't maximize fine details, it is a compromise. Of course if you OK with this compomise, then taking L is fine. Everyone decides for himself. I can't thank PixInsight enough for their color calibration tool! I use it for my images because I do not see colors right  The seeing at my current remote site varies a lot. Usually FWHM is about 2.1". Best was 1.6". The worst was 6". I keep frames with FWHM less than 2.8. This is a SCT scope so FWHM is worse than with a refractor. |
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Vitali: Thanks for the detailed answer @Vitali . I'm curious how much this hope turns into reality. Because from the tests I posted on my previous answer (here it is again, see Tim Hawkes' replies: https://www.astrobin.com/forum/c/astrophotography/deep-sky/dual-narrowband-filterosc-vs-hao3-filtersmono-comparison/?page=5), it doesn't occur to me as good as anticipated. What are your thoughts on that? |
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Kay Ogetay:Vitali: This depends on the number of images (not on the integration time) and the "quality" of dithering. Sorry I can't quantify this. More images and really random dithering produce a better coverage. Drizzle integration process produces a drizzle_weights map. You can see information about it in Juan's post here: https://pixinsight.com/forum/index.php?threads/drizzle-image-weights.9695/ And you can find the missing figure here: https://hst-docs.stsci.edu/drizzpac/chapter-3-description-of-the-drizzle-algorithm/3-2-drizzle-concept For example the drizzle_weights map for R channel from my last image contains values from 0.78 to 0.91. The drizzle integration (drizzle 1x, drop shrink 1.0) used 421 CFA frames, dithered every 5 frames. What exactly should I be looking at in Tim's replies? I see that Tim compares Ha OSC with mono and gets the expected result that OSC will get 1/4 of Ha signal. OSC is obviously not efficient for narrow band. Two following scenarios can be compared on the other hand: 1) 100 OSC images; and 2) 25 R images, 50 G and 25 B images for a mono camera. It is also expected that a debayered image will have a higher SNR compared to a drizzled image, because interpolation in a debayer process smoothes the image. |
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Vitali:Kay Ogetay:Vitali: Thanks for elaborating! This is something that I keep contemplating. As you said after the second bullet point, the drizzled image gives a higher SNR because of smoothing as well. Yet I see many people interpret this as better detail. Higher SNR calculation is not necessarily equivalent to more detail. In fact, that is not true SNR and that's why I referred to it as 'SNR calculation' instead. I think your suggestion is a good starting point. I haven't seen such a comparison yet, if there is, please let me know. I appreciate the impact of the drizzle algorithm. Even though it is an interpolation. In science, we rely on interpolation more than here. It is just surprisingly effective here (for me at least, I'm still surprised by how well it does, thanks Hubble team), very nice practical outcome. Yet my eyes were not convinced to buy OSC even with that. Or my theoretical instincts advice otherwise, but that can be overcome by some good comparisons. I believe this discussion of mono vs osc will last forever until a new technology makes a significant difference. |
