6.02
#...
·
1
like
|
|---|
Rodd Dryfoos:Gotthard Stuhm:Hi Rodd, can you point me to any great images taken with a colour cam from a bortle 6 location? *** Type your reply here *** Rodd Dryfoos: Hi Rodd! Here I am again.  It was a little bit difficult to understand your post completely. You are right in that matter, that the skills are the most important point. Indeed. But than you suggest that I could reach better results using a Mono-Cam ... and it seems that you draw in doubt, that our two pictures could be comparable. That is an idea I can't follow. The two pics ARE comparable. Let me explain: OK, I use a simple cheap reflector ... you use a high end and expensive refractor. My focal lenght is 1500, yours 1000. That are differences ... that probably balance each other out! Ok ... your image is a "real" astropic, shot in dark nights under reasonable conditions and Bortle 6 ... my pic is a "daylight"-image, the photons were collected only in times of dawn, before or after the times I try to get real "astro"pics ... and under worse humidous and wet sky conditions with maximal Bortle 7. So let us take a view on the images. I posted them in detailed views here:  Please note, that there are visible on both images exactly the same stars and some faint galaxies. The depth of both images are similar. But there is a difference: Your images has probably no "background", the background is black. All the stars and galaxies are like punched out spots, hard contoured and strongly coloured. In my image the backgrund and all objects are delicately and soft drawn ... but ... and that's a real bad feature ... a little bit too blurry. These bluriness is no artefact or caused by bad processing ... it's just the real caught bad sky! The "foggy smell" and the bad seeing ... are correctly visible. Summerizing ... I would say my image shows the same objects, the same details and a little better backgroumd than yours ... and there is no chance to get better images with a "better" cam ... the sky is the frontier. Your image indeed is more impressive ... the stars are really sparkling ... but if you take a deeper look ... this isn't due at all to a better catched material. What do you think? |
1.20
#...
·
3
likes
|
|---|
| I use both and get great results with both Monochrome and OSC. I do like having more control of the data collected from the monochrome camera vs the OSC. The advantage of the OSC is it’s a simpler setup especially if you’re on the go and traveling and time is limited. The SII wavelength is very difficult or impossible to extract from a OSC raw image, it shares the same red pixels as the Ha. The monochrome produces separate Ha, SII and Oiii without a problem. Then it’s much easier to achieve the SHO pallet in post processing. If you have only a few hours a week or so to image then the OSC is the way to go. If you can image all night or over several nights then Monochrome is definitely the way to go and will produce the best results possible. My opinion is based on using both the asi1600mm and the asi2600MC. |
3.61
#...
·
1
like
|
|---|
| My decision process continues. This is hard. For me, the decision is being reduced to practicalities as much as anything. I'm retired so time isn't an issue, per se. What IS an issue is available imaging time given the weather in the Seattle area. Every night is precious and I'm afraid I won't have the time to do mono justice. For me, my full frame QHY367PRO-C produces great images (granted, I don't have a mono to compare it against) in a reasonable time (4-8 hours) and I'm concerned that if I go mono, I will spend my limited nights of clear skies on fewer targets with the associated variability in weather, temperatures, seeing, transparency, etc. between imaging sessions that could twist me up in a pretzel too, as Rodd and others have talked about already. Not to mention the added processing time that I keep reading about. Now, if I lived in an area with a lot of clear skies, then a mono camera would definitely be my next move. Having said that, I have noticed some nice mono images with integrated times in the same range as what I'm spending with the 367. Does this make sense to anybody or am I thinking about this wrong? |
 #... |
|---|
Gotthard Stuhm:Rodd Dryfoos:Gotthard Stuhm:Hi Rodd, can you point me to any great images taken with a colour cam from a bortle 6 location? When I judge an image it is based on what the image looks like. What you say may be true, but that just means the conditions were so poor that you could not generate an image of a certain quality. These images are meant to be viewed at normal viewing. Not zoomed way in. Your image lacks the internal structure of M13 and the fuzziness you mention is a big deal. I never said my image was perfect. I said my image was a better representation than yours. Maybe under the same conditions I could not do as well as you. But we are judging the images, not the imagers. Maybe your background is better. But if you hung the two images on a wall side by side I think most people would think my M13 looked better over all. Maybe it is because of the conditions. But one should not say their images are better than Hubble’s because the conditions are much worse. We just judge the images. This is just my opinion |
#... |
|---|
Paul O’Brien: I was under the impression that osc is the harder processing route with the debate ring. Also, changing filters is not manual it takes no time. Theory would say that a Osc needs more data than mono due to the physics. So you might be able to collect more data, not less. It would probably be a wash. Maybe a little less, but you need less. But I am not familiar with osc-it’s just what I have heard. |
|
3.61
#... |
|---|
| Rodd - I wasn't necessarily thinking about the time in changing filters, rather the total time spent in imaging a target with LRGB, Ha, etc. I understand the physics of OSC vs. mono (I'm a physicist by education in a galaxy far, far away). My primary concern is the time I have to image. From what I understand, the total time in imaging with, lets say, LRGB and a NB Ha filter will generally be considerably more than an OSC. I'd love to hear from people with both types of cams. If true, then my imaging availability concerns comes into play. If not, then I'd more strongly consider a mono. Processing - you got me there because I don't know what's involved in processing mono, only what I've read and heard. I don't find OSC processing to be too onerous but I don't have mono to compare against either. |
11.87
#...
·
2
likes
|
|---|
| Paul - forget about luminance imaging, which is a highly efficient way of building SNR, and let us restrict to plain RGB. Given a fixed imaging time, for a broadband target, a mono with dichroic filters will do better than an OSC simply because the Bayer array filters of the OSC are not as efficient. The only advantage of the OSC is that if you have less imaging time than you planned for, you still have a full (though inferior) data set and can process the image. If clouds roll in sooner than anticipated, the mono may have too little data in one or more filters. People confuse this with thinking that an OSC is somehow superior to a mono. It is not. It is just more convenient. If you want to image really deep - like the tidal tail of the Hamburger or the IFN, the OSC will get its clock cleaned in comparison to a mono that can do luminance, given the same imaging time. |
|
3.61
#...
·
2
likes
|
|---|
| Arun - I used the filters only as an example in my comments on imaging time. I may have not been clear but my concern revolves around the opportunities I have in Seattle to image vs. the time involved in mono capture. I would be the last person to suggest that a OSC is “better” than a mono. I would love a mono setup. But, if I have to spend say 10-20 hrs. to adequately capture one target with a mono setup and don’t have the clear skies to do it, then what’s the point? I’m not prepared to spend several days or weeks trying to nail one target, given our weather. I could take my QHY367 out in a couple of nights and be fine with the image quality in half the time. It’s not because I don’t want a mono or don’t want to spend the additional time in processing a mono image, it’s the limitation I have in available imaging opportunities. I have had a similar discussion on CN and have yet to get a good answer on image capture/processing time with a mono vs. OSC. Seems that there are too many variables and opinions. One very experienced CNer told me that it wouldn’t take any more time than my OSC because, although capture takes longer, processing time is easier. Another responder laughed in his face and said it takes a lot more time to do both. Hence, my continuing quandary on what to do. For those of you that are experienced in both OSC and mono, I would really appreciate real world, practical feedback on this question. I’m ready to pull the trigger on mono but still have too many questions. Thanks! Paul |
#...
·
1
like
|
|---|
Paul O’Brien: There in lies the myth. What makes you think that you need 20 hours with mono and only a few hours with osc? That does not make sense. You need less data with mono for the same quality image |
3.01
#...
·
1
like
|
|---|
I've used both and I would stick with the mono for the same reasons that people already mentioned here. OSC has two advantages in my book, but both are to satisfy my laziness, and not necessarily valid from technical point of view:
|
6.80
#...
·
3
likes
|
|---|
|
Hi Rodd, This topic (mono vs OSC) has been debated endlessly already on cloudynights and other forums. I highly recommend you read this CN forum post (all of it). A calculator in the form of a spreadsheet is given whereby you can experiment with comparisons of different configurations (mono, OSC). I have found the spreadsheet/calculator well thought out and VERY useful. I've even sent the author follow-up questions (and he's answered promptly). I suspect it can help you too. Cheers, Doug https://www.cloudynights.com/topic/682340-monochrome-vs-one-shot-color-%E2%80%93-by-the-numbers-please/ |
#...
·
1
like
|
|---|
Michel Makhlouta: Agree totally. Number one is usually because of weather and the Moon. I suspect it does not happen very often at a site that has fewer (much fewer) cloudy days. I will add one to the list--planets, at least for me. Many people do RGB on planets and it astounds me. Timing is so critical due to planetary rotation. I know Winjupos can derotate, but how can software add data to an image that isn't there (because the imaging session exceeded 3 min, or whatever the time is for not loosing a feature over the rim.) |
#... |
|---|
Doug Summers: Thanks Doug. If I get serious about OSC this will no doubt be a great resource. If money wasn't an issue, and I had two mounts, I would get a OSC and use it to collect color data with one scope. Because I only have the ability to use one scope at a time, its not practical for me. I avoid changing anything for long periods of time due to a very limited amount of imaging time (and the propensity for thin spaxcers to be almost impossible to unthread without resorting to nuclear tactics. I appreciate the insights though. |
|
3.61
#... |
|---|
| Doug - That CN thread looks exactly like what I’m looking for. Thx. |
|
11.87
#...
·
1
like
|
|---|
| Hi Doug, thanks for that excellent link. It confirmed some of what I thought I knew about OSC versus mono and corrected me in some other points. It confirmed that when we do LRGB imaging, we gather significantly more photons than with an OSC in the same time. Where I was wrong was in thinking that the mono is superior even when we do just RGB imaging ( no luminance). Because the Bayer filters actually cover a greater wavelength range than mono filters, the OSC is at least equal to a mono with filters and perhaps even superior in color fidelity. |
#...
·
1
like
|
|---|
Hi Doug, thanks for that excellent link. It confirmed some of what I thought I knew about OSC versus mono and corrected me in some other points. It confirmed that when we do LRGB imaging, we gather significantly more photons than with an OSC in the same time. Where I was wrong was in thinking that the mono is superior even when we do just RGB imaging ( no luminance). Because the Bayer filters actually cover a greater wavelength range than mono filters, the OSC is at least equal to a mono with filters and perhaps even superior in color fidelity. I don’t agree. When you use a osc you only collect 25-50 percent of the color you collect with mono, because you are not using all the pixels. |
2.11
#...
·
1
like
|
|---|
|
Hi Rodd my 2 cents worth - I just purchased a OSC. My idea is to only use it only for wide field shots using a F2/125mm lens. Mono cameras work best for deep sky objects but the advantages reduce significantly once you go wide field in my opinion. Using a OSC in this way allows for more portability as well, so i will use this setup with a small battery powered mount to allow me to go into the field where skies are darker and power options more limited. |
|
6.80
#...
·
2
likes
|
|---|
|
Hi Rodd, Unfortunately, ARun H is correct and you are mistaken. The author of the CN post/spreadsheet has done his homework and the work has been vetted thoroughly. The story in a nutshell is just as ARun H has stated. As odd as it sounds, an OSC up against a mono cam in a dark sky for equivalent time units and a pure RGB exposure set will outperform the mono due to overlapping bandpasses in the OSC and bandpass gaps in the mono filters. The mono will close the gap quickly and significantly pull ahead if luminance enters the scene. OSC in light pollution won't come close to Mono. The 25-50% logic you've given (and the reason why) is common, but just wrong. On average, the Mono can be seen to be on the order of 15-20 % more efficient, but definitely not 50, and it definitely depends on how the camera is used. Sorry, the math is all there....as soon as you take the time to read and understand. Best wishes, Doug |
#... |
|---|
Doug Summers: Then why don’t most remote hosting facilities like DSW and others use more OSC? |
#... |
|---|
Doug Summers: And the mono will still collect more photons because it uses all the pixels for red green and blue. There is no way a Osc collects as much blue (or red or green) as Mono in the same amount of time. I don’t see how the overlapping band passes help. When the data is debayered you get a red green and blue sub and you make red green and blue stacks. You don’t want green in your blue or red in your green. And the resolution will be higher in the mono. Also, you have to factor in bad subs. A cloud or plane will ruin all data with a Osc. Not do a mono. Only one channel is impacted. They reduces efficiency even more. I do not get why you say it depends on how the camera is used. Collect an hour of data with a Osc and I will collect 2” minutes of blue. You think the Osc blue stack will have more signal than the mono? |
|
6.02
#...
·
2
likes
|
|---|
Rodd Dryfoos: Hi Rodd, my impression is, that there are simple facts which are permanently ignored. The simple fact is, that a chip with a certain area and a given pixelsize collects always the same amount of photons ... Mono either Colour, no matter! Exactly the same amount!!! That is caused by the simple multiplication of area and physically pixelsize! The difference results of using the single pixel. If you would use a filter in front of a colour-designed chip ... that would be silly, because you only would use this single colour ... with bayer-matrix you got 25 % of red or blue or 50% of green photons. But OSC user aren’t silly ... they always collect ALL colours at the same time ... that means 100% of the effective incoming light. The at the same time resulting Luminanz collected by an OSC chip is 100% of the natural physically possibility. With a mono chip You always collect a filtered 25%-part of the light ... but with the 4times larger area ... so that you reach the same amount of photons. A relevant aspect is, that the OSC collects an disproportionate amount of green, so that 25% of the collected photons can’t be used at all for colourprocessing tasks. Even if the debayered area seems to represent a quasi binned wider area with less resolution ... I suppose, that the lost of resolution is not signifikant. And ... assuming there is a information about a red lightquant given by a certain debayered 4xpixelarea ... it is possible to relate this single red quant to a distinct subpixel! Reading all that posts and thoughts ... I got a second impression, Rodd. Is it possible, that you are asking for the abilities of OSC without real interest in getting new information or even changing your equipment. It seems that you are absolutely convinced in the old mono-technic that you can’t see the upcoming advantages of OSCs? I tried to explain, that my images captured with a Canon DSLR content the same data or even more than your mono-image, which can be seen on a zoomed in area of the picture, but you said ... these data on pixel scale are not important, what counts is the visual impression ... that sounds like preferring processing with photoshop. But than ... why thinking about a better cam? Photoshop IS an alternative! I am really interested in your motivation to find the best equipment. What are your criteria? What are iyo the best indicators to judge the quality of cam and image? Best wishes for 2021, stay safe and always cs! |
6.89
#...
·
2
likes
|
|---|
Rodd Dryfoos:Doug Summers: Hi, The point is RGB collects blue+red+green at the same time. The CN post makes the assumption incoming light is uniformly distributed, i.e. in one minute you have incoming R,G,B = 12,12,12 photons on the surface of the sensor. Assuming it captures exactly 25% of R,B and 50% of G, then in one minute it has collected 3+3+6 = 12 photons. With mono, one minute total exposure means 20 seconds each color (1/3rd of minute) so it has collected 12/3+12/3+12/3 = 4+4+4 = 12 photons. So: 1) mono collected more R and B than OSC 2) OSC collected more G than mono 3) total number of photons collected is the same There are of course other things at play: spectral responses, the fact that incoming light is *not* uniformly distributed (it's an image after all, not a gray background). But theoretically at least, "no way" is incorrect. Cheers, Dimitris |
|
11.87
#...
·
4
likes
|
|---|
As Dimitris mentions - when gathering color information, both mono and OSC use all the pixels all the time, they just use them differently. John Upton's calculation is probably the best comparison I've seen done between OSC and mono and a lot of other questions are also answered in that CN thread. So I'll just answer one here:Then why don’t most remote hosting facilities like DSW and others use more OSC? This is because the mono is very clearly superior when luminance is added to the equation. Mono is also very clearly superior for narrow band. Most us who do LRGB use equal time in L as we do in R+G+B. In that specific (and commonly used) scenario, the mono will be over 60% superior to OSC in gathering photons and hence constructing a deeper image.This is something John mentions as well. The deepest images are most efficiently gathered using a mono. But that doesn't mean the mono is right for everyone. I think as Doug mentioned - a lot of what we are debating here has been better covered in that CN thread. Anyone considering a mono versus OSC would do well to read and understand it. As with anything in life, there are tradeoffs. Having the data put in a manner like what John has done helps us understand what they are and make informed decisions. |
11.14
#... |
|---|
Rodd Dryfoos: Because for them, choosing equipment is an investment made for running a business. Other factors like support, service and durability come into their equation they have to optimize. It is for the same reason your work PC is a branded one with its manufacturer providing 24/7/365 on-site service, while your leisure PC is custom built, probably with better specs and for less cost. I am not implying that expensive is better, just that within the cost a manufacturer may provide features which are more desirable for a client who runs his/her own business. |
|
6.02
#...
·
1
like
|
|---|
|
An additional annotation, Rodd. Things I wrote above are in respect to produce colored images either with OSCs or Mono-cams ... and your predication that OSCs don’t use all pixels. If you want to pic up photons for grey-scale images based on full spectrum photons, than there is a mono-cam in advantage, because you can remove all filters and collect the fullspectrum Luminanz. You can use this L by a workaround to improve the quality and sharpness of your color-images, if your telescopes deliveres a homofocal sharp image over the full spectrum. One advantage of monocams is indeed the possibility of focussing different wavelengths at its own if there are lenses involved in the optical path that can’t compensate the chromatic aberration. Maybee that’s the crucial point to choose a Mono-cam. Under my sky ... doesn’t matter ... the horrible seeing compensate that efficiently ... and I use a color neutral reflector. |
