Monochrome VS. Color CCD Cameras

[steppenwolf]

I think Steve has this on the go?

Indeed I do - and great fun it is too when the skies play ball!

[Stephen]

Indeed I do - and great fun it is too when the skies play ball!

:shocked:

[Cath]

Just as a comparison ..

Above shows the difference (close up) between a non-bayered image (left - foveon sensor) and a bayered image (right - bayer sensor). The blurring you get is due to the interpolation not guessing the correct pixel values, sometimes the interpolation will guess the pixel correctly, sometimes it won't.

If you have enough over sampling (more pixels than is really needed) then I guess the bayer/interpolation won't have a great effect on the final resolution image.

Difficult choice to make between mono and colour CCD, as others have said, it's much easier to go colour CCD if you get very few imaging opportunities.

The way they overcome the bayer/interpolation in professional video cameras is to use 3 mono CCD's in parrallel with a prism that splits the red/grn/blu light and sends it to the 3 ccd's - this means full colour resolution and sensitivity without tbe dreaded bayer/interpolation problem.

Anyway, just thought I'd show what the difference actually looks like up close for those interested.

Merry christmas!

[petercoxphoto]

On the resolution front, while I haven't compared OSC and mono CCD cameras (for astronomy, anyway), I have done so for 'normal' cameras.

I use Phase One digital backs which are medium format (6x4.5cm-ish) CCD chips in my regular landscape photography. I recently did a field test between a P45+ Achromatic and an IQ180. The Achromatic is a 39mp sensor with no bayer matrix - a true mono CCD. The IQ180 is an 80mp sensor with a bayer matrix.

Photographing the same subject at the same focal length showed that the Achromatic came (visually) very close to the resolution of the IQ180 - but not exactly the same. So using that pair as a data point, empirically I would say that losing the bayer matrix gives you just under twice the resolution in a real world scenario.

Translating that into AP, (and please, the more experienced people shoot me down if I'm getting this wrong) for the same megapixel count, your luminance data (assuming binned RGB channels) should be significantly clearer in mono over OSC. Unless of course the resolution gained outresolves the seeing conditions on the night, I presume.

Olly - you've said that imaging with the mono cameras is faster than OSC. I can see your point, but wouldn't that do away with the "I can get a complete image in a single night, even if the clouds roll in" argument? Surely if you're left with missing data in one of the colour channels, you'd have a less than satisfactory collection of OSC subs as well, and you'd want to go out and get more on another night? Or am I missing something?

Cheers,

Peter

[hot_ice]

I am relatively new in Astro imaging, I read the threads wit interest. I started with DLSR (Canon ESO 550D) and thought I get great results until I decided to go mono with ATIK314L+ and filter wheel. Like most of us I cannot decide whether OSC or Mono with filter wheels. The following images of the orion nebula was taken in November and December this year and after stacking I thought the result is 100 times better then a DLSR although I have no OSC to compare with.

DLSR

Atik Mono using HA,RGB filter

[petercoxphoto]

From what I've read, DSLRs tend to get the colours wrong; particularly with M42. Even that aside, the difference in quality here is significant!

[Coco]

There really are no winners, Ive jumped camps twice.. For ultral faint stuff Mono wins.. but are you saying you 'need' ultra faint objects, if so fine. if you live in the UK dont expect to image much each season..

here is a wonderful site buy a guy who uses a DSLR and a Newtonian... thats not even cooled!

http://www.distant-lights.at/index.htm

[pete_l]

From what I've read, DSLRs tend to get the colours wrong; particularly with M42. Even that aside, the difference in quality here is significant!

Assuming you shoot RAW with your DSLR, the colour balance is largely under your control.

From a philosophical PoV, it's difficult to say what colours are right or wrong, if the spectral range, response curve or intensity is outside what the human eye could see.

Having said that, there are some combinations that appear to be more popular, or generally accepted than others.

[Sp@ce_d]

I recently moved on from a DSLR to a mono Atik 314L+ & EFW2. I have to say that during that time I have failed to acquire enough data for all the required channels to complete a satisfactory image with it due to the weather. Yet the same amount of time using my DSLR would at least have been enough to produce a reasonable usable result. So for me at the moment, the impression is that it will take longer to acquire enough data with the mono than with a OSC.. at least with the weather in the UK. However, one thing that does stand out is the sensitivity & lack of noise compared to the DSLR. Now, I'm lucky enough to have an obsy and a dual scope setup so I'll be experimenting with combining the 314 & DSLR. Going by the way the weather has been over the past couple of years, I'm expecting to be tempted towards either adding a cooled OSC CCD or another mono CCD & FW in an attempt to get enough data without having to wait for the target to come around again the next year to get the rest of the data!!

[Black Knight]

There really are no winners, Ive jumped camps twice.. For ultral faint stuff Mono wins.. but are you saying you 'need' ultra faint objects, if so fine. if you live in the UK dont expect to image much each season..

here is a wonderful site buy a guy who uses a DSLR and a Newtonian... thats not even cooled!

http://www.distant-lights.at/index.htm

That's a great link Guy. I think I've seen this guys stuff before, a long time ago, but I never saved the link!

[Black Knight]

I recently moved on from a DSLR to a mono Atik 314L+ & EFW2. I have to say that during that time I have failed to acquire enough data for all the required channels to complete a satisfactory image with it due to the weather.

I got my Atik 314 in the summer. I couldn;t say I've used it properly yet, just for test stuff at the moment. The only times I've been able to get out (and the weather has been kind), the window of opportunity has been so short that I simply went with the DSLR, just so at the end of the evening I had something in the can, so to speak. Very frustrating, but serves to illustrate the central dilemma quite well.

[RAC]

For me anyway I'm looking more for a ccd to add to my dslr images. Also to be able to do nice bi-colour shots using ha and o111 then there is only too sets of data to get and my city LP won't have the effect it does now.

[Gina]

II'm using my 314L+ and EFW2 with just Ha and OIII filters ATM for suitable DSOs and my cooled 1100D for larger and brighter nebulea and galaxies. Or should I say on the couple of clear nights since I got it several weeks ago! I shall be adding to the Atik system sometime in the New Year. I still have plenty to do with a DSLR.

[Gina]

Probably the first extras for the Atik kit will be guide scope rings to enable my to mount it with a telephoto prime lens to cover a wider field. Then I can run Atik and Canon imaging at the same time collecting NB plus colour data.

[kirkster501]

I think that's a very fair point, given the weather in the UK over the last year or so.

I think that is the central crux of this discussion. The fact that a mono setup can create superior images goes uncontended. It is more a matter that in the UK, with our preposterous weather of late, is that the best way to go for many time pressed AP wannabees? We will each come to our own conclusion about that one! I have only had seven "imaging possible" nights since 20th September for instance. With mono I'd have only had opportunity to work on one target......

Merry xmas, Steve

[Uranium235]

It is more a matter that in the UK, with our preposterous weather of late, is that the best way to go for many time pressed AP wannabees? We will each come to our own conclusion about that one! I have only had seven "imaging possible" nights since 20th September for instance. With mono I'd have only had opportunity to work on one target......

Merry xmas, Steve

Exactly my reason for adopting both camps simultaneously by using mono (ccd) and OSC (dslr) on matched optics. It seemed daft having a 1000d sitting there doing nothing when it could be put to work collecting colour data. All too often this year Ive had to put a project on hold while we are subjected to yet another biblical downpour, which makes optimising the clear sky available the #1 mission. But if I were to get another CCD it would not be OSC - its just not flexible enough, and when the moon is about it will be next to useless.

[Gina]

When I eventually get LRGB filters for my Atik system I plan to focus accurately with the L filter and bin 2x2 on the colours. Then instead of taking all L, all R, all G and all B I shall use the alternate setting of LRGB, LRGB, LRGB, etc. That way I will have at least some complete colour sets if the clouds come in Using the ED80 without FR and f7.5 I think the filters will be sufficiently parfocal, particularly binning 2x2 on the colours.

There have been nights however, when a clear sky has been virtually guaranteed - a nice high pressure situation lasting a day or two. I do remenber previous years when we have had weeks of high pressure conditions and clear frosty nights. I'm still hoping we shall get such weather conditions next year - I know we won't be this year.

[kirkster501]

Gina, you're still going to use the ed80 with the CCD rig? I am Trying to visualise the totem pole of stuff hanging off the focuser!

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[Coco]

- its just not flexible enough, and when the moon is about it will be next to useless.

Yes and No..

Back in the early days I used an astrotrac and astro modded 40D, I used an astronomic Ha clip fllter on Moon evenings..

This was using only short 3 min subs, on a decent mount you would get a great image..

[Gina]

Gina, you're still going to use the ed80 with the CCD rig? I am Trying to visualise the totem pole of stuff hanging off the focuser!

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Yes indeed I'll take a photo of the setup - don't think I've taken one of that as yet. But it's not as much of a totem pole as the cooled 1100D

Here is a photo of my setup with cooled 1100D versrion 1 :-

[Sp@ce_d]

When I eventually get LRGB filters for my Atik system I plan to focus accurately with the L filter and bin 2x2 on the colours. Then instead of taking all L, all R, all G and all B I shall use the alternate setting of LRGB, LRGB, LRGB, etc. That way I will have at least some complete colour sets if the clouds come in Using the ED80 without FR and f7.5 I think the filters will be sufficiently parfocal, particularly binning 2x2 on the colours.

I tried that, still haven't got enough satisfactory data and that's using my ZS66 @ f5.9. I haven't tried the 80ED with it yet as I need to make spacers to use the reducer to achieve f6.3. I did a focus test with my Baader filters. I have the LRGB and Ha SII OIII. Looks like the LRB and Ha SII come to focus in the same place, with refocussing needed for the G and OIII

[Sp@ce_d]

Exactly my reason for adopting both camps simultaneously by using mono (ccd) and OSC (dslr) on matched optics. It seemed daft having a 1000d sitting there doing nothing when it could be put to work collecting colour data. All too often this year Ive had to put a project on hold while we are subjected to yet another biblical downpour, which makes optimising the clear sky available the #1 mission. But if I were to get another CCD it would not be OSC - its just not flexible enough, and when the moon is about it will be next to useless.

Yup, I'm of the same opinion. why is it that the only clear nights are when the moon is blazing away right near my target!!

[Gina]

Yup, I'm of the same opinion. why is it that the only clear nights are when the moon is blazing away right near my target!!

Ah yes!!!! I've had that problem too One reason for narrow band - even with DSLRs, before I got the Atik. Using Astronomik Ha and OIII clip filters.

[kirkster501]

Yes indeed I'll take a photo of the setup - don't think I've taken one of that as yet. But it's not as much of a totem pole as the cooled 1100D

Here is a photo of my setup with cooled 1100D versrion 1 :-

Very nice.

Very similar set up to me except the focuser What's the piece of wood doing atop the EQ6?

Nice horizon there in the background....

Steve

[opticalpath]

But, and here's the rub, if you are cut off in your prime by the good old English weather you can end up with LRGCloud, which is not a lot of good. I don't want to speak for Steve but when we've chatted about this in the past he's given this as a major reason for his liking OSC. I can quite understand that. My own reason is that I do this for a living and can be running round between mounts like a headless chicken, so having at least one simple capture going on is rather nice!

I agreee with all the points in Olly's excellent summary of the pros and cons .... and agree that a dual setup would be the ideal way to make the most of the rather infrequent good spells we get in the UK.

I'd just like to make one point, though, about the 'LRGCloud' frustration when using mono camera plus filters. If you're fortunate enough to have a scope that doesn't require a focus change between filters (and I've found that to be the case with the MN190 for example) then it's possible using Maxim or similar to control camera and filter wheel to minimise this problem. Rather than imaging long runs of one colour at a time you can program an imaging sequence that goes R,G,B,R,G,B.R,G,B .... etc. so that, if your session is brought to an abrupt end, you will still have a balanced (albeit smaller) set of R, G and B images and not be left missing one filter entirely. I always work this way, doing RGB on the poorer nights and saving the better nights for long runs of luminance or Ha.

Olly, I know you're not keen to control things unnecessarily via the PC, but this is one instance where a PC-controlled filter wheel is a real benefit.

Adrian