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ollypenrice

Monochrome CCD is the fastest of all systems.

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This is my contention, based on theory and experience, and here's my effort to prove it. I chose an image for which I had the orginal captures and I selected from the dataset exactly three hours' worth of capture. No cheating! Three hours is a reasonable time and does not require you to live in the Atacama to collect.

Why is mono imaging in LRGB or HaRGB faster than one shot colour?

Because, while you are on the luminance stage, you are capturing red and green and blue simultaneously though you can't distinguish between them.  A one shot colour camera does not do this. Its pixels capture only red, or green or blue, so a quarter of the camera catches red, a quarter blue and a half green. The luminance stage in LRGB is three times faster than any OSC system. Mono RGB is captured at about the same rate as OSC.

What about HaRGB? Why does HaRGB in a mono beat OSC in an Ha sensitive OSC camera? Two reasons. 1) It captures the critical Ha signal on all its pixels, giving four times the signal and far better resolution. (Only the red pixels pick up Ha on an OSC chip, so that's one in four. 2) The narrow bandpass of the Ha filter gives more contrast and picks up the Ha structure of the object better than a broad red filter. In processing this will work to your advantage. You will not have to work the post processing as hard when your Ha has come through a narrow filter rather than a broad red one.

So here's a picture. California Nebula, Tak FSQ85, Baader 7 Nm Ha and RGB filters. (No luminance this time.) Atik 4000 monochrome CCD. Each colour had 3x10 minutes and the Ha had 3x30 minutes.

3%20hour%20image%20HaRGB.-L.jpg

Have a look at it in full size by following the link and clicking on the picture. http://ollypenrice.smugmug.com/Other/Takahashi-EM200TEC140/i-BPGrpKg/0/O/3%20hour%20image%20HaRGB..jpg

The Ha was applied to red in Blend Mode Lighten and at about 10 percent as luminance.

Now it is perfectly true that using a one shot colour system might be less frustrating in on-off cloud but setting aside the psychological or emotional side of things monochrome CCD is the fastest of them all.

That's my contention.

If you'd like to play with the data it's here.

https://dl.dropboxusercontent.com/u/63721631/Ha90.tif

https://dl.dropboxusercontent.com/u/63721631/RGB3X30.tif

Olly

Edited by ollypenrice
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Plain physics. A highly sensitive, low-thermal-noise photosite with largest possible fill factor and no filters or other optics to obstruct the access of photons to it will be best. So a cooled, back-illuminated, monochrome CCD works best. Guess why the professionals use them

Monochrome CMOS chips can come close,especially if they have micro-lenses to increase the effective fill factor.

As Scotty used to say: "Ye cannae change the laws of physics, Capt'n."

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So why did you post this, were you just bored or did you want to start an argument ?   :)

Nice pic though.

Dave

Edited by Davey-T

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So why did you post this, were you just bored or did you want to start an argument ?   :)

Nice pic though.

Dave

Because Olly said he would in another thread where the merits of OSC, Mono CCD and DSLR's (CMOS) sensors were being discussed....

I think the idea is to compare it to the "best" 3 hours worth of OSC or DSLR data ideally of the same target and with similar  optics.......

Peter....

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So why did you post this, were you just bored or did you want to start an argument ?   :)

Nice pic though.

Dave

I posted it because of an earlier thread discussing this question. I said I'd do an experiment to see if I were correct in arguing the case for 'mono as fastest.' This is the experiment duly performed. I do think I was correct but that's not to say everyone will agee with me! As a refugee from the world of English teaching the word 'argument' carries no pejorative associations connected with 'quarrel' so I'm just extending an ealier discussion and avoiding thread hijack! It's interesting stuff, though, if you enjoy imaging or are debating which kit choices to make.

Olly

Edited by ollypenrice

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I'd tend to agree with this as well as the flexibility of mono imaging.

However, as you often say Olly, real world examples say a lot. I'd like to see a side by side comparison under the exact same conditions. You must be pretty near to being able to do that with the twin shooter setup. Any plans?

Sent from my iPhone using Tapatalk

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What I'm really keen to see (if you can arrange Olly or anyone else?) is a true comparison ... three hours vs three hours similar/same conditions same setup?

PS Mono all the way :D

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What I'm really keen to see (if you can arrange Olly or anyone else?) is a true comparison ... three hours vs three hours similar/same conditions same setup?

PS Mono all the way :D

I have Ollys' old Atik 4000 OSC so will try a comparison, don't have a Tak unfortunately, any volunteers ?

Don't think there's any doubt about the out come though.

Dave

Edited by Davey-T

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I think a comparison with the same equipment but under the UK Sky Conditions is a very good idea. We can all see the potential of a ccd camera.

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Our dual rig uses mono on both, alas.

My real point here was not to do a strict shoot out but to post an image which clearly demonstrates that using mono and filters is not a long winded process. It's a fast process.

Another issue that comes up is ease of processing, with many folks assuming that mono and filters must be difficult. I don't think this is true. This image was incredibly simple to produce from the data.

I ran the RGB through DBE in Pixinsight and then killed the green noise with SCNR. This gave the colour balance and gradient freedom that you see. After that it was just a stretch, star colour enhancement from Noel's Actions and a bit of NR on the darker parts.

I opened the Ha in Pixinsight to consider DBE but there was no point. It had no gradients. I stretched it hard, noise reduced the faint stuff, ran it through LHE in Pix and then combined it with the red as explained.

I'm just keen to de-mysitify monochrome CCD, really.

Olly

Edited by ollypenrice
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Surely to get a real comparison there should be no luminance or Ha applied at all.

Wouldn't it be a case of RGB vs. OSC?

I'm not debating which is better mono vs. OSC because in my limited experience the answer is mono and I do use both.

What a lot of us don't have is the sky, opportunity or budget to always do what is 'best'. That's also why I use a DSLR and a webcam.

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Well I have to say as a OSC user I was completely unaware that you have to de-bayer the image in processing. When I took my first shots I thought there was something wrong with my CCD as they came out in greyscale, even though I specified colour. After lots of research on the web I discovered that I had to do this 'extra processing' to get a RGB image. I didn't expect that as when using a DSLR the image is automatically RGB.  Strangely enough I decided on a OSC because it was 'easier' and cheaper. Next time I buy a CCD it will be Mono. 

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My only experience with OSC cameras is a DSLR, so I can't offer up any comparisons but I can quite happily say that with the same optics from the same location under as similar as possible conditions a Mono CCD and filters wins by a country mile. I suspect that for a OSC CCD it will be closer but as above simple physics tells you Mono LRGB must be faster to achieve a given quality of image.

One thing I can add is that shooting LRGB with typical UK light pollution - like wot I haz - I still need a lot more than 30min per colour plus 90min luminance to get a good separation of target from the skyfog with broadband objects. In Ha though, I can get results I am happy with in under two hours. This was 11x 10min subs at f/5 and 3.3"/pixel through a Baader 7nm Ha filter, if someone has a comparable OSC equivalent.

post-5915-0-08846100-1396441428_thumb.jp

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Surely to get a real comparison there should be no luminance or Ha applied at all.

Wouldn't it be a case of RGB vs. OSC?

I'm not debating which is better mono vs. OSC because in my limited experience the answer is mono and I do use both.

What a lot of us don't have is the sky, opportunity or budget to always do what is 'best'. That's also why I use a DSLR and a webcam.

For me this would serve no purpose since I already know that there will be no significant difference and the OSC would be easier. This debate arose from an assertion on an earlier thread that when time is short you are best with OSC.  My entire point is based on the time you spend in mono using all the photons at once (for Ha) or catching all the colours at once (using a luminance filter.)

Tell you what, though, I could process three hours' worth of RGB to compare that with the three hours which includes the Ha. I'll do it. That would be a comparison which would make or break my point.

Olly

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Hesitate to link to one of Ollys own OSC pics, but I think this image is testament to what can be achieved with OSC, no doubt it could be improved on in LRGB/HA but I'd be very happy with it.

Dave

http://stargazerslounge.com/topic/57332-pleiades-a-new-approach/?hl=atik+4000

I'm not bashing OSC. Absolutely not. But I am saying that LRGB is faster.

I got a bit deeper on the Pleiades by using everything I could find on the subject from whatever camera! http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-Z8vdsft/0/L/M45%20COMPOSITE3%20FL-L.jpg

Olly

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OK, more information. I took my full RGB data of an hour per channel (6x10 mins) and processed it a little further to make it a standalone image. Most people would agree that this is more or less what you'd get in an OSC. Why would it not be? In comparing this with the Ha version, also three hours, you see some some clear advantages to the first version. The slight application of Ha as lum has reduced the star sizes. The nebula is more structured and contrasty. It's also deeper. The Ha as lum has dealt with the blue issue around that bright star (which could be processed out but I leave it in for comparison.)

I was working quickly so I didn't adjust the colours to be identical but this could be done if you so wished. I tried to keep the processing consistent where possible.

3HRS%20RGB%20only-L.jpg

Olly

Edited by ollypenrice
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OK, more information. I took my full RGB data of an hour per channel (6x10 mins) and processed it a little further to make it a standalone image. Most people would agree that this is more or less what you'd get in an OSC. Why would it not be? In comparing this with the Ha version, also three hours, you see some some clear advantages to the first version. The slight application of Ha as lum has reduced the star sizes. The nebula is more structured and contrasty. It's also deeper. The Ha as lum has dealt with the blue issue around that bright star (which could be processed out but I leave it in for comparison.)

I was working quickly so I didn't adjust the colours to be identical but this could be done if you so wished. I tried to keep the processing consistent where possible.

3HRS%20RGB%20only-L.jpg

Olly

Spent a few minutes looking at them both (changing tabs back and forth) and you're right. The 3 hour HaRGB image looks cleaner than the 3 hour RGB image and I agree that it seems to go deeper too :).

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The HaRGB image wins. Having said that,I would not be happy with the "OSC-mimicking" RGB image. I would be over the moon with an image like that :D 

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The Plieades image is about the same time 200min compared to 180min for Californina Nebula, so data can be captured in the same timescale, obviously two completely different subjects so a side by side of the same object would be good.

I would be quite happy to courier the 4000 OSC to Olly to try this but having read all his horror stories of couriers I'd be worried it might end up at the bottom of a mountain gorge :)

Dave

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Whoa, this is going beyond the objective I set myself. What I set out to do was to debunk the idea that 'with all those filters' mono has to be slow going. I posted a half decent California Nebula (neither particularly bright nor particularly faint and no more than an 'OK image) captured in 3 hours. OK, so I'll do a reprocess using just 2 hours!!!! You're hard to please on SGL.  :grin:  :grin:  :grin:  This is a good thing...

Olly

Edited by ollypenrice

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2 hours!!  How about 1 and half hours on this target (tho, per pane as the original is a huge mosaic)? :D

Done with the QHY10 OSC camera by Dr.Yuriy Toropin, Moscow, Russia. 2x2 pane mosaic. Each pane 6x15min exposures. He used a Nikor 200mm F2 ED lens I believe. :)

So who says you can't achieve amazing results in very short time with an OSC CCD camera? :D

Flying_Monsters_Scorpius_QHY10.jpg

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