Which CCD - colour or mono (with a twist)

[dmahon]

One shot colour or mono + filters?

With regard to colour vs mono, I am talking the same amount of money spent, not the same CCD. The cost of the filter wheel and filters for a mono camera will mean I can afford a colour camera with a much higher overall resolution.

Eg. Atik 314L+ mono & filter wheel v Atik 383L colour

Has anyone done this kind of comparison, rather than a straight colour v mono on the same chip?

[ollypenrice]

Yes, I wrote an article for Astronmy Now on this subject comparing Atik 4000 OSC and mono on the same target. But first a warning; the 383 chip may not be very good in OSC format. My regular guest Frans Kroon is very disappointed with his SBIG using this colour chip. Here's what he says;

Deep Sky Astrophotography by Frans Kroon Latest Pictures

I don't know why this is but maybe the Bayer Matrix makes too big a dent in the small pixels? However I think you might be glad of the Heads Up, so to speak, so you can ask more questions. Of one thing there is no doubt at all; with a 314L mono you can take world class pictures. There are large chip colour cmaeras at the same sort of price and, while they do pretty well, I have never seen them give the kind of results that we see on here from Rob Hodgkinson and others. The Sony 285 chip is a dream. Its only drawbiack is size.

It is true that the filters and wheel (just get a manual one!!) add a lot to the cost. What you gain with mono;

-Speed. It is faster. (Yes!!) Shoot bin 1 Luminance and Bin 2 colour when the clouds are menacing.

-Efficient Ha and a full range of other narrowband filters. (Sometimes it is only clear when the moon is around...)

With colour you gain;

-convenient shooting with no filter changing, disturbing the scope, making mistakes.

-Convenient use of a single flat. This is great!

-Perfect colour alignment and no sky-induced changes for a particular colour.

I have both and like both, having bought the test camera, but it would hurt me not to have full res Ha available. I quite often do an OSC image and add Ha from the mono.

I find that Ha apart there is very little to choose between them. On a perfect imaging run I would give it to the mono but when the sky is variable the OSC handles it better. Nothing much in it.

If contending with LP the OSC may suffer more than the mono. But overall I would be very sceptical when being told that OSC does not give good results. Here is a shamelessly quick, three hour grab of the Lagoon in the One Shot, no Ha added. It deserves more effort but this gives an idea of a 'quick and dirty' image;

Olly

[dmahon]

I appreciate that there is a loss of resolution with OSC (though it is far from the 1/4 resolution that you might initially expect, due to interpolation of the missing pixels from the other pixels)

Is your 4000 OSC v mono available online? Ideally I want an article comparing a 4000 mono vs a camera with 4x the resolution of the 4000 in OSC. Ignoring the specifics of the camera, if the saving of the filters/wheel means that I can buy a OSC camera with 4x the resolution of the mono, the OSC will have far better overall resolution given interpolation (and resolution should be at least as good with Ha filters, and better with filters that are activated by more than one colour).

What I don't know is what this means in practice.

[ollypenrice]

You can't buy such a camera, as far as I am aware. It would be a 16 meg chip and cost a bomb. Even the 11 meg OSC Atik 11000 (which does tempt me) is approaching £4k.

You are quite right that the loss of OSC resolution is largely compensated for by the synthetic luminace layer generated by the software. In processing it is often useful to isolate this layer and process it separately. I generally sharpen the brighter parts and smooth the fainter if I have to. WHile a true luminance layer does look better than a synthetic the effect on the final result is not great.

Another good discussion of this is to be had on Dietmar Hager's site which should Google okay. He discusses OSC v mono at length and has more APODs than you can shake a stick at.

Practice versus theory is interesting. I am not all that well up on the theory of CCD imaging but I do a lot of it and get to see many cameras in use. Having a good look at the images posted on here is quite revealing. If spending around £1500 it would be Atik 314L mono for me and no messing. I'd also have a 383 mono but I like the 4000s with their decent format and big sensitive pixels.

Olly

[dmahon]

Interesting. Hasn’t helped me decide though:

314L+ mono, wheel + filters – 1.45 megapixels

383L+ OSC 3362 x 2504 pixels – 8.4 megapixels

The 383L+ still comes in cheaper, and has more resolution even if were I to attach a narrowband filter. I see the QHY9 is the same chip, and even cheaper still. Not much written about it though.

A QHY10 would be the same price as the 314L+ mono + bits.

Argh, so difficult to decide. Am I missing anything?