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Old 13-01-2013, 09:29 AM
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gregbradley is offline
Join Date: Feb 2006
Location: Sydney
Posts: 15,618
Ah yes the old whats better mono or one shot colour CCD argument!!

I've shot extensively with DSLR, modded DSLR (several), one shot colour and several mono cameras.

I would argue the camera that is best is the one that bests suits your intended images, time, budget and mount/scope. A high end heavy mono camera on a scope with a weak focuser is a waste. Same with a poorly tracking mount. You won't get happy results. I thinking its about matching your gear up well.

One shot colour cameras are improving all the time. The ideal ones for some reason do not seem to be on the market yet or the one shot colour crowd have't ordered them specifically or some such. They really need the later developed Kodak True Sense sensors. Why? Because your standard colour is created by a filter matrix of RGGB repeating pattern called a Bayer Matrix. Its in almost all DSLRs and colour chips. Kodak developed a ClearRGB matrix to improve low light performance. Per them this improves low light performance by 2 to 3X. Sensitivity of these chips is only a little bit below a standard mono chip. So you could have the best of both worlds.

Starlight Express, FLI, Apogee may have these. You can specify a sensor with these brands. Starlight would be the cheapest. But all 3 would be out of your $1000 budget though.

Otherwise I would agree that one shot colour is quite limited for DSO in heavy light pollution. Although I think its Allan Gould has posted some high quality images using just that from Brisbane. Judicious use of a light pollution filter is probably a must.

One shot colour because 4 pixels are taken up to make one colour dot in an image are handicapped for narrowband. You can take Ha images with them but with greatly reduced sensitivity as only the red filtered pixels are really contributing to the Ha image so thats 1 in 4. It works out a bit more than that but not much.

With mono on the other hand every pixel counts.
For narrowband work you normally look for a sensor with high QE (quantum efficiency that is the sensitivity of the sensor to light) and low noise. 15 to 20 minutes is a good exposure time so that puts pressure on your tracking and autoguiding. Once you add in filters and a filter wheel $1000 is not enough to get a mono, filter wheel and filters. You would also need some software to process the images.

So one shot colour is still your best bet. Its a lot of fun and you get instant images, less prone to clouds moving in stopping a sequence (you need 4 filtered images to make a colour image from mono usually - LRGB).

I hope this helps. QHY8 is a popular choice and is likely to be in your budget. Theres a QHY14 which has more megapixels that seems nice.

Modded 350Ds are very cheap and a very high performing astrophotography camera as an alternative.

A number are using cooled 40Ds and they seem to shine. A modified Canon 5D would be an awesome alternative. There is always a chance of picking one up on Astromart from time to time.

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