Quote:
Originally Posted by uwahl
Where astro CCD cameras really score is if you want to do any science (eg filter photometry)
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That's a really good point and one reason to look at a CCD for sure.
Quote:
Originally Posted by alistairsam
DSLR's are usually 12bit or 14 bit, OSC's are 16bit. the difference does allow for a greater range in shades of grey or colour.
I found I could stretch my qhy8 images much more than the dslr images.
just my experience though.
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That's interesting. Clearly the difference between 14bit and 16bit let alone 12bit - 16bit is very large. I'd be interested to know the ADC process though. Is it really that the ADC just chops that dynamic range, clipping extremes, or is there a more intelligent compression process that precedes it? If there is, how efficient is that algorithm? It might sound like a significant loss of dynamic range, but it could be less than it sounds. Just a thought.
Quote:
Originally Posted by alistairsam
QE - although most CCD's are above 55% QE (broadly speaking), I don't know if there would be a difference with QE measurements between the D50 and QHY8 as QE calculations for the dlsr aren't that straightforward.
The D50 is an exception amongst a few others in that it uses a CCD vs CMOS in canons. the QE of most canons are calculated to be between 25 and 40% with the exception of one or two that are quite high.
binning - as someone else mentioned, this is also an advantage with CCD's depending on your sampling and system image scale.
As for your broken CCD, why not get a replacement if its under warranty?
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The pixel size on my D5100 is 4.78um, whereas the pixel size in the mono Atik 314e that I bought is 4.65um. Additionally, I found a QE figure for the D5100's sensor, which is 48, vs 45 for the Atik 314e.
As for getting the CCD fixed, well it's already been "fixed" once, and given that I bought it over two months ago, I'm not really inclined to send it back for another long wait while it gets sent through the retailer, back to the manufacturer, which may or may not result in me having a usable camera at the end of it. I'm not convinced that the image quality will be a significant improvement over that of my D5100 now either.
I think probably the best "bang for buck" prospective for me right now is to just use my D5100 and get a decent intervalometer which will enable me to take exposures over 30 seconds.
Quote:
Originally Posted by LightningNZ
CCDs generally have bigger pixels for the same area - that's an advantage for the obvious light gathering potential but it also makes processing much quicker. Mono images are also likely easier to process.
For the same money you tend to lose a lot of area though. Why don't you just get a mono'd D5100 with a cold finger cooler? So you lose a little on fill (which is normally compensated by the micro-lens array) and you definitely lose on QE, but that's still a big, high-quality sensor right there.
-Cam
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A mono D5100 with a cold finder would be really attractive; unfortunately cost is prohibitive. I think by the time all of that was done (I wouldn't do it myself as I already fried a brand new dSLR trying to spectrum mod it once before) I'd have been able to get a decent CCD (as opposed to the low-end CCD I've bought previously).