Re: Best Webcamera for Astroimaging currently?

Chris L Peterson wrote:
On Sun, 15 Feb 2009 08:39:05 -0500, "Jason Banco" <a...@xxxxxxx> wrote:

You can say that, but I find a different conclusion. Also the fact that the cooled cameras are 16 bit for the most part.

There is no such thing as a 16-bit camera. The best astrocameras are
nearly 14-bit, but most are 12-13 bits. That's a significant improvement
over webcams which are at most 10 bits (usually processed internally to
8 bits), but you only see that advantage if your telescope is large
enough, or your exposure time long enough, to fill those larger wells.
Doing so improves S/N against a readout noise floor that is about the
same in both cases. But in bad seeing, you normally will reduce your
exposure time as much as possible, which also reduces the signal-
usually to less than 8 bits unless you have a very large aperture scope,
irregardless of what your camera's maximum well depth is.

I don't know if this is relevant, but when I was working for the imaging department for JPL, we found that 16-bits simply gave you more bits of noise to deal with. In other words, going from 12 to 16 bits simply adds bits to the low end of the response range (which makes sense if you think about it). Now, some people will say that you can extract information from those lower 2 to 6 bits, depending on a number of factors. I believe you can, but that it only affects special situations. If the images are dominated by a bright object that nearly saturates the sensor, then it matters little. Hence, for amateur imaging, most of the time, even if it is available, 16 bits doesn't add much.

I agree that going from 8 bits to 12 bits DOES improve things a lot in terms of processing the data.

[snip!]

Thousands of frames doesn't matter if the quality is not there to begin with.

Thousands of frames is the only way to simultaneously beat seeing and
get good S/N. That's a fact based on physics alone, and has nothing to
do with the type of camera. Lucky imaging is called that for a reason.
The worse your seeing, the more frames you will need to get lucky.

This has been known to professionals for years before the amateurs got a-hold of this. And it's been know to the military for far longer for guidance applications since the 70's at least.

I once imaged Venus with it was low, and none of the thousands of frames showed anything close to a half lit disk. I stacked them anyways, all of them, and there was a sharp half disk ! I DO agree that you get better results, especially on very find details, if you start off with good quality images, but I agree with Chris that if you didn't get good results, then something was wrong with Jason's setup or processing. And hundreds of others have gotten good results with these cameras over single-shots, as I personally experimented with and verified for myself. I think Jason's experience was unique.

Like I said, it does and I've seen this time and time again, which is why I ditched webcams and stuck with the SX.

Well, you should use whatever produces results you like. But my advice
to the OP is to not take your path, because it makes no sense and is
contrary to anybody else's experience I'm aware of- including the other
imagers you have named in this thread.
That would be my advice also. As Lazarus Long said, "The race doesn't always go to the strongest or the swiftest, but that's the way to bet."

--- Dave Nakamoto
.

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