Re: Best Webcamera for Astroimaging currently?


"Chris L Peterson" <clp@xxxxxxxxxxxxxxxxxx> wrote in message
news:nk1fp49tneeiats0qc8lvpphf1tc1ftdb7@xxxxxxxxxx
On Sat, 14 Feb 2009 21:44:10 -0500, "Jason Banco" <a...@xxxxxxx> wrote:

With the cooled
cameras, the SN ratio is greater and therefore we need far fewer frames
than
with webcams.

That's not true. For short exposures, cooled cameras have no S/N
advantage. In fact, because they are designed for long exposures, they
frequently have higher readout noise specs than good digital video
cameras. So you may actually pay a noise penalty using a cooled
astrocamera for planetary work.


You can say that, but I find a different conclusion. Also the fact that the
cooled cameras are 16 bit for the most part. Again, most folks say it
doesn't matter, but just try processing an 8 versus 16 bit image and then
you see that it does. I know, 8 bit is stacked into as much as a 32 bit
FIT, let's say, but I still see a difference if 16 bit is started off with
first.

That's true, BUT in critical cases, where seeing isn't the greatest, we
don't want more frames, we want less and good quality.

That makes no sense. The worse the seeing, the shorter the exposures
must be, and therefore the more you need. When you have great seeing,
you may only need a single exposure.

I guess I'm not making my point here, so I'll try again. Let's look at it
this way: I use a Toucam in poor to average seeing. I set for 1/15 sec
exposures and then capture 1000 frames of Saturn over and over again
throughout the night. After reviewing the frames, I find only 50 or so as
best quality and stack them. However, because the Toucam individual frame
quality is so poor, I can do no processing on these. A person then says,
well you didn't have good enough seeing. Why then can I do this process
manually, with a cooled 16 bit CCD camera, end up with 20 or so decent
frames, stack them, apply processing and the result is *always* better?
This is why my opinion differs from what others say. I consistently get
better results with the cooled camera versus *any* Toucam, videocam, etc
which are 8 bit and not cooled. Thousands of frames doesn't matter if the
quality is not there to begin with.

Ed Grafton is a good example. So is Damien Peach, especially his earliest
work. And, don't forget that Eric Ng's Toucam was cooled so he didn't
need
to capture as many frames.

Eric's camera was cooled so he could capture _more_ frames. Cooling
reduces dark current noise, which allows for a longer total exposure
time, with a consequent improvement in S/N. If you can capture your
image in just a few short frames, cooling provides no S/N advantage at
all.

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.

The bottom line is this, unless you have tried it, don't knock it until
you've done so. It's not a one night deal either. It took me a good many
months practicing technique before I started obtaining superior results. Up
until that point, no webcam, Luminera, etc ever got me to the place that the
SX camera has. As I told someone else, more patience is required because
the "manual" part of the job is much greater than with webcams, but the end
result is better and this is in poor to average seeing conditions.

The aforementioned is my final word on this topic. I see the original
poster has already decided on a webcam, so there's no point in continuing,
but I felt compelled to point out that in my personal case, I definitely
felt that the cooled cameras were superior. He may find otherwise unless he
spends a great deal of time with the latter.

Jason

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


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