Re: Best Webcamera for Astroimaging currently?

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.


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.


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.
_________________________________________________

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

Relevant Pages

  • Re: Why not make the sensor larger?
    ... 16 frames ... there were enough photons in those 16 exposures ... I understad some of the problems with doing what Doug propsed, ... Since no current cameras can shoot 16 frames in under a ...
    (rec.photo.digital)
  • Re: How do they do it?
    ... You get an improvement that is proportional to the square root of the number of frames stacked. ... In other words, one good exposure contains a limited amount of information relative to the noise in the image (signal to noise ratio, s/n), a stack of four such exposures will contain twice the s/n ratio, a stack of 100 will contain ten times the s/n, etc. ...
    (sci.astro.amateur)
  • Re: Best Webcamera for Astroimaging currently?
    ... For short exposures, cooled cameras have no S/N ... don't want more frames, we want less and good quality. ... ditched webcams and stuck with the SX. ...
    (sci.astro.amateur)
  • Re: Meade DSI pro versus firewire webcam for planetary use?
    ... My understanding is that the DSI is optimized for long exposures, ... >many more frames of 8 bit quality and stack them... ... >planets with conventional CCD cameras, but these fps rates are even slower ...
    (sci.astro.amateur)
  • Re: "The exposures are at 1/100,000,000ths of a second"
    ... multi-sided mirrors that could "flash" exposures across several ... feet of filmstock in a fraction of a second. ... cameras have been equipped with high speed ... framing module would do three 10nS frames at microsecond spacing. ...
    (rec.photo.digital)