Re: Comet like Ring nebula, or a planet

Chris L Peterson wrote:
On Mon, 29 Oct 2007 14:31:05 -0600, Greg Crinklaw
<theskyhoundyoureye@xxxxxxxxx> wrote:

While I agree that a dark sky will be critical to visual observers, isn't this a little over stated for imaging? I mean, the sky background can always be removed from the signal as long as the signal to noise is great enough can't it? Isn't that why imaging can be done from light polluted locations? Easier maybe. But I think critical, no.

You can subtract out the skyglow signal, but that glow produces its own
noise (equal to the square root of the skyglow signal) which, like any
noise, can't be removed. It sets a fundamental limit on S/N, and if we
assume that the most interesting stuff to be seen in the comet is either
very faint, or very low contrast, sky noise will prevent it being seen.
So yes, I'd say that dark skies are very important if the goal is to
tease out very subtle detail.

It is my understanding that this limit is more a practical limit than an actual physical one. Either way, I hereby freely admit that I am splitting hairs. ;-)

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

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