From: "doobisary" <tjp314@pacbell.net>

Date: July 15, 2010 10:20:19 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Impromptu ccd shootout

Milton:

I'd have to look for the file with the stats, but I probably did have the gain (brightness) set too high.  As I recall, it was somewhere left of center, probably around 400?

-Tim.

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:

Tim;

On 15-Jul-10, at 9:13 AM, doobisary wrote:

Jim:

Was this one of the Scorpions with the 9.9 micron pixels?

I did some imaging with my 1600x1200 scorpion while in Utah last  

week.  Since my NJP mount was incapacitated for a couple days (I  

broke the Celestron tripod I had it mounted on!), I did some  

unguided imaging with my Meade 2045/LX3 and Meade .63x FR.

I found it hard to take exposure longer than about 20 seconds  

without drift showing, so I kept it down.

I also found it hard to stretch the noise out so that it wasn't  

objectionable, and I wasn't too satisfied with what was left of the  

image when subtracting dark frames.  So, I kept my images on  

subjects like star clusters, where clipping off nebulosity wasn't a  

problem.

What gains level were you using (it's in the movie / frame capture  

logs if you do not remember) . My guess is your cranked the gain all  

the way up, which is where the noise comes in, especially for uncooled  

cameras.

Let me reiterate the mantra "Noise == Gain / Gain == Noise". Say that  

over and over and over :)

As I have said before, the Scorpion 1600x1200 have small pixel (3.6?  

microns if I recall right) sizes, so they are not really light  

sensitive compared to larger pixel sizes. For example a 9.9 microns  

Scorpion will be 7.56 TIMES more sensitive than the 3.6 micron  

Scorpion is. So a 10 second exposure with 9.9 micron pixels is the  

same as a ~76 second exposure for 3.6 micron pixels.

TTYL..

Milton J. Aupperle