From: Milton Aupperle <milton@outcastsoft.com>

Date: July 15, 2010 10:12:15 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Impromptu ccd shootout

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