From: "milton_aupperle" <milton@outcastsoft.com>

Date: December 30, 2009 2:03:30 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: NGC 891 Edge On Galaxy

Hi Jim;

I did get some binding once it dropped to -28°C, but a 1/4 turn of the worm gear set screw fixed that up. The heating pad wrapped loosely around the mount makes a huge difference, as at -32°C with no heat, I can barely turn the Dec axis with both hands.

Colder temperatures do help reduce hot pixels and noise levels on the CCD for long exposures. For short exposure, I don't really see much difference.

HTH..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, Jim Chung <jim_chung@...> wrote:

Milton,

Fantastic image!  I see that your heat packs appear to be working well  

in that you managed 20 minute guided exposures in -30C weather!  I  

wonder if the low temperatures have any beneficial effects regarding  

noise on the ccd.  The image certainly looks very clean.

I was trying to image Mars 2 mornings ago when it was only a mere  

-15C.  but it was cold enough that my Hotech laser collimator wouldn't  

fit into my dob focuser.  The Hotech has some rubber rings that when  

tightened allow it to self align itself but the metal on the focuser  

had contracted so much that it wouldn't fit!   I decided to forget  

about collimating, it was still pretty good from last time but the  

seeing was nasty and my feet were freezing up - so I went back inside.

Jim