From: Milton Aupperle <milton@outcastsoft.com>

Date: November 29, 2007 12:25:49 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Raising a heat issue


Hi Duane;


On 28-Nov-07, at 11:01 PM, Duane wrote:

When imaging, are you guys concerned about your body heat being near the scope when imaging? I usually position myself a ways form the scope and try to be down wind. Now that 

I'm imaging from a small observatory, I have a little less freedom in positioning. 


What about dew heater straps on scopes, will these cause problems? I have a dew buster with 

a temp sensor, which is supposed to keep things just warm enough to keep dew off (if used 

correctly), but I'm not sure. This is pretty hi-res imagery, should i be taking greater 

precautions against local heat turbulence?


Yep, it's certainly an issue if your parked in front of the optical end of the scope so your body heat rises. But up wind / downwind likely means very little difference.


I was collimating the C8 about a month using a Flea with the Laptop ago when it was around 0°C (it's now -20° dead air temp). It was amusing to see just how much heat distortion I generated just by putting my fingers in the light path to figure out what direction to turn the SCT secondary knobs. If you defocus the star into the "donut" you can see the rings move  form local (my hand) and building turbulence too. However once I removed my fingers, there was almost no local disturbence, even exhaling seemed to have little effect.


HTH..


Milton J. Aupperle