From: Milton Aupperle <milton@outcastsoft.com>

Date: December 8, 2009 3:49:27 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] cold weather..

Hi Mark;

Nope never heard of them before. Thanks for the link.

On a related "extreme weather" topic, I managed to capture a fairly decent  image  of the "Cold Crab" M1 last night despite the frigid well below normal temperatures.

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/ColdCrab_M1_LRGB_20091207_MJA.jpg 

I shot eight 12 minute Luma and then turned on Binning 2x2 to shot the RGB color channels as five frame each of R 5, G 3 and B 2 minutes exposures. This is on the C8 at 1150 mm focal length and I had the Grasshopper EXHAD camera cooled to -45°C. Applied darks (including synthetic darks), flats, stacked it and then did some image processing in Astro IIDC.

I think some of the color cast issues are due to frost / ice on the CCD, as the corrector plate had some frost on it at 2:30 am when I finished up and the CCD in the camera was 20°C colder than that. I probably should not have cooled the camera at all.

It was -28°C outside (that's 14°C below normal temps) and the air had moderate ice crystals which added haze and raised the sky background light pollution substantially, even with the Hutech IDAS LPR in place. The slightest breeze drove the temp down well below -35°C. The firewire cables were like solid rods and caused some tracking issues because they wouldn't flex as the mount moves, so I need to rethink my cable management set up. The GPUSB and Keyspan RJ12 cables were like fragile little pieces of balsa wood, stiff and ready to snap. I had a heating pad under the laptop and both of them inside a clear plastic bag to keep the heat in, which worked well as the laptop hard drive didn't freeze solid like last year, but it makes it awkward to use for focus and capture. I wrapped another heating pad around the mounts main axis, gearing and motors which worked well at eliminating binding of the HEQ5 mount with these large temperature swings. It basically can not handle more than about 15°C swing in temperatures without needing to be re-tuned, which means removing the front electronics plate screws, then loosening the 3 bottom hex bolts and then with another allan key, loosen or tighten the worm positioning bolts, all barehanded. If you live in a cold climate, don't buy a Synta HEQ5 / HEQ6 (or Sirius/ Atlas mount) or your just asking for heart ache.

One nice thing about temperatures below -25°C is you get virtually no mirror flop on the C8, as the focus knob is so stiff and slow to turn that it barely moves. I imaged M45 first then swung over to M1 and no shift in the image or change in focus.

TTYL..

Milton Aupperle

On 8-Dec-09, at 2:17 PM, Mark Gaffney wrote:

Hi Milton, were you aware of this group, 

Mark..

http://tech.groups.yahoo.com/group/extremeastronomy/