[Aavso-photometry] Calibration Frames

[Jeff Hopkins]

Hi Bob,

I spent my last few years in NY in Syracuse so know your frustration.

Darks don't expire as such, but if the ambient temperature is warm to 
hot, current temperature darks become more important.

I have a big problem with darks during the warmer months here in 
Phoenix. Typically observatory temperatures at midnight can approach 
100 F. I added a TEC to my DSI Pro and it brought he temperature down 
about 40 degrees and made the camera considerably less noisy and the 
dark frames worked much better. I have found that once you get below 
about 50 F the camera is pretty good noise wise and darks become less 
significant, but still should be used. You might consider a fan for 
the DSI Pro since your ambient temperature will be much cooler than 
the camera, you can cool the camera even further fairly easily and 
reduce the noise way down.

Good luck with your observing. I've been clouded out all of 2008 so far.

Jeff

At 13:27 -0700 01/06/2008, Bob Crumrine wrote:
>Hi Jeff,
>
>Then you understand my frustration with the cloudiness around here 
>this time of year!
>
>What's the best way to really tell if a set of darks has 'expired' 
>and needs to be retaken?  I remember early on seeing my images get 
>speckled after a while (points in the image that weren't really 
>stars), retaking the darks and then the backgrounds were dark again.
>
>Bob

-- 
Jeff Hopkins
HPO SOFT
Counting Photons
http://www.hposoft.com/Astro/astro.html
Hopkins Phoenix Observatory
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Phoenix, Arizona 85033-2439 U.S.A.
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