[Aavso-photometry] Re: How cold is too cold?

[Michael Koppelman]

At about -10F my mount starts acting funny. Stuff usually works pretty 
well until then. I cool my chip down to -45C and colder if I can. I 
have not seen fogging or the like. It sure is nice to drive the thermal 
noise down to nothing. I personally would not worry about the camera. 
The mount, if it starts struggling, is another story.

On the human side, I am a study of layers when it gets that cold. I 
probably have 10 layers or so on -- thermal underwear, thermal shirt, 
t-shirt, cotton shirt, fleece, fleece, quilted shirt, fleece, parka or 
something like that. I'm all about hoods, too. I have hoods on 2 or 3 
of my layers and they make a big difference. When you are sitting still 
it becomes virtually impossible to stay warm but with even slight 
movement and a lot of layers I am perfectly comfortable below 0F.

Cheers,
Michael Koppelman
http://www.lolife.com/astronomy/

On Jan 5, 2005, at 10:03 AM, Richard Huziak wrote:

> A local department store is offering a discount for next week based on 
> the daily temperature.  Today, I can get a discount of 34%, since it 
> is -34 deg C right now.  For us Canadian humans (with small, but very 
> intelligent, brains tucked deeply inside thick crania for 
> cold-protection), this temperature is no really big deal, except that 
> it limits our *visual* observing sessions to only a few hours before 
> we have to think about warming up a bit.
>
> However, my question is related to the other half of the equation - 
> equipment.  Vance Petriew reminded me of a conversation with Arto 
> Oksanan at the Berkeley Conference regarding winter temperatures in 
> Finland, where Arto stated that "it's so cold that when he turns the 
> CCD cooler on, the camera 'warms up' instead".  Yep - same here.
> Since I use borrowed equipment, I don't want to over-stress what is 
> not mine, and our informal rule is not to use the telescopes if the 
> ambient temperature is <-20 deg C (mostly because the underpowered 
> motors on the smaller scopes have trouble keeping up & make strange 
> noises), and not to cool the CCD below -45 deg C.  I recently emailed 
> SBIG and asked what minimum operating temperatures for their cameras 
> were and what the minimum cooling temperature was.  They replied that 
> they did not recommend 'cooling' the camera to below -30 deg C but 
> said nothing about survivability of the camera itself, i.e. - what the 
> cold operating temperature of the electronics is.  They were concerned 
> what below -30C, moisture would leech out of the desiccant and fog the 
> CCD.  I regularly cool the camera to -45C and don't see this, maybe 
> due to the usual 10% winter humidity, but am concerned a bit about 
> thermal stress.  I run on either Meade LX-200 12" or 14" scopes on 
> their fork mounts and use any one of the ST-9XE, ST-10XE or TC-237 
> cameras.
>
> In my experience, commercial equipment may not work well below -20C 
> (if cold started), and equipment built to military standards (which 
> the cameras are not), should cold-start at -40C with no problems.
> So - Cold Boys!  Those of you that run equipment and cameras under 
> extremes of temperature, can you please comment on the surviveability 
> of your equipment and problems you have in the cold.  I'd like to be 
> able to extend my -20C run temperature if possible, because I am 
> currently missing a whole lot of nights where I might be running. :-)
>
> -10C = 14F
> -15C = 5F
> -20C = -4F
> -25C = -13F
> -30C = -22F
> -35C = -31F
> -40C = -40F
> -45C = -49F
>
> -- 
>
> * * * * * * * * * * * * *
> Richard Huziak
> Manufacturing Engineering
> SED Systems, Saskatoon
> tel. (306) 933-1676
> <huziak at SEDSystems.ca>
> * * * * * * * * * * * * *
>
>
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