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

[Richard Huziak]

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>
* * * * * * * * * * * * *