As mentioned in a previous blog entry, I’ve been trying to arrange that the observatory PC can remain outdoors in our frigid winter temperatures and still start reliably when I need it. The problem has been the hard drive – at sub-zero temperatures it won’t start, and the PC fails to boot. I tried replacing the mechnical hard drive with a solid-state unit and, while this solved the temperature problem, it created other problems, and I returned to a mechanical drive.
Heating just the interior of the observatory with a heater designed to keep things just above freezing wasn’t a solution. When the ambient temperature dropped below about -15°, the heater couldn’t keep up and the pocket of air in the bay where the computer sits was still about -5°, too cold for the computer.
The deep dip on this graph was an observing run with the interior heater switched off (once the PC is running, its internal heat keeps it healthy). But you can see that the temperature was sitting at -5 to -8, even with a “no freeze” space heater running in the observatory. (Outdoor temperature was about -20 at the time.)
So, I decided to try installing a small, low-power heater inside the cabinet of the PC, with a thermostat to keep the cabinet interior just above freezing. Continue reading
Last night was the first clear night in over a month (that I was was available), so I spent it doing some imaging. The 3/4 moon was too bright for anything serious, but it was OK to work on adjusting autoguiding parameters.
It was about -20C. That’s cold. The PC wouldn’t start, so I think I am officially off the air in the cold until those enclosure heaters arrive. The LCD monitor also faded to near-invisibility, and I’m thinking I may need to apply a heater of some kind to it too. I eventually got the PC going by leaving it powered on with the “can’t find hard drive” message on the screen, until the internal power consumption heated the interior somewhat.
Then I found I was getting strange effects with autoguiding, with the Declination guiding adjustments moving four times more slowly than the RA. I suspect a problem with backlash or stiction in the Declination gear. I did a bit of data gathering to better quantify some of the effects, but I wasn’t having fun in the cold, and called it a night after a couple of hours. I’ll have a look at the Declination gears and backlash during the day on a coming weekend (in a thoroughly-heated dome).
Once I get the heaters working and the declination adjusted I think it will be practical to do some basic image acquisition in extreme cold, but it’s not fun to be trying to do adjustments in those conditions.
Big grin: this is so cool. Friend and fellow OAF Attilla created a Clear Sky Chart for the observatory. It’s not at all necessary, as there are others nearby, but it’s a wonderful perk that has me grinning ear-to-ear.
It’s been cloudy for a month now, so no observing or imaging.
I am continuing my long-term project of setting up the obervatory PC to work well in cold temperatures.
I had originally tried setting the PC up with a solid-state drive, thinking the lack of moving parts would make it an excellent cold-weather PC. The cold-weather part worked fine, but the PC was unreliable booting from the solid-state drive, and I eventually gave up on that and went back to the original hard drive.
The problem with the hard drive is that when the observatory is cold (below about 0 Celius), the hard drive has trouble getting spinning. Sometimes it fails completely, giving a BIOS error. Even when it boots, I have to believe it’s not good for it to be spinning up when things are tighter than usual because of the cold. Continue reading