SCT and Extreme Cold
Posted 09 February 2013 - 02:02 PM
Yes, I know, I am nuts, but clear skies have been far and few between this winter. I took my SCT beyond it`s usual -20 cut off.
Some things I have learnt over the years with my SCT.
1. They do take a long time to get in tune with the temperatures.
2. A dew shield is essesntial.
3. If you are going to observe in the cold, use an AC power adapter.
4. The motors will groan and protest.
5. I don`t have one, but my next investment will be an el cheapo focuser, because when it is very cold, the mirror flop is more pronounced and tough to get focused.
6. Know your hand controller, because you are not going to see it when it`s all frozen up.
7. Keep slewing distances short. Plan your session.
8. Do not attempt to roll your wires and cords up neatly. Take them in the house in the stiff frozen state that you find them in.
9. Listen to Uncle Rod.
10. A well collimated and cooled down SCT is a thing of beauty. My best planetary views have taken place with this humble 8 inch mirror.
Posted 09 February 2013 - 02:30 PM
My record is 7F. And my mount wasn't happy, nor was my laptop.
Posted 09 February 2013 - 03:02 PM
Posted 09 February 2013 - 03:45 PM
If you have 82 degree EPs, they perform really well in a cooled down SCT. Remarkable I would say. They do stay fairly true to the edge.
I should also mention, it is not wise to drink beverages from a can.......
Posted 09 February 2013 - 05:24 PM
Looks like you've been working beyond limits of scope and man.
Posted 09 February 2013 - 06:02 PM
Posted 09 February 2013 - 06:56 PM
Posted 10 February 2013 - 02:27 AM
Yes, I know, I am nuts
Who are we to argue.
But your also desperate........ Uh,.... I mean brave.....
Posted 10 February 2013 - 03:45 AM
Rather cold for my tastes. I freeze when it DROPS to 65!
Right now, at 5 p.m. in San Antonio, on Feb. 9th, it is 63F. It was a little chilly today.
Posted 10 February 2013 - 10:46 AM
Posted 10 February 2013 - 12:12 PM
Also fingers go numb during brief moment s when I need to remove the gloves for dexterity. Sometimes it is difficult to apply pressure to tighten things up. More recently I had my Orion 9x50 RACI finder fall out and the diagonal broke off ... Not too expensive a 2nd finder but very functional and expensive to replace ... I was p****d.
So I try to remenber to recheck the tension on threaded items as the temperature drops.
I find Baader Click-Lock connections are best all around and especially in the cold.
Posted 10 February 2013 - 01:20 PM
Rather cold for my tastes. I freeze when it DROPS to 65!
The coldest I've ever observed was about 42, one September night in Lockwood Valley (about 60 miles north of LA).
The coldest I've ever *experienced* was about 16 degrees, but that was on a trip to Russia, and only for long enough to get from the terminal into the taxi.
I hear of life in truly cold weather with awe, as when reading science-fiction about frosty alien worlds as a teenager...
I can't even bear to watch penguins on TV, unless it's summer.
Posted 11 February 2013 - 07:51 AM
A few extra tips for your list. I tune (clean, polish bearing surfaces and regrease) all my mounts using Molykote G4501. This is an NGLI Level #1 grease with PAO (polyalphaolefins) that is good to -60F. We use it in our equipment in the polar regions. Grease normally used in our mounts are rated to maybe 0F, and will complain a lot well above this temperature. I don't know how my new motorized focuser is going to deal with this, however.
Tip #2: I also use hand warmers slipped down the back of my gloves.
Tip #3: If you are using a battery, keep it warm in the house until needed for observing. Li-chemistry batteries do better in extreme cold than wet or gel. Regardless of battery type used, keep it warm by placing it in an insulated bag or cooler. And never place the battery directly on the cold ground or snow; place it on at least 2" thick piece of foam board or wood.
Posted 11 February 2013 - 09:19 AM
My last three sessions took place in a total combined -97 Celsius. Last night (early morning) it was -32 Celsius.
I can scarcely imagine. I have experienced 20 below in Maine, but I dang sure did not try to observe.
One thing I've done to keep the HC more legible in our much more modest cold--uppper 20s, worst case--is rubberbanding chemical handwarmer packs onto it. Whether that would work in your arctic conditions, I dunno.
Posted 11 February 2013 - 11:00 AM
Here, our best nights are often those frosty winter nights. transparent and cold!
Posted 11 February 2013 - 09:56 PM
Ditto on the dew shield - I use one every time out anyway.
I'll remember the hand warmer idea. Plan on taking the scope out tomorrow night.
Posted 12 February 2013 - 05:39 PM
Posted 13 February 2013 - 03:16 PM
I've always been afraid to take it apart and re-grease it...
Posted 13 February 2013 - 07:52 PM
Posted 15 February 2013 - 08:22 PM
Posted 16 February 2013 - 02:12 PM
Posted 18 February 2013 - 02:52 AM
1) I use a thin pair of finger gloves inside bigger, really thick thumb and hand gloves. That way, when I need dexterity to adjust something small, my fingers don't immediately go numb never to recover.
2) Both dew shield and dew heater in combination are needed for extended viewing sessions with the C8Edge, at least here where it is often somewhat humid.
3) I've started closing (not latching) the eyepiece case between switching eye pieces to avoid the lenses getting covered in frost. I usually leave the caps off for more convenient switching, the eyepieces dewing up is usually not a problem but frost on the lenses is.
Posted 18 February 2013 - 08:58 AM
More often I wear multiple insulated layers and wool socks. My observatories are both on raised wood decks with rubber mat floors. It's amazing how that keeps your feet warm. On concrete or asphalt my feet are freezing in a matter of an hour. On the observatory floors it just doesn't become a problem. And that is without the Sorrels just my house shoes.