December marks the transition here in Michigan from cool fall weather to downright frigid winter temperatures. For most of January, February and March, there is snow on the ground and the daytime temperatures will hover around freezing. Nighttime temperatures will be well below freezing, and on those few precious clear winter nights it can be unbelievably cold.
1. Wear warm boots. When I meet people new to astronomy, they always want to know what the best telescope is and what accessories to buy. I always tell them, "The most important piece of equipment you will ever buy is warm boots". When it is clear, it is cold. If your feet are cold, you are miserable. If you are miserable, you are done.
Standing on the cold, damp ground outside you’ll soon know if your boots are up to the task. If they absorb moisture, or don’t insulate you from the cold ground your toes will be crying Uncle long before your favorite Messier object clears the trees.
2. Always dress for temperatures 20 degrees colder than you predict it will be each night.
For the most part, you are not moving around a lot when looking through a telescope, downloading images from your camera or monitoring your tracking. You don’t generate any heat of your own just sitting there, and the night air has a way of sucking the warmth out of you faster than you think it will.
3. Wear a hat. Most of the heat in your body escapes through the top of your head like a chimney. Cover your head and retain body heat.
I’ve seen lots of funky looking hats at star parties. Don’t worry about fashion. Go for comfort. My deep-winter, arctic-air-repelling hat is a big leather and fur job with earflaps and a long extension in back that covers my neck. I look like one of the wicked witch of the North’s soldiers in my long coat and that hat, but I’m warm.
4. Keep your hands warm. Mittens are better than gloves, but they are awkward to use when dealing with focuser knobs, charts, pens and pencils, But if you can keep your fingers together, tucked away from the cold, they fare much better than they do as individual digits exposed to the elements. I’ve never had much luck with those gloves with the flip-top mitten cover for your fingers.
If you insist on wearing gloves, like I do, keep your hands in your pockets and out of the wind, as much as you can. Those little chemical heat packs you can buy in sporting goods stores work pretty well for a while. I sometimes throw a couple in my coat packets to create a safe haven for my fingers for a few moments between variable star observations.
If your fingers begin to hurt from the cold, go inside or get in your car and warm them up thoroughly. Frostbite can be very painful.
5. Get out of the wind. Most of the time it’s not the air temperature that gets you, it’s the wind-chill. Put a building or a hedge, or better yet, an observatory, between you and the wind and you will be able to endure the cold for twice as long. The added bonus, of not having the telescope shake in the breeze, will save you time in making critical observations.
I remember very well the night that convinced me to build an observatory. It took twice as long as usual to set up wearing gloves, I dropped a small wrench in the snow and spent half an hour looking for it, the telescope was shaking so much it was hard to see anything in the eyepiece, my eyes kept tearing up from the wind and dropping tears onto the eyepiece lens, and the wind kept blowing right up my back as I faced south trying in vain to make variable star estimates.
I spent three hours out in the snow and wind and got exactly one variable star estimate that night. That week I became the proud owner of a fiberglass, domed observatory.
6. Don’t breathe on optics. Breathing on cold glass means instant frost. If you wear a scarf over your face, be sure not to let the warm air you exhale spill out over the top of the scarf and down onto the eyepiece.
Set up your finder-scope so you are not breathing on the eyepiece when looking through the finder. On very cold nights, I sometimes have a large patch of frost on the back of the mirror cell of my Schmidt-Cassegrain, caused from my breath freezing on the back of the telescope while looking through the finder-scope.
7. If you have dew heaters, use them right from the start of your session. They are much better at preventing frosted corrector plates, secondaries, eyepieces and finders than they are at removing frost. If you don’t have dew heaters, get them.
A heated box or holder for eyepieces can be a great benefit. If you only switch between a few, keep them in your pockets to stay warm.
Another accessory I find handy is a small hair dryer. If you have electricity available, one of these can be great to warm the eyepiece up enough to prevent fogging. If the lens or corrector plate on your telescope frosts up, you can use it to carefully remove the dew or frost.
You can also use it to warm your fingers. I’ve even stuck mine inside my coat to warm my frozen torso enough to go a little while longer. I’m sure this is a fire hazard, and you’ll probably read in the paper one day, “Michigan astronomer mysteriously ignites into flames, burning down observatory.”
8. If you take notes at the telescope like I do, keep your pen warm or the ink will freeze. I have one of those "astronaut pens". Even that froze at 20 below.
I keep my pens tucked behind my ear to keep them warm. All my observing hats have a distinct black ink spot on the inside lining, just behind my left ear, from me continuously sliding my pen in and out under my cap and over my ear for warm storage.
9. Use a plastic flashlight. If you are like most of my friends who read charts and log observations using a red flashlight, you put the flashlight in your mouth to write. On very cold nights, a metal flashlight can stick to your lip and be hard to remove without losing a bit of flesh.
Don’t laugh; I’ve seen it happen!
I suppose rule 9A should be, "don’t lick the telescope!"
If I ever see anyone get his or her tongue stuck to a frozen telescope, you’ll be the first to know!
10. Take breaks every hour or half hour, depending on the weather, and go warm up. Keep an extra pair of dry socks warming on the dash of your car, or go in and throw a pair in the dryer for a few minutes. It’s amazing how a nice toasty pair of socks can change your attitude!
I’ve received several pairs of electric socks for Christmas and birthdays over the years from well-meaning friends and family, but I’ve never been really impressed by them. Considering the number of batteries it takes to actually keep your feet warm, it’s just not worth it. Refer to rule #1. Wear warm boots.
11. Be aware of battery life in cold temperatures. The batteries in your flashlight, telescope, camera, dew heaters, etc., will perform poorly in cold temperatures. They’re smarter than me. They know when to quit. Keep warm extras handy.
12. Keep your own personal battery charged. Plenty of rest, a good meal, snacks and hot coffee go a long way towards warding off the inevitable freeze.
The search for a thermos that would keep coffee hot in sub-zero temperatures was my ‘Holy Grail’ for a long time. After years of searching, I finally found one at a camping supply store. It cost a pretty penny, but it makes all the difference to me.
13. Know your limits. You have to be realistic about how much cold, discomfort or pain you are willing endure in order to get those last few observations. Don’t wait until it’s too late and then decide to tear down and pack up.
When you are really frozen, you fingers don’t work right, you move slower, you feel more tired than you normally would, and you can get careless, dropping things in the dark or forgetting how to pack your gear just so. All this means it is going to take you longer than usual to tear down.
That’s when you will meet Mr. Frostbite. It is better to take my word for it than to learn a painful lesson from him.
With a little planning and common sense you can take advantage of those long, clear, cold winter nights. Orion, Gemini and Taurus are calling. Just be careful out there.