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Keeping Warm While Observing

Cold winter nights at the eyepiece can be so uncomfortable as to dishearten some budding astronomers. I’d like to tell you some of my tricks at keeping warm. I was a hunter in Upstate New York for years, and if there is anyone who knows how to keep warm, it’s a hunter. Hunters sit for hours without moving, even minimizing their breathing motions. It’s this lack of motion that causes one to be susceptible to cold.

The first principle of keeping warm is to wear more clothing. If you are not so bundled up that your motion is impaired, you’re not bundled up enough. I accumulated, over a period of years, my warm clothing… lots of it… and on cold nights I wear it ALL. For temperatures in the 20’s, I may wear three warm pairs of leggings, three warm pairs of socks in my oversized boots, and four layers of warm stuff under my down jacket. As the temp gets lower, or as the wind picks up, I add headgear, gloves, and other body and leg clothing layers as needed. With this approach, I generally stay as snug as a bug in a rug for a whole night of observing.

Boots: snowmobile boots have a 3/8″ thick tightly matted wool liner, under which you can wear multiple socks. These boots are rubber below the ankle, but have only a nylon shell to cover the liner above the ankle. The U.S. Army makes two types of winter boots, each of which is very warm — a “wet cold” variety that comes in basic black, designed f or temps down to -20 F (fondly known as “Mickey Mouse Boots”, because their insulation makes them somewhat bulbous); and a “dry cold” variety that comes in basic white, designed for temps down to -65 F. The snowmobile boots are readily available, at K-Mart perhaps, while the Army boots are seldom available, and expensive. The Army boots are highly recommended, should you come across any of either type.

Socks: wool is best, mostly-wool is next best, and nothing else is nearly the same. Don’t wear cotton. Cotton is for keeping cool in the summer! Its insulating value is less than that of most synthetics.

Leggings: some year, spend the money to get good wool long underwear or thick polypropylene long underwear. If you use it only for star-gazing it will last many years. Wool is more durable but seems eventually to shrink or deform regardless of how well you take care of it. I have found the polypropylene underwear to be VERY warm, with some warmth when wet though with less wet-warmth than wool. It “pills” fiercely when abraded, worse than polyester. Over it, put a very thick wool pant. I mean 1/8″ thick or so. You can get these at most good hunting supply stores, or probably they will occasionally be available at places like L.L. Bean. Spend the money, for such pants will last longer than you or I will. Mine are 15 years old and hardly show wear. Warm? Sheesh! Over that, wear an oversized tightly woven pant or wind-breaker. Down pants are O.K. for an outer layer if the weather is very cold. (Down always has to be the outermost layer, for it loses its insulating ability when compressed.)

Chest: alternate tightly woven layers with loosely woven layers, so as to lessen convection between layers. At least one sweater should be a turtleneck. Over these, a thick jacket (down is probably best, but other warm jackets will probably be satisfactory). The jacket should have a drawstring at the bottom and the bottom should be below your buttocks. Insulated pockets are a desirable plus. The neck should be adjustable so as to allow you to tighten it so as to prevent air loss regardless of whether the hood is up. Most truly warm coats have a hood, which offers much better cover than a hat.
The best hoods have a drawstring around the face opening, not around the neck. North Face brand does all these things right.

Head: a ski cap under the hood is necessary on only the coldest nights. Take one with you. They’re fairly inexpensive, even the woolen ones. Yes, that means you cover your cheeks and forehead with the ski cap, if needed. These caps also cover the neck.

Gloves: a real pearl of information here — go to a store that specializes in backpacking and rock-climbing gear and get a pair of rock-climbers’ gloves. They have the ends of the fingers cut out, and they’re wool. You could cut the distal portions of the fingers off of any old pair of gloves, but you will like the non-fraying toughness, fit, and warmth of the store-bought ones. And get an over-sized pair of mittens, into which you can stuff your hands, gloves and all. Two thick layers on the hands is a big help. The mittens preferably will be wind-proof and warm, such as insulated leather with pile lining. Or, you could use insulated wind-proof pockets, but I usually find that my pockets are full of other things when stargazing, and they’re not a good place to put my hands. Since the mittens will be removed frequently to enable you to handle eyepieces, star charts, etc., it is helpful to attach a string to them, and run the string through your sleeves, as small children do.

Please note that I have accumulated these items over a number of years — sort of like accumulating gizmos for telescopes, I guess.

Where socks overlap the lower ends of leggings, I alternate overlaps. That is, I pull my long underwear over my first layer of socks, and then put on another layer of socks that overlaps the long underwear, before I put on the next layer of leggings… and so on, alternately. This type of overlap creates a friction that makes it nearly impossible to expose bare skin at the junction. I do an analogous overlap of layers at the junction of pants and sweaters and at the junction of sweaters and gloves. (That makes it impossible to see my wristwatch. If I need to know the time on cold nights, I usually keep my watch with my eyepieces or tell time by the stars.

I have rarely resorted to brief exercise to keep warm. It is effective. Remember, it’s the sedentary nature of stargazing that makes the astronomer so susceptible to cold. I have done “jumping jacks” on more than one occasion, and once I jogged a mile down the road and back! Since I usually stargaze alone, nobody knew of this eccentric activity. Generally, I have resorted to exercise only when I had come to my observing site unprepared for the unexpected cold. If you exercise, you are likely to sweat, and then you will feel cold and clammy as you cool down again.

Therefore, exercise probably should be done only if you are wearing clothing that retains its insulating properties when wet. No fabric is quite as warm when wet as when dry, but wool is best in this regard, and polypropylene is next best. Cotton next to the skin is VERY bad in this regard. I swear it’s colder than nudity when it’s wet (I have a tale to tell about that… but just believe me: it’s warmer to be naked than it is to wear wet cotton). One more thing about exercise: relying on it to keep warm can lead to sore muscles if you are not in good shape, and worse — it can lead to exhaustion. The latter is very dangerous in the cold, for when it happens you will have no further resource for warmth. Exhaustion can be delayed by having had plenty of high-calorie foods to eat recently.

Warmth can be noticeably enhanced by eating sugary foods. I expect that some of you won’t believe that until you’ve tried it. Candy bars freeze hard as rocks, but small pieces of hard candy can be sucked on, usefully. Hot liquids, of course, have a noticeable warming effect. Hot chocolate is ideal, for it contains lots of sugar. Carrying a thermos is a lot easier than whipping up a brew in the field. It’s a lot better than a pocket warmer!

I have had little benefit from pocket warmers. They just don’t provide enough heat to make a difference. Furthermore, their very principle is wrong. The body uses the extremities (hands, feet, nose, ears) to help regulate body core temperature. When your core temperature drops, circulation to the extremities decreases drastically, in order to preserve body heat. So cold extremities may mean that you need more insulation ON YOUR TORSO AND HEAD, not on your extremities. And, if your torso and head are well enough insulated, your hands will stay warm in very cold temperatures indeed. By the way, the head has the least natural insulation (i.e., body fat) and a great deal of heat is lost from it. Try that ski cap!

I think that if you get cold despite bundling up, it’s time to go indoors! Relying on exercise is a bit risky. Whatever you do, don’t push yourself to stay out in the cold too long. This is especially true if you are at a lonely observing site. Cold can kill. What if your car won’t start….

One useful source of information about this is “Winter Hiking and Camping”, by John A. Danielson. It’s published by the Adirondack Mountain Club, 172 Ridge St., Glens Falls, N.Y. 12801.

I hope this has been helpful. Happy winter observing to you!


by Roger Venable