Updated 23 January 2011

Amateur Astronomer's Notebook

Keeping Warm at the Telescope

This article will provide my (Joe Roberts) personal recommendations (based on actual experience) for keeping warm while observing on cold winter nights.

Winter skies often provide some of the best viewing (as far a dark, clear skies are concerned) however the cold weather often deters astronomers from getting out on such nights. Most people can tolerate a short time in extreme cold, but driving up into the mountains (in search of dark skies) requires a much longer duration in the cold since there may be no place of warm refuge available. I have found that there are a number of ways to stay very comfortable on even the coldest of nights, even when you have no choice but to be outside all night. I base these claims on experience with cold weather observing since 1975. Basically, the requirements for staying warm fall into two categories: (1) dressing properly and (2) using "heating" accessories . It will take longer to prepare for a cold weather observing session. You can stay comfortably warm all night in the winter if you are willing to put the extra time in!

Dressing Properly

When dressing for cold winter observing, I recommend the following:

Of critical importance when dressing for cold weather survival: avoid seams at the point where clothing meets. Make sure each layer of clothing interleaves and generously overlaps the previous layer. Make sure shirts, underwear and socks are extra long (6" more than seems necessary is usually good) for tucking in. Losing heat in seams (when bending over for example) can quickly lead to feeling cold! Tip: go to the bathroom BEFORE dressing! It's not easy to take care of business through 3 to 4 layers of clothing!

One of the critical areas in keeping warm is the head and neck. I find that hats alone are not adequate (they leave too big a seam at the neck and shoulders). A hat (or face mask) combined with a hooded sweatshirt is the way to go. The hood string should be tied! The hood eliminates the seam and keeps you much warmer. On the very coldest nights I wear two hooded sweatshirts plus the face mask!

Because you will be wearing anywhere from 2 to five layers of clothing, you will look much fatter and movement will be somewhat restricted. Agility can be restored (relatively speaking!) by making the clothing in each layer one size larger than the previous.

Heating Accessories

Despite the availability of very heavily insulated clothing that is now commonplace, in my experience devices that generate heat are a necessity for extended observing on cold nights. The following items are recommended:

Other tips

Below are some other tips and recommendations to help you keep warm on those cold winter nights:


By dressing properly and using heat generating or retention accessories, you can stay very warm and comfortable for an entire night even under very cold (like 0 degrees F) conditions. It will take longer to dress (and undress), and you will look much fatter and heavier! If you wear a face mask, you may even begin to look like you come from another planet. Follow the recommendations on this page and you will stay warm!

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