I am a novice in astrophotography. But I do have some experience in the use of cameras, computers, and accessories in cold and remote locations, including skydiving into the North Pole. Here are three suggestions.
If you have sufficient electrical service, via extension cords or batteries, you can use an ordinary personal heating pad beneath your computer to keep it warm. If using 12 volts and you have a large battery, you can find 12 volt heating pads on Amazon. If you add a box of sufficient size, (including the one you store and transport your astrophotography gear in) you can put the heating pad in the box, along with your computer, batteries, etc., Have all of the gear you plan to heat inside and warm until you need them, so that the heating pad only needs to keep them warmer, not heat them up. One feature to avoid is that many newer heating pads have a safety feature that turns heating pads off after relatively short amount of time. Our home one does so after just a half hour. Thus you may have to dig around in your's and your neighbors' closets and cabinets, for an older one that stays on for the whole night of imaging.
A second option, for smaller items such as intervalometers, external batteries, or even cameras themselves around the battery compartment, is to use ordinary chemical hand warmers placed directly onto them. I have made over 500 cold weather skydives with camera gear, and on the colder days, using ordinary elastic bandages to ensure the hand warmers remain in direct contact with the gear.With some experimentation, you can determine the number of wrap layers needed to meet your needs. Note that elastic wrap layers limit the amount of oxygen that gets to the hand-warmers, reducing the amount of heat they provide. But this can be a good thing, for it also extends the amount of time the hand warmers work. You can also use a hand-held paper punch to cut holes in the elastic wrap, allowing more oxygen in, and increasing the heat they provide, but at the cost of not warming as long.
All of the hand warmers have safety labels warning you to not put them in direct contact with skin. But when skydiving into the North Pole, and later cold, but less extreme jumps, many of us put hand warmers inside our gloves, on both sides of the hands. You can't do a lot for individual fingers while using them, but warming the palm and back side of your hands does serve to warm up the blood going into the fingers. It helps.
Edited by TWB, 19 February 2021 - 10:36 AM.