I have one of the Milwaukee battery heated jackets and wear it when shooting skeet and sporting clays in cold weather. It has three heat levels and works fine for this. As I recall the heat is on the back and front only. None in the sleeves. I’ve had it for several years and the newer ones may be different. Just checked on Amazon and that’s still the case.
If you’re going to be peering through an eyepiece for long periods, besides clothing a foam pad might help. I remember watching the Winter Olympics in Lillehammer years ago and a lot of spectators at standing-only outdoor events were carrying half-meter squares of foam rubber – like a midget yoga pad – to stand upon.
With the added benefit of putting some insulation between your feet & the cold ground.
Just came home from an evening shoot immediately after work. Loafers are not warm shoes. 
Another vote for glove liners. I have one pair with a pocket in the back that holds hand warmers in place. Also, look into something like this. It allows your to take off your glove to adjust settings but still keeps your hand somewhat protected from the elements. I just bought one as a gift for my shooting partner as an Xmas gift but she hasn’t used it yet. It have other Ruggard products & did see it hands-on in the store; it seems good.
One other thing to think about if you’re out that long & it is a cold night; do you have extra camera batteries? Cold batteries don’t last nearly as long as warm ones do.
Sorry for the delay in response; yesterday was crazy busy. Thanks for all the tips so far!
We’re doing night photography in one of the darkest places in the lower 48. A campfire kind of defeats the purpose.
I have some of those, but I’m also taking ski mittens. I like the idea of the silk liners, too.
It’s mostly going to be sitting around between shots, but I like the idea for cold other night shoots.
Yeah, I have several batteries. I also might strap a hand-warmer to the battery side of the camera, and I’ve heard of keeping fresh batteries in pockets so they get some body heat to keep them warm.
Of course, it’s all up in the air now, since BBNP is slowly shutting down. If the government isn’t fully funded by Jan 20, the whole trip will be cancelled. Grrr.
The insulating quality was the main benefit; any foot comfort the bonus. Any ground freezing the surface ice to the consistency of granite is something you want to put an additional layer or two in between.
BBNP — one of my favorites. I hope the gov’t stalemate is resolved by then so that you can make your trip.
Over the last several years, I have had problems with cold hands while wearing ski gloves at not all that cold temperatures, say 20 degrees. My wife found a pair of heated gloves on 50% sale (still $125!), and they have been very good for me. The batteries live in the long gauntlet cuff of the gloves, and stay out of the way. It’s a bit of a juggling act to get everything powered up and running, but, once they are on, they do very well. At the low setting, the batteries supposedly last 6 hours (we’ve never actually tested them to exhaustion), and keep my hands comfortable at lower temperatures. Sometimes, when my hands get chilled before I turn the power on, I turn them up to high (supposedly 2 hours), but only until things warm up.
Without them, I would be seriously limited in doing things outdoors in the wintertime.
My recommendation would be to go on Amazon and search for “fleece heated usb.” This will turn up options that will work as a middle layer and use non-proprietary batteries (usb power banks). Look for something with heating elements where you like, decide whether a vest or something with sleeves or a hood works for you, and work out how big a battery you want.
Me, I’ve got a Prosmart fleece vest and an Ororo jacket. I bought the jacket first and it’s okay but the battery doesn’t last long and it looks like it will be hard to find repalcements soon. I’ve got a spare and get 8 hours swapping the two on Medium, which works for anything Central KY can dish out.
The Prosmart has a 1000maH battery and fits under normal outerwear, so not only does it last longer but a good outer layer (like my motorcycle jacket) holds in the heat so I can use a lower setting. The downside compared to the Ororo is heating element placement - both are on the chest and back, where the Ororo has them at the back and midsection so putting your hands in your pockets accesses the heat. There’s also an element at the neck, which helps.
If it weren’t for needing a vest (my moto jacket has tight sleeves) I’d likely have gone with a Volt Resistance Omega hoodie. Back, neck and pocket warmers, power bank to adding more time is easy, looks like a normal gray hoodie, and the on/off switch isn’t glowing on your chest (which people ask about).
I didn’t like any of the 12V-powered stuff, which use commonly available but huge batteries.
I have it and haven’t been pleased with it. Just to offer a differing experience. Don’t know if there’s something wrong with mine, but it just doesn’t heat up the way I expected. I bought it a couple of years ago for walking the dog at night in the winter, she needed a good walk three times a day. But the year after I bought it I stopped bothering to use it, and she passed away this past summer Now it’s just sitting in the closet. As was mentioned, it uses the same battery as some of my Milwaukee tools so I use the battery and charger, just not the jacket.
I’m a native Minnesotan. I would do the foam pads on the ground even if you are just going to be sitting around during the shoot. Insulating you from the ground will be pretty important.
I’d do chem packs for your hands and feet - you can always slip them down between your shirt and jacket if your core is cold.
And you can get a propane heater which won’t put off much light at all. Look for something that is good for a fishhouse - it will be portable.
Speaking of fishhouse, some form of shelter? Wind can be a huge factor and getting wind off your face and ears is a huge relief when its really cold.
I’d echo the portable shelter. I sat in one of these heated by one of these for over 10 hours during deer hunting in weather that started in the teens and never got above mid 20s. Take a good sized piece of cardboard to block the heater from any breeze that comes in through the open windows. Sit your chair on a piece of carpet pad to isolate your feet from the ground. Since I was in tall grass, I also set the heater on a piece of plywood to knock down the grass around it. The stand can easily handle two adults, the heater, a cooler, and a tripod. This, and chemical hand and toe warmers along with the chemical body warmers should do it. Wear some type of face mask and you can use the toe warmers taped to your cheeks and ears.