I want to share with you today a new toy I picked up to help keep me somewhat warm on those frosty fall observing nights or in those cold winter observing nights. It is the Coleman Sportcat Catalytic Converter. I picked mine up from Walmart for $33.00. I had really considered purchasing the Coleman Blackcat Catalytic Converter (Amazom) but the cost for that was around $55.00 and cost won out on this for me. I will state that the Blackcat Converter does put out more heat and perhaps I should have gone that way. I'll let you know for sure after this winter season IF I get observing time. It's not looking good out here in Utah for new moon in November right now.
This little heater operates on a small bottle of Coleman Propane gas and it needs a match or similar device to start. To start you simply turn the switch to the on position after lighting the match, and then hold the match to the top on the side. You'll get a quick wiff and then the heater is going. You can see this in this image:
Here the heater is going and if you put your leg or hands over it, you can feel the heat kicking out. Now in reality in the field, you don't see the heat as in this image but you can feel it. The amount of heat coming out is not like a single or double burner of the kind used in ice fishing as seen here at Cabela's. That type of heater really cranks out the heat and will keep an observing area warm though this will impact night vision. You'd need to set this up away from the telescope if you use the Cabela version that I posted a link to. If you don't want one of the Coleman versions then I would recommend this heater from Cabela.
Anyway, back to the Coleman Sportcat. My Sportcat doesn't put out any where near the heat of either Cabela's heaters, but it is enough to do several things. I have used it under my fold up table and it kept my legs really toasting. I have also used it with a field blanket where I spread out the field blanket to capture the heat coming out and that has warmed me up. It is wonderful for warming up cold hands and I have also placed it in the passenger floor of my Pathfinder and cracked the windows in the front and it has really warmed the cab without running the car. Finally, I used it one evening (to see if it worked) in the backyard by the scope and it helped at the telescope to keep me and the scope a little warmer. I may have to try it on a dewy night to see if it can help with that though I doubt it.
The downsides. Don't expect this to put out enough heat to counter the cold of the night. It isn't designed for that. You still need the right clothes and other equipment to keep you warm. It helps, but isn't a cure all. Next, the Sportcat stands nicely, but has no way to be leaned over (though I made a solution by making a tilted stand where the handle grip fits into to keep it tilted). Next, if you use it in a tent or in a car/SUV/Pickup etc. you need to keep a couple of windows cracked by an inch or two, or you run the risk of hurting yourself (or perhaps even killing yourself). I one pound bottle of gas will run this unit for over 24 hours in my experience.
So though not a heat furnace, this little unit does quite well in the field for what it is. It warms the hands, feet, legs and can help take the edge off a cold night while observing. Robert and Barbara Thompson discuss the use of heaters such as these at this link from their book, Astronomy Hacks. This link takes you to a site to download the book I believe, but I am not sure if that is legal. Here is what they said:
"Sadly, fireplaces are rare at observing sites, but there is a next-best solution. Portable catalytic propane heaters put out enough heat to make heat packs and other personal warmers seem tame by comparison. Catalytic heaters burn fuel without an open flame, and are safe to use inside a tent, vehicle, or other closed location as long as you provide some ventilation.
Don't buy a kerosene heater or a non-catalytic propane heater. These units put out a lot of heat, as much as 25,000 BTU/hour or more, but they produce much too much light to be usable at a dark observing site. They also cannot be used in a closed location because they produce deadly car-bon monoxide gas.
Coleman (http://www.coleman.com) offers several models of catalytic propane heater that produce from 1,100 to 3,000 BTU/hour. (We recommend the 3,000 BTU/hour units for astronomy.) These heaters use disposable 16.4 ounce propane cylinders, which sell for a couple bucks at any hardware store and last from 8 to 18 hours, depending on the output of the unit. Catalytic propane heaters burn with a soft orange glow that is barely visible, even when you are fully dark adapted.
We don't want to overstate the amount of heat these units put out. You won't even notice the heat as you move around your observing site. In fact, the first time we fired ours up, we thought it hadn't started. It takes several minutes for the unit to start completely, and even once it's started, the heat is not obvious in the open air unless you are quite close to the unit. But 3,000 BTU/hour is a significant amount of heat if you concentrate and contain it. Figure 1-2 shows Robert warming himself with our catalytic propane heater. The blanket acts to trap the heat, and after a couple of minutes it becomes comfortably warm inside the impromptu tent.
If you or one of your observing buddies has a van, that provides the ideal solution. Simply place your catalytic heater in the van at the beginning of your observing session and start it running, leaving a window cracked a few inches for ventilation. Depending on how well the van is insulated, a 3,000 BTU/hour catalytic heater can raise the interior temperature by 20°F or more, providing a warm refuge for your observing group.
Don't forget that your coat and other cold-weather clothing are as good at keeping heat out as they are at keeping it in. When you're in the refuge, open or remove your coat to allow the heat to warm you."
I think they make some very valid points here and ones that I wanted to include in the blog. So here you have it, though not perfect, the little guy helps. I may still pick up the second link from Cabela's as I think that puts out a little more heat but I'll go by this weekend (if weather permits) and take a look at it. Once again, hope this helps someone.