With star-party season upon us once again, you’re probably confronting the age-old problem of how to protect your prized telescope from the triple threat of dust, rain, and heat. The traditional big, ugly trash bag or blue tarp works for two of those three (dust and rain), but looks bad and lets your scope to get way too toasty on a hot summer’s day. Alternatively, you can plunk down $50 or so on a proper dust cover, but if you’re like me, that cash almost always seems to go towards another eyepiece instead. Stumped? Don’t worry — a cheap, effective telescope cover is only as far away as your local hardware/camping-supply store.
For years I’ve used inexpensive, emergency sleeping bags to cover my scopes. How inexpensive? You can probably buy one with the loose change you’ll find in your sofa. (Go ahead and look — I’ll wait.) I bought one last week for $4.99 Canadian, but they can be had for less.
The bag is basically aluminized Mylar — the same stuff “space blankets” are made of. The brand I get measures 84″ by 36″, which means it’s big enough for a 16″ Dob. I use one to cover my 12¾″ scope, and there’s lots of extra room in there. And it works very well. Even in the harsh conditions found on Mount Kobau, the emergency sleeping bag keeps my telescope cool and dry. It really is a cheap and effective solution.
So what’s the downside? In a word, durability. This is definitely not a Desert Storm telescope cover. While I’ve used the same bag many times, it’s not going to last forever and I always pack a spare just in case. (Hey, at $5 a pop, why not?) Thin Mylar is pretty tough, but it has essentially zero tear strength. In other words, once a rip develops, it can quickly turn into a long tear. A hole is easy to fix if you spot it in time — just tape it closed with a bit of Scotch tape applied to the inside of the bag. It’s also a good idea to use a couple of loose bungee cords to take the slack out of the bag when conditions are windy. This will help prevent tears from getting started in the first place and cut down on the noise.
Here in Canada you can purchase emergency sleeping bags at your local Canadian Tire store. In the U.S. (and elsewhere) any good camping-supply store will have them. You can even order them at Amazon.com. (By the way, this is an ideal low-cost item for those occasions when you need to top up an order by a couple of bucks to get free shipping.)