When I was first getting into backyard astronomy in the early ’70s, most books recommended a 3-inch refractor or 6-inch reflector for a first scope. That was good advice for the kinds of things people generally looked at in those days, namely, the Moon and planets. Magazines were full of advertisements for Cave Astrolas, Star-Liners, Unitrons and Criterion RV-6’s. I, however, ultimately ended up with a 3-inch Tasco reflector — sort of the worst of both worlds. It wasn’t a great beginner’s scope, but I lived to tell the tale anyway.
If you’re out looking for a first scope today, chances are you’re considering something a lot bigger to help pull in deep-sky objects as well as solar system targets. And why not? Bigger is better, and never before has bigger been so inexpensive. Unless ultraportability is a major consideration for you, there’s no reason not to start off with a big-aperture scope if that’s what you want. The e-mails I regularly receive suggest this is exactly what’s going on. Thanks to the recent proliferation of affordable 10-, 12- and 16-inch Dobsonians, the whole concept of the beginner’s telescope is being redefined.
One reader wrote me because he wanted help choosing between 12- and 16-inch scopes. Not long ago this would have been a decision confounding only the very well heeled! So what advice did I offer? If you’re going to take that kind of plunge, there are really two things to consider apart from the specific features offered on individual models: size and price. Price is easy. If you can’t afford a 16-inch, then go for a 12. You won’t be giving up as much as you may suspect. Indeed, if you find the views in a 12 disappointing, a 16 probably isn’t going to do the trick either. Yes, the difference is significant, but going up from a 12 to a 16 gains you only about ½ magnitude in image brightness — a difference that’s likely not enough to make you say “Wow!”
Size and performance go hand in hand, but don’t forget to take into consideration how and where you’ll use the scope. A 12-inch is a pretty big machine, but with the availability of affordable, mass-produced truss-tube scopes, it is no longer something to be afraid of. Most any car is capable of transporting one of these, but check the weight of the heaviest component and consider whether or not you (and your back) are up to the task of hauling it up stairs and in and out of your car.
A 16-inch is another kettle of fish altogether. Even in a truss-tube configuration, it’s a big scope. I would never recommend that anyone purchase one sight unseen. Find a local astronomy club or visit a well-stocked telescope store to kick the tires in person. I’ll bet it strikes you as bigger than you thought it would be. If you even suspect the scope is more than you can handle, go for the 12. A 16-inch that ends up in storage will never show as much as a 12-inch in the yard.