Last week’s article was mainly about what not to do when purchasing a first telescope. This week, I’ll cover the specific things to look for when out shopping.
Regarding cost, the sky is truly the limit when it comes to telescopes. However, by choosing wisely to begin with, even a relatively inexpensive telescope can last you a lifetime. Pay particular attention to these suggestions if shopping at places other than astronomical telescope dealers.
There are three basic types of telescopes: the refractor is the familiar long tube with a glass lens at the end, the reflecting telescope uses a mirror rather than a lens, and the hard-to-say catadioptric uses both a lens and mirror. Each has its strengths and its weaknesses, but all can serve your needs if well built. First, ensure that the eyepiece (the part you look into) has a barrel diameter of 1.25 inches or more, and is made of glass, not plastic. If you’re not sure, back away. A good telescope must have a solid, vibration free tripod or mount. The tripod is usually an inexpensive telescope’s greatest weakness, and can make an otherwise good telescope into a poor one; you simply cannot see through a telescope that won’t quit shaking. One type of reflecting telescope called a ‘Dobsonian’ rotates on a flat base rather than a tripod, and is extremely stable.
The main purpose of an astronomical telescope is to gather light, not to magnify. The reason is that the objects in the sky you will be looking at are dim, not small. The larger the aperture (the diameter of the main lens or mirror), the more light it gathers and the brighter an object will be. The aperture is usually given in millimeters; that’s what the ‘50’ in 7x50 binoculars stands for.
You can safely ignore the high magnification numbers advertised by consumer telescopes; high power on amateur scopes (400x 500x 600x) is essentially unusable. I almost exclusively use 47 power, and honestly can’t remember the last time I felt the need to exceed 200x.
So, look for a telescope with a solid mount and with the largest aperture you can afford. It must also be small enough to store fully assembled, and portable enough to easily carry outside, or it won’t be used. If I had to recommend a type, I would suggest going for a ‘Dobsonian’ reflecting telescope. Dollar for dollar, they are the most stable, provide the brightest images and give you the most value for your money. If you have any questions, email me. I have a few scopes you could look through, and no end of free advise.
Choosing wisely will guarantee you years of hassle-free pleasure discovering the wonders of the night skies from your own back yard.
