Well the Holidays have come and gone again, and if the elves in your life are like the elves in mine, they really had no idea of what to give you for the Holidays. This is the start of a series of articles about astronomy equipment to help you decide what you might like. If you have questions about a specific piece of equipment, and how it compares to alternatives, send a note to me at and I'll see what I can find out.

It seems like the logical place to start is with the telescopes themselves. After all, this is likely to be the most expensive single piece of equipment you purchase with which to do your star gazing. We will discuss the basic advantages and disadvantages of these types of telescopes: refractor, reflectors, and compound reflectors (the Cassegrains) as well as cover some basic rules of selecting a telescope.

Rule #1: The best telescope for you is one that you will use frequently. This means you must be willing to set it up and align it. It also means you must be willing to carry it to where you want to use it. If it takes too long to set up or if it is too heavy to easily handle you probably won't use it as often.

Rule #2: Buy quality optics - the best optics you can afford. You may own this telescope for many years, and if it doesn't show you pinpoint stars and crisp clean craters on the moon, you will regret the purchase. Stay away from telescopes that brag about their magnification power. Buy from a reputable telescope store. Ask around.

Rule #3: Size matters. Buy the largest diameter telescope you can afford (reference Rule #1 though). Telescopes are sized by their objective's diameter. In a refractor this is the objective lens. In a reflector it is the diameter of the primary or objective mirror. The larger the diameter is the fainter the objects that will be visible through it. Magnification also comes with diameter. No matter what the package or the brochure says, your maximum useful magnification will be roughly 50 times the diameter in inches.

Rule #4: Choose the type of telescope that will fit your needs. Following are some advantages and disadvantages of the various types of telescopes.

Refractors: These are the most expensive type per inch of aperture. They are very rugged and low maintenance. They can be equatorially mounted (a must for astrophotography) or alt-az mounted. There are some very high quality refractors out there.

Reflectors: These come in two common configurations Newtonian and Dobsonian. They are the least expensive type per inch of aperture. They often require longer cool-down times, and may require more maintenance and adjustments. They also get rather long as the diameter increases. For a large Dobsonian you will need to use a ladder. Newtonians can be equatorially mounted for tracking and go-to capabilities. Dobsonians are usually alt-az mounted and are more difficult to computerize.

Compound reflectors: They are fairly compact and provide a long focal length in a short tube. They can be mounted on an equatorial mount or a compact fork mount. They may require a longer cool-down time, and may not provide performance as good as an equally sized reflector or refractor. They are fairly maintenance-free.

Rule #5: Unlike car dealers, most telescope stores will not let you take the telescope out for a test drive, and it is very difficult to evaluate it at the store. The solution, find someone with the telescope and kick the tires. The best way to do this is attend star parties. Get there early so you can see how the telescopes are set up, and identify the ones you want to check out after dark.

Rule #6: What is an F Number? For a specific diameter telescope, a larger F Number means you will have greater magnification. You will also have less field of view. It is often desirable to have a lower F Number if you are planning to do CCD photography. The CCD chip is so small that with large F Numbers only very small objects can be captured. A smaller F Number also results in faster photography times. I have an F/10 telescope. Meade has focal reducers that let me convert it to F/6.3 or F/3.3. Telescopes commonly range from F/15 to F/6.