Buying a Telescope

• Mail Order is fine, and I don't know any local sources.
• Meade and Celestron are very good brands but except for a new $200 line from Celestron, they are not cheap.
• Edmund Scientific is in Barrington, NJ (south) and is reasonable.
• The best beginner scopes are 3 or 4 inches in DIAMETER.
• The length is somewhat irrelevant - the shorter the telescope in length the easier it is to use.

but... don't buy magnification. Read on..

BIG RULE:

The useful magnification is

60 times the diameter of the telescope in inches.

For example, if you see an advertisement (click to see one) for a 60 mm telescope (60 mm is 6 cm or about 2.5") then the largest magnification that's useful is 2.5 x 60 or about 150.

So... is 675x power a fraud?

Well...that's a harsh term. A little techie explanation if you don't mind. The power of a simple telescope is the focal length of the "big" lens or mirror divided by the focal length of the eyepiece. In a formula it says: "Magnifying power = (focal length of objective)/(focal length of eyepiece)".

The objective is the expensive, large diameter lens, the eyepiece is a little, relatively cheap lens near your eye. If you make the eyepiece's focal length shorter and shorter and SHORTER, the power gets bigger, and bigger and BIGGER. Alas, it also gets blurrier, and blurrier, and BLURRIER.

So - resist those late night ads on QVC and HSN and the slick catalogues from DAMARK and SHARPER IMAGE, if they're pushing a tiny scope with huge power. Buy diameter, not power. You can always juice the power with another eyepiece, but you've got to have enough light entering the scope to magnify.

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