A crash course in buying a Telescope.

Let's get one thing straight-this post is informative.So, if you are not the least bit interested in astronomy or anything related to it, you'd do better to skip this post.
This post is for all those people who want to, or are in the process of, buying a telescope.I've given as much information about telescopes as i can fit in here.Before starting, here's a description about my telescope.

CELESTRON 31034
76mm Dia-600mm FL
Accesories: Two eye-pieces(4 mm and 20mm FL)
One Barlow lens



Any telescope consists of two main lenses:
Objective-It is the lens that recieves the light from the source.
Eyepiece-It is the lens that is near to the eye.

A telescope is as good as the apperture(diameter) of its objective lens and not the length of the telescope, as is the popular opinion.This is because a bigger apperture collects more light and hence gives a better view.In the description above, 76mm is the diameter of the objective lens and 600mm is it's focal length.Similarly, 4mm & 20mm are the focal lengths of eyepieces.Any one is used as per the viewing requirements.

Calculating Power(Magnification): Power is calculated by dividing the focal length of objective by that of the eyepiece used for viewing.Ex:When i use a 4mm eyepiece i get a magnification of 600/4=150. similarly, with 20mm i get 600/20=30.
Barlow lenses are also called doublers.They are used for doubling the magnifications.When i use a Barlow lens in combination with a 4mm eyepiece, i get a magnification of 3oo,ie 150x2.

Useful Magnification:Some telescope manufacturers claim that their small but powerful telescope gives a magnification of 600.Though this is possible using appropriate lens combinations, it may not be useful.Every telescope has a magnification limit(which depends on it's apperture size) beyond which even if you increase the power there is no visible use.A rough formula for calculating useful power is to multiply the apperture diameter(in inches) with 50.Hence,my telescope's useful power is approx. 3x50=150.So, there is no point in using my 4 mm eyepiece with a barlow lens as it would give a power of 300, way past my telescope's limit.

If you are low on budget then a telescope with appertures of 3 to 5 inches should do just fine for an amateur observer.It is quite useful to get to know how to use a telescope. As and when you think that you have utilised your "small" telescope fully and are getting serious about observing, you can always shift to bigger apperture telescopes(which are costly, i must add).

Mine is a small telescope, but it more than serves my purpose of a leisure activity.It has given me some of the best viewing experiences of my life.Someday, i'll get a bigger better telescope, but this one is my first love.

If you need more information about telescopes, binoculars or astronomy in general, visit the following links
http://www.televue.com/engine/page.asp?ID=140

http://www.skyandtelescope.com/equipment/basics

Binoculars