Factors to consider when selecting a reasonable entry level telescope?
Be very careful when looking at telescopes from general stores and toy shops (in general). Do not be mislead by colourful advertising of cheaper telescopes suggesting magnification capabilities beyond 400X.
The entry telescope you will buy will most likely be dependant on your budget and your area of interest. Possibly the best thing all new comers should do, is visit their local astronomical club. Normally you can experience many different telescopes at many different budget levels. If you ask each person what scope to buy you will get a different answer from each person... listen, learn and make up your own mind about what you will want. But if you are like me, where a nearest astronomy club is not always conveniently located nearby, this then may not be an option for all.
Well, what is your budget, and what is your area of interest? Looking at the area of interest question, do you wish to restrict your astronomy to visual observing, or do you wish to extend to photography? Many questions should be considered, but knowing what questions to ask is the problem for beginners. Here are some things to consider.
If you are ready to purchase your first telescope, be prepare to spend about $500-$800 (Australian dollars). This would be the minimum spending threshold, as a telescope is one of those things where you want to buy a decent one, or not buy at all. A cheap mass market telescope is more frustration than it is worth. Poor design, poor optics, poor focuser, light weight tripod, all the things that will result in a bad introductory experience.
To start, what type of telescope is better to begin with: a reflector or a refractor? A general rule, good refractors are EXPENSIVE to buy, whilst reflectors are normally far less expensive and work very well. Most amateur and almost all professional scopes are reflectors for this very reason. Good performance at lower cost.
Next, considering magnification and field of view, how much power do I need? 200x, 300x, 500x?
Well, magnification is not what you are looking for; aperture is the important feature. Aperture is diameter of the main lens or mirror, measured in inches or millimetres. The larger the aperture, the greater the light catching capability of the telescope. I typically use between 60 and 150x for most of my observing, with higher magnification (more than 250x) being only rarely usable because of viewing conditions. 150x-250x is ideal for most planet viewing, anything more makes the viewing blurry and possibly, highly unstable because of atmospheric conditions.
A telescope of six inches or more in aperture is ideal in regard to reflectors. With good seeing conditions, a six inch telescope is possible to see any of the messier objects and beyond. This includes star clusters, nebulas, and dozens of galaxies. A telescope of this size will also provide excellent views of the planets.
When considering a telescope, examine the tripod/ mount. If the mount is not stable your image will jump about, particularly at high power. You should be able to move from one point in the sky to another quickly and smoothly. Fine motion controls are an important feature for object tracking.
To alter your magnification, you will need to change eyepieces, and the standard size of eyepieces is 1-1/4 inch. So ensure the focuser of the telescope accepts eyepieces of at least 1-1/4 inch. Remember that your eyepieces may represent a substantial investment over time, and the 1-1/4 inch will be usable with any scope you buy in the future. Cheap telescopes use 0.956" eyepieces.
Taking into consideration the above, for a first scope I would suggest a reflector with a minimum of a six inch mirror, probably a dobsonian. But if you afford it a little extra, get an eight inch. To the right is a picture of a dobsonian, they look a little unusual, but they work very well.
A six inch to eight inch telescope should cost about $500-$650 (Australian dollars) new, and budget for a little more for a few accessories and guide books.
I would suggest you buy your telescope at a local astronomy shop. You may pay a little more, but a good store will offer assistance with your new scope, showing you how to set it up and use it.