Thursday, September 27, 2012

Advice for First Time Telescope Buyers...Contd (6)

Number 6: Computerized Telescopes
Many telescopes available today employ electronics, the main purpose of which is to help you locate objects in the sky. So called "Go to" telescopes locate things for you (you dial them up on a hand held controller). A second type (less common) type of computerized teelescope is called "push to". These will also help you find objects, but you physically move the scope while looking at a readout that guides you to your desired target.

All computerized telescopes require some kind of initial alignment (they have to be told "where they are" so they can subsequently locate things). After an initial alignment, you punch in the name of an object or select it from a list (usually through a hand held control) and the scope will go and find it for you. Do they work? Sometimes... but that statement comes with a number of qualifications. A number of the beginner go to telescopes in the market have had problems quality control and precision (although this has improved in the last few years). Some other points concerning GOTO scopes: (1) it costs money to add this feature; on a beginner scope (in my opinion) the money available should go into the optics as compared to electronic gadgetry. (2) Many GOTO scopes have libraries containing "tens of thousands of objects". The problem is (especially in the light polluted environment that most users will be in) that the vast majority of these objects are far too faint to be seen in a small telescope (even in very dark skies). In reality, the number of objects that will be visible (and interesting to a beginner) is probably less than 100 (one hundred). On any given evening maybe only 10 or 15 of these will be visible!

Personally, I am not a fan of low priced GOTO telescopes and I do not recommend them at the entry level price range. From my observations, the ones that are available in the entry level class simply do not work very well. I recently tried to help a young person at a star party who had an entry level go to scope (Meade). I was not terribly impressed with the scope's ability to locate objects. Despite a careful setup and alignment, the scope could not reliably place objects into the low power field of view (it was not too far off but for each object tried some manual button pushing was needed to get the object into the field of view). As an experienced observer I knew what to do to get the desired object into the field of view (after the scope got me close), but someone starting out would not have this knowledge. This would be frustrating to someone starting out as the scope might "just miss" showing one of the easily visible targets (the first time viewer will say "I don't see anything!). There are GO TO scopes that DO work well, however these are in a price class that (to me) is not in the entry level class (such scopes are typically over $500 and are often over $1000).
I grew up in the "old school" of amateur astronomy, that is, I learned the sky and learned to "star hop" to objects I wanted to observe. A higher end GOTO telescope does have some remarkable capabilities nonetheless. It can allow you to locate a number of objects in a short time. However, there is a drawback. While a GOTO scope can locate objects for you, it denies you the opportunity to learn your way around the sky. A GOTO scope is kind of like a car that takes you to any address you specify, but with no knowledge (or view along the way) of how to get there. With the star hop method, you learn to recognize star patterns and often you see interesting things along the way. While I am not a major fan of entry level GOTO scopes, I do recognize that some people do like them a lot, and for some applications they can be quite helpful. 

For example, if you have light polluted skies, it may be hard to use the "star hop" method of locating objects because there are not many stars that can be seen (necessary for star hopping). A GOTO scope will find things for you even if there are few stars visible to the naked eye. However, if your skies are particularly poor, don't expect to see much through the main scope either. Another thing about GOTO scopes: there is more stuff to act up and break down. A simple scope with a basic mounting is for all practical purposes a lifetime instrument, there are few if any parts that will ever wear out or stop working. Sooner or later (due to the sophisticated electronics, gears, motors, etc), most GOTO scopes will likely develop some kind of problem. So, I tend to not recommend entry level scopes with GO TO features, however that is my personal opinion. (The high priced ones are fine, but again, much more money).

Credit and Source:
Joe Roberts

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