I am often asked to recommend a suitable telescope for newcomers to astronomy. This is a rather difficult thing to do as selecting a telescope is a personal matter, for instance, like buying a car, clothes or books. Before deciding whether you favour a refractor, reflector or catadioptric there are several criteria to be considered, and ultimately there can be no “correct” answer.

It is useful to remember that Sri Lanka is in the equatorial zone and affected by two monsoons. This results in skies that are often overcast and therefore not ideal for astronomical observation. This suggests that some users may be better served with easily portable instruments.

I itemize below some other things to be considered:

(1)        Where do you live? (In a city, countryside etc.)

(2)        From where will be observing ? (Home, a National Park, Wet Zone, Dry Zone etc.)

(3)        What type of objects will you be observing? (Sun, Planets & Moon, Double stars, Deep-sky objects, Comets etc.)

(4)        Where will you store the telescope when it is not being used? (Room indoors, Garage, Garden shed etc.)

(5)        Will the telescope have to be light, portable and easy to transport, or will it be situated at a permanent location? (Balcony, Observatory, Garden etc.)

(6)        Are you reasonably fit; (i.e. can you carry your telescope to and from the observing site and if necessary up and down stairs, or into and out of, your vehicle.)?

(7)        What kind of vehicle do you have? (Car, Van, etc.). If you use a motor scooter, motor bike or public transport, then you will be best served by binoculars).

Having considered all the points I have listed above you will then have to decide as to which type of telescope will best suit your needs. In general your choice will be limited to one of the following designs.

Refractor

Pros: Very sharp images if well made. Closed tube requires little or no maintenance and never needs recollimation. Can be easily used for terrestrial observing. Best for Solar observation (when used with safe solar filter), double and multiple stars, the Moon and Planets.

Cons: Could suffer from chromatic aberration. Can be long and unwieldy in larger apertures. Usable but not ideal for Deep-sky Objects (DSOs).

Cost. Good refractors are usually expensive. For example a 4 inch at the lower end of the scale can cost USD 400 whereas a top 4 inch model can exceed USD 10,000.
(On a personal note to me a refractor is the “King of Telescopes”).

Reflector

Pros: Good images, especially if long focus i.e. f 8 or more. No chromatic aberration. Good for most objects, including planets, the moon and especially so for fainter DSOs.

Cons: Requires regular maintenance and frequent recollimation, especially if a “fast” design (i.e. f 6 or less). Mirrors deteriorate over time dimming the image and making periodic re-aluminizing necessary. Open tube permits entry for spiders, insects, dirt, dust etc. In general not usable for terrestrial objects; usable but not ideal for solar observing.

Cost A usable 6 inch reflector can be had for around USD 500.

Catadioptric

Pros: Good images, very compact - the most portable design. Closed tube requires little maintenance. Can be used for terrestrial and solar observing (when used with safe solar filters). Smaller telescopes (8 ins. or less) are possibly the best design if portability is an important consideration.

Cons: Require recollimation from time-to-time. Mirrors subject to deterioration resulting in a slow dimming of images over time. Inside of corrector plate collects dust, fungus etc. If the primary mirror gets out-of-collimation the instrument must be returned to the manufacturer for recollimation. Compact but not necessarily light.

Cost around 700 USD for a basic 3.5 inch model. Of course you can buy a 3.5inch Questar for around USD 6,000.

Binoculars

Pros: Good for the Moon, brighter Comets, Nebulae, and Deep-sky objects. Usually wide fields-of-view. Can easily be used for terrestrial observing. Highly portable. The best instrument for beginners.

Cons: Cannot be used for high power observations. Occasionally require recollimation. Beware, as there are many Poor quality instruments on the market, so buy a reputed make. Avoid binoculars with gold, ruby or red objective coatings, which are not ideal for astronomy.

Cost: Around USD 200-300 for a good basic model.  Very cheap models, while useful for many purposes, are unlikely to be satisfactory for astronomy. Of course top models can cost well over USD 1,000.

In conclusion

These are my personal views, others may have different opinions. Don’t be guided by my comments alone, research the subject, read the test reports, talk to other astronomers and “try before you buy”. Remember buying a telescope is a personal choice and only you can decide on what suits your requirements. And remember the old adage "Different strokes for different folks" and that “One man’s meat is another man’s poison”.

Finally, about prices. Costs vary greatly from time-to-time. So check on the internet for current prices.

                                    
                                                                       Quote

"When talking about telescopes it is not only the size of objective that has to be considered; there is always the man at the small end".  (Rev. W. H. Stevenson). 

© Copyright 2016 Rex I. De Silva