Telescopes & Binoculars | Second Hand Electrical Appliances & Items

Many an amateur star gazer has lost enthusiasm and left this wonderful hobby altogether simply because they made an impulsive and hurried choice when buying their telescope. In order to help you avoid this, let's take a look at the basics of the instrument. Once you know what to look for, that knowledge will go a long way to helping you make a correct choice and enjoy priceless hours of gazing at the starry skies.

Size
A large telescope on a generous mount is definitely an impressive sight but think carefully about whether it will serve your purpose. Ensure that it is not too awkward or inconvenient for you to carry it outdoors and that it will not take too long to set it up and take it down.

Aperture
The basic job of a telescope is to brighten and magnify the celestial objects and the aperture mainly determines how bright the objects will appear to you.

The aperture determines how much light enters the telescope. So clarity and brightness of the image is thus largely determined by the aperture. To make this point clearer: suppose you magnify an image without changing the aperture - the total amount of light does not change but the device tries to get into finer detail of the image. So you end up with a dim and blurred view of the object - somewhat like peering in candlelight at a coin placed several feet away.

Generally, you can have anything between 20 to 50 times 'worthwhile' magnification per inch of aperture. Any magnification beyond that would be useless. The problem with most celestial bodies is that they are too dim, so a larger aperture is necessary for viewing them. If you want to view a few dozen galaxies which are 50 million light-years away, you need at least a 4 Ω inch reflector, but if you use a 12 Ω inch reflector, then with the same magnification, you will be able to view hundreds of galaxies as if they are nearer than the moon.

Focal Length
Focal length is the next most important aspect of a telescope. The technical specification of a telescope will quote something called f/ratio. Well, f/ratio is the focal length divided by the aperture. Telescopes with higher f/ratios allow for crisper magnification. So, you may feel that the general rule is to go for the largest and longest telescope you can afford, but there is no such general rule.

If you want to concentrate on bright objects like the moon or planets, go for a telescope with higher focal length, but if you want to view large sweeps of the Milky Way, a small telescope with shorter focal length will be ideal.

If you want a little of both, the do-it-all specification may be a 6 inch aperture where once again you'll have to make a choice between wide-view (around f/5) and higher power (f/8 or more). Just in case you miss the point, please remember the longer telescope will be more difficult to carry, mount and dismantle. So, you may want to have a balance which will satisfy most of your requirements.

Telescope Mounts
This is the next most important part of a telescope. A good mount should be steady, sturdy and should move smoothly. There are basically two types of mounts - the equatorial mount and the altazimuth mount.

Equatorial Mount
This mount allows movement along celestial north-south and east-west. So, if you align one axis of the telescope with Polaris, you can view celestial objects as the Earth rotates just by rotating the telescope around this one axis only. Many equatorial mounts come with electric motors which do this for you. Using motors to move the telescope in the desired direction comes in very handy if you want to do telescope photography or use the telescope for group viewing. The downside is that equatorial mounts are generally bulky.

Altazimuth Mount
This mount moves up and down (altitude) and right and left (azimuth). A camera tripod is the best example of an altazimuth mount.

You have to continuously move the telescope in two planes to track celestial bodies as the earth rotates on its axis. Those who use these mounts master this apparently difficult task within a very short time. Another advantage is that these mounts are a lightweight and compact,

Eyepieces
Most telescopes come with a few eyepieces, but you should increase your collection to cover a wide range of magnifications. You might like to consider buying a Barlow lens. It multiplies each eyepiece's magnifying power two to three times. Thus you effectively double your collection of eyepieces by using a Barlow lens.

Finder
A telescope shows you a tiny piece of the sky and at times you seem to loose your bearings and can't find the object you are looking for. A finder does that job for you. High end telescopes are sold with finder scopes which actually are tiny telescopes mounted on the main telescope. Crosshairs on the finder scopes' eyepiece help you to train the main telescope on the desired target.

Binoculars
These are graded in terms of magnifications and apertures. So, a 7x50 binocular is one having a magnification capability of 7 times and an aperture of 50mm. The binoculars get heavier as the magnification power increases. So, it's advisable to stay within x10 when choosing binoculars for general use.

If given a choice between a pair of good binoculars and a small telescope, you should opt for the binoculars because they are convenient to use and would not perform any less well than a small telescope. Cost-wise, binoculars also very reasonable to buy and compare favourably with the cost of telescopes.

Conclusion
Take time when choosing your telescope or binoculars so that they suits the tasks for which you will want to use them. Make sure that your choice is simple to operate, not cumbersome and not too heavy.

Whichever type of telescope or binoculars you choose, never look directly at the sun, even if you use a dark filter. This will almost certainly and irreparably damage your eyesight.