Choosing and using a telescope
With the holiday season upon us you, or someone you know, may be shopping for a telescope. For the novice stargazer, it can be hard to sort through marketing hype. To reduce potential cases of the ‘closet telescope syndrome’, I present the following guide to help you make the right choice.
You may already own a great tool for stargazing – a pair of binoculars. Use binoculars to scan the rich star fields along the Milky Way and view large objects like the Andromeda Galaxy or the Pleiades star cluster. Binocular use is second nature for most people. When combined with a planisphere – the star wheel indexed with dates and times – binoculars provide a low cost way to find out if stargazing is a passing fancy or a passion. For beginners, I recommend a pair of 7×50 binoculars. Anything larger can be hard to hold still
Be wary of colorful packaging touting phrases like ‘450 power wonder scope’. Magnification actually means very little when selecting a telescope. The primary function of any telescope is to gather light. The larger the opening, or aperture, the more light the telescope can collect from a given target.
Large aperture will give brighter images and resolve finer detail. Magnification is adjusted by changing eyepiece lenses. Observe compact and bright objects like stars and planets with a medium to high power. Try a medium to low power for a distant galaxy or nebula. If you find a planet or stars hard to focus into a crisp image, move back to a lower power. As a general rule of thumb, the practical limit of magnification for any telescope is 50 times the aperture size in inches.
Telescopes, like people, came in a variety of shapes and sizes. The most common designs are refractor, reflector and hybrids like a Schmidt-Cassegrain telescope (SCT).
Refractors use a lens to direct light to the eyepiece. They are compact and require little maintenance. But, high performance models can be quite expensive. Refractors are best suited for lunar and planetary observing.
A reflector uses mirrors to direct light to the eyepiece lens and is the most cost-effective design per inch of aperture. On a simple mount, a reflector is the scope of choice for many amateur astronomers. Deep sky objects like nebulae and other galaxies appear best in a large reflector.
Hybrid telescopes like SCTs combine elements of refractors and reflectors with both a lens and mirrors. They are compact and many models offer computerized ‘GOTO’ systems. The hybrid design is a versatile choice offering good views of both planets and deep sky objects.
To narrow down the field, ask yourself these questions.
- What type of objects am I most interested in observing? Planets and the moon or deep sky objects like galaxies, star clusters and nebulae?
- What quality of sky do I live under? If your night sky is washed out by city lights, the moon and planets are your best targets. In a dark rural area, it may make sense to spend a bit more and get a larger aperture telescope. A good choice for apartment dwellers is an easily portable telescope that takes up little storage space.
- What is my physical condition? A telescope that is a hassle to get outside and set-up could seem burdensome and deter your interest in stargazing.
- How techno-savvy am I? Computerized telescopes can have a steep learning curve, but once mastered save time by helping track down celestial objects.
Take time to weigh your options. Attend events sponsored by your local astronomy club. Go to a star party and look through a variety of telescopes to see how celestial objects appear in different designs and magnifications. Notice the position you need to be in to reach the eyepiece lens. Is it too high for children? Do you need to stand or can you sit? Ask the owners why they chose the telescope they use.
Good luck with your quest and take the time you need to make a choice that will bring many joyful nights under the stars.
