Some Frequently Asked
Telescope Questions

A: Generally speaking, one should buy the largest aperture one can afford. However just because a scope is bigger doesn't mean its necessarily better. Believing this falsity is what some amateur astronomers often call "Aperture Fever." In reality, the larger a telescope gets, the harder it is to maintain the tight tolerances of precision optics. Many bargain Dobsonian telescopes boast HUGE apertures, but not so great mirror quality. Don't ever forget that you often get what you pay for. Additionally, a large-aperture scope will not be well suited for use in an urban setting, where light pollution many negate the positive effects of a bigger scope. As a final word of caution, consider one of the finest telescopes ever made: the famous Questar Maksutov-Cassegrain. This scope produces some of the finest images available, and the system itself is a virtual work of art. By the way, its aperture is only 3.5 inches. 

Q: The more it magnifies, the better it is, right? 

A: Nope. This is a common ploy used by low-quality telescope makers to seduce to inexperienced beginners into buying their telescopes. For any scope, what is more important than magnification is the ability to gather light and the ability to resolve it. In general, most telescopes will yield poor images when magnifying more than 300x. In fact, seeing conditions must be excellent to use powers this high. Additionally, many deep-sky objects look best at lower powers. To calculate an eyepiece's magnification, divide the focal length of your scope by the focal length of your eyepiece. For example, a 2000mm scope with 20mm eyepiece yield 100x magnification. 

Q: If I get a Barlow, I'll be doubling the number of eyepieces I have, right? 

A: Yes and no. If you do your shopping wisely, you will double your eyepiece collection. But be careful-- you might double an eyepiece to an ineffective power, or worse yet, you may just duplicate a power you already have. Research before you buy any eyepieces, and be sure to check the Eyepiece Selection section. 

Q: How can I prevent dew from forming on my Schmidt-Cassegrain? 

A: Dew plagues many astronomers, but it is an especially big problem for SCT owners. With a large, openly exposed front corrector plate, SCT owner's often find themselves getting fogged over in the middle of an observing session. The dew forms when the temperature of your scope and equipment falls below the dew point. If you discover dew forming on your scope in the field, it may be best to bring it in and let it warm up slowly until the dew evaporates, leaving the dust caps off. NEVER WIPE DEW OFF-- you may scratch your scope's optics. If you're in the field and you're desperate, you can use your car heater to dry the dew and continue your observing. 

To prevent this, you can do one or all of the following things: 

First, you can get yourself a dew shield, which will keep an area of warmer air in front of your scope, but only for a while. Next, you may want to purchase a corrector plate heater such as the Orion Dew Zapper or Kendrik Dew Removal System. These devices wrap around your scope, heating it just enough to prevent dew from forming. Another option is to purchase a small DC operable hair dryer, often sold in automotive stores as a windshield defroster. These units can be used to gently warm anything you have that fogs over, such as eyepieces and finders. Finally, you can move to a higher observing point. Dew is heavy, and sinks into valleys and lower areas, leaving higher ground dew free.