Finding the Scope for You...

There are a lot of factors which need to be addressed in deciding what type and size of telescope you wish to own. I feel that there are almost as many types of amateur astronomers out there as there are stars, and hence almost that many addressable factors in choosing the most suitable scope for you. But here are a few critical things you should consider before acquiring your own scope. Let it be known straight away that there is NO perfect scope size or design available. Every plus side of a particular scope style or aperture size is also met with a negative side in terms of what is best for your particular situation. Be that as it may....

1) Style - There are 3 basic types of telescope; reflectors, refractors, and catadioptrics. Newtonian Reflectors use a mirror to gather and focus light. They are the cheapest to produce per size of aperture. They offer no false color aberrations. But the design can suffer from coma and requires a secondary mirror to deflect the focused light to the eyepiece, thus partially limiting the light gathering capabilities and image quality. Refractors are the classic lens telescopes. Although these scopes are mass produced because of their classic appearance (when someone is asked to draw a picture of a telescope, this will invariably be the type of scope they draw), it is not an optical system that lends itself well to mass production in terms of quality optics. A fine quality refractor is a treasure to look through, but it will cost you a bundle to get one. Special lens making is required to eliminate chromatic aberration, and large aperture refractors are VERY long scopes because no mirrors are used, thus limiting portability for aperture size. A Catadioptric scope is basically a shortened reflector. They are very hard to make as an amateur telescope making project. They use a primary mirror and a large correcting lens to allow the production of a shorter scope. In many ways, they offer a great balance between refractors and reflectors and they are readily available commercially at reasonable prices. They are often the choice for astrophotography since their short length per aperture lends itself very well to photographic set-ups. The downsides are similar to reflectors and they tend to be laden with technological gizmos that may be a detraction to some. I have not listed all the pluses and minuses here with respect to each design, but I have covered many important ones. More studying will be required by you in order to decide which style suits you best.

2) Aperture - In astronomy, size is everything. The basic rule is that the bigger the primary lens or mirror, the more light gathering capability. The greater the light gathering, the better the ability to resolve more closely spaced objects. In astronomy, resolution is the most important thing that is strived for. Magnification helps to aid resolution, but the primary factor that affects resolving capability is the amount of light gathered from a particular object being viewed. So, you want as large an aperture as is reasonable for you. The key word here is reasonable. Large, quality optics are expensive. Large and inferior quality optics are relatively inexpensive, but you won't be able to see decent images through them because of their crappy quality, so why bother? Large optics also require everything else to be large....the optical tube....the mount....everything. Therefore, the larger the aperture, the less portable the scope will be. If you have a permanent observatory in mind, then go as large as you can or want. If you want to transport your instrument to star parties and elsewhere, then you must consider how easy it will be to get it there, to it set up, and to dismantle it. Remember that if the size of your scope restricts your viewing time, then a large precision-optic scope is far inferior to a smaller average-optic instrument. Astronomy is about looking through your scope, not at it. And so the bottom line is that if you aren't using your scope, then why bother owning it?

3) Your intended use - This seems like a vague parameter in comparison to those above, but it is no less important. What do you wish to use your telescope for mainly or exclusively? Viewing, photography, teaching? For viewing, what do you wish to look at mainly.....the planets, the moon, the sun, the stars, deep sky objects (galaxies, etc.)? For photography, what do you want to photograph....the moon using eyepiece projection or deep sky objects using long exposure guiding with film or CCD imaging? You must weigh each of these factors into your decision. For example, if you want to take deep sky pictures, it is best to have your scope polar-aligned and motor-driven so that it can track an object that requires long exposure (minutes as opposed to a few seconds) to photograph.

To sum all this together by example, let me tell you about my particular situation. Keep in mind that my situation is not yours....you have to figure yours out. I live in cold Wisconsin. Accessing the winter sky (very nice in the northern hemisphere) requires standing out in often very cold weather. I have two young children that I like to spend time with, that I want to expose to the cosmos, and that tucker the hell out of me during the day. I don't want to take pictures of celestial objects anymore. I have done that, it is fun, but it is more time consuming than I wish to accommodate. I wanted portability. I live in a light-polluted city with a fairly tree-obstructed backyard. And finally, I wanted to build my own scope. When I weighed all these factors together, I decided that a 6" f/8 Dobsonian-mounted reflector was my best ticket to the cosmos. It is a relatively large aperture, but not too large to move around and set up. Its long focal length yields good planetary views, important to jazzing my children to the above. The Dobson mount is simple in the extreme, requiring virtually no set-up time, and thus making it very easy for me to plop it down outside and start viewing soon after deciding that I want to stargaze. I can't take deep sky pictures with it and I don't care. I have digital setting circles, a starbeam finder, and a 2" focuser (large field-of-view capabilities), thus making it very easy to locate objects in my light-polluted neighborhood. A Dobson reflector is probably the easiest of all scopes to make yourself. All in all, for me, this is the best scope that I could come up with for my particular lifestyle. Good luck in your choice.

One final note: If you are just starting to dabble in amateur astronomy, don't underestimate the utility and power of a good pair of binoculars. Most good binoculars have a tapped hole in the front of the central pivot, which will allow you to attach them to a tripod using a commercially available adapter. This will give you hands-free (no vibration) binocular views of the cosmos using two eyes instead of one. I understand that you may really want a telescope, and I can sympathize with that feeling. But if you want to jump right in and start exploring, binoculars are an easy and relatively cheap way to do this.