We often have questions about what telescope an aspiring amateur astronomer should buy. The “correct” answer can be elusive and is highly dependent on a lot of variables, including the expectations of the questioner, budget, storage capacity, available transport, etc. Rather than type all this advice over and over, I’d like to offer this post in the hopes that it can be made “sticky” so others can add to it, and it can remain near the top of the astronomy forum.
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Before you spend a dime, find a local amateur astronomy club, and see if you can attend meetings as a guest.
Get there early and mingle. Let the members know that you are interested in pursuing astronomy and that you are open to suggestions about what kind of gear might be appropriate for you. You can get valuable guidance that way. Next, arrange to attend the club’s next star party. Often they are open to the public as an outreach effort. Again, show up early. This is valuable for you in many ways. You will get to see what kind of transport requirements are involved in owning and operating a range of telescopes and mounts. You will also get insight into the simplicity/complexity of setting up various types of gear. Also, you’ll get to observe through a variety of instruments so you can get an idea of their strengths and weaknesses. Observing will also help dispel high expectations brought on by aggressive marketing by telescope vendors. The nice color images of nebulae in the ads are a come-on. You’ll see varying shades of (mostly) greenish-gray at best. You can see colors in stars and planets through modest amateur scopes, but not in galaxies or nebulae. The pretty pictures in the ads are made by skilled astrophotographers. Your eyes cannot integrate photons over long periods of time like cameras can, so you will not see colors in dim objects.
Another great advantage to hooking up with local amateurs is that lots of observers are gear-hounds, and they may have scopes in their closets that are gathering dust while they use their newer gear. You could get a great deal on a used telescope, and best of all, you’ll get to try it out before you buy it.
Now, do you really need a telescope?
Even a modest instrument can bring you a lot of enjoyment. If you buy a nice pair of binoculars and a decent set of charts, you can see a lot of objects, and learn your way around the night sky. My advice is to get a pair of no-frills binoculars from a high-end optics company. While you won’t get the options available on their pricy models, you’ll get binoculars made with the know-how and quality-control of the high-end company, so the quality of their basic instruments is often impressive. It’s a bit of a cliche, but 7×50 binoculars (7 power with 50mm objectives) are great for general use. They are with me during every observing session and are the go-to instrument for quick peeks.
If you still decide that you do need a telescope, what are your options?
The best bang for the buck comes in the form of alt-azimuth-mounted Newtonian telescopes. You can get a pretty impressive aperture for reasonable money. Newtonians on German equatorial mounts are no better optically in general, but cost more because of the extra expense of producing the amount that can be polar-aligned and driven to compensate for the rotation of the Earth without field rotation. Another choice, though generally more expensive still is one of a wide range of catadioptric telescopes. These are relatively compact telescopes with folded light paths. These can be made fairly portable (compared to Newtonians of similar aperture) but are generally slower (longer focal lengths) which gives images that are not as bright as those of the (usually) faster Newtonians. At the higher-cost end of the field are the refractors. Not the cheap department-store refractors, but high-quality instruments often made with exotic high-dispersion lens materials. Such refractors can deliver very high-contrast views in part because there are no central obstructions in the light path, unlike the Newtonians with their diagonal mirrors or catadioptrics with their central secondary mirrors. Each type of telescope has strengths and weaknesses.
Next, learn a bit about optics, if you can.
Many inexpensive Newtonian telescopes hit a price/aperture price point by compromising on mirror quality. This means that you will be paying for spherically-figured primary mirrors and not the more difficult-to-figure parabolic mirrors. Google on “spherical aberration” to see why you might want to consider paying a bit more for better optics.
To add to your confusion, there is a dizzying array of mounts and automation. It is possible to buy simple alt-azimuth mounted Dobsonians equipped with encoders that can help you find objects. Many German equatorial mounts and fork mounts come equipped with encoders and computers, some loaded with tens of thousands of objects. These “aids” can be very attractive to a newcomer to the field, but in my opinion, it is not worth the money to get trapped into automation. When the encoders fail, the computers fail or get corrupted, how will the purchaser get service? Pack up a delicate scope, ship it somewhere for service, and hope the manufacturer has a stock of the failed parts and can fix the instrument?
I may be anachronistic, but my advice is to buy an optical tube assembly that is suitable for your purposes on an amount that is no more complex nor automated than absolutely required. I have a 6″ apochromatic refractor on a German equatorial mount. The mount has electric drives on both the right ascension and declination drives. Top-quality optics on a really basic mount. I don’t need automation and computerized slewing to find objects, because I learned my way around the night sky with charts and star-hopping. When someone asks “what’s that star?” I have a catalog of them in my brain – no computer required.
OK, got a telescope?
Next, you’ll want to consider accessories. Please do not buy an assortment of eyepieces right away. Use your association (hopefully membership) with the astronomy club to figure out what eyepieces work well with your telescope. Most amateurs are pretty stoked about their favorite EPs and will pop them into the focuser of your ‘scope to show you what the buzz is about.
If you’re a beginner on a budget, please be aware that some well-heeled members may have some exotic EPs that cost more than your entire ‘scope, with accessories, so be polite if they are a bit hesitant to hand them all around. I have a well-corrected f:8 refractor and it performs well with Plossels, and I have only one Nagler. People with high-end short focal-length reflectors often gravitate to very expensive exotic EPs to get top performance, negating some of the economic benefits that can come with sticking with big reflectors.
Find out what works well with your telescope, and let that experience guide your eyepiece-shopping. Next, you’ll need to consider EP focal lengths. You WILL want to buy a Barlow lens to let you use your longer EPs (with a better field of view and eye-relief) for high-magnification observing. Before you pick a Barlow, consider what EP focal lengths you might want to use. If you have a 10mm and a 20mm EP, and you buy a 2x Barlow, you’ll end up with only one extra unduplicated magnification. Stagger the focal lengths of your (planned) EP upgrades to give you a good spread of magnifications. Remember that you should spend money wisely on a high-quality Barlow, because you’ll use that critter more than you think, and it will allow you to get a lot more flexibility out of your rig if you plan properly. Consider Barlows of 2x, 2.5x, 3x at a minimum and spread-sheet the resultant magnifications with EPs that you might have on your wish-list. You can waste alot of money for little effect if you don’t plan.
Good luck, no matter how you proceed.