Beginner's Advice

Hello! I see you have found this page and are interested in buying a telescope for the first time.

Before you get a telescope, I advise a few things first:

• Learn a few constellations and whatnot first. In order to spot objects with a manually driven telescope, you have to be able to use these constellations to find very precise areas of the sky. This is not to be taken likely.
• If you wish, purchase a pair of binoculars, preferably around 50mm in aperture. Good astronomical binoculars are made by Barska, Bushnell, Canon, Celestron, Meade, Nikon, and Orion. When looking for binoculars, remember not to buy any perma-focused or high-power ones. I recommend 10x50s. If you do want binoculars, don’t spend more than $100 or so, otherwise you’ll be eating into the budget for your telescope). Some people (like me) can hold much larger binoculars up to 70mm, and some people can't even hold 7x35s steady due to their shaky hands. If you are one of the latter, then you may skip this step.

Aperture is the diameter of the main lens or mirror in your telescope or binoculars. When I say “8 inches” or “100mm” I am specifying aperture. The more aperture, the more light you gather, and the more resolution.

Focal length is the distance from the surface of the primary mirror or lens in a telescope to the point where the light that hits it is focused. The longer the focal length, the longer the tube, the fewer the optical aberrations, and the higher the magnifications with a given eyepiece.

Focal ratio, f/ratio, f/number or f/# is the ratio of the aperture relative to the focal length, written as f/(number).

Refractors

When most people picture a telescope, they picture something like what Galileo used - a long skinny refractor.

A refractor uses a lens to focus light. Galileo and friends used a single-element lens (singlet) refractor. The problem with simpler lenses is that they don’t focus all colors to the same point, causing purple halos to appear around objects, known as chromatic aberration. This could be solved by having really long focal lengths, which resulted in really long tubes (some on the order of 100 feet) and really high magnifications. It didn’t help that at the time nearly all eyepieces had problems of their own in addition to narrow fields of view.

In the 1800s a lens called the achromat or doublet lens was invented. It is made of two types of glass cemented together. Only 5% of the purple halo, or chromatic aberration, remained. In shorter-tubed achromats, the purple is easily noticeable, however in longer ones it is barely visible.

Some really high-end (over $700 without a mount) refractors have apochromatic triplet lenses using exotic, ED (extra-low dispersion) glass. These are typically small telescopes but they do have very sharp images. These are not good first telescopes.

Reflectors

The next major type of telescope is called the reflector.

Reflectors usually require their mirrors to periodically aligned (collimated). They also have an obstruction of light in the middle (central obstruction) caused by the secondary mirror. Due to this, they lose a bit of brightness and contrast. However, they are less than half the price per inch in aperture as refractors.

To focus light, all reflectors use a parabolic concave primary mirror, or a spherical primary mirror with a corrector lens of some kind placed either before or after light hits the primary mirror.

• Newtonian reflectors are the most common reflector. They use one parabolic mirror and one flat mirror. The concave primary mirror focuses light, but just before it reaches focus the flat secondary mirror (mounted at a 45-degree angle) deflects it off to the side for viewing. The main problem with wide-field Newtonians with a fast focal ratio is coma, which causes stars at the edge of the field to be oddly shaped. Newtonians also have decreased contrast compared to a refractor due to the secondary mirror obstructing some of the light.
• Bird-Jones telescopes are Newtonians which use a spherical primary mirror and a cheap corrector lens mounted in the focuser, reducing brightness and contrast in addition to making collimation difficult. Approach short-tubed 114mm Newtonian telescopes with caution, and always avoid 127 mm Newtonians. Beware of short 6” Newtonians as well.

• Cassegrain reflectors, in their classical configurations, are mostly homemade now. The reason is that the fast focal ratio (f/2 to f/3) primary mirror is very hard to make with a machine into a parabolic shape, so most manufacturers use a corrector lens at the front to correct for the problems in a spherical mirror, turning it into one of the types listed below. Cassegrains use a concave primary mirror and a convex secondary mirror, which bounces light through a hole in the primary mirror. All Cassegrains have a central obstruction by the secondary mirror above 25%, and typically around 30%.
• Schmidt-Cassegrains (SCTs) are highly popular because of their compactness and lower maintenance than Newtonians. The only reputable manufacturers of SCTs are Celestron and Meade. Avoid any other SCTs!
• Maksutov-Cassegrains (MCTs or Maks) are great in smaller sizes, and better than SCTs, but their thicker corrector cools down very slowly and they are more expensive. Also, Maksutovs generally will hold collimation nearly forever. Some owners (such as myself) have dropped them several feet without any effect on the image quality.

Mounts

The most common type of mount that telescopes use is called an alt-azimuth mount. An alt-az mount works basically like a photo tripod - it moves up and down, left and right. This mount is very easy to use - just point at the desired object.

There are three major types of alt-azimuth mount:

• Fork mounts put the telescope in-between the two altitude (up and down) axis bearings. This mount can be put on a wedge (we’ll come back to that) to convert it to an equatorial mount.
• One-armed fork mounts use only one altitude bearing to save weight. These can be put on wedges, too.
• Dobsonian mounts were invented by John Dobson and are generally only used for Newtonian reflectors. The altitude bearing(s) are directly attached to the side of the tube, or (in homemade designs) are attached to a box that the tube sits in. The azimuth bearings are two circular plates that rest on the ground and swivel, one of which is covered in PTFE on one side for maximum smoothness. The tube and altitude bearings are elevated by side boards.

Equatorial mounts are more complicated. They are like an alt-azimuth mount, but the azimuth axis is aligned with Polaris, converting the two axes to right-ascension and declination. The Earth turns on the right-ascension axis. The advantage here is that you only have to compensate for the Earth’s rotation on one axis, and with a motor drive you don’t have to worry about tracking at all.

GoTo or computerized mounts are altazimuth or equatorial mounts that find objects for you. They cost a bit more, but they are really helpful, especially if you live in a city. All you have to do is find two bright stars you know the names of and center them in the eyepiece. Then, the telescope can find thousands of objects (not all of them visible) at a push of a button.

So what scopes do I recommend to the beginner?

It’s a close call, but if I were starting out and knew what I know today, it would probably be a 6-8” Dobsonian reflector. I like the 6” Dobs made by Sky-Watcher and Orion, but an 8” isn’t much of a size or price difference and has almost twice the light gathering. Orion, Sky-Watcher, and Zhumell all make great 8” and larger Dobs. Dobsonians from all of these brands come with at least 1 Plossl eyepiece, a collimation tool, and some kind of finder.

A typical 6-8” Dob sits on the ground and is about 4’ tall. If you’re feeling ambitious, a 10” Dob is still light and compact enough to use on a frequent basis but pulls in even more light. You can get a 6” Dob for $300, an 8” for $400 or so, and a 10” for under $650. All of these telescopes weigh less than 60 lbs.

What if I don’t have the money for one of these?

The scopes below are all pretty good for the price. I have put an asterisk (* sign) next to my #1 pick for each price category. This list is being updated constantly - if you don't see a scope on here, that means I do not approve of it.

$100 and below PRICE RANGE

Refractor

• None worth buying

Reflector

• *Orion Skyscanner - No tripod, very short focal length, but is stable and has generous aperture for a very low cost. The scope also threads onto a photo tripod. The included eyepieces are quite adequate. While the primary mirror can't really be collimated, the scope will deliver nice views of deep-sky objects. 
• Zhumell Z100 - 100mm aperture reflector, much like the Skyscanner above, but the Z100 base has a built-in handle and doesn't thread onto a photo tripod. Acceptable included eyepieces. Same optics and capability as the Skyscanner. Orion has better customer service and the SkyScanner is more versatile and has better eyepieces, thus I prefer the SkyScanner.

$110 to $150 PRICE RANGE

Refractor

• Meade Infinity 80 - A great scope! Identical optics to the Orion ShortTube 80, but for a much lower price and with an alt-azimuth mount. The cheapest good scope that doesn't require a table or a photo tripod. However, the short tube will have chromatic aberration, and the star diagonal could be better. The finder and eyepieces are excellent however. 

Reflector

• *Meade Lightbridge Mini 114 - An excellent scope! Basically the SkyScanner scaled up a bit, but the Lightbridge can be collimated and can't be used on a tripod. This scope will deliver brighter and sharper views than the Infinity but it does require a table.
• Zhumell Z114 - Identical optics and specs to the Lightbridge Mini, but heavier, with a built-in handle, and with bad eyepieces.

$175 to $200 PRICE RANGE

Refractor

• Meade Infinity 102 - Scaled up version of the Infinity 80. Excellent if you replace the diagonal.

Reflector

• Meade Lightbridge Mini 130 - Scaled up version of the 114. Big but again requires a table.
• *Astronomers Without Borders OneSky -  Identical specifications and accessories to the Lightbridge Mini 130, but has a collapsible tube and a different style of focuser. Also, $100 goes to science education in developing countries. However the wait time on these can be months, and you will need to make a shroud for the scope to stop glare from streetlights. If you don't like that, get the Lightbridge.
• Zhumell Z130 - Same as the Lightbridge but heavier and with cheaper eyepieces, and a built-in handle like the others.

Above $200 I'd either save for a 6-8" Dob or spend it on accessories for one of the other scopes mentioned here.

You can get binoculars, telescopes and other accessories via the Internet at sites like Agena Astro (agenaastro.com), Astronomics (astronomics.com), High Point Scientific (highpointscientific.com), Oceanside Photo and Telescope (optcorp.com), Orion Telescopes and Binoculars (telescope.com), or telescopes.com, the only vendor of Zhumell telescopes and binoculars. Some camera stores have fair selections as well, but they may not be as knowledgeable or have as many accessories.