What you need to know before you buy the best affordable telescope
Are you looking for the best telescope under 200 dollars but don’t know how or where to start? That’s a common dilemma, especially for those still learning the basics of astronomy. The sheer variety of equipment available makes it even tougher. If you’re a beginner or you think you may not have a chance to use your telescope very frequently, it’s a good idea not to splash out on an expensive model right away.
Unless you are comfortable with finding and identifying various objects in the sky and handling most of the advanced features that are available on expensive telescopes, there is no point in spending too much on them. You may also need to budget for accessories like eyepieces, filters, additional lenses, a finderscope and a sky atlas to go along with whatever telescope you buy, so it is a good idea to keep the cost of the telescope down.
While it used to be that you couldn’t find a decent telescope for anything less than $300, that’s not true anymore. Most major manufacturers like Celestron, Orion and Meade now have very good affordable ones because of advances in technology. While beginners can start viewing the night sky through a pair of binoculars, eventually all enthusiasts need to get a telescope, as more powerful binoculars are very heavy and cannot be held steadily enough for clear viewing. The clearest images of celestial objects can only be obtained with telescopes.
When it comes to choosing the right telescope, you have to take into account several factors like its main use, versatility, portability and ease of use. Telescopes can be broadly categorized into refractors, reflectors and catadioptrics, and each of these has various advantages and disadvantages. This guide will help you narrow down your choices, explain the trade offs, and help you find the best telescope for under 200 dollars.
What to look for when buying a telescope
Where and how do you want to use it?
Many enthusiasts like to have an all-purpose telescope – one that is good for viewing planets and deep sky objects (DSOs). There are many that will do a decent job of both, provided you are in the right area while viewing. If you want to use it at home in a heavy light polluted area, it is pretty much impossible to view DSOs, so there’s no point getting a telescope that’s best suited for DSO viewing. However, viewing the moon, some planets and a few bright nebulae and star clusters is very possible even in these areas as long as you can move the instrument at least a little to get into the best position for viewing them.
How experienced are you?
If you’re an absolute beginner with telescopes, you may want a telescope that’s simple to use and easy to maintain. Refractors fit these criteria but they can get very expensive as they get larger, and smaller ones will only be good enough for planetary viewing.
Do you have adequate storage space and how heavy a load can you carry?
In general, the better the telescope, the larger and heavier it will be. If you want to take it with you to a dark sky location, make sure it will fit in your car and you can carry it. The best telescope really is the one that you use most often and not the most sophisticated one that sits in your closet!
Specifications to look for
Aperture or size of lens or mirror
A large diameter optical piece will collect more light, making faint deep sky objects more visible. However, refractor telescopes become too expensive as the aperture increases. They go up to 6 inches, but 4” is most common. Reflectors typically start around 4” and can go to 10 or beyond, but 6 to 8 inches is excellent for any DSO astronomer.
The ratio of the focal length to the aperture is what gives you the focal ratio. A larger ratio gives you better image quality and is best for planetary viewing. However, this narrows the field of view making it difficult to find and view DSOs.
Magnification or Power
Magnification depends on the focal length of the telescope and eyepiece. Large magnification is good for sharp and detailed planetary and lunar viewing.
Needing higher magnification, however, does not mean you should get something that products in department stores boast of having something like 300x. Pushing power too much can result in objects looking blurred and faded, particularly in less than perfect atmospheric conditions. Even though in theory, magnification can be infinite depending on the eyepiece you pair with your telescope, in practice, even a large 10 inch aperture scope should not be used to create more than a 300x magnification at the most.
To know what magnification you get with various eyepieces, divide the focal length of the telescope with the focal length of the eyepiece. To get a wider range of magnifications with your telescope and eyepieces, consider buying a Barlow lens. This lens increases the magnification provided by any eyepiece. The most popular is a Barlow 2x which doubles magnification. This way, getting a telescope with high magnification becomes less important than other factors.
In general, the maximum amount of magnification you can push to is twice the aperture in millimetres or 50 times the aperture in inches. Even these numbers are meant only for perfectly still and dark night skies.
Credit: http://www.flickr.com/photos/andyjones/379139142/If your main goal is to view planets and the moon you’ll need a scope with higher magnification or power, preferably over 150. It should have a long focal length and quality optics. The focal ratio should be at least f/8.
Many of the newer portable refractors have a shorter focal ratio of f/5, making magnification good enough for general stargazing and some photography. These are cheap and easy to maintain, as the lenses are fixed and the barrel is closed, so you don’t need to do any re-alignment.
Deep sky object viewing
To view DSOs, a large aperture, short focus telescope is ideal. Short focus reflectors with large apertures are usually best for this, but if you want to stick to a refractor, you can get a short focus one, albeit with a smaller aperture that won’t be ideal for planetary viewing.
Because of the large apertures, magnification can be kept low, making the atmospheric quality less important for viewing DSOs. Also, if you’re interested in astrophotography, large apertures will generally enable shorter exposure times.
If you want to get a telescope to use in a dark sky location away from home, you have to consider portability. Most large aperture telescopes are very heavy and large. Keep in mind that many large aperture scopes will also need a good mount, especially if you are going to use it for astrophotography too.
Types of telescopes
A refractor is the earliest form of scopes and is what most people identify with in terms of its looks. It is usually a long tube with a large objective lens at the front and an eyepiece at the end. Refractors are known for their crisp, high-contrast and high magnification images of the moon and planets. They are the best for those who want a simple to maintain and rugged instrument, as the lenses are fixed and don’t require constant alignment.
However, refractor lenses are hand crafted and really good ones are very expensive to make. Unless you don’t mind a small aperture scope, refractors will be out of your budget. The long barrel also makes them unwieldy, particularly for large apertures. Also, the eyepiece is always at the end of the barrel, so you’ll need a tall tripod to make viewing easy, and it will have to be solid to keep the long and heavy telescope from wobbling.
Since inexpensive refractors will have smaller apertures, deep sky viewing is not ideal. However, there are more expensive refractors in more manageable weights and sizes that are suitable for some DSO viewing.
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The image will appear upside down, which is fine for astronomy in most cases, but if you want to use it for land viewing there's a diagonal lens to make it upright.
The 25mm eyepiece will give you bright views of the moon, while the 9mm one will let you see details of the moon's craters and a pretty good view of Saturn's rings and Jupiter's cloud bands. You can get even better views if you buy one or two additional lenses.
A reflector uses mirrors to capture and focus light. The most common reflector is the Newtonian which uses a concave mirror near the end to redirect light back to a smaller diagonal mirror near the front. This second mirror deflects the image to an eyepiece that is conveniently positioned on the side of the telescope’s barrel.
Because the light rays are folded along the tube, even large aperture telescopes won’t be too large and are easier to store and transport. If the optics are high quality and well maintained, this is the type of telescope that will give you most value for money and can be used for both high-contrast planetary and some DSO viewing.
Because medium aperture reflectors aren’t too heavy, you can get a stable and compact mount that can be placed just about anywhere.
The disadvantage of reflectors is that the mirrors will need to be adjusted or “collimated” from time to time, unlike with a refractor. However, with practice, this won’t be an issue after a while. Another maintenance task is the occasional cleaning of the mirrors since reflector tubes are open. The mirrors may also need to be sent for recoating every 10 to 20 years.
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The equatorial mount and slow motion control makes tracking easy. You also get fully illustrated instructions and software to help you find celestial objects.
For added value, a specific type of Newtonian is the Dobsonian which features a rugged and simple mount. They are available in a large range of apertures, from about 4 inches to 30 inches. Dobsonians have become very popular because of portability, relative ease of use, versatility and value for money – all great qualities for the casual enthusiast. However, because of the use of multiple mirrors, you can expect a slight degradation in images making it less than ideal for critical planetary or lunar observations.
Best dobsonian telescope for beginners
Even though it boasts an aperture of 4", it is compact enough to store in a closet and use it anywhere.
The 2 included eyepieces are 20mm and 10mm, the latter giving enough magnification for a wide angled, low powered viewing of the Milky Way. The package also includes a finderscope and astronomy software.
Catadioptrics or compound telescopes combine the best features of refractors and reflectors. The most common forms of these are the Schmidt-Cassegrain and Maksutov-Cassegrain. They are very compact, as the length of the tube is a maximum of three times the diameter, so even the mounting can be lighter. You can even have a large aperture and long focus while still being easily portable.
The disadvantages include having to collimate the optics now and then and not having the best performance for high level planetary and lunar viewing. The cost of these lies midway between that of refractors and reflectors in relation to the aperture size. The advantage is that the tube is sealed like that of a refractor, so they are great for use in open places.
In general, Catadioptric telescopes are the most versatile for viewing all kinds of celestial objects and for use in astrophotography. There are plenty of accessories that you can buy for them if you want. Many Catadioptrics come with added technological features like computerized pointing and are called Go To scopes. However, the good ones are very expensive, while cheap ones make viewing a frustrating experience.
Best grab and go telescope - Catadioptric
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Brighter galaxies, star clusters and nebulae are easily seen through its 90mm aperture, while the f/13.8 focal ratio gives you powerful moon and planet viewing.
Use the sturdy base for tabletops or attach it to a tripod with a 3/8" or 1/4"-20 threaded post.
Included items are a 25mm and a 10mm lens, a finderscope and a diagonal mirror for enhanced night time viewing.
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It includes 2 eyepieces, a 20mm and a 4mm.
Types of Telescope Mounts
Even the best telescopes are of no use if they are mounted on unstable mounts. As the power increases, the telescope needs to be completely steady in order to view anything clearly. There are two types to consider – the alt-azimuth that allows the scope to move up and down and side to side. The equatorial mount also has two axes but they are tilted to match the Earth’s axes and allow the scope to follow the movement of objects in relation to the Earth’s movements, while the user will have a slow motion control to move it along the other axis.
For the casual observer, an alt-azimuth mount is fine and a Dobsonian provides great value for money and ease of use. More serious astronomers and astrophotographers should consider an equatorial mount because you only have to move the scope on one axis to track celestial objects. However, if you have the budget, some modern high tech alt-azimuths motorize one of the axis movements.
Using a Finder
Any medium to high powered telescope can make finding an object frustrating since the field of view is very narrow. To combat this, you can get a good quality miniature telescope or finder that you attach to the top of the main telescope near the eyepiece.