This page is provided by those Members of the Astronomical Society of Eastern Missouri who wish to help those who are thinking of their first scope or just bought one, and content is not intended to cover every topic in all details, but to cover just the basics of what every first scope owner should know.
This page is under construction (pictures and more edits are coming)
(The Common Types explained, with photos of members and their scopes)
A key point you should understand: telescopes are all about light, and the focusing of light to a clear, sharp and most important, steady view for the observer.
When thinking of telescopes don't think about "power" or magnification, but think about how well the telescope handles the light from the stars and objects in the sky, and how much light it can gather to a focus for the views you are expecting to see. In fact, if you are looking at an ad for a telescope and it uses power as a selling point, the telescope probably isn't worth the purchase.
For more details and diagrams, check out this short, yet interesting, video by Orion Telescopes on The Types of Telescope, and ASEM member Amy White's page "Telescopes are Fun" page. In addition, most ASEM members who maintain webpages with this site have photos of their scopes available to see. So, be sure to check out the "Link to Members" page via this link or the menu selection from the upper left.
Usually, for the first time telescope buyer:
But if you want to see EVERYTHING that is up there, then we would say lets keep talking (or reading) about the other factors in deciding what telescope is best, such as where it will be used, by whom, and how much?
Why all the confusion here in measurement? Well, use and demand has kind of driven this, especially in the USA. Most refractors optics are identified by their aperture in metric units (as in "millimeters"). You may notice that is the same with binoculars are too, of course. But when identifying a some types of telescopes, such as reflectors and compounds, their apertures are identified in inches.
Just keep this in mind, as we talk further, because there is some math and unit conversion needed when discussing eyepieces and magnification (below).
Size, Weight, Complexity, and Portability
If you buy a big telescope, with a big mount, you will likely need to be big to handle it.
Not to mention, so will your car.
So, if going big, like most telescope buyers want to do, bear in mind what can you handle and transport.
Location, location, location
Also, keep in mind, you don't get everything that you will need or want with the purchase of just a telescope. There are more things you haven't thought about yet. So what is your level of investment? We recommend reading the rest of this page, to think it all through.
Please do not buy a department store telescope! Their apertures are small, the optics are poor and usually plastic, and the mount included, usually is a table mount and not that sturdy to hold the image in the telescope while you focus or change eyepieces.
Otherwise, if your budget can afford more, we strongly recommend purchase of, or possibly build yourself, a 6 inch Dobsonian reflector telescope. This type of telescope, starting at 6 inches, is easy to handle and transport, gives decent views of most all objects, will work in city lights and the country, and can be found for slightly below, or above, $300, depending upon size, features and accessories.
A way around your wallet maybe to buy used. Most amateur astronomers take very good care of their telescopes, and sometimes you can find a used telescope that is still very functional, at a very affordable price. Consult your local astronomy club and check out the various internet sites and sources for used astronomy gear. If you are just beginning, others who are ready to move up to a bigger or better telescope, maybe ready to part with just what you are looking for. Regardless of where you buy, check out the source and ask questions if you can. Be sure they have all the parts of the telescope, such as the matching tripod and base. One good FREE source to consult for used equipment sales is Cloudy Night's Classifieds page at: http://www.cloudynights.com/classifieds/ Astronomers from around the country post equipment from beginner to professional level.
Even building a telescope is still an option today, and usually most consider a reflector type for the most aperture for the money (again, a Dobsonian reflector telescope). If you are interested in building, then see the Resource Library page within the ASEM DIY-ATM Special Interest Group website section, and check out ASEM member Amy White's webpage "How to build a scope yourself" within her Observing Tools page.
Consider attending one of ASEM's Beginner Meetings held on the first Thursday of the month at the Weldon Spring Center to discuss your purchase options. Directions to the Center can be found in the left sidebar at the top of the page.
Should be steady, yet easy to move
Also, in any case, if a problem pops up that you cannot over come, then consider getting help from your local club - "you are not alone" here, and someone there is likely to have "been there" with the same mount and scope.
If pictures say a thousand words, and video's I think do even more, then be sure to view the "The Basics of Telescopes" video series produced by David Fuller, who produced a very good, just the basics (please), 6 part tutorial on telescope types and accessories, with discussion and graphical content, that covers most of the same subject matter in this section. His weekly "Eyes on the Sky" program is pretty good too. Be sure to set the video quality to the highest your computer can take and maximize the video box to see the dark background screens.
Choices here are typically Telrads, LED "Dot" finders, and the use of green laser pens and mounting brackets.
All these accessories can be found at most Astronomy stores. Its worth shopping around on them.If you are in the country with good dark skies, and can see all of the points of constellations, then this maybe all you need. This will help you point your telescope to your target, provided you have it aligned to your scope's optical axis before using. Again, read the manual here too.
But, if you are in light pollution areas, and can only see some of the stars, then you need a finder scope.
If you observe under light polluted skies, this accessory can really help to "punch " thru that and give the view you would have with binoculars. They are also very helpful with hunting down those solitary objects that are not around a star or other known bright object.
Some recommendations here:
And with Finders you can get two configurations for viewing, either "Straight Thru" or with a Diagonal (right angle view of its eyepiece). You can view more comfortably with a diagonal, and If you are using Charts, then get a Correct Image type diagonal will really make life easy, since a regular diagonal will give you a mirrored image and you will have to keep thinking as to which way to move the scope to go where the chart says to go.
A finder with a Reticle Eyepiece is very helpful too. An illuminated type even more, if you can afford that, since this is usually a very expensive option.
Finally, if you have both, a Telrad (or DOT/Laser) and Finder, then it is:
1. Locate the area in the sky with the Telrad.
2. Move to the Finder to find and center the target.
3. Move to the Focuser to focus the eyepiece.
There is so much to say about this accessory category, that one could write books on the subject. The following is an attempt to note some of the significant factors, but by no means does this cover it all. In addition to this content, do some research on the internet or at your library to know more.
So, your telescope has to have an eyepiece to function, and you need to match what the telescope is good at, to what the eyepiece is good at, and with what you need and like to see.
First, there many designs, brands and types of Eyepieces to choose from and in a very wide range of cost, and with barrel sizes matching that of your scopes focuser:
It is possible to buy an adapter that will let you use a small diameter barrel eyepiece in a larger diameter barrel.
Besides the design and types, all eyepieces are identified by focal length, again in millimeters, not in power (but of course on cheap scopes, all you hear about is power).
If you bought a scope new or used, you usually will get an eyepiece or two with the scope, and that will save you some cost. If not, plan to spend some more, because for most, you will need more than one or two eyepieces to be satisfied with your telescope. Over time, you will likely have a collection of eyepieces, to use your scope to see all types of objects, and that would mean several sizes of focal length, such as having a 40, 25, 12, or a 6mm, in your accessories box. Just bear this in mind.
So, how do you determine magnification?
It is your telescope's focal length (in millimeters) divided by eyepiece focal length (in millimeters).
If you don't know your telescopes focal length, then look it up in the manual (it should be there) or on the manufacturers website. It could be in inches, and if you must first convert those units to millimeters (basic math here).
As an example, a typical 8 inch reflector or dobsonian that has a focal ratio of f/6 is 48 inches in focal length, or 1219 mm (approx). For that scope's focal length, a 40mm would then yield 30 magnification power (approx), a 25 mm would yield a 49 magnification power (approx), and a 12mm would yield a bit more than double of that, or 102 magnification power, and so forth. As you can see, most usually select eyepieces that yield a step of say twice the amount of magnification for each eyepiece size step (or reduction) would give you a nice step or tier in magnification to see various objects for your scope.
Now, once you have your initial eyepiece sizes planned out for your scope, then some other factors and options you need to think of:
Do you wear glasses? If so, then look for long “Eye Relief” eyepieces (15mm or more), especially with high magnification eyepieces. This will save on eye-strain, and having to push your eye right into the eyepiece, sometimes to the point of bumping the telescope off the target. The downside, these may take a bit of adjustment to get use too.
If you do any study of eyepieces, you will find there are all kind of "designs", such as Kellners, Orthoscopic, Plossls, Naglers, etc.. If you are just getting started, the Plossl design is the most popular now for starter scopes, but the eye relief varies with the focal length, and is very short with the 12mm or less..
Wide-field eyepieces are becoming more popular and affordable. This can enhance the view, if your telescope works with it. Low cost eyepieces are usually around 40 degrees in their (apparent) field of view (or FOV), mid cost eyepieces are now moving up and providing 50 to 60 degrees, and then it goes beyond that with eyepieces that have cost that are exponential too. For most, 40 to 60 degrees of FOV are just fine. Again, be sure to listen to David Fullers "The Basics of Telescopes" video on the eyepiece's Apparent Field of View (AFOV) and its relationship to the "Telescopic Field of View" (TFOV).
for a more detail discussion on the types of FOV with your eyepieces and telescope.
There are eyepiece series available that are Par-Focal. Normally, when you change an eyepiece out for another in your focuser, you have to re-adjust the focus. Par-focals are designed so that you don't have to adjust the focus, saving you time, and for some, a bit of nuisance (who get tired of re-focusing). But you will pay more for this feature.
There are some eyepieces that are made just for Planetary study, such as TMBs, which are considered to have set standard in this department. If that is your preference, then look for those types.
You will find that manufacturers have "series" of different types of eyepieces. Some scopes owners prefer to have just one of these series/type (design) eyepieces alone, but most first scope owners will usually buy a few different types over a couple of years until they find the ones that work the best for them and their scope.
To bottom line it, it is recommended to start slow in acquiring and spending on eyepieces. Take your time, as you get to know your telescope, you need to know your eyepieces. So, get just a few first, say 3 of them, to try them out first.
In addition, it is highly recommended to attend a local star party, before purchasing more eyepieces. There you ask and see what other scope owners are using and take a look thru their eyepieces, and if you know the person, you could ask if he could put his eyepiece in your telescope for you to see what effect that eyepiece will have. Most other amateur astronomers want to share the view and will usually help you out. You don't know till you try and try on different objects. This is something over time you will get the hang of and figure out what works for you.
Some further study can be found in the Orion's resource center, both in the articles section and in the video section. And, of course on Wikipedia. One other webpage, that is all text, but includes some pretty common sense thoughts is provided by another amateur astronomer Jay Freeman.
Again, this is one of those side topics you just need to give yourself time to learn about while you are learning more about Astronomy and how to use your new scope.
Another accessory for an accessory.
You can save cost in the number of eyepieces in your box by having a Barlow (accessory) that will double the magnification of a given eyepiece.
Most Barlows provide 2 or more times of an increase in magnification (noted as 2X or 3X, typically), and they come in the same barrel sizes as eyepieces.
Again, shop around and look'n'see first on these. Most scopes usually end up picking one of these.
Filters can really help your view of those faint fuzzy objects, such as Nebula objects, especially in light polluted skies.
There are basically just a few categories to know about:
If you like to study the moon, a Lunar filter will really help with viewing when the moon becomes bright, which is usually any day of its phase when it is greater than a crescent shape.
In addition, ASEM member John Duchek has an great explanation on how color filters can be used for enhancing the view of the moon within his page "Color Filter Study 2011". Be sure to take a look at his images there.
While it is usually recommended to have a pair of this before you get a telescope, some don't have them yet. And why are Binoculars considered an "aid" to a telescope?, because:
All in all, most amateur astronomers recommend having pair on hand when viewing with a scope.
And if you haven't shop or study whats out there, well, yes, you need to do some digging on these too. Again, there's lots of resources to find on the topic of Binoculars, such as that on Wikipedia and the Orion Telescopes resource page, that has both an article and short video on the topic.
Red lights or lamps are a must when using your scope and any other accessory while viewing in the dark, such as charts or books. Using red-light helps with dark adaptation of your eyesight to the night sky, and to keep that way. Something that is really needed to be able to see those faint fuzzies. Orion Telescopes speaks to this point quite well in their article page here.
If you don't own a red-light, most are common at Astronomy stores, but you can make one yourself, by using a simple white flashlight and rubber-banding over a few layers of red clear Saran-wrap over the end of your favorite flash light, or pick up a sheet of Rubylith film from an Art supply store and cut to fit a piece to place within the light bulb cap end.
In addition, if you are at a star party, it is courteous to use a red light when setting up or tearing down, if others are still viewing with their telescopes in the dark.
And when tearing down, some have found that head-lamps (small LED type lamps that have an elastic band and can fit around your head), that include a red-light mode are just great for this, because they keep your hands-free to picking up and transporting your gear. Such lamps can be found at hardware or sports stores.
Collimation of a Newtonian reflector, or Dobsonian, telescope is simply the process of making sure your mirrors and focuser are properly aligned. And if they are not aligned, you will start to wonder why the views of objects, under good skies, are just not as good as they should be. Sometimes this is true with a brand new scope that was shipped a long distance, and very common if you transport your reflector around frequently, which can receive lots of "bumps" along the way that can slightly loosen the screws or bolts that hold the mirrors in their proper orientation. This process is explained very well in a video tutorial at Andy Shot Glass website and in a Sky and Telescope website article, and involves adjusting your diagonal mirror and primary to correct alignment to your focuser and to each other.
So you live here in Missouri too, eh? Then you will appreciate having some tools to deal with this issue.
Typical types of Dew Fighting Tools are:
See Sky & Telescopes article on Dealing with Dew for photos and more information.
One of the best, nice sized, star charts out there is Sky & Telescope's "Pocket Sky Atlas". See the review of it on CloudyNights Telescope Reviews. This is considered a great resource to have when you are starting, a great back-up, if those electronic devices are just not working.
Remember, if it is paper and you live where the Dew is, then be sure to keep your charts, books, or Planisphere, in a box, bag, or under plastic or vinyl protection.
Planispheres are available in vinyl material, as well, so forget the Dew. The "Night Sky Planisphere" is the most popular, with blue on black, but if your eyes appreciate a darker background, then check out The Miller Planisphere, that is a bit darker with white text on black or blue backgrounds. Both are very affordable, in most stores, and sometimes at hobby stores, and are sometimes made for specific latitudes - so be sure to read the title/description before purchasing.
Keeps exterior surfaces dry and clean
Reflector mirrors - may need periodic washing but no more than once a year. Frequent cleaning can affect the life of the mirror's reflective coating. So, be very careful here, do some reading here on this.
For refractors and eyepieces, it is recommended to get a cleaning kit for lenses. For sure here, one should use only special wash and rinse. The best solution is to pick up a lens cleaning kit, such as one that is available from ASEM member John Duchek, on his Astronomy Product Page.
If your scope and gear was just brought in from under the dew or out in the cold, then be sure to let it all dry out indoors before returning everything to storage in containers or bags.
A good quote: “The more you look, the more you will
see, and the better you will get.
Astronomy is a patient hobby. Don't be in too great a rush. The cosmos will still be there tomorrow.”
When under good clear skies, the view should yield: