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 editing are coming)

Types and Parts of a Telescope

Common Types

Refractor, Reflector, and “Compound Design”

(The Common Types explained, with photos of members and their scopes)

The Refractor Remember Galileo?  These have been around for quite awhile now. They look straight, with a lens at the "star" end and a focuser at the "eye" end.  Light from a star or object passes thru the lens and down to the focuser, which usually a "diagonal", that holds the "eyepiece".	The Reflector Usually a Newtonian design (does this name sound familiar?), commonly called "light buckets", because of their large open (star) end. In this case, the light passes all the way down the tube to a "reflecting" mirror at the bottom, and then bounces back up to another small mirror, called a secondary mirror, that directs the light out to the side and into the focuser.	The Compound Telescope These are called Catadioptric, and for visual use, the Cassegrains compounds are most common, AND...the Schmidt-Cassegrain (called an SCT) or Maksutov-Cassegrain, are the most available to purchase. They are straight looking, but short, fat tubes, that also have 2 mirrors inside like a reflector, once at each end, but in this case, the big mirror at the bottom has a hole in it.  So, the light from the secondary mirror, in this case, is reflected back to the hole in the primary, and out to the focuser, at the end of the tube.  And, oh yes, there is a clear glass plate or lens, at the "star" end of the tube, that keeps out dust and can help the light get started in its travel down the tube.

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

Usually, for the first time telescope buyer:

If these objects are of interest	Then consider
Bright Objects (the Moon, the Planets, and Stars)	Refractors or Compound Telescopes
Deep Sky Objects (that are normally called "fuzzies", such as Nebula's and Galaxies)	Reflectors

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?

A side note on Aperture (inches or millimeters?)

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).

The Other Deciding Factors

Size, Weight, Complexity, and Portability - What can you handle and transport?



If going big, can your car handle it all?


Location, location, location

Where are you – in the city?  = Light Pollution

If always under light pollution, then big (aperture) is not always better.

Big aperture scopes perform their best in darker skies than those in the city, such as a bit farther out, under partial or total dark skies in the country.

Cost vs Quality/Capability vs Money (that needs to include for those 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.

Buy New, Used, or Build?

If New - Please do not buy a department store telescope !

Their apertures are small, the optics are poor and usually plastic, and the mount included is not that sturdy to hold the image while you focus or change eyepieces.

For less than $100 consider a good pair of Binoculars first; they (and you) can always use these, anytime.

For children, if it just has to be a telescope, and you under a very tight budget,

then consider a "First Scope" from Celestron or "Fun Scope" from Orion Telescope & Binoculars , or equivalent.

These are reflector telescopes, and thus gather more light than those skinny department store refractors, which in turn will provide with a better view. They are around $50, have a sturdy, locking mount, and standard 1 and 1/4 focuser, and includes a standard 1 and 1/4 eyepiece (that can be used down the road in a bigger and better telescopes), and a very easy to use "spot" finder.  The Celestron model is sometimes carried by camera stores, but can ordered, as you would have to do within St. Louis for the Orion model.

Otherwise, if your budget can afford more, we strongly recommend purchase, 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 and features.

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 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.

Even building a reflector is still an option today, and usually consider for large reflector apertures (again, dobsonian) telescopes.

If you are interested in building, then see the Resource Library page within the ASEM DIY-ATM Special Interest Group website section.  Do 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.

The Mount

Should be steady, yet easy to move

Types:

• Alt-Az (Altitude-Azimuth)
• Equatorial or GEM (German Equatorial Mount)
• Push or with drive system
•   Hand Controller that tells you where to put it or puts it there for you.

Whatever you decide, Read the Manual !

Learn the handset and how to align your mount

If a problem there, then get help from your local club - "you are not alone"

someone there is likely to have "been there" with the same mount

Telescope Accessories

Finders

Telrads and LED "Dot" finders

If you are in the country, 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 align first

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.

Finder Scopes

Usually a small refractor

Very helpful with those "lone" targets

Wide Field - 50mm best

and Low Magnification - to aid in knowing where you are

Straight Thru or with Diagonal Finder scopes

If Diagonal and using Charts? - Get a Correct Image type

Reticle Eyepiece is very helpful, and illuminated type helps even more

The Viewing End

Eyepieces

Many types to choose from with a wide range of cost

Barrel size is .75 inch (on department store scopes)

1.25 and 2 inch size is most common

And are identified by focal length sizes, again in millimeters

Large size will yield low magnification power (say 40mm)

Small size will yield high magnification power (say 5mm)

One needs only a few steps of magnification

typically – 30, 50, 100, 200

How to determine magnification?

Scope focal length (in millimeters) divided by eyepiece focal length (in millimeters)

And, do you wear glasses?  Then look for long “Eye Relief” (15mm or more)

There are various types of designs and various levels of cost

For Beginners, a Plossl design eyepiece is the most affordable and common selection

Many beginner scopes come with at least one of these

Barlows

Can increase the magnification (usually, 2 to 3 times) of a given eyepiece

There are long and short barrel barlow's now

Filters

Types - Light Pollution, Lunar, Narrow band, Color

LP's are great for those faint fuzzies - such as Nebula

OIII (that's "Oxygen 3") are even better for certain Nebulas

See another short video on Filters by Orion Telescopes

Lunar Filters - a must when moon is past 25%

Other Observing Aids

Head-lights or Flash-lights

Type - white for set-up/tear-down and red for use/charts

Simple flashlight with Red Cellophane over the end will work

Binoculars

A great complement and very helpful at times

Collimator

Got a Newtonian reflector ? - you will need one of these