Shane LaPierre's ATM Pages!
Telescope FAQ

Is a telescope in my future?
What are my options?
I've decided to build. Where do I start?
For Future Use

Why do you want a telescope? Do you want to see the planets, or are you interested in distant galaxies and star clusters? Did you know that you can see distant galaxies and star clusters? Did you know that you have to have the right instrument to see them well?

In choosing a first telescope, you must learn to manage expectations. You have expectations of seeing the universe on an poster sized scale, with elicit colors, festoons of detail, and in 3 dimensions. The likelihood that this is what you will get, especially from a first telescope, is slim to none.

You want to be able to see the maximum amount of universe, but you are compromised by not wanting a maximum level investment; of money, time, space and commitment. The key word is commitment. Whatever you buy is yours... and it's kind of like a car; it depreciates. So you must live with your investment, and use it or it's kind of a waste. I recommend you answer these questions before making any decisions on whether there's a telescope in your future:

If you answered "No" to more than a couple of these questions, you may not want to make the investment. But there are ways around some of these questions. For example, if you have not yet observed through a telescope, there are a number of astronomy clubs and star parties that you can meet people who do it all the time, and look through their scopes. In addition, the nearby club may even have a reasonably dark sky, and a permanent observatory and telescope that can eliminate your need for your own instrument. If you are short on cash, there are ways around that too... So the bottom line is if you want one, try one out and see if you like it. If you're interested go for it!

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A question like this is more than open-ended; it is loaded! Being involved in amateur astronomy is like going to Burger King: you can "have it your way", especially when it comes to instrumentation options. Let's start with the basics:

Your Eyes - Your eyes are wonderful instruments. They can be used during the day and gather enough information for excellent images, contrast, and have just the right balance of brightness... as long as you're not overdoing it. At night your pupils open up allow more light in, which makes them valuable for nighttime use as solo but dual instruments (if you have two working eyes!) Ideal targets include constellations, the milky way, planetary conjunctions (when planets appear nearby to other astronomical bodies like the moon, stars, or other planets) and meteors. In fact, most other instruments rarely are capable of displaying these events at all.

Binoculars - Oftentimes people don't realize they already own a powerful astronomical instrument. A simple pair of binoculars can reveal tens of thousands of stars and hundreds of deep sky objects that are not visible to the unaided eye. They are easy to use, can be hand-held, and you can carry them with you just about anywhere. In addition, they are affordable. The important aspects of binoculars are the aperture, the magnification, the exit pupil, and the field of view, and the image quality. The aperture is the 2nd number in a binocular specification such as 7 x 35 or 10 x 50. What it means is that there are 35 mm objectives (main or primary lenses) or 50 mm objectives. This is crucial because the larger the objective the more light is collected, hence the deeper in space you can see. The first number (the 7 or 10) is the magnification. The image is 7 or 10 times larger than without the binoculars. The exit pupil is how large a beam of light comes out of the binoculars. Your literal pupil in your eye can get up to around 7 mm, so anything bigger than that coming from any telescope or binocular is too big. That means you're wasting the aperture. To get the exit pupil you divide the aperture by the magnification. In a typical 7 x 35 you get 5 mm, since 35 divided by 7 = 5. I recommend sticking with 5 mm for most people. This means the typical 7 x 35 or 10 x 50 is a good start. If you don't have any instruments you can't go wrong starting with a pair of binoculars.

Refracting Telescope - A refracting telescope is the kind of instrument most people think of when they think of a telescope. It is generally long, slender, has an objective lens in the front, and the viewer views at the other end. These are the kind you see at department stores. WARNING: DO NOT BUY A TELESCOPE AT A DEPARTMENT STORE unless you are especially informed about the purchase. These telescopes are generally poorly built, and virtually unusable... a total waste of money. A good refractor has a quality objective, a good mount, and can be fitted with good eyepieces. It will also give very good images. You will find that good views can be had of the moon, planets, sun (with a proper filter), and deep sky objects. The bad news is they can be pricey.

Reflecting Telescope - A reflecting telescope is one which uses mirrors to collect light. Its biggest advantage is affordability, even at extreme apertures. The typical reflector is a Newtonian telescope with a primary concave mirror, and a secondary mirror that reroutes the light path to a convenient viewing position. In addition, these telescopes can be built by virtually anybody, including the optics. I'll say it again, these telescopes can be built by virtually anybody, including the optics. An amateur astronomer may grind and polish his or her own mirror, and build the rest of the components from easily obtained parts and have a quality instrument for a reasonable cost. With it you can expect very good views of the planets, the moon, the sun (with a proper filter), and many deep sky objects. This is most likely your best choice for an investment in a telescope.

Compound Telescopes - This is a broad category meant to cover anything not found above. Typical compound telescopes utilize combinations of lenses and mirrors to bring light to a focus. A popular example is the Schmidt-Cassegranian. It utilizes a primary mirror, a secondary mirror that directs light out of the bottom of the tube, and a special corrector plate or lens in from of the entire light path. The reason they're popular is because they're mass produced by a few companies, and come equipped with pretty cool features like automatic GOTO capability for thousands of objects, automatic tracking of the stars, and other advanced features. They are a little more expensive than a Newtonian reflector of the same aperture, but should be considerably less expensive than the same sized refractor. They have some problems: The tube is sealed on commercial units, and the warm air inside destroys high power images. Commercial fabrication gets sloppy too. Oftentimes the optics are not well made (but this can be true of many commercial instruments), or focusing the instrument can cause the image to shift around as the mechanical devices slop around. You can get a good instrument, however. It's just the majority of users have these complaints.

A recap and a list of Pros/Cons:

So the choice is yours. You should make an informed decision by evaluating your wants and needs, and also by trying other instruments first. I cannot help but recommend building a small to medium size Newtonian reflector as a first step, and see how things are going. I think you will find this is a versatile instrument capable of doing most of the things people are hoping to do.

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Richard Berry has a great book called "Build Your Own Telescope: Complete Plans for Five Telescopes You Can Build With Simple Hand Tools". Appropriately named, the reader can expect to find detailed construction plans for a 4 1/4" reflector, a 6" reflector, a 10" reflector, and even a 6" refractor. There is an emphasis on building the mechanical parts of the telescope, and not the optics. Either way, I have used this book as a guide and found it useful.

Dave Kriege & Richard Berry co-authored a great book called "The Dobsonian Telescope: A Practical Manual for Building Large Aperture Telescopes". I think you'll find this book has everything you need to know in building a first time small to moderately sized telescope, but it is geared towards someone who wants a large to very large reflecting telescope. If you've got a little money to build with, get the book and go for the largest size you can afford.

Jean Texereau wrote a book call "How to Make a Telescope" that is excellent if you want to make your own mirror. This book will guide you on preparing the blank(s), grinding the mirror, polishing the mirror, and through the magical process of figuring. The only problem with this book is that some of the information is out of date.

If you have internet access (what are you doing now?) definately check out the ATM FAQ Page. There's lots of info there. If you have e-mail join the ATM List. It is a group of quite a few telescope makers who are a great resource of information. You can find information on how to join at the ATM FAQ Page as well. Also check out my Links Page for more ATM sites.

I'll try to get information on my mirror making stories soon....

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