Telescope Design Page

Telescopes: Purchase vs. Build it Yourself

If you're just getting started with astronomy as a hobby, it may be best to purchase a telescope rather than trying to build one.  There are a lot of very good beginner level telescopes that you can start using right out of the box, many with full GoTo functions.  The most important advice I can give is to stay away from cheap department store telescopes, usually packaged in boxes covered with claims of high magnifications and fantastic pictures of planets, galaxies, and nebula. These telescopes become more trouble than they are worth and will quickly destroy any interest in astronomy; remember that you ultimately get what you pay for. Take a look at Celestron, Meade Instruments, Orion Telescopes, and what you can find on the www. There's always a good selection of name brand telescopes for sale on eBay.

Telescope and Mount Types 

This webpage section gives a very short introduction regarding telescopes and telescope mounts.  I have several additional webpages (tutorials written at the beginner level) that give a discussion of the major telescope types (Telescopes and Optics Tutorial), explain how celestial objects move (Celestial Motion Tutorial) and introduce the different types of telescope mounts and how they track celestial objects (Telescope Mounts Tutorial).  

My telescope building experience is limited to Newtonian type telescopes, which are simple and easy to build. With regard to telescope size, this is one area where size really does count. Large mirrors collect more light and will allow you to see more details, but there are two catches: cost and portability. Astronomical mirrors are like diamonds, a doubling in size translates into considerably more than double the price. Also take into consideration that bigger mirrors cause you to sacrifice some degree of portability and ease of set-up. With all that said, my advice is to purchase as large a mirror as you can. When I purchased my optics in 1981, a 10" mirror was considered a large telescope. The current trend in telescope construction is toward much larger aperture telescopes, making my telescope now a large-medium telescope (however I'm still quite satisfied with its performance). I would not recommend anything less than an 8" diameter mirror (about $50-60 on eBay).

There are many different types of telescope mounts, each with different advantages and disadvantages. A detailed description of telescope mounts can be found on the Telescope Mounts Tutorial.  The remainder of this section gives a very brief introduction to the most common types of homebuilt telescope mounts: Altitude-Azimuth (Alt-Az) and Dobsonian mounts.

If you only want a telescope for visual observations, then an Alt-Az (old fashioned up and down type mount) is all you need (below diagram, left image). The best all round Alt-Az telescope design has to be a Dobsonian type mount (below diagram, right image). This is what I originally constructed in my first telescope building project and is what I recommend to a first time builder. A Dobsonian mount is simply a 3 sided plywood box (pink) that sits and rotates on some type of Dobsonian bearings (usually Teflon sliding against metal or plastic). The telescope tube sits inside the telescope box (light blue), which rests on top of the 3 sided box. These telescopes are simple to build, very rugged, can take a lot of abuse, are extremely stabile, and can even be converted to a GoTo system.




If you want to eventually try astrophotography, then you probably want an equatorial type mount (one axis points parallel to the Earth's pole). This allows you to move the telescope and camera counter to the Earth's rotation for long exposure imaging. Another option is that an Alt-Az telescope that can be placed on a wedge (inclined plane) so that one axis is tilted to be parallel with the Earth's polar axis.  More information about these types of telescope mounts can be found on my Telescope Mounts Tutorial.

Design Issues

The first thing I would recommend is to just spend some time on the www looking at what other telescope builders have constructed. I would ultimately recommend you construct a Dobsonian style telescope or some variation on this theme. Stellafane.org's Building a Dobsonian Telescope pages give all the necessary planning and step-by-step instructions to build a Dobsonian telescope.

The single best article I've read on telescope building was a 3 part article in Astronomy Magazine (June-August, 1980) by Bob Kestner and Richard Berry, titled "How to Build a Dobsonian Telescope". If you can get a reprint of this article, just follow the instructions.

The last overall design comment is the most important: Keep It Simple (KIS). My experience as an engineer is that the simpler a thing is, the better it functions- there's just less to go wrong! This remainder of this section lists some things to think about while designing your telescope and looking at designs on the www:
  1.  Keep It Simple (KIS)
  2. Will this be permanently setup in a fixed location or do I need to build something that I can transport to a remote viewing location?
  3. Can I transport it assembled or does it need to be broken down for transport?
  4. Build to a scale that you can move and assemble by yourself (without injury)
  5. Will transport or my storage location dictate the maximum allowable size?
  6. Note that very long focal length telescopes may require that you stand on a ladder to reach the eyepiece.
  7. Build a system that's fast and easy to set up (in the dark)
  8. Include some details to make things easier: handgrips, eyepiece holders, etc.
  9. Design the system so it's easy to modify without requiring a complete rebuild.
  10. Design with adjustable features (where possible and doesn't violate KIS).  

Where to Find Materials

My design philosophy of keeping everything as simple as possible was also out of necessity. I live in a rural area, where hardware stores carry only basic items. As a result, most of the items I use can be purchased at a local hardware store or home center. If you have a local hardware store and access to the www, then you have access to everything you will need.  

Tools and Construction Skills

I have no special construction skills other than basic carpentry skills. My workshop is also very basic: hand tools, a telescoping miter saw, a router, drill press, and a couple of power hand tools. A basic collection of hand tools and the ability to measure, cut, drill, and tighten a bolt is about all you need. Following are a few additional tools that will really help your construction, but you can probably get by without them:
  1. A router with a circle cutting attachment-this is the best way to cut circular sectors 
  2. A drill hole cutting set 
  3. A tap and dye set to thread metal rods and holes
  4. A good all purpose file for metal and wood
                            
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