Overview




In August 2002 I started work on an 18″ f4.4 Dobsonian, this section of the web site details where I obtained the parts and materials, how I designed it and how I made it.

The scope is based on Dave Kriege and Richard Berry’s excellent book, which describes in fine detail exactly how to make a large dob. I followed this book as closely as I could, any deviation is indicated in these web pages.

Here are my “top tips” which you might find useful if you decide to build a scope. The most important tips I can pass on are:

  • Follow the book closely, the advice in it is very good and does save time, and produce a better scope.
  • Buy a good router flush trim bit that can follow patterns, or a kitchen worktop bit. This will cost you but its worth it!  Also try and get one that will cut twice your plys thickness, i.e. 30mm for two 15mm sheets for example.
  • Cut all of the ply using the router. Otherwise you get very messy edges. Firstly make a template with 6mm (0.25″) MDF or ply. Mark this shape on the ply with a pencil. Cut around the pencil lines with a stanley knife (a couple of mm is outside of the shape is fine). Then rough cut outside of this with a jigsaw. Then clamp the template back on the ply and route using a flush trim bit. Once you have the template cutting the ply is actually very quick and repeatable.
  • I had problems bonding the spider to the secondary mirror, in the end I used fish tank silicon, available from any garden centre or fish specialist. Again this is expensive stuff, but you don’t want the secondary falling on anything so its worth it.
  • Do not get any paint in the split block pole holes, otherwise it is difficult to easily insert and remove the poles.
  • Buy the side bearings and upper tube clamps, I made mine but it was difficult and they are not that good. These are available from Obsession Telescopes.
  • Go to star parties and see how other people made their scopes. Some will have some excellent ideas.

If you get stuck you can always use the contact form on this web site and I’ll see if I can help or at least pass you on to someone who can.  One last tip, I emailed Richard Berry for advice a few times, he is very friendly and always more than willing to advise.

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