step by step plans to convert 12 inch solid tube dob to truss design

[Dobman]

I'm considering converting my 12 inch Bintel Dob to a truss design.
My main considerations are:
1. more compact for storage and transporting.
2. Easy collimation.
3. Wooden construction ( I'm more confident in woodworking than metal).
4. Simple design.
5. reusing the main and secondary mirror and focuser.

I've been searching the web for step by step plans but without much luck.
Can anyone point me in the right direction to websites etc.?
Thanks in advance
Simon

[ZeroID]

Hi Simon,
I don't think you'll find specific plans to do that sort of conversion. Each manufacturer or DIY enthusiast will have their own ideas on it.
Essentially you'd chop the bottom section off your solid DOB as a mirror cell base, chop the top bit off as the upper OTA with focuser and mirror and find some solid mechanicals to rejoin them without using a big tube. Most use aluminium tube rods or similar.

The hard part is making up rigid connectors and getting accurate alignment & collimation. Or if you are going down the rocker box open scope then there are all the design elements to achieve balance and rigidity etc. Having built about 5 different scopes, mostly of open truss design and various other astro hardware it really comes down to what you think you have the resources to do. My first scope build was pretty ugly and simple but it worked and I have since built several Serrurier and open framed scopes with almost scrap wood and metal from work and the home workshop.

I'd suggest searching all the astro DIY sites\threads you can find and collecting pix and drawings then deciding on a design you like and think you can build and doing your own concept. Plenty on here will help with critique and suggestions if you post up possible drawings or ask questions. You will have to do some metal work although most should be related to fixtures. Your local hardware supplier has many options and aluminium is actually quite easy to work with.

Come up with a design concept drawing or similar, post it here and we'll all get stuck in and turn it into a working scope.

(My latest build uses a pair of cut off tripod legs as the expanding truss elements. Anything is possible :P )

[Rod]

Hi Simon

I like this site:

http://www.reinervogel.net/index_e.html

However, I would recommend you have a close look at one or preferably both of these books:

http://www.willbell.com/tm/dobtel.htm

http://www.willbell.com/tm/PortableNewtonianTelescopes.htm

The second book by Albert Highe is the one I like more and would I think lead to a lighter scope. The Krieg and Berry book is excellent too. It shows you how to build an obsession style dob. Some of the ideas are looking a little dated now - eg the main mirror cell and the truss clamps. Highe's book and the web site above have simpler solutions.

Make sure you read the sections on balancing your dob. It's easy to wind up needing to add a ton of weight to the mirror box if you don't.

Also consider whether a lighter solid tube and mount might suit you better. Commercial scope dob mounts are often made of heavy chipboard and have excessively large circular bases. You can save a fair bit of weight by rebuilding the rocker with plywood. Octagonal or round tubes made of ply can be very strong, light and attractive. I'm seriously thinking of converting my 12 inch truss dob to a light solid tube to save on set up and pack up time.

Hope that helps.

Rod.

[clive milne]

^^^^ What Rod said. :thumbsup: