Constructing a dob

Only item left now are the lower truss clamps. Still haven't decided what I want to do here. Ideally, I'd like to attach them directly on top of the mirror cell. Would keep the mirror box smaller. Any suggestions?
What would people think of these: www.focuser.com/cgi-bin/dman.cgi?page=pr...&product=TC-125D
Would they do the job? I could buy 4 of these, one for each corner and attach them to the top rail of the mirror cell.

After correspondence with Moonlite, I ordered the lower truss clamps - www.focuser.com/cgi-bin/dman.cgi?page=pr...amp;product=TC-125CL and www.focuser.com/cgi-bin/dman.cgi?page=pr...amp;product=TC-125CR . The clamps are shaped to ensure the pole can't slip right through. This way, the poles will be easier to poisition in and will remain the same length.

I pretty much have all the major parts now (or are ordered). The upper truss clamps, split bolts for the sling and the threaded inserts from Obsession are to be sent today. The only parts I really need now are nuts and bolts. Also looking for levelling screws for the collimation bolts - not easy to get unfortunately. Could also use thumb screw knobs which would take a hex head from a bolt. Will enquire at the local hardware store about these tomorrow.

Hi Michael,
I presume those truss clamps are tapered and that prevents slippage.

Have a look at this brave attempt on saving weight on a big scope.
www.flickr.com/photos/8315630@N04/

Hi Michael,
I presume those truss clamps are tapered and that prevents slippage.

Yes, they have some sort of notch or taper to prevent them slipping.

Hi Michael,
Have a look at this brave attempt on saving weight on a big scope.
www.flickr.com/photos/8315630@N04/

Brave,yes, very brave...a bit too brave for me though!

Last night I sanded down the secondary cage rings and the boards for the base. Most of the remaining parts I need are in the post now from the US. What will delay it the most is the making of the spider. Won't have that for a couple more weeks, and then I'll be on hols.

I finally got started on my dob, got the brother in law to route out the secondary rings for me last night. Will hopefully cut the struts tonight and start on the primary cell. i was going to go down the route of steel tailgate as recommended, but I will keep it simple and stick with ply. If I need to go steel at a later date then i will upgrade.

I am using a six point cell for my 12" so it should be a little easier than a 9 point or more.

will post a few pics as i go along.

Sounds good Trev.
How about keeping a photographic record of the construction and posting the images up on the boards here?

Here's the mirror cell nearly complete:

www.astroshot.com/Dob/11.jpg

www.astroshot.com/Dob/12.jpg

I need to varish the wood, then sand down the corners and stick on the support pads.
I also need to spray Hammerite on the metal of the mirror cell to protect it.

Finally, I need to come up with a secure means of connecting the eye bolts to the frame of the mirror cell so that the bolts can turn without the nuts turning loose also. Would Super Glue be strong enough or is there any other type of glue around that will do the job or will I need to weld the nuts to the frame? FYI, the eye bolts are the collimation knobs.

Thanks,

Looking good there mike. Those pics are making me reconsider a metal tailgate. anyway here is the bare bones of cage, everything fits together well and spider fits perfectly, so thats one worry out of the way. I have it held together with threaded rods at moment, but I am waiting on threaded inserts to arrive. but it was hard to find ones to fit my tubes, the ones on order are slightly larger, but the may squeeze in.


Cutting the metal for the 6 point cell at the moment.
Next steps will be to attach focuser and spider and build the tailgate and cell.