Thread: New dobsonian
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Old 10-02-2010, 11:13 AM
mercedes_sl1970
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mercedes_sl1970 is offline
 
Join Date: Mar 2006
Location: Canberra
Posts: 430
Quote:
Originally Posted by mental4astro View Post
Hi Andrew,

I just had a second, closer look at your new scope.

I must say, WOW!

Great idea with the light baffel/shield on the sec. cage. And a double wammy with the curved spider! I really like the echo of shapes. Organic. Sexy.

Any chance of some pics of it in stow mode?

I'm still to get my head around the use of aluminium for the altitude bearing surface. Is it riding on Teflon? I'm guessing it must work well, how do you find it? Nice work on bending & fixing it. Was it tricky to get the right matching of the centres with the height of the bearing/bearing pad?

Cheers,

Mental.
Hi Alex

Thanks for the comments. Here are a couple of shots of the dob collapsed - the one with the dog for scale.

The aluminium on the trunnion seems to work quite well. I chose it, partly because it's what I had at hand and also after seeing what Chris had done with his scope (http://www.flickr.com/photos/38295849@N04/).

I bent the aluminium by hand to a slightly larger radius (knowing I couldn't get it to an accurate shape) then had to pull, clamp, curse and screw it down. Under tension, it creates something close to an arc - it's not perfect but it's ok. In hindsight, I probably should have made a jig to bend it properly, or taken it to a metalworking shop but I was getting impatient.

The aluminium strip, which I polished using a light cutting compound on a bench buffer, is quite smooth in movement. It sits on a couple of furniture sliders. On the other side, I've used a carriage bolt passing through a skateboard bearing.

Matching the centres wasn't too hard - a bit of guesstimation of the amount to subtract from the altitude radius.

Andrew

ps enjoying seeing your scope develop.
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