Constructing a dob

Maybe the heavy mountaineering webbing is the way to go so- its about twice the thickness of car seat material and fairly cheap.

I dont know this material but it is very important that this material is not elastic in any way, it must not be able to stretch in any manner, otherwise the heavy mirror will shift.
The obsessions use seat belt material.

Looks great!
Will you have it ready for the Whirlpool so we can all go pawing at it!

Looks great!
Will you have it ready for the Whirlpool so we can all go pawing at it!

Hopefully - ready I mean, not the pawing bit!

That's looking brilliant Michael.

If you're having trouble finding sling material try a motor shop & ask for an oil filter opener. It's just a piece of metal with a strap on it. The strap on mine is about an inch width and a few feet long. Seems to be the exact same material they use for seatbelts.

Cost about 15 quid I think.

Trev

Hey guys,

First light achieved

It was a bit of a mixed bag unfortunately. Brought the the scope to the GAC meeting on Monday night. Knocked out of collimation, but I had me trusty barlowed laser with me and realigned. I got a bit of a shock when I looked at M13 through the EP. Horrible view completely washed out. The two mirror box baffles just weren't up to the job and we were in a carpark surrounded by those lantern type streetlamps that spill light in all directions. No way to get more than a few feet from one. So I guess I need a shroud for that location.

Brought it back home after the session and setup in the back garden. Wow, what a difference. Stunning views of the Moon, Double Cluster and a couple of open clusters before the clouds came back in.

I still have two big problems beyond the shroud one though.

1/ While movement is quite smooth the damping times are not good. I know my rocker and mirror box are rigid, so it's a combination of my pole clamps and ground board I think. The ground board is undersized as I ran out of Ebony Star (D'Oh!). Vibrations become an annoyance at powers above 150x. I must take a look at the rocker arcs again and make sure they are properly aligned.

2/ I think I need to revisit the upper cage clamps. The plywood is just not strong enough to hold the poles stiff without suffering damage. I may cut a new bottom ring from a sheet of hardwood, maybe Oak, if I can find it.

Has anyone any suggestions on how to improve damping times? What do ye use as feet for ye're groundboards?

Anyway, it's been fun building this. can't wait to fix the other issues and start observing with it

Many thanks,

Trev