Lazy susan bearing on a dob mount.

[knobby]

Good luck with the modding Michael :-)

[michaeldurban]

well, i started with my setting circle mod.

It basically started out as trying to get my Az rotation more smoothly.

I tried cleaning the teflon squares (on the 300p flex), added milkwashers,

added teflon floor pads, removed them..etc..

nothing seemed to smooth out that terrible crunchy stiction.

So, last weekend I bought a LS bearing (12") and had a 51cm degree circle

printed and laminated

Then I bought a cheap booklight and painted the lens/LED with red glass paint

I left some 'flaps' at 90degree angles so that the degree circle can rotate around the LS.

Cut out a notch from the side, and put it all back together.

The setting circle rotates around the LS, which can be problematic as the laminated circle

sometimes bulges up from the ground base.

I solved this by sticking 4 teflon floor pads on the underside of the top board, thereby the

pads press down just enough to keep the circle steady so it doesn't shift as you turn your

scope.

(sorry for the poor quality and glare.)

Finally I bought a digital inclinometer..

As a (temporary) pointer I used a simple needle, and painted it white, which

gives a nice red reflection at night.

The 'normal' setting circles have black lettering and a white background.

I had the colours reversed, for me, white lettering is more easy to read under

red light...it's just a matter of taste I guess..

So, I can (hopefully) find the elusive DSO's..

[knobby]

Nice job

[rory]

great post Michael, you've done quite abit to your set up there. can I ask what is meant by "flattening out the focuser tube" ?  ive not a clue ,but sounds interesting .

[michaeldurban]

Thanks for the replies!

Rory,

Well...I removed the actual tube from the focuser.

The part where the axle runs over the tube is flat, for friction.

Sometimes the focussing feels like it's running over little speedbumps.

So I took a metal file (fine) and flattened the flat (rectangular) part of the

focuser tube.

The whole thing is on youtube.

Search for astronomyshed, and you will find it.

The result is a smoother, more acurate focussing action.

Just make sure the flattening is level, and not too deep!

michael

[michaeldurban]

here is the link

https://www.youtube.com/watch?v=ofOSAMlqZWw

[rory]

Thanks for the replies!

Rory,

Well...I removed the actual tube from the focuser.

The part where the axle runs over the tube is flat, for friction.

Sometimes the focussing feels like it's running over little speedbumps.

So I took a metal file (fine) and flattened the flat (rectangular) part of the

focuser tube.

The whole thing is on youtube.

Search for astronomyshed, and you will find it.

The result is a smoother, more acurate focussing action.

Just make sure the flattening is level, and not too deep!

Michael

 ah right  got ya,thanks .

[sophiecentaur]

Well well well. I thought I must be the only one with that problem and look what came out of the woodwork! Thanks for all those contributions guys. I think I'll go for the lazy susan approach first for my 200p Dobs. Natch, the question arises as to which make and where to source it. Having looked at a number of sliding and folding door mechanisms and seen the variety of roughness and smoothness there, I imagine there will be good and not so good LSs too.

PS I love the washing up sponge solution. You don't have to look far for abrasive comments.

[sophiecentaur]

I have just fitted a 10" lazy susan bearing. It is very easy to fit because it can 'float' a bit. On each half, there are four ptfe studs that the two surfaces rest on and all I did was to locate the inner ring (lower surface) with some slop, with four studs, screwed into the base. The central pin holds the rotating part centrally and does all the work. It was a half hour job - just needed to get the fixings marked tolerably well. (Measure several times, drill once)

I haven't taken it outside yet but it is sooooo free, now. The washing up sponge brake will do nicely. That bearing will never wear out, either. Re-usable for the cup cakes in a later life.