How to stop a Dob turning?

[quantoid]

I have a Bintel Dobsonian and when viewing it's really hard to keep it still because the base turns so freely. Any tips for locking the base in position?

[glend]

To lock it for transport simple drill a hole through both base boards and drop in a bolt. To brake it while observing you can install a bicycle brake , or some similiar friction brake.

[vaztr]

Mike,

How about one of those 'hand clamps' that can be applied/released with one hand?

VAZ

[AG Hybrid]

Tighten the nut on the center bolt?

[Allan_L]

Firstly, having the base on a level surface is a good start.
With a free moving base, there will be a tendency for it to want to swing "down-slope".

I built a levelling base that the mount just sits into. (I chose "Form PLY" for water resistant qualities and relative cheapness) with adjustable height feet from Bunnings. Either plastic kitchen furniture legs (about $4) or metal furniture screw in legs ($20). Plastic ones seem to work better as they have a larger base and don't sink in to the grass.

Mine was a Skywatcher with a central bolt in the middle of the base. I could get some improved friction by tightening that. Not sure if Bintel DOB is similar design.
After that, a piece of carpet or soft felt furniture slides between the rotating and fixed parts of the base should help.

Otherwise
Do a google search on improve stiction Dobsonian.
or check out the projects and articles section in the left column here on IIS.

[sn1987a]

Dobstop! :D you can find this gear usually in Bunnings. Cut threaded rod to size and a bit of loctite on handle threads. Drill hole in an appropriate section of the top board.

[sn1987a]

This might work better. Just need to trim off the sticky back and black plastic of the furniture slider and let it float in the recess.

[Allan_L]

Hey! That's a really neat solution Barry. :thumbsup:
I haven't seen anything like that before.
That would have been a great addition to my previous DOB on which I did the "Lazy Suzanne" modification, which left it a bit too free and easy.

I guess you put the hole on the side nearest the eyepiece.

[sn1987a]

No worries thanks Allan, yes just reach down and snug to desired friction. A better internal threaded collet would be the wood type with self tapping coarse thread on the outside but you would then have to file it down to get it flush with the top of the board.

[SimmoW]

Locking it might be too extreme, very hard to gradually aim an object once locked. I've got a similar issue, just bought a thin doormat from Bunnings and will insert that to increase the overall friction of the base, so the central adjustment knob actually works as intended.

[Steffen]

What am I missing? Bintel (i.e. GSO) Dobs have a hand knob at the centre of the base for adjusting resistance in azimuth. It can be tightened so far as to make azimuth rotation very hard.

Cheers
Steffen.

[sn1987a]

Well there goes my dreams of retiring on the royalties from that one :sadeyes:

[Curt]

I'll order one.;)

[RAJAH235]

Dismantle the base & stick a disc of Ebony Star on the bottom of the top board.

Easy as.

[quantoid]

I think there must be something wrong with the azimuth knob then. I'll check that metal sleeve, maybe it's not properly seated in the base.

Thanks for all the tips, will see if the knob can be got to work properly.