Sticky Azimuth motion - Skywatcher Dob

[xyz]

The azimuth motion of my Skywatcher 8" Dob. is not that smooth. There seems to be a higher than expected "sticktion" so that it is difficult to rotate the 'scope by small amounts. Currently I have it perched upon a thick sheet of plywood on top of two beer crates (I am experimenting with the optimum height) and quite often, the plywood sheet rotates on the beer crates rather than the scope rotating on it's teflon pads.

The central bolt is not too tight - checked. The staples holding the teflon pads on are all below the surface of the pads.

Is there something I miss ? should I try applying silicone polish to the unpadded surface ?

Richard

[Doc]

Has it ever got damp in the past? I've heard off quite a few that have and due to the base being made out of particle board they do warp causing a high spot that causes the stiction.

[dobserver]

We had this problem with my son's 8" Skywatcher. We ended up replacing the bearings with a lazy susan one and now it's fine. I can't remember where we got it from, but it was less than £15 delivered.

[xyz]

Doc - it's a new scope so I think it's still got a flat baseboard. I may have to look into a lazy susan roller bearing system.

Thanks,

Richard

[Doc]

Another way round it is to place some milk jug washers on the azimuth bolt so to raise the height a little.

[Space Man]

I' am currently having the same problem with my new 8" Skywatcher Dob. How do I make the milk bottle washers as I can't seem to find an 8" lazy susan? Thanks.

[NGC 1502]

I' am currently having the same problem with my new 8" Skywatcher Dob. How do I make the milk bottle washers as I can't seem to find an 8" lazy susan? Thanks.

Cut some 2" approx washers out of thin plastic. These fit around the centre bolt, between the bottom board of the mount and the ground board. You need enough washers to just barely take the load off the three teflon pads to ease the movement.

Too many washers will make the mount teeter on the new washers, not enough, and no load is taken from the teflon pads, so it's trial and error to get it right.

Worth taking your time to get it just so. A Dob with smooth bearings is great to use. If the movements are sticky, it's a pain.

Regards, Ed.

[johninderby]

Best way is to use Ebony Star laminate as the Az bearing surface. Also wouldn't hurt to replace the little Teflon squares with something better.

http://www.teleskop-express.de/shop/product_info.php/language/de/info/p3876_Ebony-Star-Ring-D-40cm-zum-Selbstbau-von-Gleitlagern.html

John

[Moonshane]

I have just made my 16" dob and used laminate which only had a very slight texture with decent sized teflon pads. this created a fair bit of stiction so what I did to address it was add a further teflon pad of the same thickness at the centre pivot and also add turtle wax (dry then polish off as though doing the car) and this mad an immense difference. bearings all now buttery smooth.

if I bought a Skywatcher scope, the first mod would be to add larger teflon bearings and a centre one and then wax the underside of the rocker. if you can also buy a circle of ebony star or even some laminate (kitchen worktop laminate not floor laminate) and glue this to the underside of the rocker base then even better.

I got an offcut sheet of laminate big enough for my 16" dob base for £8 and the side bearings were about £3.

the teflon sheets were 3mm thick and etched on one side to allow fixing with impact adhesive.

[glowjet]

Lazy susan bearings can be had from www.craft-supplies.co.uk/ up to 12" is just less than £10

[Space Man]

I have just finished applying my milk bottle washers onto my Skywatcher 8" dob mount, no more stiction! On top of that, I applied a single washer either side of the scope, it now moves more freely vertically. Thanks for all the great responses.