8" skywatcher dobsonian

[poncho]

Hey,

Have a 8" dobsonian collapsible, non goto, skywatcher.

It is smooth turning left and right.
But when it try to adjust up and down after tightening it, it is jerky. Jerks in the direction then eases back a bit. This is with the knobs tightened on the sides of the scope

Any trick to make it smooth up/down?
Loosen/tighten/oil something?:shrug:

[raymo]

Hi Poncho, The altitude knobs should not need to be tightened at all if the
scope is properly balanced, just adjusted up enough to stop the scope having any sideways movement. You will have to tighten up a bit when using heavy
2" eyepieces/and/or a DSLR, to stop the scope sagging under the weight.

[Allan_L]

Hi Poncho,
I heard a tip to use a small amount of "Lip Balm" on the 4 plastic disks that support the OTA.

Another IISer told me he replaced those 4 white plastic disks with roller bearings (of about the same size).

[janoskiss]

I get teflon tape that's used for plumbing (for creating a seal when joining pipes) wrapped a few times around the plastic bearings (i.e., the plastic rests on the sides of the base that Allan's pic points out with the red lines). The teflon tape still tends to stick to itself so no need for adhesives. It's quick and easy and works well. The teflon tape will wear through over time (slowly), but you can easily add a few more wraps at any time.

There is more that can be done with the friction against the sides of the base (ebony star and teflon pads) but that's more tricky and takes more effort, required bits are harder to get. (Though it'd probably be worth doing.)

I tried many different kinds of lubricants, including dry ones (e.g., DryGlide, graphite), but have never been happy with the results.

raymo is correct that balancing the scope is very important. You should need only very light tension on the alt bearings. (It's actually compression but everyone calls it tension.)

[poncho]

Thanks guys will try some of those suggestions when i get a chance!!

[poncho]

Silly question - what do i take off to fit in a 2" eyepiece???
cant work it out!!

[janoskiss]

I cannot remember exactly but stuff either lifts out or unscrews. Just experiment, you cannot mess it up.

[raymo]

Here we go for the 159th time Poncho. Newbies have been having trouble with the set up on SW Newts for years. I can't understand why instructions don't come with the scopes.
Firstly, you should have a black collar which is labelled "2" eyepiece
adapter". It has two chrome plated screws on the side at the plain open
end. They secure a 2" eyepiece when it is inserted into that end of the adaptor.
On the focuser there is a tube that you slide 1.25" eyepieces into; the tube
screws onto a flat plate which is held in place by two chrome plated screws on the side of the focuser. Undo the screws; remove the plate; put the
bevelled end of the 2" adaptor into the focuser and tighten the two screws on the side of the focuser. You can now slide a 2" eyepiece into the open end of the 2" eyepiece adaptor, and secure it in place by nipping up the two screws on the side of the adaptor. Sounds complicated, but after doing it a couple of times it only takes seconds.
Hope this helped.
raymo

[poncho]

Thanks raymo for the detailed description...again!

Have looked through it with the pieces off the focuser, but i think im missed the 2" adaptor, i just bought hte scope 2nd hand recently...

http://ca.skywatcher.com/_english/03_accessories/02_detail.php?sid=217

Missing this one i think, and difficult to find it to buy :(

[raymo]

Poncho, Camera House in Midland have a range of SW accessories.I think
the manager's name is Russell. If he doesn't have one in stock I'm pretty sure he will get you one. Whoever sold you that scope should be ashamed of themselves, the adaptor is an essential part of the scope.
raymo

[poncho]

Thanks so much!!! Much appreciated you taking the time to help!
Will check it out ASAP. Cloudy next while anyway though :shrug:

[raymo]

He may have to get it from the the eastern states, so the cloud may have dispersed by then.
raymo