Jump to content
  • Join the online East Midlands astronomy club today!

    With active forums, two dark sites and a knowledgeable membership, East Midlands Stargazers has something for everyone.

Skywatcher Dobsonian altitude smoothness


Graham Fletcher

Recommended Posts

Graham Fletcher

Hi guys

i have a Skywatcher 250px flex tube dob and was wondering what you guys do to improve the altitude movement . I get a certain amount of “sticktion” making movement rather jerky. Are you supposed to have the clamping plastic handle on the opposite side to the focused relatively loose and just rely on the other clamping plastic handle to provide the correct tension? Is there any quick fix as to improving the “sticktion” situation at all?

your help would be very much appreciated 

Graham

Link to post
Share on other sites

The alt axis should need minimum stcktion adjustment if the tube is properly balanced in any position. It's really just enough to hold in place cos gravity does the rest when you have a well balanced tube. When I had the 8" version it did have the tensioning handle opposite side to the focuser - I seem to remember it made a difference but can't recall why.

Link to post
Share on other sites

I think it was the spacing between the supporting arms Graham. It had the effect of centering up the tube. I've been thinking overnight and I remember being totally surprised the difference it made. Of course the 12" may be built slightly differently so please treat it as a suggestion only, in the absence of anything else. 🙂

Link to post
Share on other sites

I have the solid tube 8” so not your model but I balance the OTA best I can, then remove the black handle closest to me when observing and then tighten the other side just a tiny bit, works for me.

Link to post
Share on other sites

Whatever I tried with my 12" dob, it never seemed to be "Sticktion" free and when using high magnifications, it would jump all over the place. So I bought a ten quid skateboard and destroyed it to get the bearings out of the wheels. I then made an adjustable pair of rollers that sit just under the main weight bearing plastic mount of the tube assembly and these just take enough weight to make it silky smooth. A lot of work to solve a simple problem, but they work perfectly.

 

DSCF1877

 

  • Like 2
Link to post
Share on other sites

The bolt at the bottom allows accurate adjustment upwards. The two M6 nuts lock it off and keep it where you set it, this was all made down the shed. The only part off the skateboard was the bearings, I don't know if they are cheaper now, but that was a cost effective solution back then, all the other bits I made down the shed. 

There is a bearing both sides of the support structure so that they can be independently adjusted to get the tube to move just right. They do need to have just a little bit of friction or it rocks up and down with the slightest breeze, but a bit of fiddling and it has never had to be adjusted since I first set it.

This of course was just me going off on one and probably going over the top to solve my stickiness issue. (Oh Matron!) 😆

Link to post
Share on other sites
Graham Fletcher

Would it be possible to remove the 4 nylon bosses that the OTA trunnions run against and replace them with the same size roller bearings?

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.