300p Dob - Goodbye lazy Susan - Hello control

[Avocette]

Just competed a revamp of my Skyliner Flextube 300p to add a setting circle to the base.

When I first owned the scope, I thought I liked the smooth rotation provided by the in-built needle roller lazy Susan bearing. But the imbalance between the friction of the axes, in fact the total lack of friction in the Azimuth soon became frustrating. Fine adjustment of the Rigel Quikfinder was almost impossible without a second person to hold the mount still.

So I took the opportunity to remove the bearing and replace it with eight 38mm diameter Teflon furniture sliders in a circle a little more than half way from the centre bolt to the edge of the mount base circle. This particular choice was based on experience of a 200p (three 25mm sliders at the very edge of the mount base) and a 250px (six 25mm sliders half way out from the centre bolt to the edge of the mount base).

First experiments last night observing Jupiter with Binoviewers suggests the new Azimuth friction is a big improvement and about right.

Now I need to solve the Alt axis balance issues to handle the range of uses from fully extended Flextube trusses with a single eyepiece or DSLR, to reduced length trusses with Binoviewers and two medium eyepieces.

[Uplooker]

Sounds good. Where did you source the Teflon and how did you fix it to the base?

Ian

[Mike73]

I had a 300P, great scope but hated the wobble that you'd sometimes get with the lazy susan.

If you want to make those Teflon pads even smoother get some Sailcote, I mentioned it in another recent thread http://stargazerslounge.com/topic/211041-making-a-dob-smoother/ 

[Avocette]

Sounds good. Where did you source the Teflon and how did you fix it to the base?

Ian

Teflon furniture sliders are two layers - grey Teflon top layer and black rubbery base layer. Between the two layers there is a metal washer moulded in that you use to screw them down. I bought mine in a DIY supermarket abroad but I'm sure they will be available in the UK. I'll take some photos and post them here.

[Avocette]

I had a 300P, great scope but hated the wobble that you'd sometimes get with the lazy susan.

If you want to make those Teflon pads even smoother get some Sailcote, I mentioned it in another recent thread http://stargazerslounge.com/topic/211041-making-a-dob-smoother/ 

Thanks - Sailcote is a new product for me! I've tried using furniture wax and others have talked about Turtle Wax, but Sailcote sounds ideal.

[Avocette]

Photos of the new bearing arrangements.... Please ignore the copious amounts of Blue Peter 'sticky back plastic' which were needed to repair the setting circle after a transport problem and which have no effect on the reassembled mount. Those with eagle eyes will notice the 20° offset of the North tab to compensate for the position of the degree bezel.

[Daniel-K]

tidy!

[iam4208]

Very neat.  Why don't the manufacturers incorporate something like this for the clumsy-handed like me?

[JulianFR]

That's great. I also have the 300 flex tube and I find the azimuth movement is sooo easy to move it's annoying. Like you, I can't even adjust the Rigel without it nudging the telescope out of position. L have tried tightening the bolt in the base even more but there is still not enough friction.

I'll study your solution and, if I'm brave enough, try it as well (useless at DIY!)

Where did you get the setting circles from?

Julian

[Avocette]

The setting circle is from a design made by Gandalf223 (on CloudyNights) for an 8" Lightbridge. It's a PDF file which I take on a memory stick to a printers (in South Shropshire) who specialize in exhibition posters and such like. The original would measure about 75cm diameter, and I simply ask the printers to scale it to make the outer circle the appropriate size for the scope I am adapting. They print on vinyl with a clear matt top cover layer and mount it on 3mm foamex board. I have had three circles printed so far for a 200p and a 250px (around 48cm diameter each) and now a 300p Dob (58cm diameter), each fitted slightly differently but all working well. I do the final careful cutting to shape with a craft knife. I could certainly get you a circle made, but the problem would be packaging it for the post. 

[JulianFR]

Thanks for the information. It's very good of you to offer to help me with the setting circle. As you say, it would be difficult to post ;-)

perhaps you could tell me which print-house you use?

[michaeldurban]

I tried that very same setup, with furniture sliders..

it didn't work for me, I moved to LS bearings..

With some washers and friction I removed the above mention problem,

where you can't adjust your Rigel/Telrad as the base tends to move..

Much better now..

Now I need to find the same solution for the Alt. movement,

I heard milk-washers might do the trick..