10 inch dob restoration

[Markoz (Mark)]

I'm new to this forum and astronomy but my interest was sparked by taking my daughter to a local observatory. As a result of her enthusiasm, I thought i'd have a look at whats on the second hand market, and being handy, thought i'd see what options there were an a diy telescope. Having then looked at the possibilities of carving my own glass mirror, i thought the learning curve might have been a bit steep....so fortunately i found a 10 inch dob for sale.....hand carved....F5 ... Made out of 9mm thick pvc tubing....so i knew it would also be solid!
As you can see by the first pic....its a big sucker....the glass was filthy, but even on the first night with no cleaning or collimation, we saw the rings of saturn....so i was hooked! And so was my wife! The base was solid steel, but very stiff and didnt spin. More like an engine hoist than a dob base!

Anyway, after filling a couple of holes, giving the tube a clean and sand, i gave it a few coats of cadbury purple (left over house paint!) and a couple of clear coats, and repainted the inside matt black. The tube is heavy but now nice and tidy. I cleaned the mirrors and put some feet on the base of the tube so i can stand it upright when not in its base. You can see how thick the glass and ply mounting plate is,that fits inside the tube!

Ive just started on a new base so will post more pics soon once i figure out how to load multiple images.

Mark oz


Cheers,
mark

[Markoz (Mark)]

Ok here is the new purple tube in the original base!

[Markoz (Mark)]

And the base....version 1. Note the bolts in each corner which act as a brake to slow the lazy susan bearing down. These are upturned bolts with felt glued to the top, and nyloc nuts on top to adjust their height. Works a treat! Now the problem is with the balance.....since the alt bearing is a 1 inch diameter axle, this is very twitchy, hence, mods are planned to change this and reduce the balance issues.

[Markoz (Mark)]

Oops....wrong image last time! Here is the base on its own...

[Saturnine (Jeff)]

Welcome to astronomy and telescope making, or restoration and modification at least, it's good fun and rewarding. Nice job on the base though i'm not too sure on the diameter of the altitude bearings, conventional wisdom via ATM books is that the bearing diameter should be similar to the mirror diameter for smoothness and stability. The dob mounts that I've made have worked well with that criteria in mind.
Actually the original mount that you show is very similar in appearence to the mount that my first 6" dob came with many years ago, though mine was of metal plate and pipe construction. Like you , I built an more conventional plywood mount that works very well, much better than commercial dob mounts. Not too sure on the Cadbury purple tube, but hey, it's a one of a kind and it's yours and you don't have to please anyone but yourself, vive' la difference. and you now have a solid functional telescope that should last for years.
Congrats and well done.

Kind Regards

Jeff

[ZeroID (Brent)]

Hey, nothing wrong with purple !! It has that old 'Meade' look.

to IIS anyways. And nice to hear of a dedicated DIY addict like myself.
Yep, needs bigger side bearings to give it a bit more 'stichion' and control over movement. I used some plastic drain pipe end caps, 100 mm or so IIRC. Cut a bigger 'V' in your new base for whatever you use and should help a lot. Also try to get the balance right so it will stay put. Getting a Dob to work smoothly is always a bit of a mission.
Plenty of ideas and help to be found on here so ask away.

Cheers and have fun !

[Markoz (Mark)]

The purple is always a talking point....everyone thinks the concept of a purple house is weird til they see it....yet we often have people walk in off the street asking about the color....
Anyway more importantly, yeah the side bearings were next....made with double thickness 18mm ply. Only about 150mm diameter but i'm limited by the position of the handles on the tube. The will just bolt over the top of the steel axle plate.

[Markoz (Mark)]

Still refining the shape of the cutout in the base to make sure its got perfect altitude movement but just playing with a couple of felt pads results in perfect balance and just the right amount of movement.

[ZeroID (Brent)]

The cutout can be a simple 'V' to work. Only needs two points of contact. Nice work with the bearings.

[Markoz (Mark)]

Finished......well until I decide to make some more changes!
Have made new altitude bearing disks out of a couple of offcuts from some ply left over from the rest of the base and attached the outer tube! Was actually easier than i thought just using a mitre saw and keep sawing off the corners until almost round and finished the rest by hand. The new bearings work sensationally with felt lining the bearing tracks. Now i have no problems with balance.....actually its probably even a little too sticky so will remove some felt!
Also made a box to hang off the front of the dob base for storing eyepieces, collimation tools, torch and any other odds and ends.
Note the finder is actually a 400mm lens that came with a scope with a $2 bunnings plumbing attachment and a 20mm eyepiece. Gives me about 16x magnification which is plenty for me.

Now we just need the rain to disappear and the clouds to go away!

[Blair]

Nice work. Clear skies to you.