Another Dob Mount Build, part 1

[MoonNut]

I purchased a Meade Schmidt Newtonian SN10 (LXD55) OTA a couple of years ago from Ian Sharp ( http://astro-sharp.com/index.asp ), I wanted big aperture in an enclosed tube due to the dust here in Bahrain (I did not want to spend too much money for the same reason) So the SN10 was perfect, it came with a 2" Moonlite focuser and is in good condition. I have always planned to buy an EQ6 to mount it but they need to be shipped in etc. etc. so in the short term and just to get the thing pointed at the sky, I decided to build a Dob Mount.

This is how it turned out:

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The first thing I did was sit down with a sketch pad and tape measure to rough out the basic shape & dimensions. I wanted it to be as compact as possible.

I then produced a drawing (using TurboCad 4) of all the panel sections I would need and took it to a local woodwork shop. I decided to try 1/2" MDF, I was not sure it would be strong enough but wood is very expensive here so I thought I would give it a try. They made all the sections and painted them in Satin Black as per my request for a cost of about £16

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I decided to use Magic Sliders for the Alt and Az bearings, you can see the Az sliders positioned on the base section in the picture above.

This is a close up, you position them where you want them and attach them with a screw through a hole on the centre.

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A few more sliders for good measure and a big coach bolt through both sections with a wing nut as the main pivot.

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Four big rubber feet for the base....

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Then on to the Alt bearings and cradle.

I decided to use the tube rings to mount the OTA using two steel plates bolted to the normal attachment holes, I thought it would be too weak with only one bolt or maybe it would move under load, it is actually very strong, I can lift the whole assembly with one mount.

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The bearing carriers look like this (the wooden packers on the inside edge were temporary, I bought the wrong length bolts , they have now been removed). The outer edge of the bearing is covered in thick PTFE tape (I work in aircraft maintenance so I have access to lots of good "stuff")

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When mounted on the base the OTA and cradle are held in place by gravity and two Retainers, these are held in place with nuts and bolts so that they can be removed to replace the sections of milk container that I have installed there to reduce side friction on the Alt Bearings.

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These are now painted grey and with the correct length bolts mounting the Alt Bearing to the carrier it looks much better.

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I added a grey Knob to the end of the OTA and a handle to the side of the mount, I think it all moves very well, but as I have never used a Dob before I do not have anything to compare it with.

The MDF sections, cut to size and painted were around £16 and all the other hardware came to about £25.

In part 2 I will explain a few of the finer points of the mount construction and the problems I have found now that it is complete.

[runoffshed]

Thanks for this - super write up and useful photos.

I'm just about to start a simple dob for an 8" mirror (got to build the tube first) and this has given me some great ideas.

Can't believe you got your MDF cut and painted for £16!

Looking forward to part 2

[swamp thing]

That looks nice and compact.

Nice job. How does she perform?

Regards Steve

[MoonNut]

Runoffshed... some things are cheap here, labour is one of them, petrol is another, 16p a litre. BTW, My obs is a Runoff Shed

Swamp thing.... I think it performs well but as I said I do not have anything to compare it to. I have made it a bit too low but I will explain that in part 2.

[swamp thing]

Hi

When I built my 10" f/4.5 Dob I like you kept it nice and compact.

I found in use It's great cause I can do all my observing from a drum throne very comfortably.

Eyepiece never reaches any height that causes me to stand.

It never gets so low that I am forced on to the floor either.

Plus being compact it's light as a feather too. Makes a great grab n go scope.

Get yourself a nice low adjustable seat, you'll find compactness a real bonus.

Looking forward to part 2

Regards Steve