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DIY Dob mount

Starflyer

By Starflyer
in DIY Astronomer

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Starflyer

Starflyer

Posted
Posted

Hi there,

Santa is very kindly bringing me a new (second hand) OTA, a 10" f/6.3 newt :rolleyes:

Unfortunately he can't manage an EQ6 Pro at the moment :lol: While I'm saving for the mount I thought I'd have a go at knocking up a dob mount for it.

I'm thinking of 3/4" or 1" external or marine grade ply sanded, primed and painted. I've obtained a decent 12" Lazy Susan bearing for the base, it's supposedly rated to a tonne, so it should cope with a 10" 'scope and a few lumps of wood.

Any hints or tips for the design and build?

So far I'm thinking of a round base about 600mm dia - how do I cut fairly precise circles out of thick plywood? I suppose a jigsaw would do at a push, but is there an easier way?

The bearing would be fixed between the two base sheets and a centre bolt fitted to adjust the tension for the Az movement, maybe with felt pad brakes if the bearing turns out to be too good.

Any ideas for some sort of hinged box to grip the OTA, and what is the best way to get smooth Alt movement? I'd like to be able to easily lift the OTA off and carry it inside after a session.

I would also like to fit a Wixey digital angle thingy - any ideas how to attach one of these accurately to an aluminium tube?

Any ideas and suggestions muchly appreciated.

Ian

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barkis

barkis

Posted
Posted

If you have a router Ian, just fix it to a piece of wood at one end, and pin the wood to the proposed centre of the base. Make sure the router bit is exactly positioned at the radius of the circle you want, switch on, and gently ease the route around until the circle is cut out.

Easy Peasy. Or, you could fix the router, and rotate the wood, whichever you feel happier doing.

Ron. :rolleyes:

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  • 3 weeks later...
barkis

barkis

Posted
Posted

The wood is cut assembly is about to begin!

Does anyone know where I can get some levelling feet like the ones shown on this page about 1/4 of the way down? http://www.homebuiltastronomy.com/ManualDobSettingCircles.htm

They look like cable glands of some sort but I can't find 'em on the net.

Thanks,

Ian

Ian, If you can find a depot somewhere near you, that dispose of white goods, I am sure you will find exactly what you need on the bottom of some old Fridge or Washing Machine. We have a place Called Impact Housing that do that sort of thing. They deal with house clearance and that sort of thing. My missus and I go about once a week, the wife likes to look at Ornaments Ceramics and that sort of stuff.

She is looking for the Named stuff she thinks will slip through the net you know, that she will either keep, or sell for a small fortune.

Paintings and such. I got a couple of computer monitors a while back, and sold them on for a wee profit.

Next time e are there, I will check to see if there are any adjustable feet that would fit the bill for you.

Meanwhile, if you find some, It's OK, they may do for someone elses project.

Ron.

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Astroman

Astroman

Posted
Posted

I don't bother with leveling feet on a Dob mount, as they don't have to be level to work. I take 2 regular hockey pucks, cut them in half and mount 3 of them flat side up to the bottom of the base. You get a solid feel, plus vibration dampening. And a LOT of comments on your creativity! 8) (Feel free to claim this idea as your own...)

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Starflyer

Starflyer

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Posted

Probably try B&Q etc. Leveling feet are standard fitment on loads of kitchen cabinets these days.

Kaptain Klevtsov

Thanks KK and Ron, I have looked at these but they all seem to be thin spindly things and I can see problems when levelling in the dark with cold fingers. The big chunky plastic ones (cable glands?) on that page look like they'll be easier to use.

I don't bother with leveling feet on a Dob mount, as they don't have to be level to work. I take 2 regular hockey pucks, cut them in half and mount 3 of them flat side up to the bottom of the base. You get a solid feel, plus vibration dampening. And a LOT of comments on your creativity! 8) (Feel free to claim this idea as your own...)

I was going to add an azimuth setting circle and a wixey and from my (very) limited knowledge doesn't the base need to be level for these to work successfully? I'm not going to get too hung up with the feet at the moment, I just want to get it to a stage where I can look through the thing :D

Thanks again,

Ian

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  • 4 weeks later...
Starflyer

Starflyer

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Well it's taken a while longer than I first planned but it's (almost) finished.

I cheated slightly and asked a local joinery company to cut out the parts, the router I borrowed looked like a fairly dangerous implement, and I'm too old to lose a finger or two :D The wood is shop fitting ply with a birch veneer finish, I was told that it's more weatherproof than both exterior or marine grade ply, has less voids and is glued under a much greater pressure than the other plywoods - it's damn heavy :lol:

Here's some pics I took along the way;

One of the base disks with the Lazy Suzy bearing I used later on;

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One of the side boards;

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A close-up of a notch cut into a side board;

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The OTA box parts before assembly;

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The mount parts before varnishing;

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The OTA box with hinges fitted before varnishing;

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Unvarnished part on the left and the rest with the first coat of varnish on;

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All parts after four coats of satin varnish;

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The OTA box assembled and UHMWPE bearings fitted;

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A close-up of OTA box bearing;

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A close-up of a side board bearing;

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The base disk with Lazy Suzy bearing and centre spindle fitted;

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The mount completed;

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The mount and OTA box completed - phew;

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A close-up of bearing system with tension adjustment knob;

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Waiting for clear skies :D

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Still waiting for clear skies :D

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The majority of the time was spent waiting for varnish to dry, if I had to do this again I'd wait until summer :wink:

The mount is very smooth in both altitude and azimuth. I've never used a Dob mount so I don't have anything to compare it to, but I'm happy with the result and designing / building it was an enjoyable experience.

To do: fit a 'strap' handle to the OTA box so that I can lift it out of the mount more easily, fit a handle to the base so I can lug it into the garage.

Maybe in the future I'll fit the levelling feet, setting circle and a Wixey, but for now I just want to look through the thing :lol:

Cheers,

Ian

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Naz

Naz

Posted
Posted

Compared to the Dob mount I assembled out of chip board last year when I acquired Daz's old 200 Revelation, yours looks how mine should have, had I not rushed. I am full of :D It should provide you with a reasonably quick grab & go, even after you get the EQ6 pro.

naz

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barkis

barkis

Posted
Posted

I have neglected to keep up with this thread, but I saw a post to it today, and I have returned.

I am very impressed with the quality of the work on this project Ian, and I would just like to say a big well done mate.

I don't wish to sound patronising, but you have done a great job, and you will get loads of excitement from using this splendid instrument.

Ron. :D

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Starflyer

Starflyer

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Thanks for the kind words guys :wink:

Compared to the Dob mount I assembled out of chip board last year when I acquired Daz's old 200 Revelation, yours looks how mine should have, had I not rushed. I am full of :D It should provide you with a reasonably quick grab & go, even after you get the EQ6 pro.

Cheers Naz, I was determined not to rush it - the waiting nearly killed me tough :D

I have neglected to keep up with this thread, but I saw a post to it today, and I have returned.

I am very impressed with the quality of the work on this project Ian, and I would just like to say a big well done mate.

I don't wish to sound patronising, but you have done a great job, and you will get loads of excitement from using this splendid instrument.

Ron. :lol:

Thanks Ron, Don't worry you don't sound patronising as I said I did really enjoy building it and seeing the finished result. The OTA is a thing of beauty (well in my eyes it is) and I wanted the mount to be aesthetically pleasing as well as functional.

That looks great Ian,well done !!( even if you did cheat a bit) :lol:

Karlo

Thanks Karlo, damn dangerous things those routers, can you blame me? Give me an orbital sander any day :D

Cheers Gary and Martin, hopefully you'll have plenty of opportunity to play with it at Kielder. I've got a few final refinements to do and then I'll post some pics of the finished job.

Cheers,

Ian

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beamish

beamish

Posted
Posted
,

... damn dangerous things those routers, can you blame me? Give me an orbital sander any day :D

Ian

Not at all, routers and chainsaws, really scary and require an awful lot of respect. I become particularly wary when I unpack the router, more so than some of the other kit e.g. circular saw or cmpd mitre saw. :shock:.

I hope I'll be able to get up to Kielder later in the year to have a closer look, cos it looks real smart !!

Karlo

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Starflyer

Starflyer

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Cheers Karlo, hope to see you at Kielder :D

Thanks John, I've had a chance to use it for a few hours over the last couple of nights and it really is a pleasure to use. Saturn and Mars blew me away last night at 376x :shock:

I've added a couple of anodised aluminium handles to the base, a strap handle to the OTA box and fitted the Telrad;

3627_normal.jpeg

(click to enlarge)

3628_normal.jpeg

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3629_normal.jpeg

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Still to do (at some point in the future);

Eyepiece holder

Levelling feet

Setting circle

Wixey

Cheers,

Ian

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