Home made Dobsonian Base.

[Moonshane]

Hi all

I am making a base for a relative's 6" newt and as I love dobs so much, it had to be a dob base!

I made it from stuff I had in the shed (a bit of 18mm ply and a table top for the sides - knew it would come in handy one day).

I have gone down the traditional route and hopefully the pics speak for themselves but any questions, just ask.

Cutting out the sections from the front and sides made a massive difference to weight but not at all to stability so it's well worth doing - thanks Scogyrd!

I have yet to make the alt and azi bearings but it's looking good.

I will put some pics together of the circular alt bearings and the whole thing in situ once it's finished.

As I have made it for him for free he's blummin' painting it!!

As I know it would be painted (staining would look dodgy as there's two very different types of wood used) I have just glued and screwed the joints.

I made it wider than required for two reasons - if he ever decides to get a bigger scope, this will easily also accommodate an 8" tube and also, the footprint of a 6" base in this style would be too small. This is about 14" square so still reasonably small but pretty stable.

Not perfect but this is the first time I have done this and it's good practice for when I make my 16" version shortly.

Cheers

Shane

[Telrad]

Shane, That's really cool. I love it. It looks really robust and an original design too. The manafacturers of the dobs on the market do not have designs this creative. I think the built in alt and azi bearings when it's finished will be ideal.

Good work!!

[Moonshane]

cheers matey - it's really a rip-off of my Orion Optics UK design but in timber.

it's compact. my 16" base will be lower to the ground and only about 550mm square so perhaps the size of a 12" skywatcher base in terms of width anyway.

[Rob]

Very nice mate. I'm going to make mine soon. I just need to decide on side bearings.

[Astrokev]

Shane,

The height of the "back brace" seems quite high. I guess this is to help keep the sides rigid, but with the result of increasing the overall height (to allow the OTA to swing into the base so as to reach the zenith). This will obviously make the whole assembly more top-heavy and reduce stability.

Is it possible to design with a lower back brace to keep the COG as low as possible? Did you consider this? Comfortable viewing height is important, of course, which you may have factored in.

I'll be making a dob base at some point this year so will be trying to optimise the design to achieve the right balance of low COG / low weight vs. rigidity.

Like the cut-outs though - aesthetically pleasing and serve a useful purpose.

Edited June 8, 2011 by Astrokev

[Astrokev]

Very nice mate. I'm going to make mine soon. I just need to decide on side bearings.

110mm plastic pipe end-stops are ideal for small scopes. Any big DIY shop will have them.

[swamp thing]

Looks good Shane.

I like the weight saving cutouts (might have to mod my 10" to match).

I used rubber door stops for feet ( prevents slipping and dampens any vibration too ) might help if it's to be a planetary scope.

Regards Steve

[Moonshane]

Very nice mate. I'm going to make mine soon. I just need to decide on side bearings.

go for it Rob, it's basically six pieces of plywood, anyone can do it!

Shane,

The height of the "back brace" seems quite high. I guess this is to help keep the sides rigid, but with the result of increasing the overall height (to allow the OTA to swing into the base so as to reach the zenith). This will obviously make the whole assembly more top-heavy and reduce stability.

Is it possible to design with a lower back brace to keep the COG as low as possible? Did you consider this? Comfortable viewing height is important, of course, which you may have factored in.

I'll be making a dob base at some point this year so will be trying to optimise the design to achieve the right balance of low COG / low weight vs. rigidity.

Like the cut-outs though - aesthetically pleasing and serve a useful purpose.

cheers Kev

Do you mean the short low down piece at the back or the tall piece with a cut out at the front?

I presume the latter?

In either case, you are right that it was a balance between COG and observing height as this is for a short tube 6" newt.

I got my relative to sit in a standard chair and measured the height of his eye at approximately the mid range point and based the mount on this. He can now scooch down or up a bit in the same standard garden chair and view at all positions seated.

The price for this is taller mount than I'd like but it's wider than needed and weighty at the bottom due to the cut-outs. I'm happy it will be stable enough and the cut-outs also lessen the chances of an unexpected breeze blowing it over (a la pylons!).

This also has the advantage of not having to make another observing seat for him!

Looks good Shane.

I like the weight saving cutouts (might have to mod my 10" to match).

I used rubber door stops for feet ( prevents slipping and dampens any vibration too ) might help if it's to be a planetary scope.

Regards Steve

cheers Steve,

it's a f5 6" 'generalist' newt but better than his 76mm newt (which he did not realise had a 'main cap' - he was observing through the central 40mm cap!!). I'll add some rubber sheet epoxied to the feet in due course to reduce damp ingress too.

[Astrokev]

cheers Kev

Do you mean the short low down piece at the back or the tall piece with a cut out at the front?

I presume the latter?

No, I meant the short low down piece at the back! (why didn't I use that phrase!). I think comfortable viewing position is more important, so this will ultimately dictate the height of the axis and, hence, the amount of space under the primary end of the tube to add box-bracing pieces etc.

I'm sure your design will be perfectly stable, and it looks good.

The thought of using a relative to test observing heights made me smile for some reason!

Edited June 8, 2011 by Astrokev

[Moonshane]

he's my star test dummy!

I actually made the back piece bigger on purpose to add more weight at the bottom as the front was as high as it needed to be for viewing comfort and the tube easily passes the back piece (as will a f5 8"). I thought about a cut-out on that too but felt it important to retain weight at the low end.

I need to fit some 'keeps' inside each of the sides the retain the alt bearings (pics to follow) and also a curved foam faced piece at the top of the front piece to hold the scope vertical for storage and observing.

I was going to wait for some formica but feel that given the lightness of the scope, I may just varnish the bottom and the alt bearings and then they will be smooth enough. I can always add formica later and at least he can use it for a while if it's smooth enough for that.

[Astrokev]

I was just going to ask - what have you used for the azimuth bearing? It's a while since I made a dob, but is still "traditional" to use formica and teflon pads, or is that old school nowadays?

[Moonshane]

yeah I am using teflon and was going to use formica (ebony star or something with the same orange peel texture anyway). I'll be paying for the latter so as he's getting this mount for free, we'll try it with just teflon and a varnished surface for now but if my and Russ's plan to get some locally pays off at the right price then I may add this to the base later on.

I'll certainly be using Teflon and formica for my 16" when this is done - hopefully start on this soon,

after this experience cutting (the cut-outs not the circular sections) freehand pretty accurately though, with a jigsaw, I will probably make a template and router the shapes out for my biggie.

Edited June 8, 2011 by Moonshane

[Moonshane]

did I say this was my practice run from 'free' materials which will be a good learning experience for when I use expensive double bonded exterior ply for my 'proper' one.

[Astrokev]

Be sure to post lots of pics. I may copy your design and methods!

[Moonshane]

no worries. will do - if you want pics of anything specific let me know soon as I may be taking it to Steve next week sometime.

[Rob]

Once again, nice work. A lot of thought on design gone here.

Rob

[russ]

Shane, just got to say that is wicked!

[spaceboy]

VERY NICE Shane! I take it you must be a carpenter

[Moonshane]

just call me Joseph!

nah, I am very amateur when it comes to woodwork but I broadly know what I am doing and this is (genuinely) the first time I have used a router so I am pretty pleased.

Now I know how it operates, I'll be making templates and then routering off those for my 'half cartwheel alt bearings' and rocker cut outs when it comes to the 16".

here's today's efforts (redundancy has it's benefits sometimes.....).

made some 'keeps' to prevent lateral movement.

checked the fit with some rough blocks and a single ring - spot on

I have as mentioned previously, built this with the knowledge that he may eventually buy an 8" tube so it is a little oversize but this adds to stability.

I then put the tube in and it seems to fit together well.

[Moonshane]

I thought to myself, I wonder...........and as an added bonus (and this was pure luck) the scope sits nicely within the base with the alt bearings attached, making for a quite compact and neat package - allowing it to be carried in and out in one. nice.

[Moonshane]

Shane, just got to say that is wicked!

cheers mate

quite pleased with it. just need some formica now

[scogyrd]

Nice looking mount! I like the piece of wood you put at the back to help keep it square, where have I seen that before?

I plan on making a similar mount for my dob soon. I've already bought the tube rings and made the side bearings but I've just spent a fortune on my MOT and I didn't quite have enough plywood left over from my last build so it's been put on the back seat for now. One day I'll finish it though...

[Astrokev]

(redundancy has it's benefits sometimes.....).

That's you and me both, mate!

Regarding the formica for the base, I've read of someone who used an old vinyl LP. Worth considering if you have any old disks lying around. Certainly cheaper than buying formica.....

.....and if you stick a needle in the rocker box, you could listen to some music at the same time!

Edited June 9, 2011 by Astrokev

[Moonshane]

Nice looking mount! I like the piece of wood you put at the back to help keep it square, where have I seen that before?

I plan on making a similar mount for my dob soon. I've already bought the tube rings and made the side bearings but I've just spent a fortune on my MOT and I didn't quite have enough plywood left over from my last build so it's been put on the back seat for now. One day I'll finish it though...

ha ha

cheers mate - I did mention somewhere that my mount was inspired by you and OOUK of course

good luck with your own build!

[Moonshane]

That's you and me both, mate!

Regarding the formica for the base, I've read of someone who used an old vinyl LP. Worth considering if you have any old disks lying around. Certainly cheaper than buying formica.....

.....and if you stick a needle in the rocker box, you could listen to some music at the same time!

quite positive and actively applying for jobs etc - want a new career so in seek and justify all my skills mode currently. got a decent package though so have some time and it may even work out well. my wife has a good job too and I think will be the main breadwinner for a long time to come!

you're a genius mate with the LP. I do actually have some still in the loft so bonus!!

this will enable me to get it finished while Russ and I work on a joint purchase of some laminate/formica.