New mount for my dob

[rmcpb]

Well I finally got around to finishing the new mount for my dob which I must say gives me much better motions in both directions and is much more stable.

Some features:

Lead weight at base of tube to lower the centre of gravity. This also gives more mass and stability, especially in windy conditions.
Levelling ring that the base sits in to allow setting circles to work properly.
12" side bearings with laminate surface on large teflon pads set 70 degrees apart. Any wider apart and I found the resistance increasing, any closer and it became unstable and too easily moved.
Az movement is held by a lazy susan bearing and three supersliders, this combination gives a real smooth motion that is not too easily moved by the wind, etc.
Cradle can be easily opened to allow the tube to be finely balanced if necessary. I haven't found this necessary with the 12" bearings, changing eyepieces makes no difference and I don't have to use springs or magnets any more.

I am now working on making the bearings easily removable so I can substitute smaller ones for use with the split ring mount I am working on.

This mount has really made a vast difference to observing with tracking at high power (400x plus on the moon) smooth and easy.

[norm]

Hi Rob,

For what its worth, it looks very impressive. What wood did u use and what is the overall weight ?:)

[jase]

Rob, that's a very nice looking mount you've made. It would also appear very functional. Is this your first attempt or have you made others?

[lost_in_space]

Excellent workmanship, something to be proud of. Love the quick release mech for the OTA. Everything a good dob job should be; simple, effective and... well done, very well done:thumbsup: Family heirloom material.
Got any plans for an EQ platform for it?
If you have plans and pics of how you built it please consider posting them and authoring a 'how-to' on the project. From a selfish PoV I would learn a lot, and suspect others would too.

Time for a poll maybe?

Show and tell? :thumbsup:
Don't show and tell?:(

[seeker372011]

hey Rob

that is sensational

were you out at Linden last Saturday?if so I'm sorry i missed seeing this work of art :)

[netwolf]

Rob, absolutely stunning job there. I really like your cradle idea, and the bearings are much better than those plastic things on the GSO's.
I am eagerly awaiting your Split ring mount that you have mentioned before. How would you like to make 2? ;)

Regards

[iceman]

That looks stunning, Rob! A how-to would be awesome..

Very functional, looks great.

Well done!

[stringscope]

Fantastic Rob :thumbsup: . What type of laminate did you use?

Cheers,

[rmcpb]

Thanks for the good feedback folks.

Now to answer some questions:

Norm, The base is simply made of ply from Bunnings and MrPlyandWood. The base and bottom disk of the mount are two layers of 12mm ply glued together to make the bottom as rigid as possible. The sides are 18mm ply, the bearings are double thickness 12mm. The top and bottom rings of the cradle are double 12mm and the side panels are single 12mm ply. The actual weight of the mount is surprisingly light considering the amount of wood that is in it but remember its made of softwood ply, I don't think the extra expense for hardwood ply is worth it.
Jase, This as about MK III and probably the final dob mount for this scope.
Lost in space, I have an equatorial platform that I had set up then tried to improve it but got side tracked (its still in pieces). I plan to work on a collapsible split ring mount instead as I think it will be simplier and far more stable.
Seeker, Yes I was there but you didn't miss anything, solid clouds from about 9pm but I did get to test the setting circles, they work really well.
Netwolf, I will probably end up making quite a few split ring mounts as the project evolves like this mount did but they are a step at a time events and usually pulled to pieces then rebuilt. Not quite the answer you were looking for I suspect :)
Mike, I can do a How To but will have to pull the mount apart for actual sizes so I will probably do a general overview of the thoughts so people can apply it to any size scope.
Ian, I just used a rough finish laminate offcut I got from a friend who is a kitchen supplier, got lucky on that one as he gets most of his panels pre laminated now. Nothing special but boy it works!


Cheers

[janoskiss]

Wow! It looks like a weapon, Rob! :eyepop:

[astro_nutt]

Very impressive Rob!!!...clean, neat, looks cool and very functional...now I'm jealous!!
Cheers!!!

[netwolf]

Rob, dont throw anything away, well you can throw it in my direction if you like. :)

Does anyone know any companies that would cut up pices based on a design drawings? Then it would just be a matter of putting it together.
This would be good for thos of us that are not so handy with the tools.

Regards

[rmcpb]

There is nothing in that base that a router and saw cannot produce. Very simple bits involved so don't sell yourself short in anything. You just have to be a good scrounger for things like laminate and teflon :)

[jjjnettie]

Absolutely brilliant.
A unique design that will draw envious onlookers at every star party.

[JethroB76]

Hi Rob, love your handy work on the new mount, very impressive.:thumbsup:
Just wondering how you rate the angle finder/inclinometer that is on top of your tube in the photos; are you happy enough with the accuracy?

[Starkler]

Looks excellent Rob !



That what its all about and where your off the shelf dob without mods most badly falls down.

[ving]

looks great rob! :)

got a question for ya tho. the nuts onthe inside of the alt bearing, are they welded in or something? did you remove them? and did you repaint over the spot where they were?

thnx :)

[beren]

Holy mackerel that looks very impressive , skillfully made mate congrats :thumbsup:

[rmcpb]

Next lot of answers:

IsDon - The inclinometer is OK and with great care I can usually get an object within the field of view of my 30mm BUT I am working on a new improved version that should be ready in a few weeks.
Geoff - You are surely right, the tracking on the GS mounts is very ordinary but you have to remember how much you paid and most of that went into the scope not the mount.
Dave - I removed the original alt bearing bolts and covered the holes with the black hundred mile and hour tape you see above the cradle.

I am working on the how to and will probably submit it as a seperate thread a step at a time as I get them done.

Cheers

[AstroBug]

Wow! Rob that's a work of art. Looking forward to the how-to. Thanks for posting.

[Roy G. Biv]

It seems that Dob owners are always looking for ways to improve the platform. Here's my humble contribution to the effort.
--Roy

[erick]

Hi Roy,

Perhaps some description of what you have done and why? I can work out some changes but not others.

Thanks
Eric :)

[Roy G. Biv]

Eric—
Sorry, mate. I should have provided some explanation in my first post.

First off, it’s a Zhumell 254mm Dob. Right out of the box I was unhappy with the az/el movement. My clumsiness and unsteady hand made fine tuning a bit difficult. So, I fashioned manually operated, friction-based mechanical controls both for azimuth and elevation .

Along with the above, and looking for an easy and quick way to locate heavenly bodies, I built a wooden base that incorporates a 38mm-wide track on which rides an azimuth ring.

Here’s the details:

The az control is a 13mm vertical rod which is held fast to the upper turntable mount, but free to rotate – much like an axle. Rubber grommets slipped onto the bottom of the rod and a spring tensor help to make friction contact with the edge of the lower turntable. The three short legs of the lower turntable sit in dimples drilled into the wooden base, thereby immobilizing the lower turntable. Rotating the vertical rod causes the upper turntable (along with the telescope) to rotate while the lower turntable remains stationary. The movement is smooth. Gross movements can be made by squeezing the rod away from the spring (which neutralizes the friction) and pushing the mount around. A 304mm Lazy Susan fitted between the turntables smoothes the action. (I intend to replace that Susan with a 584mm model.)

The el control is simply a combination of a hefty turnbuckle, a wooden arm that is pinned to the turnbuckle and screwed to a circular block that is friction-locked to the OT’s axle. Twisting the turnbuckle causes rotational movement of the axle and changes the elevation. As was the case with the azimuth controls, gross movement of the elevation is accomplished by releasing the friction lock pressure and lifting or lowering the OT.

Then there’s the azimuth ring. Once the base is leveled I turn the scope to Polaris (it’s Poughkeepsie, mates!), rotate the azimuth ring so that 000 degrees lies directly under the pointer, and prepare for observation. Using Stellarium, I get the real-time az/el numbers of my target, turn the mount until the pointer lies over the az number, and crank up the turnbuckle until the appropriate el number is displayed in the SmartLevel. This technique is very accurate. I can usually find the target right away if I use a 25mm or 32mm lens. Once the target is centered, I can switch to higher magnitude lenses. Finding and keeping the target centered is accomplished by steering the az and el controls.

This unit is easily disassembled and transportable.

While I recognize that -- to quote Ecclesiastes -- “nothing is new under the sun,” perhaps someone else may benefit from my setup. Regards,
--Roy

[erick]

Roy, that's fascinating and very creative. I haven't been around all that long, but I haven't seen a basic dob mount with fine adjustment controls added. I love the turnbuckle. Its brothers are probably holding anchors in place or holding down buildings!

Gives me ideas! Must resist!

What do you think the Smartlevel is accurate to. It's showing a display to 0.1 deg?

Thanks
Eric :)