Not Exactly an Observatory....Tripod Dolly

[PRejto]

My temporary observatory in Rylstone is an aircraft hangar......

After being permanently setup for years the thought of breaking down/setting up isn't exactly appealing so I set out to build a tripod dolly for my Helium Tripod, MX+, and TEC140.

After a lot of searching I found castor wheels with inbuilt top adjustable levelers. https://www.accesscasters.com/alpc-200f-top-plate-leveling-caster-220-lb-capacity-50-mm-nylon-wheel.aspx

To mount the wheels I decided to use RHS steel 75 x 25 x1.6 in a "T" formation. I decided the dolly should be able to be taken apart so I had a shop weld a plate to the RHS along with two nuts.

I used the Helium inbuilt leveler bolts to bolt the tripod to the dolly with some easily purchased nuts and washers (see photo).

The levelers work a treat! They actually feel steady enough to possibly image straight away. However, they also lift just high enough to clear a standard size brick.

My one regret about the project is that I should have made the Top arm of the "T" a bit longer. I didn't count on the wheels hitting the nut holding the tripod to the dolly. I don't think this will be a serious concern. If it is I will lower the tripod and drill new mounting holes.

My next project is to work out a way to bring the gear back to as close to the same spot as possible.

Peter

[Tinderboxsky]

Your trolley looks good Peter. You have inspired me to do something similar.
We are moving and I have just removed my permanent pier and won’t be able to put new pier in for a while. However there is a level concrete apron in front of our new garage, so, I could do something similar as a temporary arrangement.
Just one question - with the size of castor wheel that you have chosen, how have you found rolling your whole rig across concrete?

[miker]

Well thought out and executed Peter :thumbsup:
If you cut out and drill three pieces of 6mm or so aluminium plate to act as spacers between the underside of the arms, and the top side of the castor mounting plates, you might clear the nuts. Also, thinner nuts (usually in stainless steel) can often be purchased as well.

Michael.

[FlashDrive]

That's a real good out come.

[PRejto]

Thanks for the comments! I have not yet tried to move the fully loaded tripod, but I did find it easy to move the tripod and mount less OTA. Hopefully things continue to work with more weight. I agree that larger wheels would have been better...I couldn't find larger wheels + a leveler. I was surprised and happy when I found these wheels unexpectedly.

Peter

[gregbradley]

I think there are 2 ways of getting repeatability with a portable setup.

A simple one is to have marking tape or paint on the ground (assuming its concrete flooring) for the wheel. Another would be to put 3 pavers down if its grass and mark the pavers.

The other is one I used successfully for many years.
I had a laser collimater. I was using a Tak NJP mount and a roll off roof observatory but I took away the mount every time.

I got an accurate polar alignment one trip.

Then I took off the cap to where the polar scope goes on the mount and shone the laser through the hole (no polar scope). It would place a red dot on the ceiling of the roof and I put a small piece of black electrical tape there.

Next time I simply hand held the laser same way and adjusted the mount until the laser red dot was in the middle of the tape and that was it.
I would get repeatably good tracking each time. Polar alignment time this way took about 3 minutes.

If outdoors maybe you could find a fence or a tree that could serve as a laser target. If you can't shine the laser through the polar scope hole then
perhaps mount a little finder scope and shine the laser through that mounting it like an eyepiece so its repeatable.

Greg.

[Hemi]

Simple, elegant solution.

[PRejto]

Thanks for your suggestions, Greg!

Unfortunately I can't leave the bricks in place and roll the dolly over the bricks. I must lift the dolly with the levelers, slide the bricks under, then lower the dolly. But, it occurs to me that I could mark the leveler positions on the ground. I'm not sure how easy it will be to line things up, however. The laser is an interesting idea that I will experiment with. Thanks!

Peter

[gregbradley]

The laser idea does assume the mount is in the same position on the ground each time.

In my case the mount went onto a permanent pier each time so it never moved.

Greg.

[Joshua Bunn]

Nice going Peter.

About repeatability in getting the same location every time, if you had a ball and socket type location device near each wheel or a male point with a female taper that accepted the point, that would ensure repeatability. Just wheel it over and drop in down into the holes.
Josh

[legoman_iac]

That is a very nice looking t-frame. Much slicker than the wooden one I built a few years ago. The biggest issue I had, apart from repeatable alignment, is learning to maneuver it in and out the house, and over a small step. Still, a million times better than lugging it out by hand, think you'll enjoy this, and use your scope alot more now!!!

[appiice]

Hello Greg

My 2 cents worth is if you can lift the dolly ( nice design too! ) onto some " pucks " that would work.

The puck could be machined from aluminum with a dimple on the base that could fit into a hole drilled into your slab and on the top a machined recess that the dolly legs for fit into.

Second suggestion is if you mounted a laser on the dolly, ( if you didn't want to mount your existing laser bunnings have on for $50.00 https://www.bunnings.com.au/bosch-pll-1-p-line-and-dot-laser_p5660477 )
that would do the trick.

If it was mounted on one of the legs and when the mount was aligned you marked a point on a wall where the laser shone that would give you an easily repeatable reference point - the furthest you can mark the laser point from the dolly the more accurate it will be.

Hope this helps.

Ed