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Old 22-02-2020, 07:53 AM
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gregbradley
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Join Date: Feb 2006
Location: Sydney
Posts: 15,942
Quote:
Originally Posted by PRejto View Post
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-2...lon-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
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.
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