Finding the Centre of Gravity.

[Edward Fraser]

I have a Celestron C11 SCT which I would like to use on a home made, fixed latitude, wedge, mounted on a tripod.

I have constructed the wedge but can not decide on the fixing hole positions to mount it to the tripod as it will have to be offset to accommodate the offset of the centre of gravity [COG] of the scope. I want to make sure that the scopes COG when mounted on the wedge runs through the centre of the tripod to maintain stability.

My thinking was that if I positioned a bathroom scales under the foot of each leg of the tripod then temporarily clamped the wedge /scope to the tripod I could move the wedge about in relation to the tripod until all three weighing scales showed the same weight. This would show that the COG was in the centre of the tripod and the rig is perfectly stable allowing  permanent fixing holes to be drilled where appropriate.

Is my thinking correct or have I been having too many late nights?

Ed

[Eric Watkins]

How about suspending it with  loop of rope around the ‘tube above a carpeted floor or cushion just enough to allow movement of the loop to the C of G balance point.

Eric

[David Basey]

You could try this method based on one I’ve used in the past to find the balance point of a telescope tube.

1. Fit the telescope to the wedge and stand it on the floor.
2. Slide pencils in from opposite sides, level with each other, effectively making a see-saw.
3. Slide the wedge back and forwards on the pencils until it is in balance.
4. The vertical plane through the pencils now contains the COG.

The only issue you might have is if the COG lies outside the wedge and it tips over when placed on the floor. In this case you could attach an outrigger to prevent tipping before putting the mount on the pencils. As long as it is light in weight compared to the scope it will not materially shift the COG. After all it will shift in use if you switch from say a light eyepiece to a heavy camera.

Just a thought.

David

[Edward Fraser]

The rig, consisting of the fork mount, tube and wedge weights over 35Kg and I do not fancy trying to balance it suspended on a rope.

I like Davids idea, and two pencils are easier to source than three bathroom scales.

Thanks both.

Ed

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