Re: [ATM] How to find Centre of Gravity of an existing telescope

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

Bruce,

> Questions:
> How does one go about determining the CoG of the telescope/mount 
> combination?

Weigh the tube assembly, measure the height of the Alt axis (that ought to 
be at the COG of the tube assy) over a reference surface such as the bottom 
of the rocker box. Then weigh the rocker box, and find its (approximate) 
level of the COG by turning it sideways and rolling it on a broomstick of 
some kind. Then guesstimate the weight of the platform proper, and its level 
of its COG (below the reference plane - i.e. negative).

Multiply the weights with distances, add the three and divide by the sum of 
the weights.
Suppose the OTA is 10 kilos and the alt axis is 50 cm up, the rocker box is 
4 kilos and balances 20 cm up, the platform top is 2.5 kilos and 2 cm down: 
the level of the COG is then (50*10 + 4*20 - 2.5*2)/(10+4+2.5)= 35 cm above 
the reference level.

Nils Olof

>
> Once found, assuming that the CoG does NOT coincide w/ the altitude
> axis, what are the consequences.  I still need to build the table so
> that centre of curvature of the arcs is the centre of gravity,
> otherwise we have the problems mentioned above.  If the altitude axis
> is significantly distant from the centre of gravity, will the ability
> to track be compromised?
>
> I can always raise or lower the centre of gravity by adding or
> removing weight either above or below as necessary, but in any case, I
> still need to figure out how to find the centre of gravity.
>
> Thanks,
> Bruce M
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


_______________________________________________
ATM mailing list http://www.atmlist.net/