East Heavy Counterweight System for my Losmandy G11

[AMcD]

It appears to be widely accepted that an East heavy bias on the RA axis can assist with guiding, by addressing any RA backlash.  Equally, following a meridian flip, there is a need to adjust the weight on the counterweight bar in order to maintain the bias.  This latter requirement presents an issue for me, as I control my observatory remotely due to working away.  This led me to consider the 'RA String Trick' whereby a weight on a string is used to apply a constant bias to the RA axis, allowing the RA axis to be East heavy both before and after the meridian flip without the need for manual adjustment.  Using my less than refined engineering "skills" I built the following system. 

I began by fashioning a bracket to enable me to attach a pulley system to the mount so the necessary counterweights could hang free of the pier:

 

I then sourced some bearings, pully wheels, axel and fasteners to mount on the bracket in order to hold the pulley wheels that would support the counterweight string:

 

I then countersunk screw holes into the mount in order to attach the bracket to the mount.  One advantage of having an elderly, second hand mount is that it is less nerve wracking to drill holes into:

 

The mount was then reassembled (taking the opportunity to clean and re-lubricate all of the bearings):

Once the mount was assembled, the counterweight string was attached to RA axis, looped twice around the RA axis:

 

Finally, the counterweights were attached to the string.  The counterweights come from an old set of weights that I bought in a fit of enthusiasm as a much younger man and the mounting for the weights was sourced from the fitness section of Amazon:

 

Having balanced the mount, I then tested the system to make sure the mount could cope with the weight, first with 5lbs and then with 4.25lbs.  The High Torque motors I fitted to the mount last year cope very well with the 5lbs of additional weight on the RA axis.  The RA clutch, however, struggled with the 5lbs and was happier with the 4.25lbs, which was still enough to apply the necessary East heavy bias.

Whether this system will make any appreciable difference to my guiding remains to be seen.  I suspect, given the multiple variables that can impact on guiding, it will be quite difficult to definitely ascribe any improvement to this counterweight system alone, or at all.  All that said, it has been fun to build and I am looking forward to testing it whenever these seemingly eternal clouds clear...

 

Edited December 22, 2023 by AMcD
Removed duplicate photographs

[orly_andico]

My comment... is that the weight suspended on the end of a flexible cord may induce some resonance that may disrupt the guiding.  My personal experience with east-heavy bias (albeit not on a G11) is that the RA RMS guiding was cut in half when east heavy (!!) so definitely worth looking into. But I didn't use such a system, I just moved the counterweights up on the CW shaft to make the system east heavy (obviously won't work after a meridian flip).

[AMcD]

On 28/12/2023 at 21:39, orly_andico said:

My comment... is that the weight suspended on the end of a flexible cord may induce some resonance that may disrupt the guiding.  My personal experience with east-heavy bias (albeit not on a G11) is that the RA RMS guiding was cut in half when east heavy (!!) so definitely worth looking into. But I didn't use such a system, I just moved the counterweights up on the CW shaft to make the system east heavy (obviously won't work after a meridian flip).

The cord does not appear to flex.  It is paracord and is kept fully taught by the weights.   I have a considerable area of sky post meridian flip.  I have added this system as I control the observatory remotely and am not present to move the counterweight post meridian flip.🙂