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View Full Version here: : Dob Counterweights or Re-balance?


glend
29-06-2013, 08:08 PM
My 12" GSO dob has tube balance adjustment tracks where the Alt tube bearings attach, and it was balanced when I first put the bearing on the tube ( in the 0 position), now as different heavy EPs are used and when the light shield/dew shield is used the scope is top heavy and has trouble holding lower altitudes even when the bearing knobs are torqued tight. If I stick with the standard EPs and don't use the shield then its fine.

So what to do? It seems that rebalancing is only going to create problems when I don't use the light shield and lower weight EPs are used. Counterweights are they the answer? I noticed that the rear tube ring has spare holes that are tapped for bolts, are these for counterweight mounting? It seems to me that magnetic weights that can be moved along the tube might be the best solution. What the best approach that others are using?

barx1963
29-06-2013, 08:56 PM
Glen
With my GSO 12" I found that I had to move the trunions right up to the top of their range if using heavy EPs and once I added a laser pointer or a telrad that made it worse.
Solution was a couple of magnets out of old car speakers that I wrapped in foam and duct tape. Easy to adjust and cost next to nothing. Farpoint make weights that can be screwed into the locking screws holes of the mirror cell(that's another hint, throw away the locking screws!!) but are not adjustable.
One other point, is the light/dew shield essential? Usually the secondary is set deep enough in the tube that it will not get any light issues and dew on the secondary is much better solved with a lightweight heater (eg this http://www.bintel.com.au/Accessories/Dew-Control/Heaters/Kendrick-80mm-Split-Secondary-Heater/1606/productview.aspx ) I live in a very dew prone area and with lights around and never needed such a setup.

Malcolm