Currently I have a GEQ mount holding up a 114mm reflector. If I upgrade to a 10'' or 12'' reflector, like a dob, is it possible (or probable) to mount it on my current GEQ? If so, Im thinking I would have to upgrade my motor drive and the weights for balance. Any input would be appreciated. Thanks

I would hazard a guess and say that your present mount could handle a new optical tube assembly of 6", maybe 8" with little more than an extra counter weight but 10" or 12" would be too heavy.  If you load it too much it will be a strain on the motors as well as be too wobbly for good steady viewing.  If you want to get into the 10 or 12 inch range a larger mount will be needed.  Dobsonians will allow you to get into this range more cheaply but it is rather expensive to get them motorized.

L

As Leo mentioned, it's doubtful. I don't know of any 4" class scopes that are sold with mounts that are appropriate for 10" scopes.

As an example, take at look at the Meade LXD-75 mount. It's sold with scopes as small as 6" aperture, and as large as 10". A 10" on that mount is wobbly ... acceptable for visual use, but difficult to use for photography. And the LXD-75 is likely several times as massive as the mount under your 114mm scope.

There are members of this forum, and some of my observing buddies, who have mounted a 10" newtonian like the Orion on Celestron ASGT mounts (the upgraded CG-5 mounts) and actually managed to use them both visually and for astrophotography.

But unless your mount is heavy, and on a very stable tripod or pier, a 10" newtonian is going to vibrate under any but the lowest wind conditions. A 10" tube presents a large cross-section to the wind; so, even when well balanced and supported, it will be much more shaky than a 4" tube.

Thanks for the info. That will save me the frustration of mounting a big scope on a small tripod.  Thanks

Thanks for the info. That will save me the frustration of mounting a big scope on a small tripod.  Thanks

Hi,

I agree with other answers you have received  regarding a 10" reflectors instability to wind on an equatorial mount and the large expense of adding a commercial goto retrofit to a Dob.

I have a home built 10" truss tube Newtonian and this is still very prone to vibrations in low winds, despite the reduced surface area of the trusses. However this is also mainly due to my choice of mount; I built a friction drive system employing ball bearings instead of a traditional Dob friction bearing. Back in the early 80's I built a 10" Dob with a standard teflon on PVC plastic bearing (plans right out of Astronomy's June-August 1980 issues) and this mount was very stable in low to moderate winds. It would be pretty simple and inexpensive for you to build a traditional Dob mount for your telescope, and you should get pretty good stability from this mount.

Regarding adding goto capabilities to a Dob, this can be very expensive if you retrofit a commercial package. I can't remember exactly how much, but I think some of these systems can approach $500. Alternatively you can take the route I did and build your own goto system for a small fraction of the price of a commercial system. I have added Autostar 497 control to my Dob for less than $200.

Good luck with your project.

Bill