Attack of the Killer Clones: Apogee's H.D. Eq Mount (a CG-5 by any other name)

One aspect of my wonderful new Orange Tube Celestron-8 that I have mixed feeling about is the mount. It's fairly standard to complain about the shortcomings of the CG-5 and its clones: backlash in the gears, "slop" (which I must confess I don't know the precise definition of), and generally poor machining. Apogee's version (lower right corner), which Gary Hand tells me this mount is, is no exception. He does say that it's not a Synta mount, although I have yet to confirm this with apogee.

All of these problems exist, to some degree, in this version of the mount. However, I was impressed with its robustness in comparison to my cloned SkyView Deluxe. I wouldn't have even thought about taking the mount apart, except that the R.A. gear completely crapped out on me during my second night under the stars with this scope. It took quite a bit of fiddling with the worm gear assembly to find a happy medium between too tight to turn without jerky motion, and too loose for the gears to mesh and turn it at all!

So, the first weekend after I got the scope (a rainy one as it turned out), I decided to see if I could improve the motion. I had seen Jeff DeTray's instructions at astronomyboy.com, and figured that I could do pretty much the same thing to my mount as hundreds of others have done to theirs.

Here is a picture of Apogee's mount:

Looks just like a CG-5, right? Well, it is and it isn't. It's put together exactly the same, with most of the same parts in pretty much the same places: all the instructions for the CG-5 improvement matched what I saw in my garage, with two minor difference. The first one is that, even though this mount has the tapered RA housing, it doesn't have the improvement that Celestron changed the housing to accommodate: the ball bearings in the axis. So this mount is probably not capable of handling the loads that the newer Celestron versions of the mount can support.

Another difference between this mount and others' reports about the CG5 is the quality of the machining. I'm no machinist, so I'm probably not able to see the defects others can see, but I didn't feel any burrs on the internal components (maybe because it's brand new and hadn't had time to cut itself to pieces?). The plastic washers weren't scored either, but the large ones the go on either end of the worm gears look like they were made by someone with no idea of how to use a hobby knife. They vary, not in thickness, but in roundness -- they're totally jagged on the inner diameter. However, since my skills with a hobby knife are marginal at best, and as far as I know this is not a crucial dimension, so I didn't try to "improve" those washers. I figured that I'd rather have them intact and funny-looking than shredded and unable to provide the washer action that they provide.

One thing is definitely the same on any Chinese mount I've seen (grand total so far: two): the thick sludge/glue they used to "lubricate" the interior of the mount. As it turns out, due to the highish quality machining, the only thing I did when I performed this operation was replace that grease with the synthetic white marine grease people seem to like for this job, and then adjust the mesh of the gears -- now it seems much improved.

But I have one major problem now. The RA setting circle, which had been sitting in that gluey sludge, had been able to turn as the mount turned in RA. Now, with the lighter grease, it just sits there looking stupid when I crank the gear. I have no idea why.

Actually, I do. Here's my idea. There is no RA extension shaft over the retaining ring nut. On the CG-5, this shaft is the surface around which the setting circle revolves. On my mount, however, there is no shaft, and the setting circle just dangles limply:

These pictures were actually taken before I took the mount apart. In the one on the left, you can see the precarious position of the setting circle. In the one on the right, you can see the lack of extension shaft. I have no idea how to get my setting circle to work now. Anyone got a spare RA shaft extension lying around?