This is what is referred to as a German Equatorial Mount.  It uses galvanized pipe fittings, namely a T-fitting, two floor flanges, two close nipples, and a length of pipe for the counterweight.  It's important to understand that most pipe and fittings are of the National Pipe Tapered variety.  Meaning, the nipples will thread in only so far before they bind.  I searched high and low for National Pipe Straight fittings but had no luck.  I'm sure you could find them on the web but I would think the shipping would be very expensive.

My solution was to use valve-grinding compound on the threads.  By doing this I was able to work the nipples in-and-out of the T-fittings, effectively cutting the treads deeper until they engaged to the very end of the taper.  This not only made the bearing surfaces more stable but also gave me more threads on which to apply pressure with the braking system described below.  Just be sure and wash off all the compound before proceeding.

I won't go into great detail about the construction of this mount.  However, the same mount can be found in Making and Enjoying Telescopes by Robert Miller & Kenneth Wilson.  This particular support was designed by Dr. Allan Saaf, a contributor to this book.  Notice, I used poplar for the OTA end rings (as seen in the bottom photo) and poplar for the mount to match.

 

Something I am proud of, however, is what I call the "floating brakes" used in the R.A. and declination axes.

Note: all pipe and fittings are of the 2" galvanized variety.  Take care when sanding or grinding galvanized pipe, as the zinc can be toxic.  Always use a respirator when performing these functions.

The process begins by grinding two "flats" on the "T" fitting, one for each bearing.  Drill a rather large hole, I think these were 5/16", and tap to accept the proper size bolt.  It is important that these holes are drilled as close to the ends of the fitting as possible.  You want to apply pressure to four or five threads.  After cutting the heads off the bolts and trimming the threads down so they won't protrude into the fitting, I drilled holes lengthwise through the bolts and tapped them to accept a 1/4 thread, hence making a longer shaft for the brakes.  When this was complete, I screwed these shafts into the holes I drilled (and tapped) into the T-fitting and soldered them in place with silver solder.  Note: don't use stainless steel for the shafts, it is difficult to drill and impossible to tap.  Besides, you're going to paint all this anyway, right?  Finally, I purchased a couple handles at my local hardware store and fitted them with 1/4-20 threaded rod, pictured above.  Snag yourself a couple nylon bushings, small enough to slide easily into the shafts and of the proper length, and grease them up with whatever you are lubricating your bearings with.  With your R.A. and declination bearings in place, slide the bushings into the shafts and thread your handles in after.  Make sure your bushings are long enough that they won't bind but short enough that the handles will thread in four or five turns.  Note:  when tapping the shafts, I only tapped about halfway down.  You don't want your bushings sliding up and down against threads, it would wear them quickly I would think.

Once the bearings are completely assembled and attached to the polar axis, slowly tighten the brakes.  As you tighten, work the bearings back and forth.  Tighten the brakes a little more and continue rotating the bearings.  What we are doing here is cutting threads into the ends of the bushings, exactly matching those found on the inside of the T-fitting.  I found that the bushings actually mashed-up against the bearing, giving the break a larger footprint than the bushing's outside diameter.

Here is the finished assembly with the break surface circled in white...

...and here is a magnification of the same break surface.  Notice how the nylon bushing "squished" into the entire recessed area immediately under the end of the fabricated shaft.  The resulting threads in the nylon mesh nicely with the T-fitting threads.

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I have found that I can really lock the OTA in any position.  Although, once a planet or other high-magnification object is centered, tightening the declination axis does move the image a bit.  I'm not sure how to overcome this, if it's even possible.

 

Now, for the counterweight:

I began by filling the capped pipe with molten lead (also very toxic!) until I reached a weight comparable to, but just under, the weight of the OTA.  As you can see in the photo, I also added a 2" compression fitting as an adjustable counterweight, allowing for varying sizes of eyepieces.  This was necessitated by the fact that I use both 1.25" and 2" optics in my scope.  The fitting was a bit pricey, but I just couldn't pass this up, and here's why...

Begin by removing the two caps from the fitting and stretching the rubber seals, hand strength is more than enough to accomplish this task.  This allows the fitting to slide easily up and down the pipe.  Reassemble the fitting, slide it onto the pipe and make sure it slides freely before the caps are tightened down.  Now, it's a simple matter of adjusting the sliding compression-fitting to the necessary point on the counterweight and tightening one of the caps to hold it in place.  Note how the rubber seals keep the fitting from marring your paint job, this was an added bonus.

Take note, in the photo below, of the carrying handle mounted to the polar axis.  This has considerably simplified assembly in the field.  Also, the completed scope was front heavy (OTA side) so I had to rout out a cavity in the underneath of the polar axis.  Once routed, I filled the cavity with molten lead (about 15 lbs. of the stuff) and that seemed to do the trick.  I capped it with a thin, hmmm...about 1/4", plank of poplar and you would never know the difference.

 

The completed telescope; it was six months in the making but has been worth the trip!

Clear skies,

-Mac

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