Classic Aircraft Carrier Anchor
Posted 01 November 2006 - 10:11 AM
The equatorial head and axis housings were cast from aluminum and each axis has a 1.5-inch chromium steel shaft with two bearing in the polar assembly and 0.5”x 6” flanges that separated the polar assembly from the declination assembly. The polar shaft was connected to the declination housing with a steel pin that soon began to loosen so it was replaced with a larger and harder pin. The aluminum surfaces provide additional stability; however, by adding a thin disk of Teflon to separate these surfaces further stabilized the assembly and acts like a 6-inch bearing surface. The polar dive is a Mathis 10” worm drive and fitted to the polar assembly using home made hardened aluminum plate and attachment hardware to the end of the polar axis.
The declination shaft did not have bearings so a 3/8th-inch aluminum disk was machined to fit the shaft (with set-screw) in the 0.5”x 6” flange at the top of the declination shaft and a thin disk of Teflon separates the disk and flange. The disk is bolted to the aluminum saddle plate. Some sanding to the inside of the top and bottom housing allowed a thin sheet Teflon to be inserted around the shaft to act as a bearing. The Teflon surface provided roller bearing smoothness anyway.
Also, a tangent arm declination drive was machined using scarp metal and old DC motor. A ½”- 13 screw was machined from braze stock to fit inside a threaded aluminum block and associated hardware to drive the arm back and forth to adjust the declination axis. A slot was milled in the tangent arm end tightly fitted to a hard bolt to avoid backlash and to move the axis north or south.
This old mount has been around a long time and has been used by several amateurs with a variety of telescopes. I first used the mount for a 12.5” Cassegrain and then a 12.5” Newtonian then it went to Carlos Hernandez for some years before he found it too heavy and had no room to store it, so he sent it packing back to me. It is still a sturdy mount that will track celestial objects across the sky with very little backlash in the gearing. Winds of 10-15 MPH hardly effects the telescope, so after nearly 3 decades of use it is back home. Hum, guess it could use some paint!
Posted 01 November 2006 - 11:56 AM
Posted 01 November 2006 - 12:47 PM
That is a BIG scope! Nice and massive... kinda looks like some sort of big cannon. Cool!
That's my mid-size scope, here's my momma scope:
Of course, these scopes were made before we got smart and started making them lighter. I have toyed with making a new truss tube and Dob mount for the 12.5", but making telescopes is now just a dream for me. Bad knees and age gets in the way. The 16" is just too much to work with for DSO'ing and my platform (not shown here) gets in the way. It is for Mars. The 12.5" can be used with a 6-foot ladder.
Posted 03 November 2006 - 07:18 PM
Posted 04 November 2006 - 09:17 AM
That's a nice setup Jeff. It looks like the mount is actually quite short...maybe 3 1/2 feet to the cradle? In this shot, the EP looks to be only about 6 1/2 feet off the ground.
That's about right 'trainsktg,' with a 6-foot ladder I observed comet Swan the other night on the second step. With my bad knees climbing the ladder is difficult. I collimated the primary too, and that just about killed me :o I may build an observing platform around this scope like the one next to my 16". Not sure how high yet, but with Newtonians it is not easy to find the right height and width so an old guy can sit and observe. My neighbor loves to observe with me but he lost an arm and leg 10 years ago and has great difficulty climbing a ladder and focusing. With a platform we can sit to observe.
Posted 04 November 2006 - 09:40 AM
That's about right 'trainsktg,' with a 6-foot ladder I observed comet Swan the other night on the second step. With my bad knees climbing the ladder is difficult. I collimated the primary too, and that just about killed me I may build an observing platform around this scope like the one next to my 16". Not sure how high yet, but with Newtonians it is not easy to find the right height and width so an old guy can sit and observe. My neighbor loves to observe with me but he lost an arm and leg 10 years ago and has great difficulty climbing a ladder and focusing. With a platform we can sit to observe.
That's an impressive scope and mount. It looks like something that belongs in a big observatory dome. With the increasing physical limitations you cited above, it may indeed be time to incorporate some easy-access features in your set-up. I am an able-bodied 36 year old, and the thought of setting up and tearing down such a massive instrument intimidates me! I'm guessing that you do not transport this artillery piece much, and that you do most of your observing from your yard? If so, then perhaps it is time to build some sort of enclosure around it to protect it from the elements, and incorporate some kind of deck/ramp/elevator/jack/lift into your observing setup to make the eyepiece and other necessities more accessible without all of the climbing and legwork. Do you have any sons/grandsons/soninlaws/associates with strong backs and fabrication skills you can enlist?
Good luck and clear dark skies...
Posted 04 November 2006 - 09:56 AM
Well, my son is 40 and lived in San Diego with his kids. The only person to help me is my neighbor – who has only one arm and one leg. Just out of luck. That’s the story of my life though.
Posted 04 November 2006 - 10:42 AM
I collimated the primary too, and that just about killed me
Ouch...climbing that ladder a couple dozen times...checking the EP, tweaking a primary screw, checking the EP again.
But I bet the views through that long-focus newtonian are superb and worth the effort.
Posted 04 November 2006 - 02:28 PM