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The following photos are a "walkaround" look at my equatorial platform. It's a cylindrical bearing type, and tracks smoothly and accurately for one hour, fifteen minutes in perfect silence. Its stepper motor is powered by a 12 VDC lantern battery which lasts just about forever. This platform was built to swing my 150 pound 16" dob, and has been demonstrated to carry more than twice that weight without strain. The funny looking cutouts in the top board were made to clear the belt sander when it was mounted on the jig for truing the aluminum sectors.
If you are considering building one of these, See the links below.
Above: view from the northeast showing the general
arrangement. Note the rewind crank, lockdown hasps and carry handle cut-out on
lower half.
Above: view from the southeast, showing the aluminum south sector riding on its roller bearings and supported by the thrust bearings. The bearings are mounted on aluminum 2"x2"x1/8" angle sections shaped to fit. The rubber "feet" on the top board are to protect the wood and aluminum when it's stood on end during maintenance, etc.
Above: view from the west showing the sectors and sector mounting blocks, aluminum angle bearing supports, bearings, motor assembly and hold-down hasps, as well as the three rubber "feet" for standing the platform like a suitcase for storage.
Above: view from the north, showing the threaded rod screw drive, tangent arm/tang interface, motor assembly and rewind crank. The lever at lower right disengages the motor for rewinding. Crank, crank, crank... a small price to pay for what you get.
Update: This platform has been working flawlessly for five years. I'm on my third battery.
And this just in: A short, but concise, essay on polar aligning an EQ platform!
Above: a cylindrical bearing platform by Mark Hanson
And another cylindrical bearing platform by Terry Lohrey
Send a photo of your home-brewed EQ platform to the email addy below if you would like to see it here!
There sure are a lot of links to amateur made equatorial platform websites out there now. Back when I built my first one, Chuck Shaw's was the only resource available (Warren Peters' site was posted just as I finished). Fortunately, it was all I needed since Chuck lives nearby, and also belongs to the same astronomy club as I do. Today there's no excuse for not making your own, with all this free information readily available:
For the equatorial platform building enthusiast, it would be a dire mistake to miss Chuck Shaw's web page at: Cylindrical Bearing Equatorial Platform. Or send me $5000, and I will send you Chuck himself.
Another must-see site for cylindrical bearing equatorial platforms is Warren Peters' Page. (Ed. Note: oops, this link appears dead... Warren, where are you?)
Be sure to see Jan van Gastel's website. His platform features a roller drive. Good information, and a Dutch language version is also available.
A page that snuck up on me: Equatorial Platform - Reagan's Dob Tracker. Boy howdy, check out his links page... pretty impressive! And a scope drive web ring, too. Your cup shall runneth over here.
Here's a Low Profile Equatorial Platform.
This is a venerable page featuring an Evolved Poncet Platform.
Here's another example of a modified Poncet type platform: Don Odegard's Equatorial Platform.
I'm not sure what to call this page, but it has some interesting information regarding what looks suspiciously like a certain commercial design.
If you know of any EQ platform websites that aren't linked here, please drop me an email with the URL.
Email Kurt Maurer at: NGC704@aol.com