The Original 16-incher

Or, an old friend retired.

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Most of the features that made this scope such a great performer, such as baffles, filter slide and truss-mounted finder scope, have been carried over to the rebuilt 16-incher. I kept this page because it still has a lot of helpful information on it. At least that's what my email tells me.

This was my faithful old workhorse for several years: a 16" f/5, in its "observatory". Actually, it lived in my garage/shop, always ready to roll out to the driveway at a moment's notice.
Note the oversize pneumatic tires on the wheelbarrow handles. They made moving the telescope, even when fully assembled, easy and painless. Especially over rough ground.
Also note the accessory baffle located just under the upper cage, opposite the focuser. Its function was to block stray light from entering the focuser. I had one for the top end, too, but it was rarely needed. I kept it stored in the rocker box most of the time.
Finally, notice the blacked-out focuser board. That was definitely an improvement.

Right: a baffle for the mirror end of the telescope. Open "Obsession" type mirror cells are great for ventilation, but they leak light like crazy! This baffle is made from black plastic three-ring binders intended for 11x17" paper. Kydex or Formica would work just as well. It allows plenty of air circulation, which is something the 2" thick, 16" diameter chunk of Pyrex just can't get too much of.
The cooling fan had been removed for this photo.

Left: photo of my first filter slide, with my compliments to Ed Stewart, and his website which inspired it. You should make a filter slide. You'll certainly find yourself using your filters a whole lot more if you do. I included an indexing "click stop" for added convenience of use on mine.
There are three holes in the slide besides the small finger-hole. I installed a Lumicon O-III to the rear and a Lumicon UHC to the fore end. Then there's the center hole: empty and sized to serve as the all-important focuser baffle (see below).

Right: an unpainted example of my current filter slide design. It is of all aluminum construction using window screen frame material, has the indexing click-stop, and weighs considerably less than my old wooden ones (as seen above). It is a breeze to install, with just two mounting screws (the holes in the cross pieces had not been drilled yet when this photo was taken). New! Improved!!

See what I mean about the filter slide also acting as a focuser baffle? That dark circle at the bottom of the drawtube is the central hole in one of my filter slides. It blocks practically everything except the light coming from the diagonal. Sounds like I'm harping, but with a properly baffled scope, cars can drive by with headlights blazing and you'll never know it if you keep your eye to the eyepiece. For more on baffling the Newtonian telescope, please see the April 2001 issue of Sky & Telescope Magazine, page 128. Also see Mel Bartels' website.

Oh, and just in case you're wondering, the funny-looking thingy to the left, in the photo above, is part of the upper truss pole attachment as supplied on Obsession Telescopes. Savvy Obsession users "store" their wedge/cam levers in this manner to put a stop to "the dangles".

Above is the bracket for my 80mm f/5 finder scope, an inexpensive imported ST- 80. Made from plywood scraps and rings cut from PVC pipe, it is held in place in true Dobsonian fashion: by gravity. The first reaction most folks have when they see this is fear of it falling out. Well, not only has it never fallen out, but it even stayed put when my scope was blown completely off its equatorial platform in a thunderstorm (see photo at bottom of page).
It isn't a good enough mount for a guide scope, but can be adapted for such use. It certainly works splendidly as a simple 20x80 finder. My thanks to Tom Osypowski for the design concept.
Also note the dewshield on the Telrad. If you don't already have a dew shield on your Telrad, try one before adding a heater. It's made from cheap plastic binder material and attached with sticky-back Velcro.

Above is my original version of a spring counterweight, as added to rebalance the 16 after the addition of the 80mm finder scope. Barry Peckham, of Litebox Telescopes, originally published his version in Amateur Astronomy magazine years ago, then Tom Krajci came out with his sometime later. I began life with Barry's approach, evolved into Tom's, and now have gone back to the original on my rebuilt 16. Tom's is best when you need lots of oooomph. The aluminum tube on the side of the rocker box housed the spring when it was retracted, and the small diagonal spring "reeled in" the slack from the cable. This rig worked extremely well for many trouble-free years, but I'm glad to be rid of it just the same.

Left: the answer I found for perfect Dobsonian feet. They are hard rubber bumpers intended for use on boat trailers, cut in half. An intact specimen has been included in the photo for clarification.
What makes 'em great is the small footprint on one end, for contact with the ground, and a larger end for attachming to the ground board. The rubber also works well for dampening vibration to the telescope. Finally, they're extremely easy to cut and mount. I found them in my local Ace Hardware.

Ah, West Texas! Land of dark skies... and thunderstorms!!

The photo above shows my tarp-enshrouded 16-incher after it had been blown off its equatorial platform by a microburst during a sudden thunderstorm. I got lucky: no damage resulted from this little adventure. Whew!
During the day I normally leave the 16-incher locked low in altitude and free to spin, or "weather vane", in azimuth. This configuration has survived numerous dust devils and similar violent wind events at TSP and other West Texas outings. I had checked to be certain that the tarps were secure and that the scope was free to turn just before this occurred. Maybe next time I'll place a Cadillac on top to hold it all down.

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Email Kurt Maurer at: NGC704@aol.com