behind this project was to possibly build the lightest 16 inch f5 alt, az Telescope in the world! in turn reintroducing myself and my bad back,
into the world of large aperture observing. The main objective is to have
the complete telescope weigh in at less then a full thickness
16" primary mirror from days gone by. With
this in mind the heaviest component should be the mirror box at approximately
18 Lbs. allowing a finished scope weight of only 40 Pounds.
"The entire scope will be made of
In Order of Construction
12 1/4 pound, Optics was the first order of business. A friend of mine Lance Olkovik figured the 16 " by 3/4" fine annealed glass f5 primary ( known as the " Turkey Platter " ) in his basement over a two week period, the final figure came to 1/3 wave . The secondary I will be using is a 2.1" of standard thickness.
2 1/2 pound, secondary cage was the first stage of the project and is the key I think to the overall success of the scope. Making the .080" thick End rings started in my mind as being the hardest task and my jig saw agreed, 4 blades later and 2 1/2 hrs of labor one ring was completed. The next day I was complaining to Lance about my jig saw experience, when he suggested trying his router, well another lesson learned 5 minutes after plunging into the aluminum the second ring was finished and it was perfect.
5 1/4 pound, truss assembly is made of 5/8" aluminum square tubing with a wall thickness of .050". To assemble the truss tubes all you do is twist them slightly and slide them on the 1/4" pins, thus setting up for an interference fit. The top stays together because of a Spring steel hinge held in by pieces of doweling forced into the ends. The nose cone for now will be attached by 4, 1" dia. knurled aluminum nuts.
5 pound, mirror box is made of 1" x 1" x 1/8" angle aluminum bolted together at all corners, when finished it will basically become a briefcase for the mirror. The advantage to using metal and bolting things together may become more evident as the project progresses especially when I find the altitude bearing not getting enough support from the mirror box, I can then cut 4 new corner posts enlarging the mirror box to any size.
1 pound, 18 point mirror cell again all from aluminum .080" thick triangles supported by 1/4" x 1/2" rocker bars pivoting off of 3/4" square tubing rails. Mirror sling is made from the same material I used to make the spider vanes, 3/4" x .025". steel strapping. To keep cell assembly pieces from turning each triangle is bolted to a styrene plastic hoop.
The 2 , 4 pound 1/2" x 25.5" dia. altitude bearings are finally here after a lot of experimental failures laminating Styrofoam with the aluminum disks. There were two problems that arose first the PL300 glue I used never did really dry and second when it seemed good enough to test a little pulling at the plates caused the Styrofoam to separate leaving its outer skin on the plates well the rest fell right off in my hands. I soon discovered the same material but in a different form it was a styrene egg used for fluorescent light covers, a pair of pliers for cutting the plastic to size and some good old contact cement and that was it incredibly strong light weight large bearings.
15 pound Rocker & ground
support are here and the scope is now mechanically operational,.
although a few areas need touching up everything seems to be up to snuff.
The altitude bearings are riding on 1" x 1/2" x 3" rectangular Teflon blocks
that have slots milled in them to accept the .080" thick altitude disks.
So far this looks like a great stabilizer for azimuth motion because it ties
the bearing and side panel together making them work like one while acting
as a bit of a clutch ( adding some drag ). The ground support is the standard
3 points with Teflon pads. As you may of noticed the project has put on
a few pounds here and there, never the less the heaviest component is officially
the mirror box (18 lbs.) minus the bearings. Looks like the final weight
will be 52 pounds not bad considering the goal of 40!. I may do some back
tracking in the future to lose a few pounds. As far as the name 40 Pounder goes I am keeping it as a reminder
of my goal.
Quick release counter weight bar never factored into the total weight calculations. With a small amount of pressure on the arm seen in the images you can mount or dismount the 10 pound counterweight or move it up and down the mirror box to static balance the scope . A 2" ID. pipe filled with nu.7 lead shot from the local hunting store is now a completely variable weight, just pour in the desired amount tighten up the ready rod and your done. Each end or the counterweight bar has a flexing plate and is notched so it interlocks with the 1/8" thick angle of the mirror box.
1/2 pound shroud is 93% acrylic, 7% spandex, and 22" dia. Ribbing material that comes as a continues tube of material from local Fabric shops. I decided to try pulling the shroud all the way over the secondary cage rather then installing a liner around the inner radius of the cage, so far it looks like it's going to work the only problem was around the focuser, two aluminum plates bolted together pinching the material soon solved that . Also an acrylic light baffle that was cut out on my band saw was added, it stops unwanted light from mixing with the mirrors incoming light causing a loss in contrast. Slipping over the spider support bolts, it's resistance against bending keeps it locked in place.
NOV. 28/98 Nearing Completion Project to Date
DEC. 15/98 80 mm finder scope is mounted up on 24" rails do to the low profile nature of the scope. Even a 50 mm finder mounted on the secondary cage was totally out of the question it would of required adding another 5 pounds of counterweight.
JAN. 5/99 Lighten the load
Manning Park 2002
Merritt Star Quest 2003
NEW!! Going for a Drive
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