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Excited by the prospects of viewing objects in the "Southern Skies" on a trip I had scheduled to the Philippines for December, 1999...I designed and built a telescope that I could carry on with me on international flights.
This page has plans, construction details, and photos of the finished project. It is a 6-inch f/8 telescope whose parts all fit into a box 20 inches long, 12 inches wide, and 9 inches tall. The scope made the trip to the Philippines, and worked wonderfully. I had no troubles with the airlines through 6 airports, dozens of security checks and x-ray machines, and curious airport security people. It fit perfectly in the overhead compartments on a 747, a 737, and an Airbus A300. The project was a great success, and I now have a telescope that I can take with me when I travel...not some teeny 90mm wimpy scope, but a bright 6-inch aperture Dobsonian. ;-) A report of my trip to the Philippines can be found here.
Airline regulations state that to be officially legal carry-on size, a package must be no larger
than 22 inches long, 14 inches wide, and 9 inches tall. That's a pretty small package! There was
recently an article in Sky & Telescope by Jack Gelfand, describing his 16-inch scope that he made
to travel on airlines. Unfortunately, he had to have a suitcase for the major parts of the scope, just
carrying the mirror box and mirror on board. I need my entire scope to fit as carry-on luggage, so his
design wouldn't work for me.
Since I already had a 6-inch f/8 mirror set, I started designing something that would put it all in
one compact container. As you can see from the image above, the entire scope fits into a package that is
just 20 inches by 12 inches by 9 inches, leaving two entire inches to spare in width and length! I even
managed to fit the 2-piece truss tubes along the sides of the rocker box, meaning no part of the scope
has to go in checked-in luggage, it all comes with me on the plane!
The scope design is a more-or-less standard truss-tube design. I considered building a "scope like Alice,"
but decided I wanted the stability of a conventional truss design, and the light-blocking advantages of a
tube section at the top of the scope. The rocker box is made from 1/2-inch birch plywood -- you can
see the dimensions in the image at left above. The altitude bearing half-circles are on the INSIDE of the rocker box,
so that the mirror box sits completely inside when the scope is assembled. The azimuth bearing consists of Ebony Star
Formica on the bottom of the rocker box, with Teflon pads on top of the baseboard. To pack the scope up, the baseboard
comes off and, once all the other pieces are inside, goes on top of the rocker box to seal everything up. Brass drawer handles on each long end of the box let you carry the assembled box by hand, or attach a strap between them that goes over the shoulder. The entire scope package, with my eyepieces and some 8x32 binoculars inside, weighs 22 pounds.
The mirror box is also constructed of 1/2-inch birch plywood, with 10-inch diameter altitude bearings. The bottom of
the mirror box has a 6-inch circle cut out, with a 7-inch diamter "ring" mounted inside just above the cutout bottom.
Two 1-inch aluminum plates sit on this inside ring, and hold the collimation adjustment/mirror mounting screws. These
screws go into the 1/2-inch plywood mirror cell, mounted with springs as a push-pull cell. When taken apart, the
altitude bearings come off the mirror box and store at the ends of the rocker box, and the mirror box sits inside
the rocker box.
The upper section is 8-inch inside diameter QuickTube(tm) (like Sonotube(tm), a wound cardboard tubing). The truss
tubes attach to the upper tube with bolts that go from the inside of the tube to the outside, and are reinforced
with 1/4-inch white ash boards on the outside of the tube, sanded to match the tube's curvature. When taken apart,
the upper tube end fits inside the mirror box, with 1 inch from the bottom of the diagonal mirror to the top of the
primary mirror -- not much room to spare! The focuser is a 1.25-inch helical focuser bought from Orion, chosen for
its light weight and low profile. It fits in the mirror box on the tube when the tube is put in so that the focuser
points to a corner of the mirror box.
Putting the mirror box together...I decided to get a little fancy (I want this scope to look nice as well as work nice!), so I made
dado joints for the corners of the mirror box. Cutting them by hand was no easy task (I don't have a table saw and dado jig), but they
turned out pretty nice. The box joints are very strong, and look nice. This photo shows one of the corners clamped together
while the glue dries. Incidentally, see those interesting clamps on the top and bottom? These are Pony Corner Clamps...if you're trying
to build something that has to be square, they come in very handy. They cost about $4.00 each at Home Depot.
A closeup of the corner joints for the mirror box.
Here is the mostly finished mirror box sitting next to the secondary cage assembly. The spider (from Astro Systems) and focuser
(1.25-inch helical from Orion) have been installed on the QuickTube secondary cage for test fitting. You can see the ring for
the mirror cell with the mirror cell disk sitting on top of it inside the mirror box...
Test fitting the pieces...the secondary assembly fits inside the mirror box so it can all nest together and shrink down to
carry-on size. You can see that the focuser just fits in the corner of the mirror box, which is why I chose the particular
focuser that I did!
Questions? Comments? E-mail me! lefevre@midway.com
(all pages copyright 1999-2001 Paul LeFevre. No text or images from this site may be used without permission.)