My Flying Dobsonian.

26cm3kl.jpg (33977 bytes) My flying Dobsonian was built around a float glass mirror.   The  diameter is 260 mm, the optical diameter 258 mm or     10 5/32". The thickness is 25 mm. Focal length 1480 mm. Weight of the "tube" 7.5 kgs, about 17 pounds. Total weight of the scope 11 kgs, about 24 pounds.

The telescope "tube" has three main parts: mirror and secondary cage, and the "bearing" cage between the mirror cages. Both mirror cages are attached to the bearing cage by steel cables in the classic Serrurier pattern. These cables are normally used on race bikes for the gear shift system. The steel cables are put taut by aluminum tubes left and right of the telescope "tube".

The cages were welded out of square steel tube 10x10x1 mm (about 3/8"x3/8", thickness 1/25") The plywood for altitude bearings and rocker has a thickness of 9 mm (about 3/8"). This plywood is 9 ply Baltic birch, originally for pouring concrete, it has a slippery coating to avoid that concrete will adhere.
The telescope and its rocker fit in two shopping bags. The scope goes with me in the cabin, while the rocker is transported together with my other luggage.

Below the parts of the rocker. The teflon glides directly against the coating of the plywood in azimuth. Special fasteners were made to attach the side panels to the bottom of the rocker and to fasten the aluminum cross. Holes were drilled in the sidepanels in which short pieces of steel tube were inserted. These tubes were drilled and tapped M4. Other holes were drilled sideways in the panels to accept bolts M4. Wings were welded to the heads of these bolts, so tools are not necessary.

 26cm_inVerpakking_juli04_kl.jpg (42703 bytes)
26cm_onderdelenRocker_juli04_kl.jpg (80107 bytes)
 
26cm_verbPanelen1_kl.jpg (55874 bytes)
26cm_alKruisRocker_kl.jpg (46668 bytes)
26cmRockerOpgebouwd_juli04kl.jpg (85727 bytes) Assembling the rocker takes just a couple of minutes, now it's time to take the scope out of its shopping bag.
For transport the primary and secondary cage are temporarely mounted in the bearing cage. The steel cables are permanently attached between both mirror cages and bearing cage. First the secondary cage will be taken out of the bearing cage, aluminum tubes with threaded rods serve to put force on the cables. 26cm_OpbouwTelescoopBegin_kl.jpg (62699 bytes)
26cm_BuisSpanner_kl.jpg (32457 bytes) The parts for connecting the tubes and tensioning the cables were cut on a lathe from aluminum round bar. The part at left was drilled and tapped M 6, a piece of threaded rod M 6 lengthens the aluminum tube by turning the large wing. Slowly but surely the cables are put taut. 26cm_BuisVerbinding_kl.jpg (20496 bytes)
The secondary cage is in position here. The tension in the cables does not need to be very high, the aluminum tubes bow sideways if too much force is used. Playing guitar on the cables gives an indication of the tension. 26cm_SecCageUit_juli04_kl.jpg (56534 bytes)
26cmMetHoogtelagers_juli04_kl.jpg (89178 bytes) The primary cage is also taken out of the bearing cage and positioned by inserting and lengthening the short aluminum tubes. The handscrews which are used for mounting the mirror cages in the bearing cage, serve to mount the altitude bearings as well. The altitude bearings use just bare wood on teflon.
26cm_Achteraanzicht_juli04_kl.jpg (43281 bytes)
The mirror is resting on a 9 point flotation, calculated by Plop.
26cm_Zijaanz_juli04_kl.jpg (61050 bytes)

At Right: The Montagne de Lure dominates the Haute Provence. The sunlight is very bright here by day, and the stars are brilliant at night.      The scope pleases me a lot, movements are very easy. Vibrations take about three seconds to die down, which is a little bit long. Perhaps larger aluminum tubes would permit to put more force on the cables. And sandwich panels could be used for the rocker. But for me this won't be necessary, much vibration can be avoided by handling the scope gently. Furthermore eventual vibrations die out instantly when the secondary cage is touched by a finger.