Parallelogram Binocular Mount


 

Design Considerations
A parallelogram binocular mount provides a stable platform and can be adjusted for the height of various observers while maintaining the desired object in the field of view. As with my 8" Truss Dobsonian project I began by searching what was available on the internet. A variety of ready made mounts are available for $200 and up. Several sites describe the building of various parallelogram mount projects. After a review of the options I decided to build a mount with the following characteristics and features:

sidesaddle mount
similar materials to my truss dob project
utilize my existing Meade tripod
utilize the same finder as my dob to work as a "rich field" finder

 

Construction
I began by creating the shape that would be carried through as a theme in the design. The end blocks of the parallelogram came after sketching a variety of shapes. The center post and
altitude bearing were derived from that basic shape. Using a CAD program I determined the dimensions for the parts and printed plans at their finished size. These were used to visualize the size of the mount in relation to my binoculars.

The end blocks are 5 inches long and the center posts are 7 1/2 inches high. The CAD designs were transferred to plexiglass templates and cut to their final size by hand. Reference points for hardware and the decorative center holes were added to the templates. Using the templates the pieces was traced on the mahogany and a rotary cutting tool, the Ryobi version of the RotoZip, was used to rough cut each piece. They were sanded to their final shape and size using a combination of drum and hand sanders. A forstner bit was used to drill the 3/4 inch center holes.

The overall length of the parallelogram was determined by placing the observer outside the circle created by the three legs of the tripod. The observer's end of the parallelogram would need to be at least 30 inches from the center of the tripod. I also wanted to keep the counter weight end within the tripod's circle so I targeted its length at 18 inches. The aluminum channel material I intended to use comes in 48 inch lengths so the final size was built around that dimension.

The range of motion of the parallelogram allows observers from 35 to 81 inches in height to comfortably use the binoculars. The altitude bearing allows a full 360 degrees of motion. It is easy to observe objects directly overhead. The binoculars are secured to the altitude bearing by an arm that is positioned to offset the tripod mount on the binoculars to its center of gravity. As the altitude bearing is moved, the binoculars remain balanced around the bolt that holds the altitude bearing to the end blocks. A finder rides on the arm on the centerline of the binoculars.

The 6 aluminum channels provide two shelves for the counter weights to rest on. The width of the channels separates the end blocks to reduce twisting of the altitude bearing as the binoculars are tilted up and down. A total of 9 pounds of counter weight is used. The most stable counter balance was achieved by spreading the weights on the shelves. Moving the weights too close together, or stacking them, made the mount "drift" at the maximum and minimum heights. The weights are held in position by small blocks with a bolt and wing nut locking the weight to the "shelf".

The completed mount with counter weight and binoculars on board weighs 22 pounds.

 

Cost and Suppliers

The wood for the project was purchased at a lumber company that specializes in fine grades of wood. Reel Lumber in Riverside CA. had 8 board feet of 3/4 inch thick, 20 inch wide Philippine Mahogany. About 1 board foot remained from my Truss Dob project. Cost < $10.00.

The finder was purchased from Orion Telescopes. Cost $35.00.

Aluminum channel material, bolts, washers, and wing nuts were purchased from ACE Hardware. Cost $35.00.

Total cost for the project with various other materials was less than $80.00.

 

Questions, comments?

Contact: info@fesunoff.com