Building an aluminium paralellogram binocular mount.

Introduction Some celestial objects are more suited to view with binoculars then with telescopes. Especially relatively extended open starclusters like the pleiades and the coma cluster. A good bino-

mount is needed for comfortable viewing, especially when large instruments (20x80) or bigger are used. A couple of years ago, while surfing the internet, I saw pictures of a wooden trapezium binomount at the homepage of dr. Euan G. Mason (see links page for URL). The greatest advantage of a trapezium mount is that the object doesn't dissapear out of the field of view when the binocs are raised or lowered. This is especially important when persons of different lenghts use the same intrument during the same observing session. When I purchased a 20x80 I built such a wooden mount. It worked perfectly, but it is bulky and heavy. Therefore, a couple of month later, I decided to build one of aluminium. On this page the plans for building such a mount are presented. All alluminium used is square 20x20 mm alumium tubing. Detailed plans and dimensions are shown in picture 1. Parts list Aluminium tubing, 20x20 mm 3x 700 mm (2 horizontal bars and 1 bar for the balance weights) 4x 150 mm (vertical bars) 2x 50 mm (to be placed between the vertical bars) Wood 1 piece of hardwood lumber (connection of trapezium with tripod, A in picture 1) 2 pieces of 120x100 plywood (thickness 10 mm) for binocs platform, B in picture 1 2 plywood triangles to support the binocs platform Other 6 mm bolts and nuts (to connect the horizontal and vertical bars) a good two component glue (to attach the bino platform to the     trapezium) camera connecting nut, to connect the mount to the tripod

Building the mount The first part to be built is the aluminium trapezium. It's important that the two horizontal bars have exactly the same length, as measured from midpoint of bolt to midpoint of bolt. The same is true for the four vertical bars. To build the vertical parts of the trapezium, the 50 mm bars are glued and bolted exactly in the middle of the vertical bars, as illustrated in this photo. This is necessary for the trapezium to be able to move from lowest to highest position, without the horizontal bars toughing the 50 mm bars. Furthermore, the holes to connect the horizontal and vertical bars have to be exactly at the same distance from the edges of the bars. Only then the trapezium will work as planned and will move smoothly over the whole distance from lowest to highest position. It's best to use a drill standard to drill the holes for the bolts. The corners of the horizontal bars have to be rounded. If not, they will touch the the bino platform when moving up or down. The platform is attached to the vertical bars with two component glue (see photo). If you don't trust the glue, add one or more bolts and nuts. I only used glue, without any problem. The wooden lumber to connect the trapezium to the tripod is also glued to the aluminium. Because of the forces that work on this connection, its best to use some bolts here as well. In the bottom of the lumber, a camera connecting nut is glued, to connect the trapezium to the tripod (see photo). The contra weights can be prevented from sliding over the bar, by mounting a 6 mm bolt and wingnut on both sides of the weight. The exact position of the contra weights depends on the actual weight of the contra weights compared to the weight of the binoculars.

Another ATM-er who built a bino mount using these plans, is John Sillasen. Here is what John wrote me after he finished his mount, and a nice picture.