Parallelogram_bino_mount

A DIY Parallelogram Binocular Mount

Back in the 1980s I got a pair of Orion 11x80 binoculars as a present.  I never used them much because at more than 5 pounds they were too heavy to hold for more than a few minutes.   A few years ago I made a look down binocular mount for them but all too often the mirror would dew up after only a short use. 

A.S.E.M. started a DIY Special Interest Group  (SIG) and I decided to make the parallelogram mount featured on this page.  The mount is constructed out of sections of 1x2 oak and 1x3 pine for the tripod.

Before I made the mount I did some surfing for plans, pictures, and ideas.  I decided that more "degrees of freedom" would be a good thing and picked a design with four axis of movements.  The mount

  • spins 360 degrees around the tripod
  • raises/lowers at the tripod
  • swings about 120 degrees in azimuth at the binoculars
  • raises/lowers about 120 degrees in altitude at the binoculars

Starting at the ground an moving up, the mount has five sections which are described below:

  • Tripod and spreader
  • Tripod mount and central support column
  • Arms and counterweight
  • Arm/binoculars holder coupling
  • Binoculars holder
     

In operation, a 1/4"x20x20" threaded rod runs from the top of the central support column, down through the column & tripod mount, through the top of the tripod, and tripod spreader.  It is anchored at the top with a wing nut and at the bottom with a T-nut disk.
 

Tools used:

  • cross cut saw
  • router, router table, various bits
  • drill press
  • electric sander
  • hack saw
  • belt sander





Tripod

My original plan was to put the mount on a traditional photographic tripod.  It worked, but did seem a bit tippy, particularly where the mount and tripod connect.  I ended up using  a wood tripod that I'd made for a home made Berry mount.  This tripod was made out of clear 1x3s and it is much more stable (1).  You can see a picture of the Berry mount and tripod at the bottom of this page. 

The top of the tripod is a 6" round disk of 3/4" hardwood plywood with a 1/4" hole through the center.  Three strap hinges are attached to the bottom of this disk to form an equilateral triangle (2).  The tops and bottoms of the 4' legs were cut at a 18 degree angle before the straps on the hinges were screwed to the 4' long leg sections.  The 18 degree angle gives the tripod legs a good outward spread.

To make the tripod accommodate rough ground I made one leg adjustable in height (3) and trimmed the bottom edges to a 1" width (5).

To save material, I made the spreader out of 1x3 and screwed/glued the pieces into a single unit (4). To make the tripod more stable I bolt the spreader onto blocks that hold T-nuts the three legs.  The resulting assembly is very stable and all vibrations dampen out after a second.  You can also see the T-nut disk at the bottom of the spreader.

You can see the details in the pictures to the right. 

 

 

 



                                           (1)                                          (2)                                                                           


(4)



                          (3)

                                                     


                      (5)





Tripod Mount and Central Support Column

This section starts with two discs of 3/4" hardwood plywood about 4 1/2" in diameter with a 1/4" hole in the center.  The bottom disk just sits on the top of the tripod.  There is a teflon disk on top of the bottom disk that allows the mount to spin in 360 degrees about the tripod. The action is very smooth.

The top disc is both screwed and glued from the underside to the central support column above it.  Tightening the wing nut at the very top of the column increases the force needed to spin the mount about the central column.  I check the torque several times a night.  At this point it doesn't seem to loosen/tighten as I spin the central column clockwise or counter clockwise.  There is also a teflon washer below the wing nut. 

The central support column is made of three thickness of 1"x2"x10" glued & screwed together. The height was chosen based on the length of threaded rod that I had available.  Two of the 1"x2"s are parallel with the third at 90 degrees.  Prior to gluing, I routed a channel (slightly off center)  from top to bottom to contain the 1/4"x20x20" rod that runs through it's center.  As mentioned before, the column is screwed/glued to the disc below.  The entire assembly is held together by a wing nut and washer as seen in (6).  Two holes were drilled horizontally through the column to both hold the arms of the parallelogram and hold the two parallel 1"x2"s together.

I rounded all exposed edges with a 1/8" round over router bit prior to gluing and screwing.

You get a good view of the T-nut disks I use to tighten various parts of the mount in both (6) and (7).  The "tightening" nuts are made from a disc of 1/2" plywood cut with a circle cutter and a t-nut.  They are much cheaper than knobs, grip very firmly, and because of their large size, are very easy to turn.  There are twelve of these disks in various locations on the mount.

You can see the teflon disk in (7).

(6)

 (7)
Arms and Counterweight

The greatest expense in making the mount was to buy the oak 1"x2" needed for the parallelogram.  In retrospect, clear pine would probably have worked just as well.  In making the mount I "flipped a coin" and decided make the double long arms 48" long.  I decided to make the pivot points 24" apart with 1" between the end of the board and center of the hole.  This meant the shorter arms would be 26" long.  I decided to mount the arms 5" apart, originally on top of a 12" post of double thickness 1x2.  After final assembly the mount seemed a bit unstable so I moved the arms down to 9" using the 10" column mentioned above.   Even then I was a bit concerned about the motion around the tripod so modified the tripod mounting assembly to contain  the threaded 10 inch  1/4" rod as described above.  As mentioned, it is now much more stable.

The parallelogram is held together with four 5/16" bolts and nuts.  There is a washer made from a milk bottle between the rubbing surfaces and a metal washer at the ends.   In use the parallelogram is "snugged" but not overly tightened to allow for up/down movement.

The counterweight is a 10 pound weight from a long forgotten weight set in the basement.  It was chosen to balance my 11x80 binoculars.  Other binoculars would probably require different weight.  The weight can be loosened/tightened such that it's position can be moved up and down the bars as needed.  There is a block connecting both sides of the wood to keep the weight from falling free.  A slight modification to (8) is that I now mount the weight on top of the bars.

The longer arm of the parallelogram was placed on top so I could get more rise and fall.

(8)
Arm/binoculars Holder Coupling

This is the hard part!  Made well, the mount will be a joy to use.  Done poorly, you'll struggle.  Done well, you can sit in a chair and see a 120 degrees of sky.  Done poorly, you'll be moving your chair all night long.

This assembly started with three pieces of 1"x"2"x3" long.  Into the piece that would become the center I routed a channel and hole to contain the head and part of the shaft of a 5/16" bolt.  JB Weld was used to attach the bolt in the hole and channel.  About 1 1/2" of the bolt sticks out the end to the right to hold the binocular holder assembly. The other two pieces were glued & screwed to the first, with one on top and the other on the bottom.  A 5/16" hole was drilled through the three pieces, centered and 1" from the open end.  The exposed  edge was rounded with a belt sander to prevent binding as the binoculars are swung back and forth.

Two additional pieces of 1"x2" were added, one above, the other below and anchored to the front of the parallelogram arm.  The screws on the bottom piece run up into the parallelogram.  The screws on the top piece run from the back of the parallelogram into the wood.

All five thicknesses are held together with a 1/4"x20 threaded rod, with milk bottle washers at the contact surfaces.  The pieces are held together by two more plywood/t-nut tighteners.  They seem to need to be tightened fairly well to hold.

(9)

Binoculars Holder

The binocular holder (10) was made so that the center of the binoculars was even with the exposed threads on the arm/binoculars holder coupling.  The piece is held in place with a milk bottle washer on each side and another plywood/t-nut tightener.  In retrospect the vertical piece should probably extend lower to make positioning easier.

The binoculars are attached to this holder via a metal mounting support that came with the binoculars.

In use, I loop the neck strap around the top of the holder. 

The piece with a hole at the top is laser pointer holder.  (10)


(10)

Evaluation:

While everything isn't perfectly square, the holder works very well.  It holds position very well with no droop or sag even after being left for hours.  It worked well holding filtered 30x80 binoculars for the 800 visitors we had at Broemmelsiek Park for the Transit of Venus event.  It was easy to accommodate the wide range of heights of the adults and children without loosing the sun in the field of view.

There seems to be little tendency for the tripod to tip while in use. It would be possible to fix a weight to the 1/4"x20 rod to lower the center of gravity if necessary.

It is much easier to use the binoculars now. Star hopping is very easy with the mount. I have used the binoculars and mount to complete all three of the Astronomical League's Binocular Programs: 

  • Binocular Deep Sky
  • Binocular Double Star
  • Binocular Messier

The mount makes the programs easy by allowing me to constantly refer to Stellarium as to where the desired object was located without loosing my place in the sky. 

Viewing objects at the zenith is a bit difficult.  My current thought on zenith objects is to wait an hour!

 

CS

Tripod with Berry Mount



   
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