Binocular Chair

Rod Nabholz

 

Why A Binocular Chair?

 

I have come to enjoy Binocular Astronomy. The low power fields and wide views can be quite spectacular. Another aspect I enjoy is that, at least in my case, that view seems to promote a more relaxed approach than observing with a scope.  

 

As anyone who has done much of this type of observing can tell you, the nature of the equipment can mean some uncomfortable positions or shaky views.   Hand holding any binocular with magnification higher than 10X is very difficult to do well. When you add to that the awkward upward angles you have shaky and uncomfortable - not likely to be an enjoyable experience.  Astronomers have come up with many approaches to solve these limitations. Tripods, parallelogram mounts, mirror mounts, expensive stabilized binoculars are some of the solutions, and I have tried many of them. Some are good and some are lacking, but I kept feeling that the best solution was still out there.

 

It was in searching for the ultimate that I came across an article on a Binocular Chair called the "Comet Couch" by Eugene Artemyeff (http://www.cloudynights.com/item.php?item_id=800).   Eugene has mounted a parallelogram mount on a swiveling platform with a seat. This provided stable support for the binoculars and a comfortable seated position from which to use them. This looked like the answer to my quest.

 

Design Choices

 

Eugene's simple and elegant design utilized a folding camp chair for the seat.   I have never found those camp chairs all that comfortable for an astronomer of my size, so I would make a few changes to the seat, mine would be constructed with wood.

 

I wanted the mount to be portable, but I did not need it to be ultra light. Because most of my viewing is done in the backyard, or at dark sky sites where I can drive my vehicle right up to the setup location I never have occasion to haul it too far.   The mount should be easy to set up, and require no more than two trips to bring it out.

 

Finally, it should be relatively easy to build and not require any special expensive custom work or exotic parts.

 

The Chair

 

Having years earlier built some outdoor chairs from pressure treated wood, I have been impressed with the durability of that material, 12 years later they still look great.   It is also relatively inexpensive and does not require any additional finish before use.   I decided to build the chair out of pressure treated 5/4ths x 6" deck planking and a 2x8. The simple assembly would be done with screws and adhesive.

 

The build started by assembling the base.   Essentially it is a box 18" square of 2x8. The bottom of the box is three lengths of the deck planking spaced evenly across the bottom. This leaves gaps between the boards, but that is no problem, the box need not be completely closed for this purpose. The middle plank is the pier arm and it extends beyond the side of the box 13 inches.

 

The design I had in mind called for the back to be removable, and to be positioned at a comfortable backward leaning angle. My plan was to use the back of the box as a leverage point, and have the back extend into the box and come to rest against a "stop" positioned to provide the desired angle.   The stop is a 2x4 that extends across the bottom of the box, glued and screwed into place.

 

The seat boards are positioned to leave a gap in the topside of the rear of box just wide enough for the back boards to slide through. Once the back is inserted into the box and resting on the bottom, you simply lean the seat back until the bottom comes up against the 2x4 stop. It is then wedged in place against the stop and the back of the box. It makes for a very sturdy but removable arrangement.

 

The back is simply three planks of the 5/4 deck planking.   I connected them across the back where they meet the box with a cross brace and again across the top with a cap piece.

 

To get the swivel action that really makes this a great way to view, I needed a lazy susan bearing.   I ordered mine from McMaster Carr. It is 12” in diameter and is rated for 1000 lbs capacity, (should be plenty).   All this for just $9.60. The only issue was figuring how to mount it, as it came without instructions. Not having used one before, I was really stumped on how I could attach it to both the bottom of the box and the base. Attaching it to one side prevented access to the mounting holes for the other side. I finally did figure it out.   I won't spoil the puzzle for you, email me if you give up.

 

The bearing is attached to the chair bottom and an 18” diameter circle of ¾” plywood. To the bottom of the plywood I added three evenly spaced feet made from 4” squares of the deck planking.

 

 

The Pier

 

For my pier I used 1.25” galvanized pipe.   I mounted the pipe to the pier arm with a pipe flange centered and located 9.5 inches from the side of the seat box. The flange would allow me to remove the pier for transport by simply unscrewing the pipe from the flange. My hope was that pipe would be stiff enough without any additional bracing needed to eliminate the shakes.   After I completed the mount and had a chance to use it, it became obvious that I was going to need some additional support to improve the damping time.   In the Comet Couch design, Eugene used 3 stiff rods to stabilize his PVC pier, one pushing and 2 pulling. My metal pipe was quite stiff and I found that two cables pulling were sufficient to improve the damping times to an excellent level.   The cables are attached by hooks on turnbuckles to eyes on the side of the seat box.   A few quick turns on the turnbuckles and they are tensioned and doing their job.

 

 

The Parallelogram

 

Although I had built a parallelogram mount previously, this one was different in that the binoculars needed an additional axis of mobility. To place the binoculars in a comfortable position in all altitudes with fixed length parallelogram arms, the user needs to be able to push and pull the arms while keeping the eyepieces parallel to their eyes.   This requires a hinge at end of the arms in addition to an altitude axis.   I built a simple hinge that is then connected to the altitude axis that provided the necessary range of movement.

 

 

Ideally, the binoculars should hold their altitude position when released.   To make that work, a simple counterweight is perfect.   Again, using the old stand by of a ½” pipe and flange I made a counterweight shaft.   The weight of the flange and pipe and a 2.5 lb barbell weight was all that was needed to balance my 4.75lb Fujinon 16x70 binoculars.   I added a bicycle handlebar grip to the end of the shaft to make for a convenient place to grab when guiding the binoculars.

 

 

The trickiest part of the parallelogram was determining how long to make the arms.   Too long and you force the user too far to one side of the seat at certain attitudes, to short and the opposite happens. Ultimately, after lots of head scratching, measuring, and more head scratching I came up with a reasonable balance of all of the factors.   In essence the binocular position ends up past the centerline of the seat when the arms are positioned perpendicular to the side of the seat. Set up this way, when you draw the mount back towards you when viewing at the zenith it is still comfortably positioned near the centerline of the chair.

  

 

I made the parallelogram out of white oak.   All of the joints were glued and screwed. I finished it with multiple coats of satin polyurethane.

 

To connect the parallelogram to the pier, my plan was to use nesting pipes.   On the drawing board it looked great. I assumed that it would be no problem to get two different sizes of pipe, one that would fit snugly inside the other but still turn freely.   When I got to the home center I found out differently.   None of the combinations tried worked, some were too loose, some did not fit at all.   I tried black pipe, galvanized pipe, every pipe they had. No luck. I was about to give up and rethink the design when it occurred to me to try to mix the types.   Sure enough, I found a combination that worked. I found that a 1” black pipe nipple would nest very well inside 1.25” galvanized pipe.

 

I attached the 5” long 1"pipe nipple to the parallelogram pivot using (what else?) a pipe flange and some long screws.

 

For a counterweight, a 10 lb barbell weight was just the ticket. I drilled multiple holes in the parallelogram arm to allow me to adjust the position of the weight.   I cut a spacer out of a 1” dowel for the weight to ride on, and drilled that through for a ¼” bolt.   A couple of fender washers on each side keep things in place when tightened down with a wing nut.

 

All of the bolts on the parallelogram are held in place with nylon lock nuts. They allow the joints to be loose enough to move freely, but will not work themselves loose or fall off.

 

 

The Training Wheel

 

To keep the size of the seat unit a little smaller, it was my desire to keep the bearing centered under the seat. I suspected that might cause balance problems when the seat was unoccupied. When I had things nearly finished I could see that my suspicions were well founded.   With the weight of the parallelogram and counterweights extending out so far, the seat would lean towards them when the user left the seat.   Depending on where the pier arm was in relation to one of the three feet, the lean could be significant.   I addressed this issue with the small plywood “wheel” that you see at the end of the arm.   Now as the unit starts to lean, the wheel grounds stopping the progress.   The diameter of the wheel is such that it never touches when the user is seated.

 

Under the Night Sky

Setting up the mount is quick and easy. As I had hoped, it takes just two trips, base and back on one trip, pier, parallelogram and binos on the shoulder on the second. 

To set up:

Set the base down

Slide in the back

Screw the pier into the flange

Tighten cables

Insert Parallelogram into top of pier

Attach Binoculars to the head

It takes just a couple of minutes. 

Observing with this rig is a real pleasure.  The swivel bearing is smooth and requires almost no effort to move. The binoculars move easily to any position naturally with little effort or thought.  In fact I had to train myself to bring the binoculars to me, the converse of my old habit of moving myself into uncomfortable positions to meet the binoculars. 

The rig is quite stable. Vibration damps in about 2 - 3 seconds maximum.  I have found that I can move the mount slowly and evenly and avoid even those times.  You quickly discover how to move and position yourself for maximum stability. I have discovered that small tremors from heartbeats are visible at times. Moving the mount from concrete to grass reduced this issue very well.  I plan to add some cushions to the seat and back to further isolate the heartbeat from the mount.

In all, it is a wonderful way to observe.  Comfortable, natural and relaxed, doing one of my favorite things.  What more could you ask?

 

I welcome your comments and questions at

rnabholz@yahoo.com

©2005 Rod Nabholz

Twin Tube Telescope * Manual Dob Setting Circles * Binocular Chair

Kid Peek Telescope* Downward Looking Binocular Mount * Easy Alt/Az Mount Mod

Barn Door Mount * Observing Stool * Cheap and Simple Red Dot Finder Mount

PST Eyepiece Shield Eyepiece Case Key Reel Red Light Keeper

Kid Peek II * Observation Log and Sketching Forms * Telrad Dew Shield

Back to Home Built Astronomy Projects