Pierre Schwaar's 8" F/4 Binocular Chair Restoration.Pierre has left us, but his legacy lives on in his myriad optical creations. This page will chronical the rebuilding of one of them-his motorized, 8" F/4.2 binocular chair. I happened onto it during one of the first SAC ATM meetings. A lot of Pierre's equipment and supplies were left behind. Some were brought to the meeting for input on what to do with them. Someone was suggesting we split the optical tube assemblies into two 8" F/4.2 Dobs to be used as club scopes for newbies. I found this idea abhorent, so I volunteered to take it all home, evaluate its disposition and refurbish it if possible. I had a plan to install it in the rolloff roof of my Stone Haven Observatory, for use by visitors to star parties I regularly give. It's only been recently I've been able to find the time to look into the restoration. I believe I'll have most of the materials I need on hand, but some restoration of the observatory building is now in order. More on that later. In the mean time, I'll take pictures of the chair in its present state and as it gets fixed. Unfortunately, I started working on the chair before I had the idea to document the process, so I can't show everything before and after, but I started as soon as I thought of it. Most of the process will be here. I'll also be entering the plans into a CAD program to document all dimensions and so on. I hope you're sitting comfortably... Here's the only picture I know of of the chair set up in a field. If anyone knows any salient details about this, please let me know! (EDIT: I've located some more, older pics. I'll include them elsewhere, probably in the refurb pages. 8/12/12) The chair consists of four basic structures. The base, the azimuth box, the chair section and the optical tube assembly. This page will describe the base and the links will describe the other major parts. Hopefully, this arrangement will cut down on the load times for all the pictures I'll need to include. If not, I'll add more. The base is a box 15" x 15.5" with 4, 4" diameter PVC feet at the corners that raise it
above the ground by 4". It has a central spindle of 2" diameter that serves as the azimuth axis. It has
a 14" diameter gear mounted horizontally that meshes with the azimuth drive gear which is mounted on the
azimuth box. The gear is raised 1/2" above the box by 4 metal spacers. The assembly weighs 33 pounds and has a low center of mass.
The azimuth box is made of 2, 9" x9" x 9" cubes, connected along one plane by a horizontal section ~3" in height.
The final assembly is shaped somewhat like an inverted "U". It's made mostly of 3/4" plywood,
with one piece of 1/2" plywood mounted horizontally across the inside of the U. It was enclosed in the width
dimensions with 1/8" hardboard, with an interesting parque wood grain pattern printed on the surface. The same
pattern can be seen on the OTA's. The hardboard has split across the diagonal of one of the cubes, and the glue
between the horizontal member and inside vertical member failed, rendering the
box unstable and even dangerous. This section will have to be rebuilt from scratch. I intend to make it from 3/4",
furniture grade Baltic Birch plywood, and replace the hardboard with 1/8 Birch plywood, which I have onhand. The chair portion looks rather like a lawn chair of some sort, with a few modifications. In front, is a footstool arrangement
that allows the user to step into the chair. In the bottom, in place of legs, are two altitude bearings that ride on the altitude
mounts on the AZ Box.
There is a large gear mounted behind the alt bearing on the left side of the chair that meshes with the altitude motor. The OTA assembly consists of two 8" F/4 telescopes mounted in a rigid frame. Their light paths are collimated to meet between the tubes,
where a focussing mechanism focuses both images into a pair of binocular eyepieces. The original design had interchangeable 1.25" eyepieces,
but this arrangement has been abandoned, due to lack of eyepieces and a somewhat regretable unworkability of the interocular distance adjustment.
Total chair weight close to 215 lbs. So, on to the pictures and descriptions, shall we?
The base will not be refurbished at this time, since it is quite solid and requires none. If I were to do anything to it, I'd make a new one, only larger. EDIT: I did end up rebuilding the base. Mostly, it was to accommodate the redesign of the entire azimuth drive system and yes, I did make it bigger. :-) |
Page URL: http://www.stonehavenobservatory.com/ATM/Binocularchair.html