BASS -- Boulder Astronomy and Space Society

Building Portable Observatory Panels

by Bill Travis

Even under suburban skies I want to use my backyard for deep sky observing so avoiding stray light is important, and I do suffer neighbor lights. So I built a set of light-blocking portable observatory panels. Arranged in a semi-circle around my observing spot, they create a nice dark area, room for scope, chair, table, etc. and some protection from cold breezes in winter.

I made seven using one inch pvc pipe as a frame with dark cloth attached. I'm not very handy, but the commercial alternative would cost over $600 for what I made with about $140 of material. Here's the recipe: The pipe comes in 120 in. lengths, so I made the panels 74 in. tall (to block light even from a standing position) by 46 in. wide. Cut the pipe at 74 in. (one up-right), and the left-over is one cross-member. You're always one cross-bar short (because you need three per panel) as you cut the pipes. Cut the up-rights in half for a t-connector to add a mid-height, stiffening cross-member. The pipe cuts easily with pretty much any saw that happened to be at hand in the messy garage. Each panel needs four elbow and two "t" connectors. I bought the glue for these but ended up not using it, the pieces fit snuggly and I thought I might want to disassemble some panels.

The big challenge is the light-blocking material and attaching it. I went cheap, and used a woven black weed barrier (comes in a big roll, so each panel is just pennies worth of material). I doubled it up on the top (this cuts a nearby street light nicely), used one thickness across the bottom (not as critical because well below eye level), cut it roughly to overlap the frame, and screwed in to the pvc using a small, drilled guide hole, and one inch screws with a wide washer to grab the fabric. As many screws as you like, but I just used corners, intersections, and each cross-bar middle. So, no hemming or sewing! I let the top panel flop over the bottom and all sides hide the white pvc pipe.

I first used cheap (97 cent) two inch clamps to hinge the panels together (two per hinge; 12 total for my seven panels), but they didn't work well, so went with better ($4-5) clamps that have a 2-inch interior space when closed and a lock-release trigger. The panels swing quite nicely on this "hinge." Set up is just a few minutes from the garage, two at a time (can't imagine traveling with them, but they could be broken in half, and depends on vehicle; anyway, light is usually not a problem at star parties). The set-up handles wind up to 10 mph if configured to shed the breeze, but this is a lot of sail area and would need guy lines in any more wind.