Denver Observer’s Chair Modification

I found a great set of plans on the web for an observer’s chair at http://members.tripod.com/denverastro/seat.html.  The plans were widely endorsed by participants in the sci.astro.amateur Usenet group, so I gave it a shot.  Let me say first that this is a fantastic chair—observing with my 8” Dob is far more enjoyable now!!!  It is easy to build, easy to fold up and transport, and the seat can be adjusted from a few inches off  the ground to 3 feet. 

Members of the Usenet group mentioned that the chair has one quirk (which my experience quickly confirmed): it tends to tip forward if the chair is set at its lowest level.  The problem, of course, is that the pivot point is directly underneath (or even slightly behind) your center of gravity when the chair is at that position.  So, I reasoned, to correct this one would need to move the pivot point forward.  My goal was to come up with a solution that is 1) easy and cheap to make, and 2) doesn’t hinder the ease with which this chair can be setup/taken down and transported.  Here’s what I came up with… it requires a single piece of ¾” plywood (or similarly rigid material) and about $1 worth of hardware.  Please excuse the crummy finish and detailing—I ended up futzing quite a bit to get this right, and, well, it works but this particular version isn’t a thing of beauty (yet).

Pretty simple, no?  Here’s what it looks like on the chair:

The piece of wood simply attaches to the bottom of the chair, behind the front leg.  It is attached by hanging a ceiling hook on a lag screw (though there are probably a thousand other ways to accomplish the same thing, many more elegant):

I also have a turnbuckle keeping the front of the plywood firmly attached to the front leg, so I can pick up the chair and move it around with out having the plywood fall off:

You could obviously do without this turnbuckle (or again, find a more elegant way to attach the base).  All in all, it takes roughly an additional 15 seconds to throw this plywood base onto the ground under the chair, lift the hook up onto the bolt, and attach the turnbuckle.  It will not tip with this base attached!  J

Portability? You bet.  I cut the plywood fairly narrowly, so that it will fit under the chair when it is folded up: