It seems that it could happen ( and I've done it to myself)...my suggestion would to be simply not to let them sit on the chair. If they are just passersby, it shouldn't make a difference.
Stacy
You might NOT be an astronomer if you think Uranus is an anatomical feature rather than a planet.
>From: Mark Berger
>Reply-To: The Astronomy Connection
>To: sf-bay-tac@No-Spam
>Subject: [TAC] Safety of observing chair
>Date: Mon, 07 Apr 2003 14:08:23 -0700
>
>I have heard reports (from a competing product manufacturer) that those
>adjustable observing chairs, the kind that use friction to stay in
>place, can suddenly slip and let you fall to the ground. The cause is
>reportedly due to dew, insect repellant, etc. on the rails. Has this
>EVER happened to anyone or is this just advertising hype?
>
>I'm not too worried about hurting myself, but I wouldn't want an
>innocent bystander getting hurt if they wanted to look through my
>telescope.
>
>Mark Berger
>mlberger@No-Spam