Kevin's Observing Chair Project

Page last updated: 2003 October 03

Observing Chair

Start of the Project: 2000 August 09

Intro

Every year I and many other Astro-Dudes partake of the Star Party known as StarFest, held at Mount Forest Ontario. And every year we come back full of ideas and energy to do something about them. This variable height observing chair project came out of those ideas. Of our group of 8-12 transgressors, 3 or 4 had observing chairs (fixed height) and none had variable height chairs. We saw one design at StarFest but it was selling at over $150? $200? Zowee! So about August 9th. 2002 I started hunting the net for project ideas. I found the following: using http://www.google.ca/ and searching for "variable height observing chair"

Some sample designs:

Some of these URLs have since moved or expired :(

http://personal.nbnet.nb.ca/twjhnst/space/chair/chair.html Standard design that I've seen at StarFest

http://home.earthlink.net/~flyj/cperch1.html A Catsperch standard design
http://www.cableone.net/les/Astro/Chair.html A variant on the standard design. Still looks fragile.
http://www.starchair.com/ Too weird for words!... ok, I've been asked for a few words... words like US$4650, words like, can not be built by an amateur astronomer in one lifetime, not useful for telescopes, only binoculars. The whole point of this projecti s to find a variable height chair that can be built for under $100Can. This does *not* qualify!
http://www.starmastertelescopes.com/ Now this is an innovative design! I like it.. I like it a lot! Let's go with something like this! Some folks at Starfest had this one as well, although built with 2"x4" lumber... a little heavy if you ask me! It folds flat, it can handle over 100 kg, and as a bonus, when you turn it around at public observing sessions, little rugrats (read children) can hang onto it and not your scope!
http://home.earthlink.net/~tkurkowski/SCT_Tips/Need_to_Have/Observing_Chairs/observing_chairs.html A standard stool and catsperch designs... nice, made of metal, but over $100Can

Benefits

For anyone with a sore back, a longer focal length that causes the eyepiece to move up and down a LOT, or for public observing sessions with a lot of vertically challenged rugrats. It can be sat on at heights of 6", 12", 18", 24" and maybe even 30", and stood on at heights of 6", 12" 18" and 24". It had better support 200 lb+- (90kg +-)!

Design

Oak is too expensive as is aluminum. So instead went out for 1x2" whitewood and 1" wooden dowels (maple).

Parts List

5- 1"x2"x8' whitewood @$7.25
1- 1"x2"x6' whitewood @$5.27 remove from list use the extra 8'
6- 1"x48" wooden dowel @$2.88
28 #6 screws x 1 1/2"
wood glue
2 or 3 hinges



Total costs
Look like about $60 so far.

The Assembly

Start with a 1x2x8 and cut it into two 42" pieces (with 12" left over). Start at the bottom and drill a 1" hole all the way through every 6" (eg 6", 12", 18", 24", 30", 36") centred on the 2" side. Repeat for the 2nd piece. Test fit a dowel. It should be snug (it will be glued in place later).

repeat the above step. You should now have 4 legs with 6 holes each.

Take another 1x2x8 and cut it into two 42" pieces (with 12" left over). Do it again with the 4th 1x2x8. These 4 will go on the outside of the first four, holding in the dowels and making stronger legs.

Take the 5th 1x2x8 and cut off two 24" pieces (leaving 48"). These will be the tops.

OK take a hole-ly leg, attach an unhole-ly leg to it using glue and screws in between each dowel. Repeat with a second set. Insert the 6 dowels in between. Lay down on a flat surface. Square it all up. The top and bottom outside edges should be 24" apart. Add the 24" top 1x2 and glue and screw it to to form a 3 sided square. You should now have

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Do It again

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Stack these on top of one another and attach a hinge or hinges to allow them to sweep open to a 90 degree angle.

We now have a functional chair without a seat. The seat will be a piece of plywood that sits across the two "walls", which are at 90 degrees. The seat can be placed across the dowels at 6", 12", 18", 24" and maybe even 30". To keep the seat in place we'll cut and intricate pattern at the 90 degree corner so the plywood "locked in place" the two arms of this device. A 2x2 brace was added to the front edge of the seat, to help support the plywood front edge.

After the Fact

The plywood seat still had a tendency to flip up at the back when weight was applied at the front. So little 2"x2" blocks were added on the inside leg of one of the arms to prevent the plywood from moving up (much). You still need to leave a bit of room to allow the plywood to insert into the arms.

After visiting at Starfest 2000, I found another observer had built on of these out of 2x4's and this allowed him enough room to add wooden blocks under the plywood to lock on the dowels. Neat but a little heavier.