How to build an observing chair

Say goodbye to wet knees and aching joints with this DIY project – an observing chair that folds flat for easy storage.
 
Written by Mark Parish.
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Image Credit: 
Mark Parrish
With an easily adjustable seat, this chair can be used with all manner of scopes, and by big and small kids alike.

A folder containing materials to help with this How to, including full assembly instructions, can be downloaded here.
 
Observing a well-placed object in the night sky is always a pleasure, but if the object is low on the horizon or close to the zenith, you may find you have to kneel on damp ground or crane your neck to get your eye close enough to the eyepiece. It’s at times like these when an adjustable observing chair really comes into its own.
 
The wooden chair in this How to has an adjustable seat that can be positioned anywhere between 150mm and 920mm off the ground. This height range should be ideal for most amateur scopes, but there’s no reason why the design couldn’t be extended a bit. You could even have kids stand on the platform – perfect for those ‘small child, big Dob’ moments.

Tools & materials

Finishing - Treat the timber with varnish, preservative wood stain or exterior paint. The choice of colour is up to you, though bear in mind that lighter colours are easier to spot in the dark.

Sundries - Thirty 25mm No 8 countersunk screws, waterproof PVA wood glue, two M6 x 40mm bolts and wing nuts.
 
Timber - All of the plywood parts can be cut from one 1220mm x 1220mm piece of 12mm-thick board. You also need two 3m lengths of 44mm x 20.5mm softwood. For the pivots, cut up a 500mm length of 25mm dowel.
 
Tools - Coping saw, jigsaw or scroll saw; electric or pillar drill with 4.5mm, 25mm (to suit dowel) and countersink bits; G-clamps, screwdriver.
 

You can make this observing chair with a basic tool set and minimal woodworking skills, but if you own (or can borrow) an electric or pillar drill, and an electric jigsaw or scroll saw, you will be able to speed up the process – and perhaps ensure a bit more accuracy.

All of the materials you need can be easily obtained from most timber merchants or DIY stores. If you are lucky, you may be able to get the main parts cut to size for a small charge in the store when you buy the wood, leaving just the fiddly bits to deal with yourself.
 
The chair is based on one created by Canadian amateur astronomer Ed Hitchcock – which itself borrows from some commercially made examples – so its design is well evolved, and includes a number of features that will enhance your observing experience. For example, the chair can be folded flat for storage. If you want to take it anywhere by car, you can easily unscrew the spreader leg, which makes it small enough to fit across the back seat. We chose to fix the spreader leg to the rear support because this makes it easier to fit the front of the chair between tripod legs.

At the workbench

Apart from the woodscrews, all the parts are made from timber. The pivots are made from 25mm wooden dowels, which can be found in most DIY stores, though you could also use an old broom handle. You will need a drill bit to match this dowel, and sometimes a little sanding or filing is required for a nice fit. However, it isn’t too tricky to make a strong and accurate chair.
 
If you use plywood for the seat brackets, we recommend gluing two pieces together for each side to give them extra thickness – though we were lucky enough to find some hardwood (ash) in our offcuts box for these, which added a touch of quality. If you have access to hardwoods and wide natural boards, you can substitute them for the softwood and plywood parts. This improves the durability and also allows a degree of customisation. In any case, avoid using MDF or chipboard as these materials can break down when they become damp and get knocked about.
 
Using the chair is straightforward. Once the spreader leg is fixed on, simply unfold the rear support and the brace will drop into place, securing the shape. The seat can be raised and lowered easily, but once you sit on it, it locks into position and cannot drop down.
 
There are a number of additions you may want to consider. If you are planning on using the chair for long sessions, you could add a footrest for extra comfort or a second seat for a friend. You could attach a rail to the side for children to hold onto if they are standing on the seat, or add an accessory tray to hold your eyepieces.
 
However you decide to build your chair, it will be an invaluable observing companion for many years to come. Unless you use MDF, of course.
 

Step 1 - Accurate marking out is the key to success. Many parts are made in pairs, so tape them together, mark them and cut them at the same time. That way, even if the outcome is a little inaccurate, at least the two sides will be symmetrical.

Step 2 - The notched racks that the seat slots into are easier to make than they look. Clamp the two pieces of timber together and drill holes every 50mm along the joint. Mark the top of each piece before you separate them, so the notches always match up.
 
Step 3 - Some parts, like the support brackets and the seat brackets, need to be shaped. You can cut them using a coping saw or, preferably, an electric jigsaw or scroll saw. Again, tape the two bits of wood together and cut, drill and sand them at the same time to ensure consistency.
 
Step 4 - After cutting the plywood panels and timber rails, use a waterproof wood glue to stick them together. Use woodscrews, through pre-drilled and countersunk holes, to tighten these bonds. Note that it’s easier to drill through plywood and screw into timber than the other way around.
 
Step 5 - Assemble all the parts you’ve prepared to check for fit and ease of movement. Dowels may need to be sanded or have spaces cut for them to allow free movement, so it all folds down flat. Don’t paint the chair while it’s assembled, or the parts will stick together.
 

Step 6 - Mount the spreader leg so that the support section is held just above the ground. We used wing nuts and screws to fasten it, so it can be removed for transport. A block, glued above the leg, provides extra strength. Varnish or paint the parts before reassembly.


This How to originally appeared in the August 2012 issue of BBC Sky at Night Magazine.

 
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