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The rough boards were planed along the edges and some were glued together to give the appropriate width. The boards were then passed through a thicknesser machine to obtain the required thickness of 12.5 mm. Oak is a hard wood (in both senses) and not much fun to plane - if you don't have access to a thicknesser you may be lucky if you approach a local timber supplier or joinery shop. For a small fee/couple of beers they will often be very helpful (not if the wood has been reclaimed though - nails ruin the blades!).
The corners of most scopes seem to be joined using butt joints, screws and sometimes reinforcing battens. This is fine but access to a new dovetail jig was too much to resist. These jigs are used with a router and although some may feel I was cheating, the complexity and headaches involved in setting it all up (and lack of any spare material if I were to make any mistakes) meant I felt I had worked hard for the result!

Focuser
There are many options here, including buying one. However of all the home-made versions the Crayford type seems relatively easy to build and has the advantage that as uses a friction drive it has no backlash (unwanted play or movement often associated with gear or screw driven devices). This means movements should be smooth and positive and, providing a small diameter shaft can be made, fine.
I have seen simpler designs but I used the opportunity to develop my CAD skills using ProDesktop (our standard school package) and I produced this:

The parts were made on my small lathe from off-cuts found in my "bits and bobs" bin, except for the length of aluminium bar which was bored out and turned from solid 50 mm diameter to create the eyepiece tube. The 4 bearings were removed from an old photocopier (along with numerous gears, pulleys and stepper motors - a great source of this type of component!) and screwed to the upright posts on turned brass bosses. The silver steel shaft runs in a mild steel channel which is pressed against a flat face milled on the tube by turning an M4 socket head screw. In order to the friction force to be adjusted, the channel needs to "rock" slightly and it is therefore screwed to the base with a sandwich of expanded foam in between (the blue stuff in the photo).
Throughout the project I have utilised the compressive nature of foam and rubber sheet or washers when possible. The mirror cell, spider and focuser all require "sprung" elements (but relatively small movements) and I have found it easier to make parts using this technique rather than choosing/sourcing suitable springs or relying on my skills with a mastic gun!
Although I felt pleased with the look of the parts I had made, It was not until they were all assembled at the end that I was able to tell if it would work. I am pleased to report that the unit works beautifully. The action is very smooth and can be adjusted so the tube doesn't slip under load from a camera for example. Eyepieces fit well and focusing can be carried out very precisely over the full range of movement (40 mm with the current tube). I haven't included provision for motor driven focusing but this could be added later if I wish.
A recent modification was the addition of small brass inserts (cut from some thin brazing wire) at either end of the eyepiece holder.

Mirror Cell
There seem to be as many methods for building Cells - the collimation adjusters and mirror cradles - as there are telescope builders. For a relatively small, thick mirror like mine (222 mm diameter, 25 mm thick) a complex multi-point support did not seem necessary and I felt that 3 soft pads would do the trick. I had saved some small squares of rubbery expanded plastic which were liberally placed between sheets of glass supplied for our double glazing, which was recently fitted. I don't know what this plastic is although it bears a close resemblance to a material called "Plastizote" found in schools (and used on those cheap, soft rockets and similar projectiles seen in most toy shops). I cut three 25 mm discs which were placed in shallow recesses drilled with a flat bit (or Forstner bit if you can afford one!) at 120° spacing around a circle of approx 70% of the mirror's radius. The mirror sits nicely on these with a gap of about 1.5 mm below. The whole technique seems mush easier and simpler to tinker with than the "blobs of mastic method" which seems a bit permanent if, like me, your not sure it is going to work! The pads are the green circles in the photo.

You may have noticed the lovely clover leaf cut out! This was an attempt to create plenty of opportunity for the mirror to cool quickly to ambient temperature. The more observant readers will have picked up that I had neglected to create the corresponding ventilation holes in the back panel at this stage! I have now cut a round opening about 100 mm diameter in the back plate, which allows for very fast cooling of the mirror.
Collimation is provided by the usual three screws, Some designers have used four, which seems a good idea (up/down, left/right) especially with a square box. However, I had already started making mine with three before I noticed the alternative. I am pleased with the method I devised for providing the necessary adjustment. As you can see in the diagram below, the cell is held apart from the back panel by compression springs. These need to be quite strong - the first ones I tried were too soft and the whole assembly "bounced" rather alarmingly. The chosen springs are just too hard to completely squash between thumb and forefinger, as a rough guide, and were 50 mm long. I got them from our friendly school maintenance man but I have seen them since in hardware shops.

The interesting bit for me was solving the problem of smoothly adjusting the cell, which would probably not be parallel to the back panel. The answer was to use rubber tap washers. I found a standard 25 mm washer, when set in a shallow recess (made with the same flat bit used for all the holes in the assembly) with a generous clearance hole beneath, provided an excellent grip for an M5 screw with a countersunk head. The stiff but flexible rubber grips the screw head by friction and allows quite dramatic angles between the cell and back panel to be achieved! A wing nut would suffice for the adjustment but I turned some nice knobs on the lathe. Even though they are smooth it is easy to turn them with fingers (I haven't tried in gloves yet though!). To keep the springs in the right place I recessed them in to the boards slightly. I haven't worked out how to stop my children (or their friends) from playing with the adjusters though!

As my mirror simply rests on the foam pads it is necessary to hold it at the circumference. Here I have built four posts (the only space for them is at the corners of the box) which each have an expanding pad that gently presses onto the edge of the mirror. I made these posts from some 25 mm PVC rod but I am sure perfectly good ones could be made from hardwood dowel (broom handles are a good source, and certainly easier to shape that the PVC I used) The posts also have a cap which can be rotated just above, but not touching, the bevel of the mirror surface. The face of each expanding post has a sheet of the green foam attached to it and the mirror is effectively held by friction. The cap is a backup in case the scope is inverted. I did try this just to prove it worked and the mirror held fast without slipping towards the caps anyway (thankfully it didn't drop on the floor and break into a million pieces either!).

As far as I can tell there is no noticeable stress applied to the mirror and with a few turns of the screws it can be removed for transport/safe storage etc.

You can also see the one and only baffle. This probably helps a bit with reducing stray light but mainly serves to stiffen the box.

Spider/secondary holder
I really found it hard to chose here. There are lots of theories and plenty of scientific justifications given for different numbers and shapes of vanes. I deduced that a small number of curved vanes is best, but not that easy to make. As this is a part of the scope that is easy to fiddle with later, I decided to start off with a simple shape to build and adjust - three straight vanes at 120° spacing. I made my vanes from steel banding (used for holding bundles of timber together) rescued from a skip in our local builder's yard. This is 18 mm wide and about 0.5 mm thick. Although it is a bit bendy/twisty when "rescued", when it is tensioned it becomes straight and works beautifully. At the "tube" end of each vane I attached an M6 screw with the head cut off and a slot cut into it with a hacksaw. This screw and the banding have holes drilled through them and they are joined together with a primitive rivet made from a short piece of brass wire. Where the screws pass through the wooden "tube" I made some angled brass spacers (these could be any material really) to allow for the 30° slope, onto which I fitted normal washers and wing nuts for adjustment. I had planned to replace these with locking nuts when I was happy with the alignment, but they seem to have stayed put anyway!

I turned a central boss from an off-cut of mild steel, into which the vanes are fixed. This also supports the secondary mirror holder with its adjustment screws. To fix the vanes in place I simply drilled three holes axially through the boss and cut three corresponding slots with a hacksaw to form keyhole shapes. The inner end of each vane is simple bent over so it can slot into the boss from above but can't pull out radially when under tension. To be on the safe side, I flooded the holes with epoxy resin (Araldite rapid) and let it set. I am delighted with the result. The vanes need to be flexed a bit to fit into the box but when the nuts are tightened, the whole unit is very rigid and the vanes become perfectly straight and not twisted. It is also possible to position the boss in the correct place (slightly off centre by about 1.5 mm in my case according to some ray-tracing software).

Photo showing central boss and vanes Photo showing the secondary mirror in position.

The secondary mirror is fixed to a bored-out aluminium holder, which is cut across the open end to the 45° angle required. I did this by drilling out a rectangular block of wood to hold the tube. I drew the required shape on the outside of the wooden block, wedged the tube inside and cut through the whole lot with a hacksaw. The result was remarkably accurate and required only minimal finishing by rubbing the cut edge on a sheet of emery paper stuck to a board.
Inside the holder, a screw head is held in a rubber tap washer. The screw passes through the end of the tube (through quite a generous clearance hole) and threads into the centre of the boss above. Three M4 adjustment screws threaded into the boss apply pressure to a plastic disc resting on the top of the holder. The rubber washer inside the holder is always compressed so none of the adjustment screws become "slack" when making alterations to the mirror alignment. This is a neat solution to what would otherwise be a tricky manufacturing problem. I can't take the credit for this one though - I found it on the Black Knight telescopes web site (lost the link).

First Light
This is the scope on a test rig made from Dexion (big Meccano!)

First light was lamp post over the road!, then a beautiful half moon. Really crisp, bright images even with no black lining to tube, rough collimation and a sawn off eyepiece from an old pair of binoculars! This was the incentive I needed to get on with the project! I took measurements of the tube length and tried a couple of borrowed eyepieces to check whether I be able to bring them into focus. I was pleased to note that this experimental method confirmed the ray-tracing and graphical methods I had also used to calculate the length.

Truss
The truss rods are made from 25 mm square mild steel tubing. This is painted with plenty of primer, some metallic blue paint and clear lacquer to match components of the focuser. I Suppose Aluminium would have been better, although It is not so easy to get paint to stick to it. Availability was the main factor in the choice of material in this case though! I had planned to use four tubes - one in each corner - but a little trial and error suggested two would do the job. Most of the two-rod "truss" designs I have seen have the rods mounted one side of the square mirror box. This imposes additional bending forces due to the cantilever effect of the mirror box and focuser unit. I fixed my tubes in opposite corners which seems a more "balanced" solution.

Round tube is stronger than square tube of similar cross section and most scopes use it. It is much simpler to bolt square sections together or clamp things to them though (especially into the corners of a square box) and I had no trouble with the simple bolt fixings. I had planned to drill a series of holes in the secondary end of the tubes to allow for adjustment to the overall scope length. I haven't done so yet but if I do, it would be possible to change the length by about 60 mm in either direction (this should allow the scope to be used terrestrially).

Mount
I originally planned to build my own mount. The sketch designs for this probably took longer than any for the scope itself and evolved from a traditional Dobsonian mount through to the German equatorial type and eventually to a long, box-section fork. I have produced a number of drawings and novel solutions which someone else might be able to take further and I plan to make them available on this page in the near future.
I was rather impatient to get observing though and was fortunate to find a second-hand GEM1 mount for sale (in my price range!) When it arrived I was pleased with its appearance and smooth action. It is not a very substantial mount but the tripod is very sturdy and has a useful bubble level and rigid tray. It also came with a single RA drive motor with controller and battery pack.
Crude weighing of the completed scope on the bathroom scales put it at over 13 kg. Some literature that came with the drive motor suggested a maximum recommended load of 7kg. Never one to follow the rules too closely, I went ahead and mounted it. For hand-guided use it worked very well. The weight of the scope actually helped to smooth out the resistance and, once aligned, any vibration was quickly damped out. Then it was time to try the motor... result... Whoops! not very clever. Because the scope was heavy and not that well-balanced the motor struggled. Fortunately a crude slip clutch is provided that meant I was able to identify the problem before any damage was inflicted!
I was sure I could solve the problem so I stripped the whole mount down, cleaned and greased all the bearing surfaces (it was dry in many places) and added an additional 8 pound counterweight to properly balance the scope. Result - it works beautifully. the lightest touch can move it, yet it stays-put in any position, and the tiny motor tracks beautifully (30 min+ for visual use) I'm delighted!

The additional counterweight is fixed to the rod utilising the threaded hole already in the rod. This weight does not move, any adjustment being made by moving the original weight.
I will eventually build a more heavy duty mount - the cost of a manufactured one of the required spec would be prohibitive. It would also provide a challenge for when I run out of other projects (so don't hold your breath!).

Truss Clamp
In order to mount the scope, I cut two pairs of clamping "arms" from 18 mm plywood. These bolt to either end of one of the plates provided with the GEM1 mount. I had originally planned to utilise the dovetail fixing provided but this placed the scope further out from the axis of the mount and with such a heavy scope I was anxious not to impose any unnecessary loads! Each arm has a corner cut-out to suit the truss tube section and a simple clamp was made for each arm from a long M6 bolt and a block of PVC. I lined the faces of each clamp with felt to stop any scratching and allow easy adjustment/balancing. It is quite straightforward to lower the scope into the "cradle" and then tighten up the wing nuts. This is done in the horizontal position. By slackening off the nuts, the whole scope can be moved along to balance heavy eyepiece combinations or cameras.

The scope has undergone several modifications including a shortening of the truss tubes to allow for prime focus photography and the addition of a black fabric tube surround to overcome stray light from nearby lamp posts!

It is currently used on my G11 Losmandy mount, which is easily capable of holding the weight. It also now has 4 truss tubes, allowing for an easier way to fit it to the dovetail.

It still brings me a lot of pleasure and performs well, especially for planetary webcam imaging.

Background
The encouragement for the whole project came from my friends Pete Lawrence and Ian Sharp.
Pete Lawrence's Web Site Ian Sharp’s website.
They are enthusiastic astronomers and Pete had been trying to get me involved for a couple of years. I enjoy making things and felt this was a good opportunity to combine a range of materials and processes. The initial idea was to build a conventional round-tubed reflector with a Dobsonian type mount - and this would probably have been far more sensible for a first-time project than the eventual outcome! However I was very impressed with some of the wooden scopes and truss designs I saw when looking at the various ATM web sites (notably the gallery on astronomydaily.com) I found so I began to develop a few sketches.

I had, rather ambitiously perhaps, planned to build a 10" f5 or f6 reflector and was hoping to grind/polish my own primary. However just before ordering the blank and various materials Pete fortunately spotted an 8.5" primary (of unknown focal length but good price!) with matched secondary, advertised on a newsgroup, and I duly bought it. When it arrived I was pleased to see it was in good condition and was engraved on the back f=62.5". As it was actually 222 mm diameter (apparently a popular size once) a quick calculation suggested a focal ratio of f7.15 - which would be good for observing planets but also suitable for wider fields.

Basic Design
The design is essentially a straightforward one, with the primary mounted in a 10" square wooden box and the secondary and focuser housed in a similar box at the viewing end. I was determined to give the scope a touch of class and was fortunate to have "rescued" some quarter-sawn oak from a skip with my brother in law about 10 years ago. This had been seasoning nicely and awaiting a suitable project. I have seen some nice scopes made with plywood, which is good for stability but something about natural timber appeals to me.