haunting the usual place, Vancouver telescope. I have managed to find so much to interest me there. Nick seems to have new stuff most visits, and I will kill a few hours talking and looking.
This time there were a number of parts and a sonotube. It was what was left from a 10″ f/4 Dobsonian F/4 is a very short focal range for Newtonians, but quite common NOW. When this was ground, polished and then coated at Pancro in the 60’s or 70’s, f/4 was unusual. Very few would have parabolized a mirror in this range with any degree of competence.
The mirror has little to identify it: a sticker from the coating company, Pancro, and a focal length inscribed with ‘ 39.8″ ‘ a cell, spider and secondary holder by Kenneth Novak, very well known and regarded in amateur and professional circles. The focuser was only a 1 1/4″, far too puny to delivery wide field viewing with 2″ eyepieces.
I am proceeding down the same road as my 12 1/2″ build, using baltic birch plywood, a very hard and dimensionally stable composite wood product. It usually comes in standard imperial thicknesses (1/4, 3/8″ and 1/2″ are my usual picks). The size is 5 feet by 5 feet. making it very tricky to cut up to smaller sizes, even on a 10″ table saw.
I cut a strip 10″ wide and used a finger-jointing jig I have used on many other projects.
The first was a case for an 8″ Maksutov M809 by Intes, the 2nd an eyepiece case out of Jatoba and the 3rd a case fror my smaller MN-61.
Quite simple to use, you can make it yourself as you need different ones for different finger widths. The tools you need are a table saw with adequate capacity to take a dado blade set.
The part is just a board with a finger of wood the width of the dado you are cutting. The finger acts as a registration point to cut the slots, and you then put the dado you just cut over the finger and repeat until you have cut all the fingers. For each side of the box, you gang the sides together in pairs to get them identical. For the second pair, you ADD a piece of wood between the finger and the plywood to get an offset. It should be close to the width of the dado but it doesn’t need to be exact, as any unevenness can be planed off once glued up.
You can add a gusset of wood, cut at 45 degrees to reinforce the interior of the box for robustness. If you need to make the box lighter for balance or other considerations, just use your table saw to rip a section off end end
You just need to test it first to make sure the gap is correct. I am testing a few scraps out to try veneering to surface of the wood for a more refined look. I have a choice of using maple, cherry or walnut. I am leaning towards walnut but that means I will have to match and tape together sections to do each side correctly.