float

The parts of the float are done! Thanks Ballard Sheet Metal and onlinemetals.com (also, incidentally, located in Ballard). I should also mention McMaster-Carr, encyclopedic but pricy online source of almost anything mechanical, in particular, the collimation bolts I'm using. Fortunately, other than the optics and off-the-shelf components, the rest of the telescope won't require any more outsourcing. Here are some pictures of the final product, minus a few lock nuts, in situ on the tailgate. The mirror will rest on this frame via 18 points of contact formed by circles of felt or silicone of 1" diameter at the corners of the triangles. Although, with the 4-6 month manufacturing time required by most opticians, not to mention the latency of my budget for buying said mirror, there will be nothing sitting on this frame any time soon!





The idea behind the float is that mirror flexion can be minimized by distributing the points of contact to support sectors of equivalent weight, taking into account the curvature of the parabolic mirror. There needs to be a 3 fold rotational symmetry to the points as well as some flexibility to the whiffletree so that collimation can be accomplished easily. I wonder, though, whether this particular solution, found in Dave Kriege's book, attributed to Dave Chandler, and the basis of scores of scopes, is really optimal. An interesting question that I may try to solve with simulation one of these days. But for now the float is built, so that's that!

I've decided to use Loctite Anti-Seize (Silver Grade) on the collimation bolts, since it is an all stainless construction so far. I hope it suffices to prevent galling/welding of the collimation bolts to the frame under the approximately 26/3 lbs of force they will be turned against.

Next, on to the secondary cage. This means I have to buy a router (no, the other kind).

9mm

I have to say I'm quite happy with my recent purchase of a 9mm Nagler type 6 eyepiece. With my current 8" f/5 1000 mm FL scope and my planned 16" f/4.5 1800 mm FL scope, it gives 111 x and 200 x magnification respectively. The wide FOV makes it quite easy to find things, including M13, M31, M57 the other night, although from my light-polluted observing site there was not a lot of detail (damn you Bellevue!). It was also high mag enough to see Jupiter, currently at opposition, with its four moons and without its southern equatorial belt, missing since May. My medium-term plan is for an eyepiece series: 5 mm UO orthoscopic, 9 mm Nagler, 17 mm Plossl (maybe), and, eventually, a 31 mm Nagler.

welds

What craftsmanship on the welds! Wish I could do that :-)

tailgate done!

The tailgate has been fabricated! Thanks Ernie at stagesmith.com! Just 4 shop-hours. He teaches students how to weld underwater at the Diver's Institute so this was a relatively easy job for him. Here are some pictures.

Just the tailgate:


The tailgate with collimation bolts in place:


The tailgate with crossbeams from the float balanced on collimation bolts (the crossbeams will eventually have holes drilled so they can be bolted on):


The tailgate with cardboard "mirror" balanced in place:


The cardboard "mirror" with paper "triangles" and crossbeams in place (the triangles will eventually be cut out of a 1/8" thick piece of sheet metal, with holes drilled so they can be bolted to crossbeams):


This is the tack welding jig that I built. Ernie made fun of me for it, but I think he must have used it anyway. Either way, the dimensions are correct to 1/16"!


Next, on to the rest of the flotation system...

float

updated version of float metal fab plans to allow for 1/16" thick cuts:

tailgate & float

One of my primary non-work activities has been designing a large telescope. This was inspired by reading about William Herschel in the recently paperback-ed "Age of Wonder", and subsequently by buying Dave Kriege's tantalizingly detailed "The Dobsonian Telescope". On the basis of these things, I decided to start constructing one of my own, a 16" alt-az newt reflector, aka Dobsonian. The first stage involves some metal fabrication, and since I (unfortunately) do not know how to weld/drill/cut metal I have had to prepare some documentation to communicate with people who do. The tailgate and float are the first part of this system. I'm shopping around for fabricators now, so hopefully these will actually get made sometime soon! QCAD is very fun too.

1st law of thermodynamics

I'm starting this blog to document the non-work expenditure of energy that I more and more often am engaging in these days. I feel somewhat guilty about this since I always feel like I should work more, and since, according to the first law of thermodynamics, I'm contributing to the eventual heat-death of the universe by expending non-work energy. Regardless, I need somewhere to post stuff so here it is!