When the sky is capped, a fellow's mind turns to the shop. . .

Jan 20-23. I took the Meade SN10 apart to find out what it would take to adapt a better, lower focuser to it. There are commercial kits available for this, but they cost more than I paid for the OTA. More to the point, they cost more than I want to pay right now. I thought I could just machine an adapter and put the SN10 to work with an old Novak helical focuser and the Feathertouch adapter, but no: the hole in the metal OTA is too small. Enlarging it is not trivial. And the finished instrument would still have its share of mechanical problems.

Think a little bigger: remount the optics in a nice truss tube; make it lighter; mount it closer to the RA axis; optimize it for CCD use; and make sure it's easily "editted" for future mods. Truss-tube astrographs look so damn cool, too.

I spent a weekend distracted with designing the truss and attachment hardware and then with spec'ing out the order for metals. It turns out the raw metal could be purchased from Pierce Metals for about one third the price of a Moonlite focuser and mounting kit. The aluminum stock will provide hours and hours of entertainment with the lathe and milling attachment (and no small amount of exercise with the hacksaw into the bargain). See those blue connectors? I'll need 28 - 32 of them. It's possible to make amazing things when machine shop time is not only free but fun.

10-24 screws should be fine for almost everything. I just found a deal and bought almost a thousand socket head 10-24's in a couple of useful lengths. You know what they say: "To a man with a thousand machine screws, every problem..." I'll probably use a couple of stray 1/4x20's here and there just because people who only play engineers always use more metal / wood / stuff than a real engineer would. Eventually, many long socket cap screws in the trusses will end up replaced by unobtrusive setscrews. But get the dimensions locked in with easy-to-use socket-head dudes.

Expect to install aluminum webbing in the corners of the mirror, middle, and corrector-support frameworks, but try first to make them work without webbing. Both the intent and the backup strategy should aid rigidity.

If I mount the SN10 and the guide-scope without the DSBS, I'm thinking the suite won't load the G11 much more than the DSBS-mounted A-P with guide scope does. The DSBS adds a lot of extra metal and considerable extra height, hence considerable extra moment. Between the lower mount and the counterweight bar extension, I don't think we're going to push anything. We'll see.

The design is probably troubled in many ways, but some of its oddness may be mitigated by the facts that manufactured parts have to be manageable on a small lathe with a jury-rigged milling attachment and that some parts which would otherwise be done differently are "as received" from a commercial, budget-line OTA and as such were originally made on and for an assembly-line.

Material enroute (all 6061 AL):
  For frames: (3) 3/8 x 1-1/2 x 48" bar
     cut these into 12, 12" sections.
  Tubes: (5) 7/8 O.D. x 0.083" x 48"
     cut into 8, 18" and 8, 12" sections.
  For tube adapters: (2) round 7/8 OD x 48"
    cut into 28-32, 3" sections (allow for kerfs)
  For bottom rails: (1) 1/2 x 1-1/4 x 48" bar
    cut into 2, 24" sections
  5" Losmandy D-plate (to mount guide scope)
  400 10-24x1" socket head screws
  500 10-24x1-1/2" socket head screws

17-inch Losmandy D-plate (on hand)
2-inch ID AL tube for focusser (on hand)
Feathertouch Micro-focus adapter (on hand)
Novak low-profile helical focusser (on hand)

UPS says the metal will arrive Thursday. A cover for whatever rig I set up in the side yard will appear on Friday. The rest, delivered by a more mercurial service, will appear in its own good time.

Photoshop as a CAD application:
It worked for the house, it'll work
for telescope design, too.

Click the thumbnails to inspect
the current state of the design.

They're sketches... I only play an engineer on
the Internet. The plan views are mostly piles
of notes to pretty good scale. They combine
features of multiple sides in single drawings.
Think of them as visual notes to me. I'll work
it all out in more detail as
needed, maybe even before I cut metal.