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10. Tools and Jigs.
My only power tool for this project was an electric drill. (My
seamstress friend used a sewing machine.) Several special tools and
jigs helped. I bought a thin saw with fine teeth set to cut on the
"pull" stroke. It derives from Japanese carpentry, and was a joy to
use. I could split a pencil line when sawing, and my cuts required only
a few finish strokes with sandpaper, and I am by no means an experienced
carpenter. I also used a drawknife -- a very old tool for shaping wood
-- and a good set of wood chisels. I kept chisels and drawknife razor
sharp, and took great care that they cut only wood, not flesh.
I had a simple drill stand so I could use my electric drill as a
drill press -- that was extremely useful. Also useful was a good hand
miter-box saw assembly -- a fancy metal unit, with clamps and guides,
adjustable to many angles, with a high-quality backsaw.
I had a variety of store-bought clamps for gluing. The project
would not have succeeded without them. I built several special jigs.
Useful ones included some simple wooden "V"s, to support a 90-degree
angle edge down, so I could weigh down a glued joint while the glue
dried, and a strip of metal with holes pre-drilled at the design
separation of the fastener holes in opposite ends of my truss poles.
11. Packing for Portability.
Except for the truss poles, the telescope packs into roughly a
14-inch (36 cm) cube for transport. With side bearings removed, the box
nests into the rocker, and the octagon fits into the top of the box. I
found a Rubbermaid refrigerator container about 11 inches (33 cm)
diameter and 4 inches (10 cm) deep, just right to hold the primary with
plenty of padding. It also fits into the box, under the octagon. There
is lots more room in the box for small parts, accessories, and tools, or
for clothing and non-telescope stuff, either as padding or to distribute
weight more evenly among pieces of luggage. The ground board and side
bearings fit around the rocker, to make up the rest of the cube.
Even though all the parts mentioned do indeed fit into the cube, I
actually packed for traveling by putting as many small, heavy parts as
possible into my other piece of luggage, and filling gaps in the
telescope case with clothing and other light items. All the fasteners
used for motel-room assembly traveled this way. Without doing so, the
case would have been very heavy and awkward to handle.
12. Other Case Features.
The container I bought from Atlas Cases has an interior that is
approximately an 18-inch (46 cm) cube. It came with two inches of foam
lining, which I trimmed with a bread knife for a snug fit. It has
handles and latches; I drilled holes for a long, bicycle-lock style
padlock, which seems enough to deter casual pilferage. Anyone who
steals the entire case can take it somewhere private and open it with
power tools, so a fancier lock won't help. But the case is stout
enough that I can dance on it.
I added threaded inserts to the case bottom, for simple rubber feet,
sized to sit on Celestron vibration-damping support pads. Thus I can
sit the telescope atop the case when I am working near the horizon, to
raise the eyepiece from a rather awkward 40 cm to nearly a meter.
That's steady enough for deep-sky work at 106x -- the magnification I
found myself using most often -- and surprisingly so, since the case
flexes easily. The explanation seems to be that the light finger
pressure required to steer a well-balanced Dobson isn't enought to
distort the case noticeably.
The vibration damping-pads worked well. I noticed no jiggles when I
was observing. Wind-induced vibration is sometimes a problem with
telescopes, but when sitting on its case, the 10-inch showed no
wind-induced vibration at the eyepiece, even at wind speeds sufficiently
high that I had to keep a hand on the telescope to keep it from turning
like a weather vane.
13. Spare Parts and Supplies.
When I am putting something together away from home base, I can
count on finding a crack in the earth that goes clear to the antipodes,
because I am certain to drop into it some fastener the whole project
depends on. So my rule about spare small parts is, take 50 percent
extra, but never less than two. If the gadget needs one 1/4-20 by
two-inch Allen head machine screw, I take that one, plus two spares. If
it needs six, I take nine. And so on.
I bring enough tools to get by if I lose one. A "Leatherman" or
similar pocket gizmo is a handy backup, but do put it in checked baggage
to keep airline security happy. I take stuff like Epoxy and grease, for
repairs and maintenance. I have a spare truss pole. And don't forget
duct tape, so if the universe breaks down, you can fix it, too.
14. Shake-Down.
I lucked out. The 10-inch Dobson came up smoothly. Everything fit
together. The pieces all fit in the case. The focal point was where I
intended. The balance was a little tail-heavy with the solid truss
poles, but the extra weight of the joints for the cut poles put it dead
on. I worked hard to get the telescope ready weeks before traveling, so
there would be time for modifications, but none were required.
Yet I learned a lot from the use I had of the telescope, before my
first trip. Some of it was relearning the habits of Newtonians: I have
made thousands of observations with them, but it has been a long time
since I used one extensively. Some of it was familiarization with this
particular telescope -- it went together a lot quicker the second time
than the first. And some things were useful new ideas, suggested by
experience -- the bit about putting feet and vibration dampers under the
case, to use as a stand for working near the horizon, was one such.
Anyhow, after five nights' experience and over a hundred objects
logged, I was ready for my first trip south -- to Hawaii.
TO BE CONTINUED
Reference:
Kriege, David, and Richard Berry, 1997. _The_Dobsonian_Telescope:_
_A_Practical_Manual_for_Building_Large_Aperture_Telescopes_,
Willmann-Bell.