THE 201-INCH
by Bill Close

How can an amateur build a 201-inch telescope? Simply apply the mathematical formula pi r² to your 16" Pyrex disc and presto! chango! There you have it. 3.1416 times 8" squared or 64" equals 201". However, there the simplicity stops. 

Having reached a degree of completion after three years and two months of
work on my 16", I do not choose to stand modestly by and say, "It was easy."

On the contrary, it takes a great deal of work, unending anxiety, buckets of
sweat, considerable "cussin'", and just plain dogged perseverance. That
comes from a man known for his honesty and humility. The reward far
surpasses the effort when you can spend hours with good friends watching the
"greatest show on Earth."

It began some years ago. I had finished a fair six-inch telescope and had
gotten a great deal of pleasure from it. One night I walked into Dr. Calder's office where John Brown and Conrad Meaders were arranging to order 16" blanks which had been advertised for $12.50. I was invited to order one at the same time, with the enticement of possibly saving a little on express charges by ordering them together. Having conquered a six-inch and being entirely innocent of the "pit" falls ahead, I readily acceded, and a few weeks later was notified that the disc had arrived. Being somewhat conscious of my approaching middle age and expanding mid-section, I began to be a bit
squeamish about my physical ability to wrestle with such a project. But once
in my possession, the "blank" look of the disc was unbearable to me, so I
immediately "pitched" right in. 

Using an article on tile tools in Sky and Telescope (January, 1949, by George
F. Joyner) as a guide, I ran into my first problem, scraping cement from
hexagonal tile set 1/8" apart. From hours of experience, I would recommend
the use of square tile. It would also be advisable to make sure they are of
sufficient thickness and set in cement at least three inches thick. Having
finally completed the tool, I placed it on the stand, threw on a handful of
#80 carbo, sprinkled it with water and carefully (how else can you handle a
50 lb. piece of glass?) placed the disc in position, and began to shove. 
Above the immediate din, I heard such remarks as "sounds like a freight
taking off!" Then came the question, "How long do you think it will take?"
Being rather uncertain, I said nothing, but Mr. Rose who was standing nearby
ventured, "At least three years." I need not repeat what I thought of that
remark, but in order to show the degree of accuracy in Mr. Rose's statement,
I can say it was three years to the month that I got my first look through
the 201-inch. 

Foolhardy enough to jump from a six- to a sixteen-inch, but not quite
irrational enough to tackle the complexities of a compound telescope, I had
figured that an f/5 Newtonian would be most practical from a mounting
standpoint. Several tools were required before reaching the desired
curvature-one having been ground completely through the tile and another
disabled when some of the tile parted company with the cement base in
attempting to free a stuck disc. 

The pitch lap was next. No statement has yet been uttered or written which
can adequately describe the perversity of pitch. The problem involves melting
three pounds of pitch, pouring it onto the pre-heated tool, then gently
sliding the (still 50 lb.) disc, with a deep curve, onto the pitch and
establishing perfect contact. The most convenient vessel at hand in which to
heat the tool and disc, was the bath tub. The pitch had to be melted in the
kitchen at the opposite side of the house. I do not know how a bachelor
amateur would cope with the problem of heating the tool and disc in the
bathroom, melting the pitch in the kitchen, and getting the two together at
precisely the right moment, but I was ably assisted at this point by a
long-suffering "glass widow." I would like to state here that the married
TN's work is made 100% easier by an understanding and lenient wife. My wife
faithfully tended the pitch and appeared with it promptly at the right moment
with pitch in perfect condition in answer to the family whistle during the
sixteen attempts before succeeding in making a satisfactory lap. My wife
standing over the hot stove, stirring the sticky, viscous mess of pitch
continually with a big stick to avoid air bubbles, was thoroughly aware of
what Shakespeare meant when he wrote, "Double, double toil and trouble." But
cleaning up the bathroom after an unsuccessful attempt, I must confess I felt
more like Brer Rabbit when Tar Baby got through with him. I obtained my
final result by covering the mirror with a thickness of wax paper, pouring
the pitch onto the wax paper, and slapping the tool into the wet pitch. I am
still not convinced that it is possible to make a pitch lap for a short focus
16-inch in the conventional manner. 

First polishing disclosed a hole in the center sufficient to warrant a return
to fine grinding to bring it back up. Final figuring was accomplished with a
nine-inch tool. And to the best of my judgment, with the dubious accuracy
obtainable with the Foucault apparatus used, a correction of 98% was
attained. John Brown's help was invaluable in testing and recommending
treatment for the particular difficulties that arose in figuring, and I don't
think I missed any. His original advice was that I should make several small
mirrors just to get the experience. I did not make the small mirrors, but
there is no way around it, because I certainly got the experience before I
finished. 

The tube and mount were designed from parts obtained from the junk yard, or
rather, the parts available at the junk yard produced the design. The
retractable screw of an aircraft landing gear was mounted on a cement base at
approximately the right angle for this latitude, with lugs for final adjustment. The screw came equipped with a differential gear at one end. With the main bearing (about a four-inch roller bearing) used as the polar axis and a 2-1/2" shaft slipped through where the axle would normally be, it serves very satisfactorily as a German equatorial mount. In order to use a larger declination axis, I replaced the roller bearings at that point with bronze oil lite bearings. 

Considerable thought went into the design of a tube. This proved a
considerable waste, for no junk yard could produce the needed materials. 
Spying some T-shaped aluminum alloy beams 3¬ x 2" and acquiring same, I
gradually developed a monstrous, oblong, box-like structure in the basement. 
When the pieces had been cut and fitted together, I recalled hearing about a
man who built a boat in his basement and then couldn't get it through the
existing doorway. Well, believe it or not, the 201-inch telescope was in the
same predicament. So, it was taken apart and reassembled in my wife's sewing work room where it resembled a telephone booth. My little five-year old
daughter described it more picturesquely when she excitedly called her mother
to the window one day. My wife, expecting to see a flying saucer, was met
with, "Look, a flying telescope!" Needless to say one of the neighborhood
boys was flying a box kite. 

The cell was made from the drip section of an Army coffee urn which is
conveniently equipped with very sturdy handles. The mirror rests on a
nine-point flotation system of cast aluminum. Most of the work was done with
hand tools and a small electric drill. There is only one welded joint and
that is where the plate which supports the tube is attached to the
declination axis. Although the telescope was built with a minimum of machine
work, the necessary and very vital machine work was generously contributed by
Rob Maulsby who is building a six-inch, and by Jim Stusak who has gone to the
other extreme from my homemade affair in building a very beautiful, perfectly
machined instrument. 

The telescope is in a state where it can be used with some unhandiness. Much
remains to be done, such as rack and pinion focusing, final alignment, and
clock drive - for I want to use it photographically too. Accomplishing these
things will have to be stretched out for if I could really call it finished,
I should have to become an observer instead of a Telescope Nut. Yet from what little looking we have been able to do with it, I am looking forward to
becoming an observer. I have seen faint, wispy nebulae, possibly never seen
before from Georgia soil; M-13 resolved beautifully - to borrow John Brown's
description, "Like a handful of diamonds on black velvet;" and the Orion
Nebula was exceptionally brilliant with splendid detail and pinpoint images,
much like the photographs taken by the observatories - except that I was
looking millions of light years out in space - and it was real - had color
and depth - and life.


A Historical Footnote . . .

The 201-inch telescope served well for many years in the Close's backyard. 
When the trees and city lights finally made the site a poor one for
astronomical observing, Bill donated the mirror to the Club, and it was given
to Howard Landis for use in his photometric work. Years later, it was mounted
by Tim Puckett and Jerry Armstrong in a fork mounting built by Tut Campbell
and his father. Earlier this year Jerry and Tim used the 201-inch to make
their famed discovery of a supernova in M51. A prestigious history for the
South's first large amateur telescope.