Rev. C. J. Renner, Trenton, Ohio (population 636), has managed without much actual cash expenditure to accumulate two good telescopes plus a serviceable observatory, and the letter he writes sounds as if he had had a great deal of fun in doing it. The two telescopes (Figure 1), one an 8" reflector, the other an 11", are built largely from spare parts-an iron wagon tire for a base, cast-iron 1 drain pipe for a pedestal, steering knuckle for. a polar axis, half of a rear axle housing for another. Such parts come ready made and in good proportion for adaptation to the needs of a telescope mounting.

The larger telescope has a tube skeletonized to obviate stray air currents that sometimes circulate within conventional tubes to the detriment of good seeing. Simply, ovals are cut out of it. This telescope has a flat instead of a prism for diagonal mirror and Rev. Renner says he found making it a most interesting job though it took a long time. He was permitted to machine the mounting at the Miami University shops, where he was helped through the woods by Prof. Wm. Albaugh, himself interested in telescope making. Leo J. Scanlon, of Pittsburgh, lent patterns for the castings.

"One great thrill," Rev. Renner writes, "was to build the little observatory. [Not yet finished when Figure 2 was taken.-Ed.]. Its total cost was less than $15, because it is made mostly of parts from the junk yards. I used water pump pulleys from Model A Fords for rollers under the revolving dome and the sheet metal was second hand, though the shutters are of new metal." He adds casually that, while doing all this, he also has been making household furniture and helping build a parish house. Maybe country parsons have more fun than city ones.

Tragedy? Not altogether. Suppose you had put in the spare time of two months grinding and polishing the concave mirror for a reflecting telescope, and then accidentally dropped it on a concrete floor, knocking the long slice off its edge that shows in Figure 3. That's what happened to Eugene R. Jolly, 3523 Fourth Ave., Los Angeles, California. Yet no great harm was done to the actual optical performance. Jolly made a new mirror, which incidentally required only 10 1/2 hours because the experience already gained enabled him to go straight ahead with the second job without running up blind alleys. Only then did he discover that the remains of the first mirror performed as well as the second one. There is no theoretical reason why a mirror or lens must be round. The base of Jolly's telescope mounting (Figure 4) is cast integral with the two uprights forming the polar axes. The two setting circles are 16" lids obtained from the American Can Co. and laid off to appropriate angles.

The electric drive is equipped with a variable speed motor, Model V-1OR, made by the Bodine Electric Co., Chicago, and the gears are from the Boston Gear Works. A three-way remote control switch permits the operator, while at the eyepiece, to run the drive at speed, or at approximately sidereal rate, or to stop it. Jolly states that experience in building this drive proves that there is no substitute for a good motor with plenty of power, which will save headaches later on.

He also comments on the fortunate fact that among amateur telescope makers there are as many ideas for telescope design as there are amateurs. He found telescope making fun, also that it taught lessons in patience and perseverance. He winds up: "I know of no greater thrill than the first night performance, when all the trials and tribulations of building were repaid a thousand fold by the first glimpse of the moons of Jupiter, the rings of Saturn and the Great Nebula in Orion."

How many who have made telescope mirrors can say that the work greatly increased their tenacity as applied to other things? In this sense it rates as a real character builder.

SUPPOSE the glass tool is broken? 0ne amateur says his tool broke squarely in two during coarse grinding a he glued it together, later used it as the base for his polishing lap, and got a fine figure on his mirror without trouble from this source. Another tells how he practically destroyed the tool by accident; it broke into about eight pieces. Yet, when cemented to the plate with pitch, it worked all right. Before doing the cementing he took pains to bevel the sharp edges, otherwise chips would have broken off and caused bad scratches.

Of course, if the tool should break after all grinding was done, and during polishing, a lap could be made any other rigid substance which was not warp (as would happen if wood were used, for example). Russell Porter, when a beginner, broke one and remade the lap on an old stove lid, and this dodge worked satisfactorily.

RAMIFICATION of amateur telescoptics is spectroscope making at spectroscopy, either for astronomic or laboratory use. Unfortunately, this ground never has been organized more than sketchily for amateur purposes-that is, there is no convenient amateur's manual of spectroscope making and spectroscopy. The existing literature is scattered, fragmentary and mostly takes for granted that the reader already is a physicist and knows much about the subject. For years about one request for such a manual has reached the editors each month. A little preliminary skirmishing revealed the probability that amateur spectroscopy, except possibly in limited way, is largely a contradiction in terms, because spectroscopy so quickly leads into the advanced physics that underlies it. In fact, on this account some assert that it simply cannot be made elementary or easy.

Now, in order to pay its own way the world, any book must be assured of a sale of several thousand copies, not merely the one or two hundred copies such as the limited number of advanced amateurs undoubtedly would absorb. Is the desired book on amateur spectroscopy then not possible?

The solar spectroscope is relatively simple; there is an abundance of light from our nearest star. For a few

other bright stars you also can rather play with a small spectroscope attached to a 4" or 6" telescope, but, in order to do much with the other stars, you need a considerably larger light gatherer. To the amateur this leaves only laboratory work in spectroscopy, using artificial light sources. On this the articles on the spectroscope and spectroscopy, in Glazebrooks "Dictionary of Applied Physics," are helpful but not elementary. W. E. Forbe's "Measurement of Radiant Energy" contains 33 pages on the adjustment of spectroscopes but, being aimed at the physicist, takes for granted a general familiarity with spectroscopes and spectroscopy. S. Judd Lewis's "Spectroscopy in Science and Industry" is an excellent little book. The Journal of Applied Physics, Nov., 1939, contains a bibliography on spectrochemical analysis, and the American Society for Testing Materials, Philadelphia, also has published such a bibliography. Yet none of these is really elementary, Lewis's book, named above, being the most so. The "Proceedings of the Optical Convention of 1926, Part II," shows the construction, but not actual instructions for the construction, of a rather elaborate goniometric spectroscope.

In short, the amateur who exploits spectroscope making will have to be resourceful in filling in the big gaps between existing pieces of literature, themselves hard of access.

There still are, however, quite a few amateurs who already know something of the general background of spectroscopy and spectroscopes and who might make their own instruments. For example, Austin F. Trumbull, Airline Liaison, Aeronautical Radio, Inc., National Press Bldg. Washington, D. C., has built the instrument shown in Figure 5. "I never fail to read the section of Scientific American on telescoptics," he writes "although my interest in optics does not center primarily around the telescope. I built this spectroscope for less than $50, around two old surveying instruments, one for the collimator and one for the telescope, which I bought for $10 each. One came from the Union Pacific and one from the City of Cheyenne and, from my inquiries, I gather that there are hundreds of these old 'transits' throughout the country. A base plate, the two transits, a good prism and a bilateral slit, and you can start to assemble. The only real problem is the slit, which is difficult to make. [See "ATM," pages 247-8.-Ed.] This particular assembly is not suitable for celestial work."

Asked to describe the instrument in detail, Trumbull begged off for one year because of absorbing preoccupation with a certain task of that length. Who among the readers can jimmy this subject open for the average amateur?

SITTING down instead of standing up is the really luxurious way to make mirrors. On the night in June, 1925, when your scribe first visited Stellafane to gather the material to write a story which started this hobby off among our readers, he showed Russell Porter a sketch of a sitting down grinding rig, the mirror to be rotated by the feet. Porter said this wouldn't be sportsmanslike; you must do it the hardest way (sacred New England tradition, no doubt). Not yet having made any mirror, and feel humble, your scribe subsided and it standing up.

Now comes Robert E. Smith, D.D.S., Medico-Dental Building, Sacramento, California, with the creation shown in Figure 6. He says: "Being dentist, I am on my feet much of the time and, after a long trek around the barrel at night, grinding a mirror my doggies sure do howl. Hence, he continues, "the machine that allows me to sit.

"The turntable lifts off, and removable galvanized pan catches all overflow. The motor and worm gear on the

concrete-filled tub base were taken from the slow motion of my first telescope. Fins were put on the motor shaft to slow it down. There are two gear reductions, 10 and 20 r.p.m., and a flexible shaft goes to the worm gear shown. The latter carries a pulley, and the belt gives the spindle, inside the pedestal, one revolution per 100 seconds, which may perhaps not be orthodox, but worked splendidly [is OK, and exact speed is orthodox.-Ed.].

"The spindle runs on ball bearings top and bottom. The turntable is removable (slot and key), facilitating quick, complete clean-up after each size of abrasive used, simply by moving and cleansing the annular pan."

Note the Doctor's stool, with its patent adjustment and soft cushion, plus a spiral spring near the bottom. What sybaritic luxury! Being 1azy, your scribe always wanted one of these but is also too lazy to build it, so what?

HINDLE grinding machines of the alligator type, described in the fourth edition of "Amateur Telescope Making," have made good; there are numbers of them in use. The one in Figure 7 was made by Alfred Bryant, 516 Eggleston Ave., Kalamazoo, Mich., who confesses he built it at first mainly to watch its wheels go round, since he felt that "making a mirror by hand puts the personality of the worker into the mirror." Later he "'fell for" this machine for mirror making.

He secured his speed reduction from an old washing machine, as he also did the alligator drive-it had been a wringer post drive. The take-off that drove the revolving cylinder of the washing machine, when reduced to half speed, worked out well for the side-throw motion. Result was 28 r.p.m. on the drive part, 6 r.p.m. on the side throw and 1 1/2 r.p.m. on the turntable. There is, of course, no cast-iron law about these speeds, many write to inquire for the "rule." The rule is, simply, use common sense. Don't give it so much speed that it performs like a speeded-up motion picture doing a crazy act but, instead, as calmly deliberate as a good hand worker moves.

Bryant had made eight mirrors by hand, so he started the machine on a 12 1/2" Pyrex disk. He found he still had a few new things to learn, but says the machine seemed uncanny with its variations of stroke. Grinding in all stages went like a top, and so did polishing. The machine even brought the mirror, an f/6.6, to a paraboloid "by first intention," as Ellison says. "Really," Bryant writes, 'it is a wonderful machine and does things impossible to do by hand. The way the mirror rotates in the opposite direction to the table, due to the loose rubber bumpers, is a corker, and it merely floats on top, just as Hindle states."

Bryant's log for the f/6.6 12 1/2" Pyrex mirror runs as follows:

Suppliers and Organizations

The Society for Amateur Scientists
5600 Post Road, #114-341
East Greenwich, RI 02818
Phone: 1-401-823-7800

Internet: http://www.sas.org/

At Surplus Shed, you'll find optical components such as lenses, prisms, mirrors, beamsplitters, achromats, optical flats, lens and mirror blanks, and unique optical pieces. In addition, there are borescopes, boresights, microscopes, telescopes, aerial cameras, filters, electronic test equipment, and other optical and electronic stuff. All available at a fraction of the original cost.

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