"The telescope has a synchronous motor clock drive as well as electric fast and slow motions, push button controlled. The electric drives, which I constructed myself, are all ball bearing equipped and operate perfectly. All polar axis controls work through the same drive gear using a differential for the slow motion and an electric clutch for the fast.

Interchangeable sleeves for the tube are used for the Newt-Cass transfer. There is no hole in the mirror so a lower prism is used. The telescope is very rigid and easily controlled.

"Any other ammeters wishing more information about this telescope can obtain it by writing to me."

And Mr. Diller writes: "I am employed in the Glass Section of the National Bureau of Standards and, being associated with experts in optics and engineering, I became interested in astronomy and then in building the telescope. I consulted with Dr. Ritchey, the well-known telescope builder, and my instrument is of the fork type mounting similar to that used by him on the 40" 'scope that he built for the U. S. Naval Observatory here.

"I ground and figured the 12-1/2'' mirror by hand, doing the work evenings and in my vacation periods over a time of about five months. I also had the use of a machine shop and the machine work was done nights and Sundays over a period of one year. The patterns and castings for the forks, bearing mountings, and uprights were made by local firms and the large 20" driving gears, as well as the other various gears and worms, were purchased from the Grant and Boston gear works.

"The synchronous motor drives the polar axis through a 20" worm gear. One motor drives for fast, the other for slow motion through the same 20" gear, by using a differential for one and an automatic clutch for the other. There is a motor drive for declination, and all motors are controlled through a push button unit which is carried in the hand by the observer.

"The instrument may be used as a Newtonian or Cassegrain by interchanging the top sleeve, one sleeve having a prism for the Newtonian, the other for the secondary. With the assistance of the Rev. Dr. Sheehy and Mr. Ernest Valada I obtained permission to mount the telescope at the Catholic University."

Data on the clock drive of this telescope will be included in "A.T.M." Vol. II, the renamed "Supplement."

OLD stereopticon lenses make good finders for telescopes, according, to Cyril C. Wates, 7718 Jasper Ave., Edmonton. Alta. "I bought one cheaply in a secondhand store," he states, "and discovered that the front combination was semi-achromatic covered a very wide field and gave lots of light. With a cheap 1" eyepiece and No. 40 cross-wires it makes a splendid finder. There must be thousands of these old lenses on the market. Remove the rear lens, solder a tube on the back of the mounting, and focus by means of the rack and pinion already found on the lens. Such groups as the Pleiades look fine in the finder."

Readers often inquire what use to make of such lenses, and here is the answer.

AN English firm (Watson) advertises an odd but interesting stunt: a 15" single lens hung in a front window. "If the 'observer is 6' from the lens the distant objects appear enlarged 1-1/2 times, and the greater the distance of the observer the greater the magnifying power of the lens. One may recognize the visitor far down the drive and, if desirable, establish an alibi in time, also watch birds and so on." It ought not to be difficult for the amateur to fix up something similar. It wouldn't be achromatic, but probably would distinguish a bill collector in time.

A WRITER in Nature suggests that the unsteadiness of the images so often given by reflectors arises largely from the fact that their mirrors are so near ground level where the air is disturbed by temperature differences. As refractors generally give steadier images than reflectors, this is a point to reckon with. The mirror lies closer to the ground than the objective of a refractor. In past generations acres of paper have been covered with published arguments about the superiority of the reflector, over the refractor, though many reflector owners concede the point to the opposition, in their franker moments. But it is easier and less expensive to build a fair-sized reflector.

WAY back in prehistoric days when the telescope making hobby was evolving from the ape stage, we published (Feb. 1929) a letter from Dr. J. J. Byl, 430 S. 13 St., San Jose, Calif., describing his telescope, and in it he wrote: "I am a retired physician well along in years but have great anticipations of joy in so profound a study as the boundless Universe, and I am sure that my days will never he shortened by a loss interest in life." At that time he had already made a 10" and a 12" telescope. Seven years have gone by and here is what we now hear about the same Dr. Byl, written by Ralph Dietz, 330-1/2 S. Fifth St., San Jose. "I enclose a picture I took of Dr. J. J. Byl and some of his many 'scopes. He is a rather elderly man and all he lives for is to build telescopes He has on hand, that I know of. two 12", four 10", several 8", one 15", and, 'The Howitzer' or 22". The photograph shows the last named two. His mind is 1 running on all six and he will try anything once."

And so Dr. Byl's own prediction very happily turned out to be true. So far as we know, this 22" is the largest amateur telescope, though Hindle is now building a 30". No doubt when Dr. Byl hears this he will tackle a 31"!

WITH so much amateur talent constantly dwelling on every corner of optics-and having what the professional lacks, namely, the leisure time to think-the whole ground is continually being gone over and over, like a hungry monkey in a cage hopefully pawing over the straw for a few uneaten peanuts. The special ground covered by tests seems to be exploited the most with the result that new tests are being found, and old tests which have been lost sight of or never learned of are being dug up, often several times and independently. An amateur who independently discovers a valuable test which other amateurs or else professionals have long since used, usually feels but little cheered upon being told that, anyway, the high regard with which it has been held "for the past century or two" does flatter his judgment in developing it independently. Every little while, for the past decade, a report of a newly discovered test has been sent in, and it takes courage to reply to a man who believes he got there first that the discovery, even if original is not the first. Of course, the standing rule in science is that the first fellow who publishes gets the credit. Often this works hardships, but it also helps forestall arguments.

There are tests and tests. Some are of major importance while others are of lesser though considerable importance. In a few instances workers have claimed invention or discovery of things that seemed almost self evident-though the ones to be described below are not to be thought of in that light. Hundreds of other inventions have been re-invented several times. Recently we read of the invention of the safety pin in the last century. But MacCurdy's "Human Origins' shows pictures of safety pins, almost identical with our common modern diaper pins, from Bronze Age deposits in Greece. The invention was evidently lost and re invented in the last century. The power loom, metal pens, and many other things were invented long ago, forgotten and then re-invented. But all of this is not meant to discourage amateur opticians from reporting their original ideas, whether they turn out old or new.

Last year, on July 12, Floyd L. Frazine, 868 Central Ave., St. Petersburg, Fla., suggested testing a convex surface by means of interference fringes between it and a concave test plate. Thirteen days later Wilbur Silvertooth, 273 Ximeno Ave., Long Beach, Calif., independently suggested making "a concave master, using the tool for the final convex secondary and figuring to appear flat in conjunction with the test mirror; then polishing the concave and figuring by checking on the concave master until the fringes are straight. But," he added, "I have learned, since having this idea, that all Cass secondaries by Zeiss are figured by interference against standard masters." Largely on account of the last statement publication was put off, and last March, J. V. McAdam of Hastings-on-Hudson, N. Y., wrote that he had figured out a way to short-circuit hard work: "Fine grind the convex with a concave polish the mirror, lay it on the tool and observe the interference fringes through the tool." The same general idea.

Well, this makes three who have independently thought of this method, and it is too bad it proved to be an old one. Perhaps other amateurs can give them a cheer anyway; it isn't their fault that they were born 30 years too late! Still further, Ellison comments: "I too have found that it is not difficult to test Cassegrain convexs from the back, treating them as concaves. There is an error, but it is not great, and can be allowed for." And Hindle: "I have never used this method, on account of the danger of scratching the surface, but I believe the system is extremely old, and in very general use amongst manufacturers for checking the curvature of convex lenses."

A similar case of independent discover was that of Joseph E. Boehm, 3511 N. Seminary Ave., Chicago, who tested a 14" perforated primary against an 11" flat placed inside the focus. His letter was referred to Hindle, since the latter was known to be especially interested in tests, but without knowledge on our part that the same test had actually been published by him in English Mechanics (April 20, 1923). Another case of independent discovery. Boehm found the test invaluable to short focus mirror workers, he states.

Several amateurs discovered different ways to make the Ronchi test quantitative but it now looks as if Ronchi himself published the first method. If we could read Italian we might be more certain about it.

About 1933 Alan R. Kirkham suggested a test in which the pinhole is placed at the focus of a paraboloid, the rays being reflected as parallel rays and received by another paraboloid, then brought to focus and cut by the knife-edge. This was published only as a multigraphed sheet which not everyone saw, and in 1935 William Mason of Lorain, Ohio proposed exactly the same test. Even then we failed to publish it, and later that year James Hart Wyld of Princeton University made the same proposal. By that time Kirkham had actually tried it and, when shown Wyld's letter, he wrote, "This is my test, but I'll be darn glad to give it away; I don't remember who gave it to me or I'd kill him. The main trouble is collimation, also diffraction effects." We did not publish this, and not long afterward S. H. Sheib of Richmond proposed the very same test. That makes four separate optical geniuses or else one optical genius and three geniuses in mind reading.

We now publish these various notes on tests in order to forestall others who may be devoting good time to the re-invention of these earlier ideas, but not, however, to discourage anyone from discovering an important new test which would add to the prestige and standing of the amateur telescope maker and be an aid to science.

MANY different dodges have been worked out to avoid spending long hours in polishing telescope mirrors. J. J. Stoy, 501 City Hall, Atlanta, Ga., states that he polished a 12-1/2" Pyrex mirror in less than 9 hours, by using a suggestion of another TN, Mr. H. E. Bussey, in his city "Settle No. 303-1/2 for 60 minutes, first stirring it thoroughly. Siphon off the water. Settle 24 hours and dehydrate. Mix the residue in 3 tablespoonsful of water and 1 of glycerine, to neutralize the evaporation effect as far as possible. Grind in 10-minute wets, alternately with mirror and tool on top. Mix the water and glycerine before putting in the emery; otherwise trouble."

TO answer those who inquire about the new book (Supplement or "A.T.M,' Vol. II) on which we are still working, and ask when it will be ready: at present (May 28) about a score of major contributions are in and "ready for printer." Three still remain to come. Hence it is yet impossible to name the date.

Exhibition: International Astronomical Exposition, Sociedad Astronómico de España y America, Señior Don Federico Armenter de Monasterio, Secretario General, Calle Cortes 573, Barcelona, Spain, in October. R. L. Beardsley, 2515 W. 21 St., Los Angeles, Calif., who is a member of this organization, states that the society wishes to get in touch with American amateur societies and supply dealers who will exhibit. Leo J. Scanlon, 1405 East St., Pittsburgh, Pa., plans an exhibit and is open to suggestions regarding material, which is to be sent to Spain Aug. 1.

One hundred amateurs wanted, once and for all time, to verify or destroy claim that a 6" telescope can "read a watch at half a mile." Send reports to Exaggeration Dept., in care of Ye Olde Scribe, this magazine.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.