"The photograph, Figure 1, shows the mobile mounting truck. The retractile (swinging) stabilisers are used for alining the polar finder upon Polaris, as explained later. The steering tongue is detachable. The brace rods were found materially to reduce the oscillation of the mounting, which is inherent in the slender pedestal shown.

"The worm gearing of the hand drive is made with a V-form thread, the wheel having been hobbed with a 5/8", 11-thread USS tap. The V-form gear tooth is satisfactory for this service, if an arrangement be provided for accurately adjusting the backlash or looseness of the worm and wheel.

"The equatorial mounting was made, partly, from parts supplied by Mr. Elias. It is provided with babbitted bearings, which are found to be superior, in point of performance, to the ball bearings installed in an instrument built previously by others. Ball bearings have so little inherent friction that the instrument will not retain a given setting unless the brakes are set with some force.

"The circle wheels were made from gear wheel castings. The outer rim (in which teeth are cut) was turned down and that surface given a 1/8-inch coating of hard (bronze) solder. This was again turned down until a smooth surface was produced The circumference was divided in an engine lathe, using the lathe's gearing as an available indexing or dividing device.

"The polar axis finder, a new feature (Figures 2 and 3) designed by the writer, is arranged to compensate, semi-automatically, the angular distance of 1 degree 07" between the celestial pole and Polaris. The constellation Ursa Major is represented upon a disk, which is revolved until the position of its markings corresponds to the apparent position of the constellation itself in the sky at the time. If the main mounting of the telescope proper is then adjusted until Polaris is seen at the juncture of the cross hairs in the polar-axis finder, the polar-axis of the mounting will be found to be almost precisely parallel with the axis of the earth. The finder is mounted in gymbals (Figure 2) at its upper end, and the eyepiece draw tube is passed through an eccentric hole in a disk, which is rotatably mounted upon the frame of the equatorial mounting. This disk is engraved with a representation of the constellation Ursa Major and Polaris.

"First, the mounting is roughly set into alinement with the celestial pole, and the triangularly placed hand screws on the base are turned down against the ground. By varying the relative adjustment of these hand screws Polaris is brought to the intersection of the cross hairs in the finder. As shown in Figure 4, if Polaris is seen at the intersection, then the polar axis of the instrument will be almost precisely alined upon the celestial pole. I made this finder from the lenses of an old Kodak, and it was found to be quite satisfactory for its purpose."

WALLY EVEREST, that famous landmark of Pittsfield, Mass. (15 Allengate Ave.), after being teased and teased (he is so shy) has kindly furnished us several pictures of "The Old Town Pump," also a noted landmark in that quaint New England hamlet. How did it come to be e called Ye Olde Town Pump? Well, somebody thought the polar axis looked like a pump handle and, after that, that was that. Ye Olde Towne Pump has a Pyrex mirror, and look (turn the page) at those Ronchi bands! Everest had made 149 optical surfaces before he turned this one off, and this was his 150th. What we like about it shows best in Wally's "longitudinal cross-section" (as some genius recently described it): its rigidity. Study the details of that tapered polar axis. Then take a squint at the diameter of the declination axis. Then note the unusual setting circles-the indexing does not show, in the photograph, on either circle, as the light evidently caught them wrong. The declination circle is the light colored streak, in line with the polar axis. Note also the worms and the rollers. A fine design. We also received some other photographs of Everest as an artist's model but this is not an arty magazine, hence they had to be suppressed even if Anthony Comstock is no longer an obstacle. Too bad- they were beauties.

AND now we learn that Mary A. (Mrs. A. W.) Everest, same address, has made the first feminine aplanat on earth, so everybody give three cheers and three times three! And here, in the photograph, is Miss Sylvia Petersen, 963 Tenth Ave., St. Petersburg, Fla., with a Newtonian telescope she made. The moon in the background, likewise the stars, are not the real ones. Miss Petersen was chosen "Miss America" in a recent beauty pageant.

SEVERAL have worked out ways-some rather complicated and mathematical, some less so-for making the Ronchi test quantitative as well as qualitative, and the first to be published was that of J. H. King in the Journal of the Optical Society of America, Sept., 1934. We have been asked who was the first to work out a method, and the answer is, we do not know. Several evidently were at work on this problem at about the same period-Loren L. Shumaker of Dayton being one. Alan R. Kirkham of Tacoma, for example, sent us an outline of his method in March, 1934, and he has now, at our request, sent us the following succinct statement which is a paraphrase of the one he sent us then, and which we unjustly mislaid and overlooked at the time.

"The Ronchi test may be used to measure the overall correction of a mirror very simply, in the following manner: Adjust the grating so that two bands at the center of the disk are 1 inch apart (say) and mark the position. Now move the grating back so that the bands are 1 inch apart at the rim.

The move should amount to if the correction is right." This statement should be substituted for the one on page 267 of "Amateur Telescope Making" where it states that "the Ronchi test is not quantitative," and in the next corrected reprinting of the same book; it will be so substituted.

THE following is our present list of clubs of amateur telescope makers. Prior to its publication elsewhere, we wish to obtain all corrections for this list, also similar data regarding telescope makers' clubs not now listed in it. We wish also to compile a separate list of purely astronomical clubs.

Telescope Makers of Springfield, A. D. Baker, President, Springfield, Vt.

Astronomical Society of the Stanley Club, A. W. Everest, President, 15 Allengate Ave., Pittsfield, Mass.

Tri-City Astronomical Club, Bernhard Nordblom, Jr., Secretary, 929 Grand Ave., Davenport, Ia.

Amateur Telescope Makers of San Francisco, Dr. Frances P. Epley, Flood Bldg., San Francisco, Calif.

Amateur Telescope Makers of Berkeley, Dr. W. T. Bush, American Trust Bldg., Berkeley, Calif.

Amateur Telescope Makers of the Golden Gate, a federation of the San Francisco and Berkeley clubs named above, with Oakland and other Bay cities clubs, addresses of the latter unknown.

Academy of Science and Art of Pittsburgh, Astronomical Section, Leo J. Scanlon, Pres., 1405 East St, Pittsburgh, Pa.

Amateur Astronomer's Association, Telescope Makers' Section, Ramiro Quesada, leader, American Museum of Natural History, New York, N. Y.

Amateur Telescope Makers of New York, Lew Lojas, 1510 White Plains Road, The Bronx, New York, N. Y.

Amateur Telescope Makers of Chicago, William Callum, Sec., 1319 West 78 Street, Chicago, Ill.

Amateur Telescope Makers of Cincinnati,

W. Clemmer Mitchell, Sec., 2390 Wheeler Street, Cincinnati, Ohio.

Amateur Telescope Makers of Indianapolis, V. E. Maier, Sec., 1306 Parker Ave., Indianapolis, Ind.

Amateur Astronomical Society of Los Angeles, E. A. Letscher, 1016 S. Normandie Ave., Los Angeles, Calif.

Amateur Telescope Makers and Astronomers of Tacoma, George Croston, Sec., LaGrande, Wash.

Eastbay Astronomical Association, Telescope Makers' Section, Franklin B. Wright, Chairman, 155 Bret Harte Road, Berkeley, Calif.

Amateur Telescope Makers of Buffalo, Thaddeus Czerniejewski, Chairman, 113 Franklin St., Lackawanna, N. Y.

Amateur Telescope Makers of Dayton, William Braun, Sec., 115 Bolton Ave., Dayton, Ohio.

Detroit Amateur Astronomical Society Howard Morehouse, 4336 Dickerson Ave. Detroit, Mich.

Amateur Telescope Makers of Boston Wagn. H. Hargbol, Pres., 600 Beech St., Roslindale, Mass.

Amateur Telescope Makers of Kansas City Edward F. Bowman, Pres., 1406 Ewing Ave., Kansas City, Mo.

Westinghouse Astronomy Club, Fred C. Wilharm, Box 63 Homestead Station, Pittsburgh, Pa.

Astronomers' Guild of Jamestown, J. Elwood Johnson, Pres., 28 S. Main St., Jamestown, N. Y.

Amateur Astronomical Association, Joseph A. McCarroll, Pres., 521 Palisade Ave., Teaneck, N. J.

Louisville Astronomical Society, O. W. McCarty, Pres., street address unknown, Louisville, Ky.

WE are running to rather lighter stuff this month, as relief from heavier stuff, past and future. Here are two items from men who believe the world is flat. Whoever supposes that such people do not exist in this century should sit for a few days at the receiving end of an editor's mail.

Arthur C. Bates, 322 B St., Marysville, Calif., who asserts that he is the only authority on the flat earth theory, claims that the earth is a huge island and says that the sphere theorists (that's the rest of us-or so we suppose) claim that the earth is round. But, he says, they cannot account for the fact that if this is so, the River Nile must run uphill for over 30 degrees. Mr. Bate challenges all believers in the sphere theory of astronomy to prove their theory, and disprove his claims that "the earth is a huge island, flat, so-called."

Unlike Mr. Bates, who claims to be the only authority on the flat earth theory, Mr. H. M. Tozer, 8 Victoria Road, London, S. E. 19, England, says he is only a keen student of the same theory. He wonders, he says, how people can go on asserting that the earth is a ball, when there is so much evidence against it, and then proceeds to cite various evidences.

Come now, all ye who dare risk being proselyted to a flat earth theory, and write to Messrs. Bates and Tozer. But please, kindly, leave us out of it; we have our regular job to attend to, and to keep out of an argument we would almost agree that the earth is a huge island, flat!

IN the February, 1934, number we published a discussion of photo-electric telescope guiding, by L. Jackson Bulliet, and followed this up in July and August, 1934 with contributions by Messrs. Silvertooth and Barkelew, respectively. Mr. Bulliet has been working on the problem, in the meantime, and while he does not claim to have solved it-a formidable task, we fear-he does send in an interesting progress report.

"Upon my return to Indiana University in the fall of '34," he writes, "I adopted this matter as the problem for my master's thesis, and immediately banged into the trouble predicted by Mr. Kirkham-star light is so exceedingly feeble that only the most sensitive photo-cell can be considered for use and this must be supplemented by remarkably powerful current amplifiers. I soon saw that our research budget would not permit buying four cells and four amplifiers. However, I saw I could cut it down to one of each by confining the operation to drift in right ascension. This is permissible in stellar photography, since the north-south drift may be entirely cut out by careful orientation of the polar axis. Of course this precludes using the machine on comets and planets which drift appreciably in declination.

"Having decided to stick to right ascension (or clock inaccuracy) guiding, I saw that the drive clock could be deliberately set ahead or behind sufficiently to mask the irregularities of going, and thus always give a net drift in the same direction. Hence we can use one cell and have it energized whenever the star image drifts off a knife-edge in the focal plane-it won't drift the other way.

"Well, I built such a machine, using a special cell made by Dr. Kunz of Illinois University and General Electric's FP-54 amplifier tube-33 dollars each for these two pieces. It seems to be sensitive enough to respond to the very brightest stars, but there is always a little erratic current of about the same order of magnitude as the cell current. So the arrangement is not yet ready to use for photography. I am still hopeful of increasing the sensitivity, but find my time limited by my duties as assistant in the department. I have delayed writing, in hope that I might have definite positive results to report, but decided to let you know that I am still plugging away at what I still think is an important problem."

HERE is a hot one! It seems that R. W. Porter and Byron L. Graves (A. T. M., 136,358) were standing on a street corner in Los Angeles talking about telescope making and mirrors in general, and Graves was frequently using the expression "surface of revolution." The next thing that happened was a sudden descent on these two bewildered optical enthusiasts by a police radio car with a small riot squad. It appears that some woman, passing by while they talked, had breathlessly notified the police that "two desperate looking characters were plotting a revolution,-she had heard them-right on the streets of Los Angeles!" O. California! O, Los Angeles!

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.