No matter how hard you try to eliminate all mistakes at the time of the proof stages of a technical book, you may be morally certain that some mistake will "hide out." The previous edition of "Amateur Telescope Making" was in use four years before some of its mistakes were discovered and reported to us. In the new book we corrected the 25 or 30 of these we knew of, by patching the plates. Readers who find further mistakes in the new edition are asked to report them early, so that an erratum sheet may be prepared.

"Amateur Telescope Making" should have contained a chapter on clock drives, mainly electric. An amateur specialist in that corner of the game promised us one but did not come through. Who therefore will contribute a compact, concise chapter on this subject, written for the man who knows nothing about it, and full of practical, concrete, not merely general, facts? The best one will be published in this department, with credit to its author. Payment in the form of "glory." About 1000 words-no more. Also, who is in a position to contribute equally practical instructions on designing setting circles for various types of telescopes and on making them? This telescope making hobby is becoming so ramified that we lean more and more on those who have worked up exhaustively some one special corner of it. The chief trouble is to locate these modest shrinking violets who are working out new information, yet who omit to transmit it to us and through us, to others.

AS a Christmas card, Gustavus Wynne Cook of Wynnewood, Pennsylvania sent us a 10-by-13-inch photograph of the moon, made with his new 28-l/2 inch Fecker reflector, and we now reproduce this "card" here. Another photograph shows his 40-foot focus photoheliograph. This consists of an 8-inch heliostat inspired by II and III, Figure 36, Part I, of "A.T.M." and made by himself, with a five-inch lens photographically corrected. The eight-inch Pyrex flat is unsilvered and is wedge-shaped so that the rear-surface reflections are deviated about two degrees. The focal plane shutter at the rear of the house (through small window and a "tunnel") is operated electrically from the pier. Other pictures of Mr. Cook's equipment were published in the August 1932 number, page 74. (See also the new "A.T.M." page 139.)

FRANKLIN B. WRIGHT, 155 Bret Harte Road, Berkeley, Calif., sends a photograph which we reproduce, and states that "this is the mounting of the 6-1/2 inch telescope I used as the basis for the article I sent you a short time ago. (Now chapter Vl, "Accuracy in Parabolizing a Mirror," Part X, "Contributions by Advanced Amateurs," of the new "A.T.M."-Ed.)

"A four-watt Telechron motor geared for sun time is used for clock drive to 100-tooth worm gear below Ford brake drum, which carries a right ascension sidereal time circle to be set on a known star at the beginning of an evening's work. The simplicity of the gearing arrangement more than compensates for the error of the clock (four minutes a day). ~

"The telescope tube rotates in its cradle to get the eyepiece into a convenient position. With a 1/2-inch eyepiece, giving 125 power, the mirror plainly shows Cassini's Division in Saturn's rings, the shadow cast by the disk on the rings, several belts on the disk, and at least four of the satellites."

A LONG time ago we harped a bit on the superiority of wooden tubes over metal tubes. Since then a few have been made and there seems to be a fairly general agreement that the amateur observers in Great Britain are right in preferring wood, because that material tends to diminish temperature troubles. One type of wooden tube-octagonal-was used long ago, by Sir William Herschel. Oswald Hardy Evans, Casilla 48, Valparaiso, Chile, has copied an old drawing of one by that maker, now preserved in the Radcliffe Observatory, at Oxford and this is reproduced here. The drawing is self-explanatory, though it is doubtful whether the mounting itself is as efficient as a modern equatorial would be.

Miguel Angel Mendoza, Jr. and his father, Dr. Miguel Angel Mendoza, San Lazaro 305, Havana, Cuba, have made a telescope with an octagonal tube of oak. It is a six-inch of f/10. Now the junior Mendoza is at work on a 10-inch. He wishes to get in touch with other Cuban amateurs.

Winston Juengst of the University of Rochester states that boiling lump rouge vigorously for an hour so will reduce it to fine particles. This is done in professionals' shops he adds. Try it.

Another interesting item is that a club named "The Detroit Amateur Astronomical Society" has been formed with 25 members. Eight telescopes have been finished. The secretary is Howard Morehouse, 4336 Dickerson Ave., Detroit, Michigan.

Frederick E. Ward, Box 25, Calumet, Massachusetts, states that he checked a synchronous electric clock in New Jersey against Arlington time and found that the errors ran up to 13 seconds. Has anyone any further sidelights on such scandalous performances of supposedly synchronized time?

Dr. H. Page Bailey of Riverside, California, protests our description of his mounting (January number, page 51, as a "Porter type." It is always hard to say just exactly what a design is, because one type so often shades off into another. Bailey's mounting uses a double yoke in connection with the Porter split ring, and so it's a Porter type if you accent the ring and a Bailey type if you accent the yoke. As Porter has not contested it, let's accent the yoke and all stay happy.

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