"Having completed the concave mirror in good shape it did not take long to mount it temporarily and, after a few crude attempts at seeing the moon, using a small looking glass for the diagonal, I commenced to believe that the job was worth finishing. So I made a prism of ordinary plate glass to replace the rough diagonal mirror, bringing each face of this prism flat to within a wavelength of light. Two eyepieces were made from lenses secured from a local camera repair man and these when used with the telescope gave magnifications, respectively, of 80 and 130 diameters.

"The mounting I finally made is admittedly a bit light but is satisfactory when there is no breeze to shake the telescope. It has 3-1/2 inch dividing circles which were indexed from a 72-tooth gearwheel. This gives me a fairly accurate line for every five degrees of declination and every 20 minutes of time in right ascension. The finder is an eight-inch length of half-inch tubing with the eye end stopped down to an eighth of an inch. No lenses are needed and it works well enough.

"How much did the telescope cost? Well, all my spare time for six weeks, some gibes from my family (previous to completion; afterwards quite the reverse) and the exercise. The moon provides an interesting sight. So also do Jupiter with his four visible satellites, Venus, a number of double and other interesting types of stars and a myriad of stars where to the naked eye there is blank nothing."

Mr. Groh requests the Telescope Editor to comment on the glass he used, that is, common plate glass. This is the kind used by all amateurs (and by professionals, too) on sizes up to 12 inches in diameter. Expensive optical glass would not serve the purpose better. For a six-inch mirror the glass disks should be three fourths of an inch thick. These disks may sometimes be secured locally, but they can be obtained from a special dealer, all put up in ready-to-begin-work form, with the correct kind of pitch and abrasives, for about ten dollars. Other parts, required several weeks later after the essential concave mirror is complete, may run the cost up to about twenty-five dollars, but the finished product should perform on a par with a 300-dollar instrument. A six-inch reflector equals a four-inch refractor in general performance.

F. L. SCARBOROUGH, 2105 Fourteenth Avenue North, Birmingham, Alabama, has made one of the telescopes of the type described by John M. Pierce, in "Amateur Telescope Making." Mr. Scarborough. writes, "This simplified design was followed closely because the writer's knowledge of mountings, upon beginning the job, was negligible. There was only slight difficulty in any part of the work. My first attempt to make a polishing lap was a failure, but on reference to 'Amateur Telescope Making' it was decided that the a pitch of which the lap was made was too hard, so it was tempered slightly with turpentine and a softer lap prepared from it. Polishing with this lap was uneventful and the job was soon finished. (In the average case this takes about six hours-Ed.) "Silvering by the Brashear process, as per instructions, was successful upon the first attempt. The directions for silvering were followed explicitly, using every precaution against contamination of the solutions.

"The results obtainable with this simple instrument are surprisingly good, amply repaying the slight expense, in this case about fifteen dollars which included the ready-prepared mirror outfit. The topography of the moon is strikingly clear and the effects due to changes in its phases are a wonderful sight. The planets are a delight. One view of Saturn with his rings and satellites, is generous compensation for the production of a telescope of this kind. These sights, together with others too numerous to mention, inspire one to a systematic study of science."

Mr. Scarborough's experience is typical of many others. It is perhaps difficult to believe that a raw beginner, with no more skill than is implied by the ability to do various handy jobs and with the possession of a little patience, can make an astronomical telescope that is more than a mere toy. But a six-inch mirror-the size best suited for the beginner-will magnify 100 diameters, and even at the large observatories it is seldom that more than 400 diameters magnification is used in studying planetary detail. That much magnification can be had with a 12-inch mirror which the amateur should be able to make after making first a six-inch mirror and preferably another intermediate size. Usually the beginner inclines in advance to regard the job of making the mirror as a task, but soon finds it is a real pleasure and wants to do more of it, so he makes a second and larger telescope; some have made several.

THE letterhead of Thomas F. Scanlon, 1405 East Street, N. S. Pittsburgh, Pennsylvania, gives evidence that he is a plumbing and heating contractor, but in his letter he says "I am a plumber, and I admit it. " Mr. Scanlon's telescope is mounted almost entirely with various pipe fittings and plumber's accessories. This, of course, has been done before, though not so thoroughly, and this method has amply made good. These fittings are inexpensive and readily obtainable anywhere. The yoke that holds Mr. Scanlon's telescope tube was stated to be part of an old toilet tank and the retaining bands came from an old bricklayer's level. Their ends consist of brass sink bolts soldered on.

"The tube," writes Mr. Scanlon, "was made of 22-gage galvanized iron and cost one dollar fifty-six. The mirror is a six-inch and was completed during the evenings of two weeks. The eyepiece socket is part of an old wash-stand drain and some pieces of lead sink waste pipe, while the extension was made of nickeled tubing from an old wash-stand trap.

"The cell is a seven-inch perforated brass ring, a stock item in our business, having a raised seat on which the mirror rests. Three brass sink bolts were soldered radially to the circumference. These bolts fit into slots in the lower end of the tube and are held by wing nuts with washers. Similarly the mirror is held to the brass ring by three more sink bolts on which it rests. This perforated cell allows half an inch clear all around the mirror, permitting ventilation of the mirror at all times. (A fine idea, as it controls the temperature changes that may distort a mirror and affect its performance-Ed.)

"Results?" Mr. Scanlon inquires. He answers his own question, "Yea, bo!"

THIS letter shows what a wide variety of picked-up second-hand dingbats an ingenious amateur can adapt to use in a home-made telescope. Most plumbers, in our own experience, are not half so resourceful, at least on jobs you get them to do for you. This, however, may be why Mr. Scanlon, who describes himself as a plain plumber, is really a plumbing and heating contractor. Readers having a nasty disposition may wonder whether a plumber when he is doing this kind of work for himself, ever has to "go back for his tools." How does he figure up his time, and does he charge himself any profit on it? An anxious, breathless world would like to obtain these scientific data from a brother telescope maker who is presumably on the "inside."

ALL telescope makers are invited to send in photographs of their completed telescopes.-A. G. 1., Tel. Ed.

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.