MR. W. L. Chamberlain, 519 Liberty Street, Meriden, Connecticut, sends in a photograph of his telescope and writes as follows:

"A talk on telescope making by one who had made a very successful telescope himself, inspired me to attempt the same thing. A friend loaned me a copy of 'Amateur Telescope Making,' and after securing glass disks and other materials, a start was made. The photograph submitted shows the finished instrument, a six-inch Newtonian reflector of 48-inch focal length.

"In grinding the mirror mistakes were made, as is usual with the novice, but the work proved to be so fascinating that the extra time required to make corrections was not regretted, for it was a good schooling in the art.

"Not wishing to be confined to a post and one location, it was decided to make the mounting of the alt-azimuth type, so that a tripod could be used as well. The sockets for the fork stem are identical on each. The fork, which has an offset angle, allows the tube to clear the post when directed at the zenith. The whole sky is seen. "The post is an iron pipe 3-1/2 inches in diameter, surmounted by a metal ball which just fits the inside diameter of the pipe. This ball is drilled and tapped for a short piece of steam pipe which makes the fork socket, and is held in place by three pointed set screws which are inserted through threaded holes near the top edge of the post into countersunk holes in the ball, one half of which protrudes out of the post. Two of these set screws are placed so that they form an axis on which the ball socket tube can be tilted over toward Polaris, thus forming a polar axis by which the telescope can be converted quickly into an English equatorial. The third set screw looks the ball in either position. The fork has two removable pins at the angle which, being reinserted in other properly located holes, straightens the fork as is usual in equatorial mounts.

"When the telescope is used as an alt-azimuth, the eyepiece is inserted in the end of the declination axis. This gives the observer the great satisfaction of always having the eyepiece at the same height from the ground no matter where the telescope is pointed, and always directly above the post. This makes it possible to use a detachable bicycle seat on the post.

"The performance of the instrument exceeds my expectations. The definition is good. With my strongest eyepiece, estimated, with my focal length, to give 90 diameters magnification, the components of Zeta in Ursa Major are thrown wide apart that is, Sidus, Alcor, and Mizar; and then the larger component Mizar is again split up into a close but clearly defined double. Star cluster M13 in Hercules gives momentary glimpses of individual components.

"I want to say a good word for honeycomb foundation strips in bringing up a low center when figuring a mirror. It is a most valuable addition to the possible methods of doing it."

AN interesting, though brief, letter has been received from Mr. G. O. Neser Senior Science Master at the Boys' High School at Paarl, South Africa. He writes:

"Sir:

"As I recollect seeing only one photo of a South African amateur's telescope published in your journal, I am sending you a snap of my reflector. It has a six-inch mirror, focal length fifty-two inches, and is mounted temporarily and rather precariously as shown.

"I am very much indebted to the SCIENTIFIC AMERICAN for initiating me into the mysteries of mirror making. I am starting on a 10-inch one shortly. Kindly have your book department forward me a copy of the latest edition of 'Amateur Telescope Making'."

MANY amateur telescope makers have jumped from six inch to eight or ten inch size on their second instrument, or even to larger sizes. Few have jumped quite so far, however, in refinement of mounting, as Mr. Ralph C. Patton of the Patton-Macguyer Co., Baker Street and Virginia Avenue, Providence, Rhode Island, makers of stampings and novelties. At our request Mr. Patton has prepared the following description of his instrument:

"The telescope shown in the illustration has a clear aperture of 12 inches and a focal length of about eight feet. The mounting is of the English fork type, which is inherently balanced without counterweights. A tapered cylindrical aluminum easing, threaded inside throughout its length to break up light reflection, forms the main tube, and is forced into the short cast-iron barrel which acts as the lower end of the tube. This barrel is also threaded inside, so that no part of the interior presents a reflecting surface.

"The cast-iron fork has a tight, forced fit on the end of the polar axis. The latter is made of chrome vanadium steel, heat treated and ground to exact size.

"The principal mirror is about 12-1/4 inches outside diameter, and is about two inches thick. It weighs 20 pounds and is mounted in a revolvable cell, with three sets of push-and-pull screws for adjustment. The revolving feature was devised so that true axial alinement of the mirror could be determined readily.

"The sky end of the tube has a cast aluminum revolving head, carrying eyepiece and finder to insure a comfortable position for the observer, regardless of the altitude of the object being observed. The finder has a two-inch aperture.

"Five eyepieces are provided, and these can be used interchangeably in the finder or main telescope. In the latter they give magnifications varying from 64 diameters to 500.

"The mounting has closely divided circles, and is provided with clamps and slow motions for both declination and right ascension motions. The principal right ascension dial is rotated continuously during observation by means of a synchronous induction motor, which drives it through three sets of worm reduction units, having a combined ratio of more than 2,500,000 to 1.

"In using a synchronous motor drive for a telescope, it is necessary to interpose a pair of meshed gears having respectively , 365 and 366 teeth, in order to change mean solar time into sidereal time. These have helical teeth to reduce vibration.

"The frame which carries the main tube is provided with two precision spirit levels for zenith setting. The declination axis and the polar axis run in eight ball bearings, which are protected from dust by felt washers within brass guards. All gearing is totally enclosed and runs in grease.

"The approximate weights of the principal parts are: base 1060 pounds; fork 410 pounds; polar axis shaft 104 pounds; assembled tube in ring with trunnions, mirror, cell, finder, and so on, 492 pounds; the total weight being over a ton.

"The telescope is housed in a sliding roof observatory, 15 feet by 18 feet, and the roof, which weighs about 2600 pounds, is moved on and off the building by a small -electric motor, operating through sprockets, tracks, and pinions.

"The telescope was designed, constructed and built in about two years. The mirrors were furnished by Mr. Wilbur Perry, of 'Springfield, Vermont. Inspiration for the work was furnished to a great extent by your book 'Amateur Telescope Making.' "

Amateur telescope makers may be surprised to learn that the first man to see the image of the new trans-Neptunian body on the photographic plate at Lowell Observatory was one of their number, Mr. Clyde W. Tombaugh. When the find was announced all the newspapers told how Tombaugh had made a telescope. Suspecting he might have used "Amateur Telescope Making" as his guide we looked in our file of purchasers, which is arranged by states, and found that he purchased the book in 1926. A wire brought from him the reply,

"I used 'Amateur Telescope Making' in the construction of my telescope." Apparently, however, when he made his telescopes he never sent in a picture of the instruments for publication.

In a letter he now tells us that he has been swamped with correspondence since the discovery was made but appreciates our interest, as a brother in the mirror art. At spare moments he says he is working on an article describing his construction of three telescopes, an eight-inch, a seven-inch and a nine-inch. In a later communication he apologizes for failing to keep his promise as he has been side tracked with extra work, but ultimately will do so.

We hope this matter will reach us in time for the next number. It appears that the construction of his telescopes led Tombaugh to throw in his lot for astronomy. He asked for a place as assistant at Lowell Observatory and was accepted. Quite romantic, as it turned out.-A. G. I., 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.