"For many years I have been interested in optics. I have computed and constructed two microscope objectives, one condenser (N.A. 1.32), two photographic lenses, and one 60-mm. apochromatic, three-element telescope objective. All this before last year. Then I chanced to meet the Lowers, local Tychonians, and my downfall was assured. They had a 12-inch reflector. I decided to build a 12-inch, and to do it backward. First, I made the mounting, placed in it two flats which I had made long ago, and used the 60-mm. objective. See photograph."

And now it is time to explain this telescope a bit. The picture [lower left] shows the counterweight turned up, and the temporary telescope in its baffled hood turned down. When in use, these are reversed, as in the right-hand picture, and the objective, shown turned earthward in the left-hand picture, is turned heavenward, as in the other. The optical train is: Through dark hole to a 60-mm. O.G., to a diagonal flat behind O.G., down to a second diagonal flat in the big pipe cross, and back up to the eyepiece which you see in the picture. On the head end of the dinosaur's body (the polar axis). Now imagine a 12-inch Cassegrainian mounted in place of the temporary box and O.G. part, and you have the job as Selby intends to complete it. This is the first time we have published an unfinished job, but it is an interesting one. Now to return to Selby's letter:

"Next," he says, "I made three 31-cm. flats on Pyrex, five surfaces of which were flat to about 0.1 wave, except for quarter-and half-wave edges. That was three months ago, and these surfaces have now changed, one by 0.4 wave. I then made eight more flats, for fun. Next I made an f/1 sphere for testing the Cass hyperboloid, à-la-Hindle." We wrote to Selby for more details about his telescope and here is the answer: "The base is of 3 : 2 : 1.5 concrete, in two piers 3 by 1.5 by 4 feet deep. This holds the grasshopper legs, of 2" extra-heavy wrought iron (E.H.W.I.) pipe, which support the mount proper. The polar axis is of 4" E.H.W.I., within the 6" E.H.W.I. body, and runs on two roller and two ball-thrust bearings. The bearings contain 160 quarter-inch rollers and 160 quarter-inch balls. They are housed in two 6-6-2-2 crosses. The head is constructed of one 6-6-6-6 cross, one 6-6-2 tee, one 6" close nipple, one 4" by 6" nipple' which is the declination bearing, a 4" by 15" flange and a 6" to 4" bushing with lock nut. The counterpoise, a 4-4-2 tee with plugs and lead, is carried by 2" E.H.W.I. pipe. All construction and design are my own, but such heavy lathe, work, done at night on a borrowed lathe, caused me many a back and headache. No machinist, I took a hundred hours to do what an expert would have done in 25, but it was fun, and the finished job is rock-steady at 300 diameters, even when slapped, and the movements are very smooth and precise. By means of four hand wheels, which are always within reach, the fine and coarse declination adjustments can be performed while observing, as can the fine polar movement.

"The optical system comprises a baffled hood, 12" long, a 7-cm. apochromatic triplet, two flats, and a series of eight oculars from 50 to 2.5-mm. e.f.l., all of my own construction and computation, save two oculars -a 2.5 mm. Beck and a 7 mm. Tolles The performance is good. Dawes' limit can be reached with the greatest ease. Using a microscope giving 200 diameters per inch of aperture, star disks are round at focus and on the rarely found fine evening the extra-focal images show clean, sharp ring structure.

"The mount is for the 30-cm. Cass, which is not finished, and is a hybrid embodying some features of the Coudé, Repsold's overhung astrograph, the Springfield, and Ritchey's 60". The stationary eyepoint is Coudé, the counterpoise is Springfield; the undercut mount, which will clear the Cass in an complete revolution, is Repsold, as is the complete visibility of every point in the sphere; and the hollow polar axis, for very long equivalent focus work, is Ritchey."

Commenting on Selby's telescope, Harold Lower says: "The present objective is a triplet, and is a fine job. Selby knows his stuff. He has also built a grinding machine."

A NEAT, unusual job is a reflector, apparently of about 12-inch aperture made by Chester A. Howard, president of the Dallas Astronomical Society, 3120 Princeton Ave., Dallas, Tex., assisted b C. H. Huvelle, N. E. Bucklin, and Dr Langenour. "The whole job," Howard writes, "is just like Gibraltar, so far a vibration is concerned. Both axes rest on double rows of SKF ball bearings, self alining and made for thrust as well as bearing. Size of polar axis 2-7/8", dec. axis 2-1/4" The weight is 640 pounds, not including the concrete pier. The castings are iron, except the saddle and prongs, which are aluminum. The hand wheels are brass and the one at the upper right rotates the tube on ball bearings-one of the greatest features, I believe, to be had on any reflector. I see very little if any of this feature on the many instruments shown in the magazine." This handwheel, which Howard mentions, works a longitudinal shaft, through bevel gears, and this shaft in turn works a spur gear which shows in the picture, the latter turning the tube by means of an encircling spur gear. It is all very professional-the whole job commendable-particularly those heavy 2-3/4" axis shafts. And-"rock steady."

PARTS like those described by Selby and by Howard-extra heavy wrought iron pipe legs and six-inch pipe fittings, also 2-3/4" axis shafts-mean real rigidness, rigidity, or "rock-solidity." In a recent letter, Ellison mentioned that some of the mountings he had seen described in this department seemed to be "whippy," and he is right. A telescope which magnifies 50 or 100 times, also magnifies vibrations in exactly the same measure; so that the builder should always think of the vibrations caused by the breeze as if the telescope tube were extended to about 100 feet in length, and he were trying to obtain a steady look. Some of the mountings we have seen might as well be built on a buggy whip tied to a fish pole, as on the thin little axes, skinny and anemic, which they have. Wally Everest got us stirred up enough to write these ugly comments, saying "Give 'em Hell about it," and this is it.

While we are at it, we will get off our chest another pet peeve that burns us up and temporarily wrecks our sweet (?) disposition every now and then. This is the matter of photographs. At a casual glance the average photograph seems to be in focus, but close scrutiny of many show that this is not true for the whole depth of the telescope photographed. A dodge for this is simply to stop down to about 32 and take a time exposure. Result: whole telescope in sharp focus.

AND now, while we are speaking about rigidity, look at the forks on the two telescopes shown in the photographs below. W. A. (Bill) Mason writes from 1303 Lakeview Ave., Lorain, Ohio, that the Cass with the short finder (left) belongs to John Clouhessy, a machinist, and the other is his own. They are nearly the same, John Clouhessy's having 190" f.l. and the other 170". "I did all the machine work," he says, "and made the castings, all being of aluminum. We also made our own patterns." Co-operating with these two were Jim Clouhessy, machinist, and Dick Curran, molder.

The main features of these jobs are: 12-l/2'' Pyrex primaries. 39" f.l., and 3-3/4" secondaries. Pyrex diagonals 0.1 wave. Screw focusing eyepiece holders with 1/8" double acme thread. These swing around ends of tubes, for convenience. They will take up to 2" O.D. eyepieces. Lower half of tube of each telescope screws off the trunnion ring, and contains the cell. Slow motions in dec., worm gears-same for R.A. Drive: governor-controlled induction motor ("Green Flyer"); worm gear reductions, made by John and Jim, 30:1 and 24:1. Timken roller bearings. Polar axes, 2-3/4" diameter. [Ha! Same size as on the Dallas job. This one won't quiver, either.] Both axes can be slipped on the slow motions. Weight of each job about 180 pounds, 125 of this being aluminum.

WILLIAM S. VON ARX of 573 Monroe St., Brooklyn, New York, writes: "Several years ago I purchased my now well thumbed and tattered copy of A.T.M. Greedily I soaked up its contents and set to work on the inevitable six-inch Newt. Success greeted my first attempt at parabolizing and I immediately branded myself a born optician. With the heavens plopped in my lap, so to speak, I spent many hours feasting my eyes on the splendors above. Then I was suddenly gripped with the desire of photographing these wonders. Night after night I lay awake planning a suitable equatorial drive and camera. Finally I reached what I considered a perfect solution and set to work. Within the year I had completed the drive, camera and other necessaries and found on trial that I didn't know two twits about what I was trying to do, so I took the whole thing apart and started all over again. This has occurred five times within the past four years [which means he started at about 14.-Ed.] and now I think I have achieved my goal in the result which you see in the enclosed picture.

"It is a fork type mounting, driven by a disk motor and an elaborate gear speed reducer. In the fork are two cameras and three telescopes. A three-inch glass of short focus for guiding, whose triplet objective made me recant my former pride as an optician, and a one-inch finder for it, then a 1-1/2 inch telephoto camera giving an equivalent focus of 37-l/2 inches and a finder for it. All these things are mounted on the primary camera, which is an f/4.5 of 12 inches focus. This lens is the only one I bought: all the others are home-made, be cause I found with experience that lenses are expensive.

"With this equipment to start with, I gradually added gadgets, such as flap shutters, objective prisms, and so forth, for the cameras, and a polariscope, Zollner eyepiece spectroscope, iris diaphragm, micrometer eyepiece, a set of filters, zenith prism, and several high-power and one ultra low-power eyepiece for the three-inch guiding glass. With things arranged in this way my equipment is equally effective, either visually or photographically. And, too, with the accurate drive, diaphragm and trick eyepiece, it lends itself admirably to both lunar and planetary detail.

"This trick eyepiece I believe deserves a bit of explanation. In essence it is a disk with eight lenses in it, each lens of higher power than the one preceding it. Thus it might be called an octo-revolver. The lenses of the whole series are negative, thus making the telescope Galilean. When the power of the negative ocular gets as high as those I have put in this turret, the field is not reduced, as is usually the case in the low-power negative ocular. The angle of the field is as large if not larger than an equivalent Huygens ocular. The lenses in this turret are double concave, with radii of curvature ranging from 1-1/2 mm. to less than 1/2 mm. Needless to say, I nearly lost those pinhead lenses under my finger nail a score of times, but after much sweating and rather noxious language, they found their way to their respective cells. With a bit of stopping down with the diaphragm, and careful focusing, lunar and planetary detail pops out surprisingly well for such a small glass. Then too, the accurate driving helps enormously by keeping small objects accurately centered in the field.

"This drive, which I have fashioned after much experimentation with varied forms, is the most satisfactory I have ever used. It will keep a guide star centered accurately enough to get round images with the 12-inch camera up to two hours exposure. The 37-1/2 inch holds true for three quarters of an hour or more without guiding.

"One ever-present difficulty in photographing the heavens is dewing. I overcame this difficulty by placing a 1000-ohm resistor in the hood over the lens. The heat of the resistor was sufficient to keep the air above its saturation point, and thus prevented dew from forming on the cold surface of the lens. Now, when I find dew forming, I merely throw a switch and it clears within two or three minutes.

"Another gadget is a field illuminator which facilitates seeing the spider lines in the reticule of the guide telescope. I have a little variable resistor that doctors use for opthalmoscopes, and so on that gives from 0 to 6 volts variable output. This, in connection with a 6 volt bulb in the tube of the telescope, gives any light brilliancy desired."

Harold Lower says von Arx's photographs are the best he has seen.

THE tenth annual get-together and convention of amateur telescope makers will be held at Stellafane, near Springfield, Vermont, on Saturday, August 3. For details, if you don't know about these informal pow-wows already, write to R. J. Lyon, secretary, The Springfield Telescope Makers, 252 Summer St., Springfield, Vt. Come, if interested in telescopes, but leave your tail-coat in moth balls.

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.