SHOWN BELOW is what Norman J. Ulam of 1590 Bonnie Brae St., Warren, Ohio, a member of the Mahoning Valley Astronomical Society, describes as "my first attempt at making a telescope." On general and detailed examination it proves to be a finer instrument than many of us could make on our third attempt-or perhaps our tenth. The more it is studied the better it rates, not only mechanically but in appearance-two qualities that need not conflict, but are not too often joined.

"The main idea," Ulam writes, "was to design a mounting that would allow the 4 1/4-inch objective lens, made for me by one of the old-timers of telescope making, J. W. Draper of Warren, to work 1mhampered by the 'buggy whip' action found in so many telescopes. The mounting is as rugged as it looks. It seems a shame," Ulam continues, "to see an amateur glass pusher work many long hours producing a mirror or objective lens that is perfect, and then nullify his beautiful results by hanging the gem in a mounting that vibrates like a hummingbird's wing. Yet 90 per cent of all telescope mountings are not rigid enough."

From time to time readers of this department urge that if only the need for rigidity in telescopes were pointed out, telescope makers would stop making limber mountings. Perhaps these readers are optimists; at any rate, many workers refuse to heed the warning, possibly through a lack of instinctive feeling for mechanics. The book Amateur Telescope Making does point out that common standards of rigidity, as in ironing boards or portable music stands, are far below minimum for telescopes. Many ordinary things that look rock-steady- for example, a two-inch post driven into the earth-would be found to be vibrating in the breeze if we set up a microscope close to them.

The eight-foot-high pier of the Ulam telescope weighs a ton, and half of it is underground. The polar and declination axes are each made of one-inch drill rod, turning within ample housings.

The tube is of stainless steel painted dark gray, with fittings of bronze and brass.

"The eyepiece focusing arrangement," Ulam points out, "does not consist of a direct rack and pinion, as these often are jerky, but is compounded with a 24tooth worm gear on the pinion shaft, all running in little ball bearings. The tube to which the rack is attached slides in two adjustable-tension stuffing boxes packed in hard felt. This arrangement gives a very smooth-running fine-focus action that is light to the touch."

There is, however, an advantage in the focus control of any optical instrument that permits sweeping rapidly past. the optimum point and returning to and on past it in a series of in-and-out movements of decreasing amplitude, before the mind forgets and before the eye can try to assist accommodation and thus bring about residual muscle strain during observation. Can any reader contribute data on the physiological optics of focusing optical instruments?

The finder of the Ulam refractor is itself a useful telescope of two-inch aperture (f/9) that gives a beautiful image of wide field. It has its own rack-and-pinion adjustment.

The finest mechanical features of the Ulam telescope are those shown in the detail drawings made by Roger Hayward. Ulam writes that "the clock drive is housed beneath the mounting in a compartment fabricated of 1/4-inch steel plate, the door on one side and the window on the other being of 1/4-inch Plexiglas. Inside is a small light. The drive uses a 1/150-horsepower synchronous motor (Bodine Electric Company, Chicago) rotating at 1,800 revolutions per minute, with a built-in speed reduction to 300 r.p.m. It operates on 110-volt, 60-cycle current from a flexible cord which is laid across the lawn from the residence whenever the telescope is in use. There are no spur gears in the drive, all speed reductions being by worm gears, most of which were cut on my nine-inch lathe by following Russell Porter's instructions in Amateur Telescope Making-Advanced. The large gear was made with a half-inch 20 tap.

"A part of the nearly vertical drive shaft is a pair of home-made universal joints that replace a flexible steel cable that caused periodic leaps in the drive. As these joints operate through a very small angle (five degrees) they give a smooth flow of power. Objects stay in the center of the field of the eyepiece for as long as three hours without apparent lag or lead. This doesn't take into consideration the correction for atmospheric refraction, but it is more than good enough for visual work. Every shaft in the telescope is mounted on ball bearings, mostly taken from a war-surplus bomb sight."

The features along the two axes of the Ulam telescope are well worth detailed study, and the drawing of them is published because of its value to others who plan mountings. Along the polar axis, beginning at the bottom, are: 1) a single-ball thrust bearing and adjustable sleeve bearing; 2) a six-jaw drive clutch or clamp similar in principle to a drill chuck; its tension regulated for either driving or intentional slipping by the large, thin, threaded nut shown; 3) a conical cast aluminum member to which is attached the main-drive worm wheel with 362 teeth; 4) the hour circle, divided into four-minute intervals of time (small enough for visual use, since the finder takes up where the circle leaves off).

Along the declination axis, beginning at the bottom, are: 1) the 42-pound counterweight; 2) a bronze sleeve bearing; 3) a ball thrust bearing; 4) declination circle divided to half degrees; 5) a worm gear, with slow motion worked by hand, by a long rod from the eyepiece end of the telescope, 6) a clutch or brake similarly worked by a rod just behind the first rod in the drawing; 7) the tube cradle.

The head casting of the mounting is made of aluminum, as are all the castings, and the patterns have been preserved. "I would be glad to furnish details of this telescope to any who may want them," Ulam states, "and also to hear suggestions for better design, as there are many changes I would make on another mounting, and many places where I did dumb things. Some have said that I put too much work on this telescope."

If the builder was having fun all along, then it would be difficult to show that he put too much time on his telescope. Theoretically a telescope is a means, not an end, but this logic applies poorly to a hobby in which fun is where you find it.

T0 reduce the reflection of light inside optical instruments, including refracting telescopes, lampblack is usually applied in some liquid vehicle or by direct smoking. This is called flatblackening. Another method of flatblackening is described by Louis J. Rick, Secretary of the Black River Astronomical Society, 685 N. Ridge Road, Lorain, Ohio. "We amateurs here have made experiments with black flock for the insides of several refractor tubes. This produces a velour-like finish that absorbs the light and is darker than the inside of a pocket."

What is "flock"? In a small poll taken among those first encountered, all the women polled knew the answer, but none of the men, including the writer, had even heard of it. This ignorance was relieved by the answer to a query sent to Coast Industries, flock manufacturers, 1509 West Manchester Ave., Los Angeles 44, Calif., who wrote: "Flock is composed of tiny filaments, precision-cut to size and length from either rayon or cotton strands, and then dyed. An adhesive is spread on a surface and the flock is shot on with force so that it is deeply imbedded. For telescope tubes we recommend cotton flock, since rayon flock is shiny. Flock samples are enclosed." These look like mouse hairs cut to one millimeter length and dyed. Applied flock has the appearance of suede or velvet.

"Flock is available at larger paint stores," Rick writes, "or Coast Industries will supply three ounces, enough to cover 15 square feet, for $1. It is applied to surfaces, usually for decorative purposes, with a special spray gun. We couldn't get the gun inside the telescope tubes and work it there too, so we spread an even coat of tacky varnish (we found that shellac and lacquer set too fast) and threw in a handful of flock. By rotating and patting the tube vigorously with the palm of the hand, an even, thick coat of flock was made to adhere to the inner surface. This was allowed to dry 24 hours, and the surplus flock was then blown out for use on another telescope."

William A. Brandt of Upson Downs, Kutztown, Pa., a professional instrument maker, says he has used flock, but applies it electrically. A suede finish is made in that manner. One lead from a high-voltage transformer of perhaps 20,000 volts, such as a neon-sign transformer, is attached to the surface to be flocked. The other lead is attached to a sheet of metal, standing on insulators, several inches below this. The work is gradually moved toward this electrode. At the correct distance, the alternating electric field causes the particles of flock to dance up and down. They arrive endwise at the adhesive surface and stick fast-all parallel. Extreme caution must be observed because of the high voltage. Brandt suggests rotating the telescope tube on rolls during the process, with the long lower electrode not touching the inside of the tube.

Commenting on this more elegant electrostatic method of flocking a telescope, Rick states: "When we first decided to try flocking we recalled an article on the electrostatic deposition of abrasives in the manufacture of sandpaper and emery cloth. But before we could find that article someone suggested the simpler method already described, and this worked very satisfactorily. The remarkable part of it was the way the flock stood on end to stick to the adhesive coat-possibly because of an electrostatic charge on each filament of it. The results were so good that we decided an electrical method would give too little improvement, especially considering its lethal high-voltage aspect."

AMATEUR telescope makers customarily measure and keep track of the increasing depth of the curve during grinding by wetting the mirror, shifting a light about near the center of curvature and observing the behavior of its reflection. By this method the practiced worker can locate the center of curvature within half an inch. But he can seldom feel sure he is correct; the method is inexact and inelegant. An alternative method of locating the center of curvature, by estimating the sharpest focus of light from illuminated holes in a sheet of tin, may give no more exact results. Both methods leave the worker with an insecure feeling. So he tries making a metal or glass template to fit against the curve, and for once feels he has hold of something definite and quick-perhaps forgetting to count the time needed for making the template. Often, however, it proves that the template was made wrong; it is far from easy to make an accurate template.

So he next dreams of owning an optician's spherometer, which measures the depth of the curve mechanically, precisely and in almost a jiffy. With this he will be sure to feel that he is on the right track all the time. Thus the conductor of this department rubbed his hands in anticipatory pleasure when, some 20 years ago, he was told that a spherometer was headed his way. This proved to have been owned and long used by the professional optician C. L. Petitdidier of an earlier generation; it is inscribed with his signature. Its radius is two inches and its central screw reads to a ten-thousandth of an inch. Unfortunately, the faith that this pretty plaything would provide exact answers proved to be another of life's illusions. It is easy to set it time after time within one scale division or .0001-inch, and to avoid bias by working "blind," that is, with averted vision, using only a light sense of "feel" against the edge of its dial, and noting at the same time whether the legs or the central screw bear an undue share of the weight. Yet in spite of these and other precautions, such as trying it off-center in case the mirror might not be spherical, the spherometer has never equaled the less elegant methods of finding the depth of the curve.

It finally was found that too much was being expected of this type of spherometer; the chief source of inaccuracy lay in the design itself. As F. Twyman says in his book Prism and Lens Making, a closer measurement may be had if a complete ring, or inverted cup, is substituted for the three isolated legs. Others have noted the same superiority, and it therefore seems justifiable to recommend the ring type of spherometer over the leg type.

After the war Lieut. A. F. Bzura, then stationed on Iwo Jima, and later of the Rome, N. Y., Army Air Field, was tinkering with the mathematics of a slide rule when he hit on what might be called a special spherometer that eliminates the necessity of substituting in the formula d = r²/2R ( more precisely, R = (r² + d²)/2d or d = R - (R² - r²)^1/2 to derive R, the radius of curvature. The reciprocal of the dial reading is itself the focal length of the mirror-provided the spherometer is given a ring diameter of four inches. Example: Dial reading, .02-inch. Mentally divide .02 into 1. Quotient, 50. Focal length therefore 50 inches. Armchair geometricians will be 'able to find a theoretical error in this convenient special-case relationship for a four-inch spherometer; the exact answer is not 50 inches, but 50.005 inches.

This discrepancy is not of sufficient size to stop the heart of the practical optical worker.

Recommended, therefore, is the Bzura spherometer with a ring-or else plodding along with the same old wet-mirror tests which, after all, serve pretty well. Perhaps it boils down to about this: A spherometer is a pretty thing to have.

AN article in the August number of American Forests contains a hint for a new and different, even unique, amateur astronomical group. Since 1904, 10 men in Colorado Springs (not amateur astronomers) have spent their Saturday afternoons together hiking in the nearby mountains, and their evenings eating and swapping discussion around a campfire, without drawing up a constitution, without choosing a president, first or second vice-president, treasurer or other officer, except informally the custodian of the coffee pot, without reading the minutes of the last meeting or even choosing a name. In order to write about them, a local reporter about 20 years ago called them The Saturday Knights. But their "organization" has lasted 45 years.

STILL another source of puzzling scratches on optical surfaces is suggested by Walter C. Durfee of Boston, Mass.: grinding too long without rotating the mirror. This, if continued, produces a deeper curve on one diameter of the mirror than on the one at right angles to it. The curves on tool and mirror tend to change from spheres to cylinders and the mirror is astigmatic. Then, when the mirror finally is rotated, it no longer fits the tool but bears at only two points at the edges. Greatly increased pressure there leads to crushing, glass edges bite into glass faces, and scratches occur.

This source of scratches was suggested by the behavior of a surface that was purposely ground astigmatic. Scratches occurred in very great numbers and to very great depth and were arranged in groups at opposite sides of both disks.

Suppliers and Organizations

The Society for Amateur Scientists
5600 Post Road, #114-341
East Greenwich, RI 02818
Phone: 1-401-823-7800

Internet: http://www.sas.org/

At Surplus Shed, you'll find optical components such as lenses, prisms, mirrors, beamsplitters, achromats, optical flats, lens and mirror blanks, and unique optical pieces. In addition, there are borescopes, boresights, microscopes, telescopes, aerial cameras, filters, electronic test equipment, and other optical and electronic stuff. All available at a fraction of the original cost.

SURPLUS SHED
407 U.S. Route 222
Blandon, PA 19510 USA
Phone/fax : 610-926-9226
Phone/fax toll free: 877-7SURPLUS (877-778-7758)
E-Mail: surplushed@aol.com
Web Site: http://www.SurplusShed.com