Most of the description of this telescope is in Roger Hayward's drawings. Other details are given by Sharp.

The main supporting leg is a lightweight box of 24-gauge sheet steel. "Practically everything that comes apart on this instrument comes out of a slot," Sharp says, referring to the braces attached to the leg which have "slightly angled, snugging-up slots that drop over studs and are held in place by gravity." He adds that "although my telescope, which I call 'Portable Pete,' smacks of baling wire in spots, it performs beyond my fondest hopes." This is a telescope that could be made by a beginner, yet it contains luxuries.

The driving-gear train between the clock and the telescope is simple. The wheel that drives the minute hand of the clock, turning at the rate of l0 teeth an hour, meshes with a 30-tooth spur gear on the ball-bearing jackshaft, which is thus driven at the rate of one revolution every three hours. A 24-tooth gear on the upper end of the shaft then drives a six-inch, 192-tooth gear on the right ascension axis at the rate of once every 24 hours, a solar day. Corrected speed for the sidereal day of 23 hours, 56 minutes, 4.09 seconds is obtained, or rather approximated, by adjusting the speed of the clock. The gears are numbers G174, 171 and 189, obtained from the Boston Gear Works of Quincy (not Boston ), Mass., and their cost was $4.30. The pipe fittings used on the declination axis-floor flange, T, and reducing bushing-are a full two-inch size.

"This is clearly a poor man's telescope," Sharp writes, "though not 'cheap.' Slight imperfections of the gear teeth will cause slight hour-angle variations, producing oblong star images if celestial photography is attempted. Even in this respect the drive will serve for all except ultra-microscopic results, but its main purpose is as a luxury during ordinary visual observation, to keep the heavenly bodies from crawling out of the field of view because of the earth's rotation as soon as they are located. If the telescope is used as a camera, precise alignment of the polar axis with the earth's axis will be as important as correct clock rate, and this cannot be accomplished in a hurried assembly.

"Ball bearings on the jackshaft and ball-bearing rollers under the right ascension base plate reduce the friction so that the clock is strong enough to drive the telescope. If the clock used is not strong enough, the addition of a spring-loaded sector that can be cocked will supply enough torque for an entire evening, the clock then serving largely as a time control.

"While the hour circle may be inscribed on the 192-tooth gear, this is perhaps superfluous, since the gear has 8 teeth per hour as a sufficient guide.

"Both right ascension and declination bearings are of the disk type with annular contact and shims of 0.01-inch sheet metal. The disk-type bearing is unequaled for ease of fabrication and smoothness of operation. It combines maximum steadiness with minimum frictional overshoot, an annoying characteristic of hand-powered telescopes resulting from spring in the mounting combined with high static friction. When the object is not centered well enough in the field of view of such a telescope, the observer pulls the telescope to center it. On the first pull nothing happens, so he pulls harder. Suddenly static friction is overcome and the telescope moves too far. Well-lubricated bearings of large radius and area greatly reduce this overshoot."

By loosening and reclamping the wing nut on the jackshaft, the user of the Sharp telescope can employ the convenient slip-ring principle described by Russell Porter in his chapter on the design of mountings in Amateur Telescope Making. This method enables the observer to "bring any bright known star into the center of the telescope field and set the circle to that star's right ascension, taken from the ephemeris," thus freeing himself from unnecessary drudgery for the entire evening of use.

The six-inch mirror is mounted in a generous seven-inch tube. The cell, made of aluminum, has no rear-end protuberances. Its little central hole assists in lining up the prism.

When Sharp was invited, as other workers are, to criticize his own telescope by pointing out spots he might improve if he were building it again, he listed the tube-clamping strap with spring catch, which permits the tube to rotate for the most convenient eye positions in only one direction, but snubs it in reverse; a tendency of the jackshaft wing nut to work loose; and the absence of a declination lock.

Such self-criticisms are useful to other builders. They underscore the often-given advice that the beginner, instead of attempting to make the final large and perfect telescope on his maiden effort, should approach it by building a series of instruments, perhaps one a year, in the course of which many of the things that "would be done another way another time" are certain to be found.

FRONT-WHEEL spindles from an old Ford, tapered roller bearings, hubs, and hub flanges with their axle and steering connections burned off provided the main parts of a mechanically and esthetically excellent mounting built by Lewis Batson of Wiggins, Miss. The mounting, suitable for any ordinary telescope, is shown in the lower part of the drawing on the right. The right angle between the axes was set by first making light welds at the edge of the parts and then bending these welds slightly to allow the spindle flanges to conform to a square held against them.

"I have used this mounting for my 10-inch f/3.4 reflector and it is very satisfactory," Batson states. "I am particularly pleased because the construction did not require much modification of the original parts nor any creation of parts out of the whole cloth at all."

The mounting is bolted to a six-inch channel iron with a brace, and is set in a concrete base. The drawing shows the mounting ready to receive a telescope.

Batson puts a self-accusing finger on one detail that would be done another way another time. While the axes have excellent rigidity, the counterweight, a length of 5/8-inch steel carrying a 50-pound lead weight, "is a source of vibration, the only one of serious moment."

The telescope has a stubby tube for which the Ford spindles are sufficiently rugged, but Batson agrees with the suggestion that truck spindles would perhaps be better with longer tubes.

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