Just beyond this run-off roof a third has now been added, to house a camera and mounting. The roof of this addition rolls off to the north, and the south gable visible in Figure 1, near the telescope, is hinged and lets down on a post.

Thus, John Bunyan, a pilgrim originally from New York State, has progressed from one to two, and from two to three, observatory entities. The recently added camera assembly (Figure 2) was built, Bunyan states, largely with the help of Carl Conder, a good local mechanic.

Bunyan writes: "The supporting frame and the rectangular polar axis are built of 5" channel steel. The ends of the polar axis are of 2", steel shafting, the lower, which carries most of the weight, resting on a thrust ball bearing. The upper bearing is plain. The declination axis is made of 2" steel shafting with one end threaded and screwed into a steel plate which is bolted to a piece of 3/4" plywood, 16" square. The camera and guiding telescope are fastened to the plywood.

"The counterweight at the other end of the declination axis is a steel pulley partly filled with concrete. The right ascension and declination circles are turned out of 3/4" plywood and are bound with brass strips (kind used to cover joints in linoleum). Tightly fitted over the brass strips are circles formed of 45" lengths of steel tape. Thus each 1/8" on the declination circle is 1°, and each 1/8" on the R.A. circle represents 4 minutes of time.

"The camera lens is a 4 1/8" group portrait lens of about 25", focus. The camera box is built of wood and is equipped with plate holders for 5" x 7" film. The eyepiece used in the guiding telescope is homemade. It has a biconvex lens and the crosshairs are made from tungsten filaments taken from an old style 25-watt lamp. These are illuminated by a flashlight bulb. A full sized dry cell, contained in a can mounted beside the telescope, furnishes the current. A volume control from an old radio is used as a rheostat to dim the light.

"A 12" cast-iron worm gear (Figure 3) with 96 teeth moves the polar axis by means of a friction clutch. This gear is driven by a single-thread hardened steel worm fastened to a steel shaft which carries a 30-tooth worm gear. The latter is driven at sidereal rate by a double-thread steel worm which turns at 1 rpm. A Hansen synchronous motor, with shaft geared to 1 rpm mean solar time, furnishes the timing and acts as a brake against the pull of a weight and sashcord over a plywood pulley on the polar axis. Interposed between the 1 rpm motor output and the 1 rpm sidereal rate of the last-mentioned worm are spur gears giving a ratio of 364 to 363, which is the closest I could approximate the sidereal rate with stock gears. However, the error is so slight that it is inconsequential for the periods the camera is at work.

"There is a clamp on the declination axis with worm for slow motion. A worm connected with flexible cable moves the whole assembly in R.A., for manual guiding whenever a selected guide star strays from the crosshair.

"The whole outfit is carried on a heavy concrete pier and no part of the building touches it. Moving around in the building does not set up any vibration at all in the instruments."

SUNDIALING is a kind of cousin to amateur astronomy, and of course the average amateur's general reading in astronomy enables him to pick up its principles relatively easily. Figure 4 shows a stone sundial made by Bunyan, who also is the author of the chapter on making a sidereal clock, in "A.T.M.A." The base of the gnomon ("substyle") is 15" in length and this gives the scale of the other details. The lines and numerals were not incised, but sandblasted at a local marbleshop, and, are 1/8" wide by 1/8" deep. In cutting inscriptions, marble cutters, until a generation ago, used a hand chisel and mallet. Then came the pneumatic chisel, and now this has been supplanted by sand blasting The flat stone is first covered with a coat, Of elastic material and the desired lines, and letters are cut through this covering- like a stencil. When a continuous blast of; air-propelled sand from a nozzle is directed against this prepared surface, the sand grains rebound from the coating but strike the stone wherever it has been cut, away, and thus they rapidly eat away the stone. This method explains the deep inscriptions on the more recent tombstones- cuts far too deep and narrow to have been made by percussion tools.

Bunyan's dial is set up near his observatory. If really carefully designed and painstakingly made, a dial will give accurate time within about one minute, provided the daily correction for equation of time is made. Naturally, only a dial of this kind would suit the pride of the average amateur telescope maker.

This department often is asked for the "inside figures" on the total number of telescopes made since "Amateur Telescope Making" first appeared in 1926. We don't know. To obtain really solid data on this would be difficult. All we can do, therefore, is "guestimate." Over 30,000 copies 'A.T.M." have been purchased since 1926, but what percentage of purchasers actually made telescopes? What percentage made two? Three? Five? Ten? (Yes, some have made that many). Our guestimate is 20,000 telescopes-what's yours? Some think this figure too conservative. Perhaps. Perhaps not. Anyway, let's say 20,000.

It's fun to imagine all these 20,000 telescopes assembled in one place. Let's allot each one ten feet square and one observer. That represents a Telescope Farm of about 50 acres, solid. Go aloft in a plane look down at them all!

To make it more interesting, let's have them all pointed at one object; it might as well be the plane, and there'd be a poetic justice in having in the plane the man who, more than any other man, made all possible-Russell Porter. Maybe he'll wave a hand over the side (this story is becoming melodramatic).

Of course, not all these telescopes are now in actual use. There must be a few thousands which could be put in other hands to good advantage. Readers also ask us, now and then, where they can purchase a second hand telescope. To test whether any good could be done by thawing out this frozen situation we shall be glad to publish, in one number, the names and addresses of those who have second hand telescopes they would be willing to dispose of.

FUN to make your own eyepieces. Whole battery of them (Figure 5, top and bottom) were made by H. J. Gebelein, 1314 Carey Ave., Davenport, Iowa, and are respectively 1 1/4", 3/4", 1/2", 1/4", 3/16" and 1/8" efl. Middle photograph shows some of the innards of the same eyepieces -those of the 1/4", 3/4", 1/2" and 3/8" The eyepieces are the solid type (see "A.T.M.," page 178). The glass used was Chance Brothers C. C. Crown 1.51.

Gebelein also built an 8" Gregorian with 23" f.l. primary and ratio 6. "This telescope," he says," has given me many hours of real enjoyment."

ABRASIVES are becoming scarcer, and methods for husbanding them, described by Lewis A. Parsons, 125

Brentwood Ave., San Francisco, California, should prove useful until the war is over.

"In washing, or levigating rouge, the particles flocculate or bunch up, and thus the finer parts are dragged to the bottom with the coarse. I therefore disperse the particles, settle them, pour off the finer 3. parts and then purposely flocculate these so that they will settle.

"Put, say, 4 oz. of rouge into a cleaned one-gallon bottle and add about 1 oz. of sodium silicate (ordinary water glass). Then fill the bottle with water, shake it thoroughly, and let it stand an hour. Next, siphon off the top half into another bottle, to which add perhaps 2 to 4 oz. (determine empirically) of lime water, a solution from slaked lime. This flocculates the rouge, which settles almost at once, permitting the clear water to be siphoned or decanted off. Then refill the first bottle shake and repeat the operation. When the first bottle stops producing more, throw away the residuum. As the sludge settles 3 in the second bottle, flush it into a mason jar and from time to time decant off the water. Use it as a cream or paste and do not let it dry. This produces beautiful rouge-not a scratch in a carload."

The following will similarly recover rouge, also Carbo and emery. The dispersing agent is Igepon AP Extra sold, by General Dyestuff Corporation, 435 Hudson St., New York, also 38 Natoma St., San Francisco, at a rather low rate in five pound lots. It is a detergent comes in powder or flakes.

"Grades of Carbo coarser than 240 settle so fast anyway that the finer is best washed out first (elutriated by a gentle upward stream of water) and then dispersed and separated into its fractions. Carbo or emery that has been used a couple of times will yield as fine a product as desired. After the dispersed abrasive has been siphoned off, it is flocculated. The best all-round flocculating agent is ferric chloride. Caustic soda could used for Carbo alone. Caution: Don't use it together with ferric chloride.

"The technique is simple. Shake up the abrasive in a bottle or jar with a little Igepon (experiment for exact proportion). Let it settle for a time based on the size you are after. Siphon off. Flocculate with ferric chloride. Continue the cycle til no more good stuff comes off. Dump residue into a coarser size. Nothing is lost.

"Many use too much abrasive with too little water, which prevents free settling. The grains hinder each other and there may be some big chunks in the part siphoned off. Use not over a quarter pound dry abrasive weight of abrasive, to a gallon of water. For the very fine sizes and double levigation one would probably do better with five gallons for the final settling.

"There are evidences that glass will not flocculate and can be decanted after the good stuff has settled. "Iron can be removed from the dried abrasive powder with a magnet. "Some more work remains to be done on these methods.

"If some of the abrasive is placed on a slide under a microscope, the field will be seen to be made up of grains that fall in one size-group, yet the sizes are not all the same. Sticking out are usually a few much larger grains-enough to scratch. These are the grains whose grooves must be ground out with the next finer size, and which slow down the grinding process."

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)
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