"The mirror is a disk of No. 5 Carpenter stainless steel, forged to 8-1/4" x 1", machine to 8" x 7/8", ground, polished and figured. It weighs 16 pounds. The secondary is of N 3 Carpenter stainless steel similarly handled. Both are chrome plated. The focus of the primary is 34", radius of curvature of secondary is 10-1/4''. P measures 5.75" and P' 47.25", e.f.l. being f/32.

"The tube is made of six duralumin tees. The fork, polar axis housing, cell, short tub around cell, and support for secondary are all aluminum castings. The axis has roller bearings. The declination axis is 1".

"The tripod is made of three 1-1/2" O.D. duralumin tubes. The eyepiece holder is fastened to a tube which swings around the optical axis. Having used some telescopes which require the observer to be a contortionist, I determined to arrange my instrument so that after using it some time I could look the neighbors straight in the face. The observer can be seated while at work. The total cost was $59." [The details of grinding and figuring this metal mirror will not be presented here, having been included in a chapter on that subject in Vol. II, "A.T.M." This is now at the printer's and will be announced when ready-considerably later in the autumn.- Ed.]

HEAVY oak tripod legs instead of the spidery legs sometimes seen on tripods characterize the 6" telescope in Figure 2, made by Newman E. Brown, 414 Connecticut Drive, Erie, Pa. He says: "The tube consists of a sheet of rawhide fiber, 060" thick, rolled up on a mandrel to three thicknesses. I cemented each layer as I went around, and riveted the final edge. This makes a tube of remarkable rigidity, and exclusive of optical parts, weighs only 9-1/2 pounds.

"The mounting consists of a worm gear steering unit from an old automobile. The gear shaft serves as my polar axis.

"All material, except optical parts, I obtained from scrap of a large industrial plant at a total cost of about three dollars."

"WHAT interests me is the new found use for another flivver part-the rear axle housing, as a pedestal," Russell W. Porter commented when shown the photograph in Figure 3, Welby Powell, R.F.D. 1, Clarksville, Tenn., is the maker. His letter:

"I have completed my first telescope, which has an 8" mirror of Pyrex. I used your book, 'Amateur Telescope Making,' as a guide and picked up some 'Don'ts' of my own.

"My mounting is a portable type which I built from discarded machine parts, excepting the tube which I rolled from 20-gage iron. I wanted to get away from the necessity of following the eyepiece into so many inconvenient and almost impossible positions, so I fitted it into the journal of the declination axis. You might call it a portable mounting with a fixed eyepiece." [Note that all of the telescopes in Figures 1 to 6 are portable.-Ed.]

MOUNTING a 12" telescope semi-portably is no problem if you don't have to trundle it far. Figure 4 shows such a one, made by Edward J. Hejna, 3358 Jasper St., Philadelphia, Pa. It is a "Wheelemout" Type.

"I read about the 'Twelve Inch Club' in the June number, "he writes, "and am sending a photograph of my telescope, which has a 12-7/16" mirror of f/8 ratio. The polar axis shaft is 1-3/16" in diameter, solid, and runs on ball bearings. The base is on ball bearing casters and the total weight of 550 pounds may be raised on three screws, making the telescope very steady." Mr. Hejna wishes to exchange photographs of telescopes with other amateurs.

VERY portable portable is shown in Figures 5 and 6, and was made by Merle Foster, 677 32nd St., Oakland, Calif. "While it is portable," he says, "it can also; be readily attached to a stationary mounting. But when the atmosphere does not permit clear observation it can be placed in car and easily taken to a better locality "The backbone has a focusing and folding mechanism, like a slide rule, and this also permits focusing on relatively close terrestrial objects, as well as compact folding. It has a rack and gear."

ONE telescope which is not portable-it weighs 1000 pounds-is shown in Figure 7. Joseph E. Boehm, 3511 N. Seminary Ave., Chicago, Ill., is the maker and he says he has been plugging at the job, which is an unusual one, for the past five years. It is a 14" and, in its observatory (Figure 8), is situated at Lake Geneva, Wisconsin. But let us have the description from the tenacious maker. A man who will stick to a job five years must have determination.

"The telescope is a Cass Newt combination. The f/5 primary mirror is used with a 4-1/2" x 6-1/2" Newt diagonal to cover a wide field for photography.

"Tube assembly is of all-aluminum construction and consists of a tube, internally reinforced, having a cast ring at its lower end which supports the threaded, removable mirror cell. Duplicate threaded tube outlets permit accessories to be interchangeable for either Cass or Newt observing position. A declination setting circle and 4000 to-l slow motion are provided. Declination bearings are bronze.

"The hollow cast aluminum fork was bored out undersize and hydraulically pressed on the 3-1/4" steel polar axis shaft. Upper polar axis bearing is bronze, while the lower bearing is a 6" annular ball bearing. Th R.A. setting circle is electrically driven to eliminate setting calculations.

"The cast-iron base weighs 600 lbs. and is mounted on a concrete pier extending 12', below ground level.

"Weight of the entire telescope is around 1000 lbs.; the tube assembly alone weigh about 150 lbs. Contained in the instrument are 32 castings, for which 19 patterns were made by myself."

Mr. Boehm's description of the electric drive of this big telescope, with its design has been included in "A.T.M.," Vol. II, as an example of a drive for a telescope o larger size, such as more and more amateurs now aspire to make. He continues, with regard to his observatory building (Figure 8).

"The 12' x 12' building is mounted on six concrete posts, 10'deep, due to the unsteady ground conditions. The sliding roof is split at the ridge, each half being counterweighted and sliding independently on rubber rollers. Only about half the total roof area is movable. The roof overhangs, as well as the lower one third of the roof are stationary, the latter being depressed to allow the sliding portion to pass over it. This depressed portion also supports the sliding roof when in open position. This construction greatly reduces the weight of the sliding roof, requires no external roof support and helps to preserve the trim lines of the observatory building when the roof is open.

"When observing near the zenith, a cushion on the upper edge of one of the sliding sections of the roof makes a convenient observer's seat. The roof can easily be 'inched' to follow the telescope movement during use. Besides protecting the instrument and observer from wind, the building materially assists in preventing dewing troubles. Merely closing the roof will postpone dew-up for several hours. "

PITCH testers again. F. C. Woods, 100 North Cherry St., Galesburg, Ill., has made two, and writes:

"Here is a picture of a pitch tester which I believe overcomes some of the difficulties which I encountered in using one I built after the illustration in the October, 1935, Scientific American. Of this type I built a rather elaborate one (Figure 9), only to discover that the pivots had to be quite tight to take care of the upward thrust given by the point as it enters the pitch. In the one I have devised (Figure 10) the only moving part is the central rod which carries the needle point (.0395" diameter).

"The degree indicator can be quickly removed and the micrometer head put in its place, thereby enabling the hardness of the pitch to be measured in l/1000". Neither the degree indicator nor the micrometer head is necessary, as divisions could be made directly on the shaft and read from a pointer attached to the standard. The rulings should probably be in thousandths of an inch and read with a magnifying glass.

"In the operation of the machine the shaft is set so that the pointer is at zero, and the shaft is held stationary by the thumb screw at the upper cross bar. The pitch is then brought firmly to the point and locked hl position; then, with watch ready, the thumbscrew is loosened for the predetermined period and again the thumb nut is tightened, locking the shaft.

"If anyone should build a pitch tester after this design, it would be best to make the shaft that holds the point and weights 1/2," in diameter if a micrometer is used. I have already redesigned it to prevent flexing of any part of it."

Just as these pages are put together this scribe is down from Vermont, after the eleventh annual convention, get-together or powwow of amateur telescope enthusiasts held at Stellafane. This year the attendance was 248, considerably larger than ever before. The amateur astronomical and telescope making movement "marches on," and one wonders what and where it will be in another decade.

Persons who are in a good position to watch statistics note that there never has been a retreat since the movement began. Instead, there has been a steady growth all along: "one man tells another." It looks as if everybody and even his wife would ultimately be pushing glass.

No ballyhoo methods-none of the artificial inflation methods so dear to some public relations counsels and "builder-up men"-have ever been used. It was thought better from the first to give the hobby its head and let it develop naturally, going wherever it wished. We have even been reproached, in a few instances, for not "developing" it by various available high-pressure means. A really '1ive" organizer, we were told, would have blown the hobby up to much greater proportions in many fewer years. This is true-it could have been done. But then the bubble would have burst the sooner, leaving only that "morning after the night before" feeling. What such a thing really would have done is simply to inflate the hobby with a lot of people who lack sufficient carry-through to stick to telescope making more than three months or so. On the other hand, the hobby is its own quiet salesman to the right kind of folks-meaning by this, the kind of fellows who can handle the work and like it, and who don't peter out.

The Stellafane powwows are a lot of fun, chiefly, some think, for a reason which is of a piece with something mentioned above-folks come and are pretty generally left alone to do what they please. They add themselves to the crowd and begin chinning with the first telescope nut they see; and so it goes, all the (Saturday) afternoon and evening-all night for the owl fraction- and part of the next day, when the holdovers drift away. The only semblance of a "session" is a group of informal "speeches" at dusk, mostly made in shirt sleeves.

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