YERKES WAS A CHICAGO TRACTION MAGNATE with plenty of wealth. The late Dr. George Ellery Hale tactfully made him realize that man is mortal and that after a few years the world would forget his name and his multi-millions, but by donating a big telescope to science, he could become an immortal. Hale got the money for the 40" telescope and Charles T. Yerkes got his immortality-which included burial in a crypt in the telescope's pedestal.

Amateurs who have made exceptionally good telescopes may, too, become immortals without the bother and annoyance of being rich, by dedicating these instruments to some educational institution or other corporate body (the burial beneath is not a requisite; in time it might even prove embarrassing). Cyril G. Wates, 7718 Jasper Ave., Edmonton, Alberta, whose 12y2" Newtonian reflector (Figure 1) was briefly described in this department in December 1941, has now thoughtfully dedicated it to the University of Alberta, at Edmonton, Alberta, Canada.

Figure 2 shows the group present at the ceremony. Wates stands between Hon. J. C. Bowen, Lt.-Governor of A1berta (with cane) and (toward the reader's right) Dr. R. Newton, President of the University. There were ceremonies, Dr. J. Pierce, Director of the Dominion Astrophysical Observatory at Victoria, B.C., gave the address, and Wates, not brawny enough to hand the president the telescope, handed him the eyepiece instead. Such a party is a Big Day for the donating immortal.

Asked to describe the telescope and dome, Wates writes:

"The 12 1/2'' mirror is Pyrex, ground and polished by hand, but figured on a Hindle machine. Focal length 110".

The tube is cedar, glued up from 20 strips and then turned. It is strengthened with cast-iron rings. Just above the mirror cell is a lead counterweight, made in four segments and encircling the tube. The head of the tube, carrying the finder, eyepiece adapter, and 2" Bausch and Lomb prism, rotates on ball bearings, and is turned by a handwheel and pinion working in a circular rack, which was filed out with the aid of - a" hardened steel template.

"The finder is a 4" RFT with aluminum tube. There are no cross-hairs, as the telescope is to be used for clusters and so on as well as for a finder.

"The main tube is mounted in a frame of 2 1/2" angles, in a similar manner to the 100" at Mount Wilson, but the declination bearings are offset a foot from the polar axis, to provide greater accessibility to the circumpolar stars. There is a 150-pound counterweight to balance the tube.

"The lower end of the polar axis rests in a conical roller bearing, and the upper end turns in a heavy ball bearing. Provision is made for adjustment of both axes, by means of push screws. The drive, not yet installed, will be a modification of the Boyd Brydon drive, with a slip clutch.

"The declination scale is a strip of Celluloid, engraved with a tool made from a Schick razor blade and stamped with steel letters from an old Addressograph. This scale is bent around a semicircular block attached to the polar axis frame, and is viewed by means of a simple periscope from a point close to the main eyepiece. The hour angle scale is an iron hoop 3' in diameter, enamelled white and carrying black markings.

"The main dome is an exact copy of the dome. of the observatory at the Rensselaer Polytechnic Institute, Troy, N. Y., and was built from blueprints furnished by Dr. Carragan of that institution. The ribs are cedar, with a covering of Masonite, painted aluminum The slit is fitted with a curved shutter, conforming to the dome and moved by endless chains running on sprockets, operated by means of a worm gear hoist.

"South of the dome is an extension with a roll-off roof, housing a 4" refractor, a transit, and a zenith telescope These instruments and the reflector are mounted on heavy concrete piers running below frost line-which is about six feet in these parts! The mounting for the refractor was built locally from my designs, and works very smoothly."

Because of cramping and bad lighting it is notoriously difficult to take a good photograph of a telescope within a dome. This hazard was obviated by using a combination of daylight and flashlight-a point possibly worth remembering.

ONE way to lay out a setting circle is to make full use of the work already done by others in laying out gears. Figures 3 and 4 show how one amateur, a Wyoming physician who prefers anonymity, did the job, and are almost self-explanatory when studied.

In Figure 3 the blank is being faced in a lathe. In Figure 4 is the special set-up devised by the doctor, consisting of an 80-tooth wheel bolted to the head. stock spindle, a supporting piece screwed to the bench, a 72-tooth wheel, and a ratchet engaging the latter. Figure 3 reveals the missing small gear, having 16 teeth.

The ratchet, working on the 72-tooth wheel, would alone give divisions of 5°. To reduce these to single degrees a 16-tooth wheel on the same spindle meshes with the teeth of the 80-tooth wheel, giving a reduction of 5 to 1.

The ratchet has a rubber band spring. The maker states that, using a

carbide tool ground to a long taper and whetted on an oil stone, he was able to make the degree marks on a 4" blank in about 40 minutes.

Lesser details and the maker's name and address are available to especially interested readers.

JOHN R. HAVILAND, 426 Second Ave., Lyndhurst, N. J., author of the 22 famous book-length chapter on the objective lens, in "Amateur Telescope 23 92 Making-Advanced," sends us the following on the Barlow lens:

"So many inquiries have been made regarding Barlow lens behavior that the following is submitted to relieve 2 my 'homework' on the subject.

"In July, 1937, the method of designing a Barlow lens was described [also by Haviland.-Ed.] in this column but no exposition of what happened in a telescope system was included. So here -2' goes:

"In 'A.T.M.A.', page 231, there appears a formula for separated lenses, viz., F = (f_l X f₂) / (f₁ + f₂ -d), where F = focus of combination, f_l = focus of telescope objective, f₂ = focus of Barlow lens, and d = distance between the two lenses.

"Suppose we had a Barlow of focal length -18" (minus because the lens is diverging or negative) used with a 6" reflector of 48" focus. Suppose further that the Barlow is placed 2" inside the focus of the mirror. What is the new focal length? What is the magnifying power? We get out our pencil: "Substituting in the formula:

F = (48 X -18) / (48 - 18 - 46)

= - 864/ - 16 = + 54.

"Note that the eyepiece has to move 6" out to the new focus. As the Barlow moves in toward the mirror the eyepiece moves out and the magnification increases.

"The magnifying power of this combination may be found by dividing the length of the cone cut off by the Barlow into the length of the new cone formed (Hindle, in 'A.T.M.', page 215). Referring to Figure 5 it will be noted that the cone cut off is 2" long and that the new cone is 8" long. The quotient of these is 4. Thus the magnifying power is equivalent to that of a telescope having four times the focal length of the original.

"A magnifying: power of four is about the maximum desirable. Make the Barlow lens of sufficient diameter to include slightly more than the diameter of the cone of light from your objective when the Barlow is placed as far within the focus as it will be used. 3/4" would be about right for the example above, since a 1/2° diameter field is about this size 2" inside of focus in a 48" focus telescope.

"As in any system which magnifies, the intensity of illumination goes down. In the above example the image of the Moon would be about 2" diameter. No ordinary eyepiece would accept an image this size. The illumination when using a 1" (equivalent focal length) eyepiece with the Barlow will be the same or better than when using a 1/4" , eyepiece without it-the magnification being the same in each case.

"The advantage of the Barlow is that 9 the cone of light from it has a more acute angle at the vertex than the cone from an f/8 reflector. Thus, cheap eyepieces (Huygens or Ramsden) will perform satisfactorily with it and will be comparatively free from the bad color and spherical aberrations which they produce when fed the wide angle beam from a large aperture-ratio objective. Despite the imperfect achromatism of the Barlow, the overall result will be an improvement over the common reflector and Huygens eyepieces. Most of us can't afford the trick eyepieces needed to give good color correction on reflectors, so the Barlow is an easy way out of this difficulty, as well as furnishing an exercise in making an achromatic lens of not too rigorous limits of figure and achromatism."

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