How, in the first place, did Porter happen to become an amateur telescope maker? To understand this we must jump back 15 years farther, to 1894, when we discover him working his way through the Massachusetts Institute of Technology and studying architecture. One evening he heard Commander Peary lecture on the Arctic, and from that moment he was down with a bad attack of "arctic fever." He laid plans to get himself included in one of Peary's polar parties but was defeated through an unsuspected influence, though Peary had intended to include him: his mother secretly begged Peary to turn him down. Just then, along came a certain Doctor Cook, unknown but affable and entirely plausible. Yes, indeed, he was willing to accept the youthful Porter to go on an expedition to Greenland. Porter went, and the ship was wrecked and sunk (See Cook, "The Cruise of the Miranda.") In 1896, however, he went with Peary as far as Greenland. In '97 he led his own party to Baffinland. In '98 he started overland to the Klondike, reached the headwaters of the Peace River far up in British Columbia, but could get no farther by that difficult route. In 1900 he took a party to Greenland on Peary's ship. In 1901 he went to Franz Josef Land with the first Ziegler Expedition, and in 1903-4-5 he was with Fiala on the second in the same high latitude. In 1906 he went to Alaska with Doctor Cook. The doctor had not yet been "shown up" but, as almost any arctic explorer will tell you today, he was a personally lovable man despite his weaknesses. Cook announced a plan to ascent Mt. McKinley, highest on the continent, but also cooked up a plausible excuse to send Porter in another direction while he was ostensibly climbing the great mountain.

On all these expeditions Porter was not only the official artist and surveyor but the expedition astronomer. He picked up astronomy as he went along-the brilliant arctic skies aroused his interest.

By 1907, Porter's "arctic fever" had finally burned out and he married and settled down at Port Clyde,

Maine. An old friend, Governor James Hartness, head of the Jones and Lamson Machine Company of Springfield, Vermont, Porter's real home town, sent him several copies of Popular Astronomy. In one of those he found an article by a man named Holcomb, of Decatur, Illinois, who described making a reflector. Through correspondence with Holcomb, Porter learned of the book, "Glass Working by Heat and Abrasion," by Paul Hasluck, now out of print. He set up the pedestal shown in Figure 1, made of wood sunk in the soil of the gloomy old cellar, and started work on a 10" disk. "I shudder even today," he recently commented, "when I recall its horrible figure." Encouragement for the tyro! Porter afterward made approximately 100 mirrors.

In Figure 1 is a stone pier having a ledge. Originally this pier supported four fireplaces in the rooms above, but it proved to be squarely in Porter's way when, some time after his beginning, he wished to test a 16" mirror whose radius of curvature was 36'. The ledge represents the cut he therefore made in the pier, to enable him to make the test diagonally across the cellar. At another time, during Mrs. Porter's absence, when he wanted to try out a polar type refractor, he slashed a hole straight through the dining room wall of the house. She's still talking about it. Well, can you blame her?

Your scribe has visited this house and seen the cellar, in which various mirror-making accessories - glass tools, laps, and so on-remain, neatly arranged just as they were left about 25 years previous. They still remain Figure 2 shows the house, built in 1819, and on it may be seen the small wing which Porter added as a study. Above this wing an unpainted vertical strip may be seen. Here the Porter polar telescope, shown in "A.T.M.," page 51, at V in Figure 42, once was attached.

Near the old house stands the fieldstone castle shown in Figure 3, built about 1910 by stonemason Porter, who wielded his own trowel.

Figure 4 is an interior view in this castle, showing Porter drawing heavily on a pet pipe. What looks like a picture of a ship is really a stained glass window showing the expedition ship America held fast in the ice near Franz Josef Land in 1903, just before she was crushed and sunk there, leaving the explorers on half rations for two years. (See Fiala, "Fighting the Polar Ice," which contains a section by Porter). This window was made by Porter, of pieces of stained glass and lead "came."

Near the stone castle are the only remains of Porter's first observatory --a low circular stone wall on which before it rotted down, stood a wooden fixed wall surmounted by a canvas dome.

If Porter hadn't heard Peary Lecture one night in 1894, he probably would have escaped his ten years of

arctic fever, and thus his interest in astronomy. He therefore would not have wanted a telescope on his final return from the Arctic. The telescope making hobby would not have been expanded when it was; and so you, instead of making telescopes might have been building bird houses for a hobby, or helping the ladies grow roses.

AS Everest says, in "A.T.M.A.," a long stroke is scarcely sufficient for parabolizing a very short focus mirror, because after it reaches a certain depth it refuses to dig farther. Cyril G. Wates, Edmonton Alberta states that he therefore tried a star lap, as Everest recommends. "I cut a star in the middle of a disk of heavy cartridge paper, boiled this paper in paraffine wax, warmed up the lap and cold-pressed the paper disk into the lap, thus obtaining a star in relief. The result was good. This is essentially similar to Everest's method of pressing down facets with thin paper but is more drastic.

WHEN a mirror has a very short n focal ratio, say from f/2 toward f/0 (properly described as a "greater" focal ratio, though the number used is smaller), it is doubtful whether much or any gain in time will be made in attempting to parabolize from the usual sphere. Recently we told here how Buchele, of Toledo, worked 14 hours to excavate a paraboloid from a 12" sphere of f/2.4 More recently, Ferson, of Biloxi, Miss., started out to parabolize a 12 1/2" f/1.4 sphere by the ordinary method. Here r²/R was more than one full inch. After 20 hours of perspiring he found he had gained only a quarter of this and leaned back to puff; and while puffing he suddenly decided to charge off the time thus far expended to experience and do the rest with Carbo.

He therefore gave it about three hours of No. 600 and then a little 303 1/2 emery, and when the curve was approximately down to the desired point (as determined by giving it a brief polish, good enough to afford a rough knife-edge test), he did the regular full polishing and figured with pitch laps of 3", 6", and 12" diameter. In this latter sub-diameter tool technique there is a good deal in common with working the correcting plate for a Schmidt.

STUNT for controlling fineness of rouge was described several years ago in a letter from C. A. Spickler, Yardley, Pa. He siphoned the rouge water from a bowl into a tea cup placed at a lower level, using a strip of woolen cloth. The fineness of the rouge deposited in the cup is regulated, he states, by the quality of the cloth. This may be the answer to some workers' trials with scratchy rouge.

CONSERVATIONIST James G. Hayden, New Lexington, Ohio, urges others who are hard up to follow his example. With a "biscuit cutter," or rotating metal ring armed with abrasive, driven by a motor, he cut up two old glass tools of 6" and 10" diameter into two 4 3/4" and two 3 3/4" mirror disks and now has four extra mirrors where none grew before. Of course, if you count your time--but don't count your time.

FOR the benefit of non-mathematical readers, Ellison, in his treatise on the objective lens, according to Royal W. Woodring, of Woodring and Mattie, masons, 202 Highland St., Roxbury, Mass., "explains the meaning of the term reciprocal, goes into his 'rule of three,' and, in general, does a lot of hopping and skipping around to confuse the reader. I have reduced his equations to order."

We can't admit that Ellison's equations are confusing, though the Ellison presentation probably would strike some who do not need such help as containing much that is superfluous. Anyway, for those who have already mastered Ellison and Haviland on the objective lens, the compact framework offered by Woodring undoubtedly will be a big help. It is as follows:

First Curve

Crown lens: Radii of surfaces as 2:3.

Flint lens: One surface fits one surface of crown. The other is plane (or very nearly so).

(Decide on the focal length you want for completed objective and call it F).

= number corresponding to [0.22185 + log F + log (cr u - 1) + log (cr V - fl V) - log (cr V)]

= number corresponding to [0.69897 + log F + log (cr u - 1) + log (fl u - 1) + log (cr V - fl V)- log 5 (fl V) (cr u - 1) - 2 (cr V) (fl u - 1)]

[Formula for r₄, above, being too long for the column, its numerator and denominator are each broken in two pieces. Similarly with single term under vinculum, above.]

Second Curve

Crown lens: Radii of surfaces as 3:2.

Flint lens: One surface fits one surface of crown. The other is plane (or very nearly so)

= number corresponding to [0.39794 + log F + log (cr u - 1) + log (cr V - fl V) - log (cr V)]

= number corresponding to [0.69897 + log F + log (cr u - 1) + log (fl u - 1) + log (cr V - fl V) - log 5 (fl V) (cr u - 1)-3 (cr V) (fl u - 1)]

Third Curve

Crown lens an equi-convex.

Flint lens plano-concave. Its concave surface has the same radius as either surface of the crown.

2F (cru-1) (crV-flV) r, = cr V

= number corresponding to [0.30103 + log F + log (cr u - 1) + log (cr V - fl V) - log (cr V)]

r₂ = r₁

r₃ = r₂

= number corresponding to [0.30103 + log F + log

(cr u - 1) + log (fl u - 1) + log (cr V - fl V) - log 2 (fl V) (cr u - 1) - (crV) (fl u - 1)]

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.

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