Albert Ingalls and the Roof Prism Gang. by Peter Abrahams. May 2002. The history of telescope making by amateurs is filled with interesting sidelights, among them the war time efforts of patriotic ATMs. For example, in 1918, during World War I, George Ritchey at Mt. Wilson worked with a team of students & assistants to produce the optics for Army gun sights. During the Second World War, amateur telescope makers in the United States assisted the war effort in several ways. At Harvard U., James Baker worked with the ATMs of Boston in the Observatory Optics Project, a secret optical fabrication unit that mainly produced aerial photography lenses, shutters, and film mechanisms. Also during WWII, the U.S. War Production Board attempted to fill the immediate need for 350 lens grinders, by working with Frankford Arsenal, Bausch & Lomb, and Eastman Kodak, to publish a standard procedure for producing optics for the M-1 Circle Aiming Instrument. But the largest ATM war effort was a project to produce roof prisms for military use. These were used in a variety of optical devices; telescope sights for field guns, anti-aircraft guns, tanks, rangefinders, and gunsights, but not binoculars. The Italian Giovanni Battista Amici (1786-1864), invented this prism, and because he was an important telescope maker, a few words on Amici are in order. He designed & built many types of instruments, including a Newtonian reflector of 8-foot focal length, and achromatic telescopes with lenses which he ground and polished. The 28 cm lens for the Arcetri Observatory in Italy was the second largest objective at that time (1839) and is often described as Amici's masterpiece. It is still in use for astronomical observations. By 1827, he had built a reflecting telescope, possibly a siderostat, described by a contemporary: "vertical tube and a perforated mirror at the top that was movable in all directions, reflecting the light down the tube to a spherical or parabolic mirror which reflects back through the perforated mirror to the eyepiece". Also developed by Amici were micrometers which he personally used in astronomy to improve angular measurements. He is known for his reflecting microscopes. And the prism: a development of the simple right angle prism, made by grinding & polishing two angled surfaces into the hypotenuse. These are still used in 'correct image' star diagonals; in military elbow telescopes, gunsights, anti-aircraft sights, and the panoramic field-gun sight with a rotating right angle prism in front of the objective. The elbow design allows the gunner to look into a horizontal eyepiece on a concealed gun and aim, adding corrections for windage & drift, from a hidden position. If you think about viewing from a foxhole with a spyglass, you can imagine the importance given to an elbow design. However many big guns there were in WWII, that is the number of roof prisms that were needed. The needs of the U.S. military forces for these prisms were partly met by a group of amateur telescope makers, known among themselves as the Roof Prism Gang. Albert Ingalls, then an editor at Scientific American magazine, was the major organizer of the Roof Prism Gang. Ingalls was probably the single most important person in 20th century ATM, but he was a quiet & retiring person, only occasionally speaking in public. There seem to be no high quality published photos of him & the only biographies are two articles in Sky & Telescope, by Bob Cox & by Tom Williams. Ingalls was born in Elmira, New York, on January 16, 1888, an only child, and grew up in Watkins Glen, New York. He graduated from Cornell University in 1914, worked briefly as a telegraph operator in Buffalo for one dollar a week, hunted employment in mining and timber camps in Ontario Canada, but could only find work cutting wood, and returned to Watkins Glen without a dime. He worked in the municipal library of Philadelphia, enlisted in the New York National Guard, performed military service in 1916 on the Mexican border, and served in France during World War I. In 1923 Ingalls joined Scientific American as an editor, remaining until he retired in 1955. He described his job as "obtaining articles, editing articles, finding the illustrations, writing the captions, reading the proof and, in general, being wet-nurse to six major articles each month, all the time badgered by no end of inquiry letters to answer on non-telescoptical subjects." Ingalls read & responded to an article on telescope making by Russell Porter in Popular Astronomy. Porter had discovered telescope making in a note from a 1911 Popular Astronomy about a telescope made by Leo Holcomb of Decatur, Illinois. Holcomb had been motivated by an article with brief instructions by John Mellish in a 1907 Popular Mecanics. Ingalls met Porter and then visited the group of ATMs in Springfield. He wrote an article on his visit in the November, 1925 Scientific American, adding that if enough readers sent letters, a follow-up article with instructions on how to make a mirror and mounting would be published. 368 letters were received in the next weeks, and the first ATM article appeared in February, 1926, written and illustrated by Porter, on making a paraboloidal primary mirror for a Newtonian, followed in March by an article by Porter on telescope mountings. In April, 1926, John M. Pierce, one of the Springfield Telescope Makers, wrote about a simpler process for a very basic telescope. The first Stellafane was on July 3, 1926, with 17 attendees. Also in 1926, the first edition of the famous Amateur Telescope Making books was published. They were astonished at the response these articles brought -- surprised at the volume of correspondence, over 1000 letters in a year, amazed at a group in Indianapolis who made a three-ton reflector three feet in diameter, and it is not known what they thought about a wife in California, whose husband became a serious glass pusher until she sued for & won a divorce. Ingalls wrote very little about his own telescope making efforts. In March of 1927, the column was titled, 'Even an Editor Can Make a Telescope'. He describes an open 'tube assembly' consisting of a plank from the mirror box to the secondary, housing in succession a 6 inch f8, 7 inch f7, and 8 inch f6 mirror. In 1957, Walter Scott Houston was editing the Great Plains Observer, and published a note from Ingalls including a list of 6 mirrors he had made (in 1925, a 6 inch f8; 1926, a 7 inch f8; 1927, an 8 inch f6; 1927, an 8.5 inch f7; 1929, a 10 inch f8; 1945, a 10 inch f8). The 1925 mirror was kept on his desk in 1954, when a cleaning lady gave him some pieces of broken glass, saying 'Sorry, I broke your paperweight'. At the Convention of the Astronomical League in 1951, Ingalls accepted an award with these words: "I have contributed to amateur astronomy the ATM books, and, for a quarter century, my monthly articles in Scientific American. For twenty years I did most of this work at home as a side line to my principal job which consisted of securing and routinely editing my magazine's articles on the pure sciences....There has, however, been a third kind of contribution which I cannot so easily describe. From the beginning in 1926, I have never left a stone unturned in my extensive correspondence, not only to go all out in answering inquiries well and roundly and the opposite of perfunctorily, but especially in making use of every possible opportunity to connect one amateur with another, and I am sure this had a significant effect in the furtherance of the fraternity.....the reception of the story by our readers resulted in the exodus of the movement into all parts of the universe. Thus it was a link in TN history. I suspect it has been quite forgotten and thus, while old stuff, will be new stuff to most of you, if you survive it." He retired in June of 1955 to Cranford, New Jersey, to study genealogy, traveling on a motor scooter around New York state until he was hit by a car, his injuries resulting in paralysis. After a year of immobility and pain, Ingalls died August 13, 1958, at 70 years of age. Albert Ingalls was the instigator & maintainer of the Roof Prism Gang, an organization of craftsmen who typically did not meet but were brought together by the U.S. Mail. Ingalls addressed his correspondents as prismartyrs, prismachers, and fellow workers. Roof prisms are very difficult optics to make using amateur equipment, and the story of how this group, perhaps 40 people, were recruited, trained, and supported, is worth remembering. These 40 RPG members made 28,360 roof prisms, equalling approximately 3 1/2 months production by the largest professional producer. Almost half were made by two particularly skilled opticians, Fred Ferson & Paul Linde, who made more than 11,000, about 99 percent of them acceptable. This is an outstanding acceptance rate for a very difficult optical part; the two prism surfaces that meet at the roof must be kept flat, and the angle between the roof planes must be square to two seconds of arc, a tiny angular distance -- if you're looking at someone 30 miles away, their two shoulders subtend two arc seconds. The persons whom Ingalls called TNs (Telescope Nuts) were notified in 1937, that a war seemed to be imminent, and if it happened, those with optical skills would likely be able to render significant assistance. Fred Ferson, of Biloxi, Mississippi, a serious ATM who became a professional optican, had anticipated that roof prisms for gunsights would be needed in very large numbers and realized that the technical difficulties in manufacturing them would be a major bottleneck to war production. In 1940, by which time as an ATM he had made only small lenses, three telescopes, and three flats; Ferson quit his old business, built a shop and machinery of his own design, and developed a procedure for producing roof prisms. Also in 1940, Ferson obtained a contract with the Spencer Optical company for providing roof prisms. Porter, in California, was also at work, by Sept. 1941, he had approached the Los Angeles Astronomical Society, hoping to find opticians for making roof prisms. Porter, Ingalls, and Ferson went to the Army's Frankford Arsenal near the end of 1941, and proposed that the amateur group make a batch of sample roof prisms, which would be tested by Frankford and rated for quality; and contracts would then be issued to opticians who passed. Frankford supplied 24 prism blanks at first and then 100 more blanks. Eventually 2 blanks were sent to each of about 80 ATMs by Ingalls, fabricated into prisms, returned to Ingalls and then forwarded to the Arsenal. After testing, Ingalls arranged contracts for those who succeeded, stipulating payment of $15. per successful prism. Ingalls described the group as 'mature, middle-aged men with established vocations… a metallurgist, a biologist, a steel worker, a cabinet maker, two physicists, two chemists, a candy manufacturer and a gravestone manufacturer (who work as partners), several engineers, an accountant, a physician, dentist, decorator, geologist.... A group in one community comprised a microscopist, teletype engineer, telephone engineer, paleontologist, and a herpetologist (snakes) - all working in spare hours.' There were no instructions available to provide to these workers; none of the knowledgeable persons had any inclination for writing such a text, and the experts felt that 'the subtleties of the higher precision optical skills were too elusive to capture and put into writing'. However, Ingalls had developed, for 15 years, a tradition of far-flung ATMs using written text to communicate instructions. Porter was working on the Palomar project in California by this time, but contributed an article on testing prisms. Ferson did the bulk of the writing, describing what he had been forced to teach himself because there was no earlier record. Herschel Ice (real name) had worked at Frankford Arsenal for 6 months, and wrote about their prism procedures. These texts were assembled into a mimeographed, Roof Prism Gang newsletter, mailed about monthly. In addition to this bulletin, a very large quantity of letters were sent to Ingalls with problems or solutions, who replied and also forwarded them to Ferson & Porter for further comment. A military censor saw problems in this quantity of correspondence, and demanded that all participants take a fictitious name and not mention their address. This requirement resulted in an amusing but highly confusing story. Ferson was Amos, Ingalls was Andy, Porter was Mist Van Potah, Paul Linde was Pavel Uvaroff, G. Dallas Hannah was George Ellis, Horace Selby was Daniel Widdicomb, William Buchele was Robert Gray. These pen names make the newsletters exceptionally difficult to utilize as a historical record; and there were alternate nicknames as well, Ferson was also Sandy McTavish. Fabrication of these prisms is an involved procedure. According to Ordnance Document 1065, 'Angles having the requisite accuracy cannot be produced directly, but must be carefully approximated by usual manufacturing methods: after which the faces must be carefully polished by a skilled operator and individually tested until the angle is so nearly correct that the image is not doubled.' To begin, glass can be pressed or molded to a rough prism shape, but usually, slabs of optical glass are sawn into rectangles and after rough grinding, cut diagonally to an approximate shape using circular saws with blades of sheet metal with abrasive embedded in the edge. A quantity of rough blanks are cemented, using hot wax, to flat iron plates and as a group are ground on other flat iron plates, to the approximate final thickness and squared shape with parallel faces, in several stages of cementing - grinding - removing - rotating - cementing - grinding. Then, as now, the machines used were rigged up rather than purchased from a commercial manufacturer. Here is an example of the designs they discussed. After this stage, the 90 degree angle between the entrance & exit faces is corrected in fine grinding. Then groups of rough ground blanks are cemented into V grooves in discs of plate steel and fine ground to the final dimensions. The two roof faces are ground onto the hypotenuse while the prisms are held at an angle in the V grooves. Assuring that the roof ridge is in the exact center of the prism, is parallel to the sides of the prism; and is exactly 90 degrees, is a formidable task, for correcting any one of these conditions will alter the other conditions. The angle between the roof face and the entrance / exit faces is 60 degrees. Ferson says, "After the roof faces are ground on, the 60° angles are corrected by hand retouching against an iron plate with fine abrasive-a very ticklish, fatiguing task. Using pitch laps & optical rouge, the prisms are polished and made flat to optical tolerances. The prisms are cemented with paraffin to an iron plate, this plate being flat to optical tolerances; and the prisms must be seated with great care so that the corrected angles are not changed with further work. A metal ring is placed at the rim of the plate, plaster is poured around the prisms, the ring is removed, and the bottom iron plate is removed by warmed the paraffin. The top layer, about 1/6 inch, of plaster is removed, so the prism faces protrude slightly, in relief, and the plaster is shellaced to waterproof it. Then all that remains is make the protruding prism faces into a big optical flat, working face up on a Draper machine. Plaster is not dimensionally stable with changes in temperature, so that air temperature must be controlled. First the two entrance & exit faces are polished, with reblocking in between the work, then a third recementing and reblocking to work one roof face. But before the second roof face is worked, the roof angle is hand-corrected to a right angle, in hopes that after the second roof face is worked in the block, the roof angle will be true to 2 minutes. Very pure abrasives must be used here, since any tiny chip on the roof edge will be visible. Ferson reported that 1000 grit carborundum can cause fractures on the roof edge, and recommended very fine emery powder. After the second roof face is worked in the block, freehand correction with rouge is performed to perfect the roof angle. Ferson writes: "Thus all four optical faces have now been polished, and next comes one of the most thrilling operations known to me in optics - correction of the roof angle by freehand polishing on a small flat lap of pitch. Correction of the roof angle is not in itself so difficult, but the lap must be held flat at the same time - flat within precision tolerances - without astigmatic fringes or turns. The crux of the operation is the preparation of the lap and the use of strokes which will produce the desired results - and, of course, a skilful man doing it. Such a man, one of the most skilled hand- correctors in the country, is Pavel Uvaroff [Paul Linde], who has corrected as many as 55 roof prisms in a single day. Here is work where money and fancy equipment cannot substitute for the man. "As the angle is being corrected, frequent testing is necessary. A target of crossed thin lines is placed about 30 feet distant and its image is viewed through the prism by means of a 20x telescope. The vertical lines do not double unless astigmatism is present in the prism. The horizontal lines double to a greater or less degree, depending on the angle error. The aim is to correct the prism till they coincide and are as sharp and clear as the vertical lines. With greater magnification we have proved that an error of 1 second of arc can be discerned." Measurements and tests are made over 50 times during this process. "In producing the prisms, all angles except the roof angle are controlled in grinding and polishing to 2 seconds of arc. This is assured if there is a light-tight reading under a fine standard square and a 60 degree gage. The roof angle is then brought to 90 degrees, plus or minus 2 seconds, by hand correction on a flat lap of pitch." Ingalls initially thought that amateurs could make prisms in evenings & weekends, but found that the job was too exacting to do after a day's work. Gang members who produced thousands of prisms had quit their jobs and concentrated on prism production full time or double time. The single exception, who produced 1700 roof prisms in spare time, after full time work, was the team of Ralph Franklin of Patchogue, N. Y., Frank Cameron, Inwood, N. Y., Mrs. Cameron, and one employee. In 1944, the program became unnecessary for the war effort and was terminated. In November of 1944, Ingalls wrote a wrap up, including these interesting sentences: "When World War III comes (compare with the history of Rome's three Punic Wars, in the third of which Rome virtually erased Carthage when Carthage was once more found to be rearming) When World War III comes let the amateur hit his optics early, hard, and unitedly, and with no inferiority complex." -------------------- Gang members of note included: Fred B. Ferson was the most skilled craftsman and the most effective teacher in the group. He was born in 1897 in Galena, Ohio; moved to Mississippi in 1912; graduated from Tulane U. in mechanical engineering, served in World War I, and worked in newspaper advertising and insurance. In 1933, he made a 6 inch reflector, followed by a few other mirrors and flats. In 1936, he built a Springfield mount; creating wood patterns; casting, machining and assembling the metal parts, from plans provided by Russell Porter. Ferson then wrote a text on how to fabricate the mount, for Ingalls' ATM book series. The imminent war motivated Ferson to quit his career and begin work as a professional optician, teaching himself how to make roof prisms. His experiences were the main source of technical knowledge behind the Roof Prism Gang. Ferson also wrote the long chapters on 'Lens Production', and 'Prisms, Flats, Mirrors' for later editions of the ATM books. During the war, Ferson, then in Biloxi, Mississippi, worked with professional optician Paul Linde ("Pavel Uvaroff''), from Crossville, Tennessee, as the Ferson-Linde Optical Co., of Biloxi. Ferson's second order was for 1700 prisms and Linde's second order was for 300. Together they made 11,160 prisms, with one full-time helper for grinding. Both were excellent craftsmen with a 99 1/2 percent acceptance rate. Linde continued his optical career after the war. Ferson went on to start Ferson Optics after WWII, originally to make amateur telescopes and other optics. A three element refractor designed by Horace Selby of San Diego was the first product, and was further improved based on consultations with Selby. Since 1953 the company was based in Ocean Springs, Mississippi. Increased government business during the Korean War caused the decision to cease producing amateur telescopes. Ferson made quartz windows for experimental aircraft and the Mercury and Apollo space capsules. Also made were Baker design tracking cameras for White Sands and Aberdeen rocket testing programs. Ferson optical flats, especially larger sizes, for the National Bureau of Standards were considered by NBS to be the finest flats they owned. Fred Ferson remained President until 1965, then chairman of the board; the company was purchased by Bausch & Lomb in mid 1960s, when it had about 125 employees at two facilities. Ferson died April 28, 1969. Peter Lenart, Jr., director of Ferson Optical; was born in 1918, and in 1936 began amateur telescope making. During WWII, he was trained to maintain artillery sights and sent to Normandy with the invasion, serving at front lines and in Berlin. In 1946 began work with Ferson. Ferson Optics was known for their '1216' telescope, 16 inches aperture, f/4 Newtonian and f/14 Cassegrain foci; rotatable tube in a single fork mounting, digital readouts; designed by Ferson engineer Shatzel; and costing $23,500 in 1967. 1216 Telescopes were sold to Colgate U.; Las Cruces; St. Marks Academy, Dallas, Texas - currently being restored & moved to the Dallas Astronomical Society site in southern Oklahoma; Werner Von Braun in Huntsville, Alabama - still in its dome but missing some parts & not functional, with optics said to be superb; Naval Academy, Annapolis - now in a West Virginia public school. In 1967, Ferson announced 3 new telescopes: 12 and 15 inch Maksutovs, and a 16 inch Cassegrain; all with three foci: Cassegrain, Cassegrain-Coude, and Newtonian. With a single fork mounting, rotatable tube, electronically controlled drive with positional readouts in declination and right ascension. Accessories included spectrographs, photometers, cameras, and power supplies. -------- G Dallas Hannah, whose first name was the letter G, was born in Arkansas in 1887 and died in 1970. He graduated from University of Kansas in 1911, worked at the Bureau of fisheries in Alaska, returned to school and received his Ph.D. from George Washington University in 1918. He was Curator of Paleontology (and later Geology) at the California Academy of Sciences, in Golden Gate Park, San Francisco. He published about 450 abstracts, articles, reviews, & scientific papers , on subjects including land mollusks of Kansas, mammals of the Pribilof Islands, amphibians from the Carboniferous of Illinois, birds of Golden Gate Park, a fossil whale from the Miocene of California, mollusks of the San Francisco Bay region, the geology of Sharktooth Hill in Kern County, preserving nudibranchs, illustrating fossils, diatoms of many types, and how to repair binoculars. His specialties were mollusks - fossil & contemporary, terrestrial & marine; and diatoms - fossil and modern, especially Californian. For microfossils, he devised a micro- manipulator, and an improved mounting media. During World War II, Hanna headed a group of amateurs at the Academy who were making roof prisms, and made 165 prisms himself, until on request of the U.S. Navy, they changed direction, to recondition fire control optics and then 6,000 Navy binoculars. Hanna was director and Waldeyer the foreman of the 50 person work force, which included ATMs J.A. Steinback, D.A. McLaren, L.A. Parsons, Carl Wells, & Karl S. Bailey; and 'non-ATMs' Allyn G. Smith, C.C. Church, and Edwin Over. Hanna wrote a chapter for 'Amateur Telescope Making, volume 3', detailing his processes for adjustment & overhaul of binoculars, and on the principles behind the work. Included were instructions for building an autocollimator around a telescope mirror, for testing prisms. Hanna writes, concerning binocular prisms: "these errors [angles between surfaces of prisms] left uncorrected, then the prisms must be matched in pairs in a particular manner so that the angle error of one cancels out the pyramidal error of the other; otherwise they will be additive, spectral colors will be bad, and the instrument cannot be collimated." He cites mil specs for the standard US 7 x 50: prisms, tolerance on all angles: 5 minutes of arc. "I received my instruction from a master teacher, Mr. Daniel Brower, then stationed at the U.S. Optical School at Mare Island, California, and who was detailed by Commander F.R. Kalde (U.S.N.R.), then in charge of the school, to assist the California Academy of Sciences in setting up an overhaul shop for naval optical instruments in World War II. As a result of this instruction we completely overhauled over 6,000 binoculars of many types and put them back in service." --G. Dallas Hanna, The Overhaul and Adjustment of Binoculars, ATM volume 3. After the war, the shop was converted to civilian use. Hanna supervised the design & construction of the California Academy Morrison Planetarium. He modified the Zeiss planetarium design, and built a planetarium projector using 3800 stars, each on a mask made by aluminizing glass with a grain of abrasive at the correct spot, the grain later removed to reveal a hole in the aluminum. A traveling microscope was designed to properly place each grain. Hanna made a thousand mile journey from Bristol Bay to Iditerod and back by dogsled. He worked in Alaska on field exploration for petroleum; also on a job sampling the ocean floor in mid-Pacific from research vessels. On mounting diatoms, Hanna wrote in answer to a question about how long it would take to learn the mounting technique: "It took me about six weeks, but you should be fairly proficient in three. I started out in the Pribilof Islands off Alaska, it was thirty below zero, and my hands shook a lot!" -------- In Toledo, Ohio, William Buchele made 7300 prisms, about 98 percent acceptable from the beginning, with the help of his wife, son, father, and brothers. He was an ATM who had made several telescopes, including a one ton, 20 inch reflector, described in Scientific American of October 1939. Buchele went on to a career making motion picture lenses, and at least one astronomical refractor lens by him is known. In Detroit, L. H. Sampson and several other amateurs made 4500 prisms, and produced other optical products, on which they planned to base a post war career. Dave Broadhead, 2,850 prisms, Wellsville, N. Y., 98 per cent acceptance. The Wellsville Optical Co., Wellsville, N. Y., was run by David Broadhead, a physician known as "Jim Fogarty" in the May 1943 newsletter. He was assisted by two part-time employees and by Mrs. Broadhead, and produced 1850 prisms. His first trial order was of 50 roof prisms, 47 of which were found acceptable; later batches were even better. Horace H. Selby, of Encanto, Calif., submitted his first four, all of which were all accepted, and he put a shop in his basement, with two employees, to produce 700 total. Selby later turned to war work in his profession of chemistry. Selby wrote the chapter on eyepieces for the ATM books and worked as a lens designer; the first product of Ferson Optics a triplet refractor designed and later improved by Selby. C. S. Walton, Wheatridge, Colo., and Anton Bohm, Denver, Colo., made 488 roof prisms. K. E. Dykoski, assistant in astronomy, University of Minnesota, 300 prisms. A. H. Johns, decorator, Larchmont N. Y., 165 prisms. F. R. Varela, engineer, Tenafly, N. J., 50 prisms. G. E. Gordon, photographer, Natick Mass., 25 prisms. F. A. Jasset, podiatrist, with F. Richards, Newton, Mass., 24 prisms. F. L. Frazine, jeweler, St. Petersburg, Fla., 18 prisms. A team of Strong and seven local ATMs worked together in a very crowded shop George Ellis led a group of five men in one shop. Dakin combined with Sloane to make a team. (Ralph Dakin?) ================== Bibliography. Cox, Robert E. Albert G. Ingalls, T. N. Sky & Telescope 17 (Oct. 1958) 616- 617. Ferson, Fred. Prisms, Flats, Mirrors. Pages 77 - 110. Ingalls, Albert (editor). Amateur Telescope Making, vol. 3. Richmond: Willmann-Bell, 1996. Hanna, G. Dallas. The Overhaul and Adjustment of Binoculars. Amateur Telescope Making, Book Three. N.Y.:Scientific American, 1953. (58pp, includes biographical notes) Hanna, G. Dallas. Making Rhomboid Prisms. Amateur Telescope Making, Book Three. N.Y.:Scientific American, 1953. (6 pages). (Used in collimators.) Hanna, G. Dallas. A Reflecting Autocollimator for Precise Measurement of Prism Angles. Amateur Telescope Making, Book Three. N.Y.:Scientific American, 1953. (13 pages). Ingalls, Albert G. Acceptance of the Astronomical League Award. Proceedings of the Astronomical League Convention 1951. Ingalls, Albert G. Even an Editor Can Make a Telescope. Scientific American 136 (March 1927) 195-196. Ingalls, Albert G. A Hobby Goes to War: Scientific American's Amateur Telescope Makers Find Their Peacetime Optical Skills are a Wartime Asset. Scientific American, May 1943, 202-205. Ingalls, Albert G. Potpourri of Amateur Astronomy. Scientific American 183:3 (Sept. 1950) 108-112. Ingalls, Albert G. Roof Prism Makers. Telescoptics, Scientific American, November, 1944 Ingalls, Albert G. Roof Prisms (an Addendum to the Article "a Hobby Goes to War", page 202f.). Telescoptics, Scientific American, May, 1943. Ingalls, Albert G. Telescoptics. Scientific American. February 1944. September, 1944. November, 1946. November 1953. Williams, Thomas R. Albert Ingalls and the ATM Movement. Sky & Telescope 81 (Feb. 1991) 140-143. ============================================== home page: http://home.europa.com/~telscope/binotele.htm