Binocular telescopes by W.C. Edgecomb, Mystic, Connecticut. (Photograph: http://home.europa.com/~telscope/edgecomb.jpg Twin Telescope, no maker’s name, some parts are stamped with numbers. Style & origin (found in Mystic) indicate Edgecomb. Objective: 50 mm clear aperture, 600 mm focal length, f12. Air spaced doublet with edges of lenses in contact. Individual focus at each tube with rack and pinion. Interpupillary distance & horizontal collimation adjust with wheel between oculars and knob at yoke. Vertical collimation by knob at right ocular, lens is carried in ring inside ocular that moves on threaded rod attached to knob. These two adjustments do not appear in the models shown in the Edgecomb catalogs. Inverted image, near focus about 20 feet Original ocular probably equivalent to 12-15 mm focus. Left ocular missing eye lens. Right ocular, eye lens flaked where burnished in cell.) =============== William Cary Edgecomb lived from 14 August 1845 to 28 June 1906 in Mystic, Connecticut, at 64 Edgecomb St, where he had an observatory & taught astronomy. He manufactured & advertised binocular telescopes, at least 5 of which survive. One has 5 1/4 inch objectives mounted in cells that allow for collimation of the two tubes. The others have 2 3/4 and 2 inch objectives. One is at Mystic Seaport Museum. ===== 13 page catalog 'Binocular Telescopes', penciled date August 1895. "In the home at the seashore or in the country, wherever the desire of bringing distant objects nearer and seeing them more distinctly is felt, the binocular is the instrument that should be provided, for it produces this result in the most perfect manner, while at the same time it invests the objects observed with a charm and beauty never shown by the single glass." --2 3/8 inch, 34 inch focal length, variable power eyepieces 35x to 50x, rack & pinion focus, oak or mahogany tripod, $175. (no prism, unclear if there is a lens erector system or if this is an astronomical binocular only) --3 inch, each objective is cut along one side to allow the centers of the two to be placed 2 1/2 inches apart. 50x to 75x, rack & pinion focus, $325. --5 inch, about 6 feet long, various eyepieces are used to change magnification, to 60x - 80x for terrestrial use, & higher for astronomy. "In the one now in the writer's possession, the optical part and its arrangement is by Sir Howard Grubb." Prism erectors serve for interpupillary adjustment. "Price, with different powers, $850." Penciled note, "Sold to Mr. O.G. Jennings". --6 1/4 inch, optics by "Alvan Clarke & Sons". Focal length of the two lenses is "about 94 inches....they do not differ in focal length by an amount exceding 1/100 inch." "Price, with different powers, $2,500." ======= 8 page catalog of 'Reflecting Telescopes with Silvered Glass Mirrors'. --Mystic 1, alt-az, 6 1/2 inch mirror of 50 or 60 inch focal length, finder & 3 eyepieces, $165. --Mystic 2, equatorial, 6 1/2 inch mirror, 60 inch focus, 4 eyepieces 60x to 180x, $225. --Mystic 3, equatorial, 8 1/2 inch mirror, 72 inch focus, 4 eyepieces 70x to 560x, $350. --Binocular telescope, 2 1/2 inch objective lenses, variable power eyepiece 35x to 60x, alt az on floor standing tripod, $150. With each telescope a silvering outfit is furnished, sufficient to keep the mirrors bright for 10 years. Grinding & polishing of mirrors is by machine. Testing of mirrors is by the Foucault test, as developed by Draper, checked by viewing separation of fine lines or close double stars. Diagonals tested using diffraction bands, method of Steinheil, Hastings, and Brashear. Another copy of this catalog has '1/4 off' and '1/5 off' penciled in by the prices. ====== 12 page catalog "Silvered Glass Reflecting Telescopes" "The eye should be trained to see, and the mind to know what to see. It is the mind that sees." --The Alt-Azimuth. Improved mirror support without adjusting screws. 5 1/4 inch, $125. 6 1/2 inch, $150. --6 1/2 inch equatorial, pier mounted, rotating tube. $250. --8 1/2 inch equatorial, heavier pier, rotating tube. $425. (pier with 6 1/2 inch tube, $335.) --15 1/2 inch equatorial, 115 inch focal length, weight driven clock drive of Brashear type, price upon application, divided circles available. --Eyepieces: solid (Hastings design, or B & L made) or Huygenian recommended. Edgecomb "takes care to adapt each eyepiece to the mirror with which it is to be used." 6 1/2 inch is supplied with 65, 150, and 260 powers. 8 1/2 inch with 85, 200, and 350 powers. Other eyepieces available at $5. ====== A binocular telescope signed 'Edgecomb Mystic 1898', 5 1/4 inch objectives, 65" overall length without sunshades, prism erectors, single focus knob, objective cells adjust for collimation, mahogany tripod, was offered for sale in the 1990s. Another, signed 'Edgecomb Mystic', 43 to 48 inches in length, used image erecting variable power eyepieces. This was offered at auction in 1987 but withdrawn after it was learned that it had been stolen. ====== Daniel Webster Edgecomb, b. 1840, was William's brother and an amateur astronomer in Mystic and Newington, Connecticut. Daniel bought a 6 1/3 inch objective by Henry Fitz in December 1865, for $400, mounted & used it, and sold it in April 1874 to Hartford High School for $450. He ordered a 9.4 inch Alvan Clark steel tube refractor in July 1873 and received it 24 August 1874, paying $1650. Daniel had built an observatory in Newington in 1872, where he mounted the telescope, selling it in 1880 for $2250. R.B. Tolles made a 5 inch telescope of 51 inch focus and sold it to Daniel in 1882, who used it as a portable instrument. Daniel detected the nebulosity around Merope with a 12 inch reflector in 1886; and had a 15 1/2 inch reflector the next year. Both brothers were very acute observers, recording the companion to Sirius, the white spot on Saturn, the fifth & sixth stars in the Trapezium, and more. They were friendly with Alvan Clark, who told them (as Daniel writes), "they had seen (the close double Eta Coronae Borealis) with 12 1/4 inches, but only by tilting the O.G., so that the rings of (diffraction) were thrown away from the small star" (4 July 1878). Daniel wrote: “I have long been interested in binocular telescopes, and have put many together with objectives from 2 1/4 inch upwards. When in England I had Sir Howard Grubb make for me one of his binoculars with prismatic eyepieces, and object-glasses five inches in diameter.” There is no further documentation of Grubb’s binoculars, including the new book length history of his firm. Edgecomb describes the instrument as “somewhat remarkable” in use, noting that the focal lengths of the two objectives differ by about one tenth of an inch. When Edgecomb commissioned Clark to make his 6 1/4 inch instrument, Clark estimated he could produce a pair of lenses with focal lengths matched to one hundredth of an inch. The two lenses were cut from the same pieces of glass, ground & polished by Lundin, and Edgecomb found them to be indistinguishable, with a focus of 94 inches (any mismatch undetectable at under 1/100 inch) and identical color correction (color free mid field, with a small remnant of color off axis). The prisms, also worked by Lundin, were 2 7/8 inches long and 1 5/16 inches thick, the light passage through the prisms totaled 5 1/2 inches; and Edgecomb could not measure the absorption but roughly estimated it at 20 percent, offset by the brighter appearance of objects seen by both eyes. Long previously, Daniel had asked Alvan Clark about making a binocular telescope, but the reply had been that making a single perfect objective was challenge enough, and that a matching pair was not going to be produced in the near future. Clark told him while making the binocular, that the instrument required skill equal to any of their earlier work. Daniel wrote a long article describing his use of the Clark binocular telescope and extolling the virtues of this type of observation. Faint detail is more certain, vision is less fatiguing, objects seem larger, and seeing is improved because only one eye needs a steady image. 'Jupiter is no longer a figured disc but a floating globe....the beautiful perspective of the billowy masses of the belts'. "The Moon, a disc to the naked eye, becomes a globe in the field of the small telescope." "The beauty of all objects is greatly enhanced." He also notes the "limitations and defects....ghosts of bright objects in the field produced by reflections from the prism surfaces". Magnification is limited by collimation, above 300 requires re-alignment when changing eyepieces, Daniel found his personal use limited to about 400 power, and the inexperienced had problems above 250. Holding the head steady & in place is more difficult than with a monocular. Daniel advertised the binocular for sale in Popular Astronomy, vol. 17, 1909. ============ Sources: Ashbrook, Joseph. Sky & Telescope, January 1974. Edgecomb, D.W. Reflectors. Popular Astronomy, April 1895, #18, pp366-70. Edgecomb, D.W. On the Performance of a 6 1/4 inch Binocular Telescope. Popular Astronomy, vol. 10, 1902, pp523-31. Glass, Ian S., Victorian Telescope Makers: The lives & Letters of Thomas & Howard Grubb. Institute of Physics, 1997 The English Mechanic. May 31, 1895.