regards, Bruce

TINSLEY

In 1926, Clayton R. Tinsley, a high school teacher, formed a company making telescopes,mirrors and telescope making kits, in Berkeley, Calif. A Tinsley Optical 12 inch Cassegrain telescope, circa 1929, was listed at Mt. Wilson in 1932 and 1935, where astronomers found that the optics were imperfect. It was then placed at the visitor's hotel at Mt. Wilson, later owned by David Levy, and then Bill Marriot, who measured the primary at f/3.8 & undercorrected, and polished the back of the secondary to find it full of bubbles & striae, and of a spherical profile -- thus possibly a Dall-Kirkham. Max Bray began his career in 1933, at Tinsley.

An undated catalog 'Supplies for the Amateur / Telescopes for School and Home', address 3017 Wheeler St., Berkeley, was issued during the 1930s but before 1937, when ATM 2 was published. Products are identical to the catalog described below, but including draw tube spyglasses 7/8 inch to 2 1/4 inch aperture, vulcanized fiber body. The 'Saturn' trademark was already in use. Tinsley sold the company to Donald A. Jenkins in 1937. An undated catalog, noting 'sixteen years of research and experience' (which must reflect Clayton's pre-professional experiences), includes the ATM 2 book and so is post 1937. It uses the 3017 Wheeler address, and an identical catalog uses the address 2035 Ashby Ave., Berkeley.

These catalogs list: -Cassegrainian, f/16, equatorial on pier, electric clock drive, with 3 Ramsden or Huyghenian eyepieces; 6 inch $390, 8 - 10 - 12 - 14 - 16 inch, 20 inch $5500. -Newtonian, f/8, equatorial on pier, electric clock drive, 6 inch, 8 inch; 10 inch $675. -Four inch f/8 equatorial Newtonian, 'Saturn' mount, tripod, $175. Also altazimuth mount. -Equatorial mounts & rough castings for mounts, mirror cells, parabolic mirrors 4 to 12 inches, objective lenses to 4 inches, telescope making kits, mirror blanks, objective lens blanks to 6 inches, eyepiece lens blanks, Foucault tester, spherometer, focuser, terrestrial eyepiece, Ramsden & Huyghenian eyepieces 1/4 inch to 2 inch focal length, solar Herschel wedge, prism & mirror diagonals. -Services: correction work on customer's mirrors, silvering mirrors using Brashear process (lacquered on request); aluminizing using 'new Pancro process', an alloy of magnesium and aluminum, overcoated with aluminum oxide (panchromatic meaning true colors, reflectivity across the spectrum is superior to aluminum).

During WWII, the company made binoculars and optical parts. The "Optical Elements Code Chart, 9 March 1944, Ordnance Fire Control Sub- Office, Frankford Arsenal", notes the glass parts were required to be identified by maker on the rough ground edge of the optics, using a letter code in black ink or a color code in 2 dots; Tinsley Laboratories codes being TLA, or white-green.

During 1946, Tinsley incorporated, and began manufacturing a line of spotting telescopes and riflescopes. Two inexpensive amateur refractors, on altazimuth mounts and wood tripods, were introduced in 1955; a 44 mm for $48; and a 3 inch for $199. By 1955, the address was 2350 Grove St., Berkeley, Calif. An undated brochure for Tinsley Laboratories / Saturn Precision Telescopes, uses the address 2526 Grove St., and notes a quarter century of experience. -The Saturn Junior Refractor was 44 mm, 60 power with a 4 lens erecting eyepiece, at $48. -3 inch ($199) and 4 inch ($345) refractors, altaz on portable tripod. -3 inch ($860), 4 inch ($1,185), and 5 inch ($2,750) f/15 refractors, equatorial mounts. -8 inch ($1,412), 10 inch ($2,148), and 12 inch ($3,480) Cassegrains, f/16, equatorial mount on pier. -6 inch ($960), 8 inch ($1,266), and 10 inch ($1,864) Newtonians, f/8, equatorial mount on pier. -Other unspecified products: Maksutovs, Schmidt systems, mounts, binoculars, spotting scopes, eyepieces, flats, mirrors, lenses, prisms, Abbe prisms, Wollaston prisms, Amici prisms, aluminizing and coating.

In 1957, Jenkins retired & sold the company to a group of employees and investors. Tinsley then was producing telescopes for universities, and Schlieren optical systems. Tinsley became a public corporation in 1961. A 20 inch triplet apochromatic refractor was made during 1963-4 for Ben Morgan, who paid Tinsley about $250,000 for it, and sued Tinsley over its performance. Lowell observatory purchased it circa 1963 for $100,000 or less, where John Hall tested it and thought it was good enough. The objective was returned to Tinsley for work once or twice; and taken to the U. of Arizona optical shop, where Don Loomis reworked & respaced it. At Lowell, it was intended for lunar mapping, but it was not a successful lens, and it need to be stopped down to about 16 inches to provide a sharp image. The telescope is shown in the Dec. 1964 S & T, p368, in a Tinsley ad, which describes it as 'ordered for lunar mapping'. The objective is now on display at Lowell, and the dome & part of the mounting are still in use.

For Boeing, in the mid 1960s, Tinsley made a wide field optical collimator using a modified Wright-Schmidt design, 18 inches aperture, with a 5 inch flat focal plane. This was used in a vacuum housing, which gave the Schmidt corrector plate the proper profile. An undated brochure is devoted to The Tinsley Five Inch, Maksutov Cassegrain, 5.65 inch primary, 5.1 inch corrector, f/15 overall, focuser uses a Starrett micrometer, near focus 22 feet, single arm fork mount; DC variable speed drive, rheostat speed control, rechargeable battery. $1450. Accessories include a 'photographic module' camera adapter with flip out diagonal mirror, which replaces the eyepiece housing. A 12 inch Tinsley Cassegrain is being restored as of 2001 by the Peninsula Astronomical Society near San Jose, Calif. Collimation is difficult because the mirror cell has no adjustments for centering or tilting the primary; the mirror is installed by placing the forward surface against a stop and the telescope back is then bolted in place to hold the mirror. Speculation is that the primary might be spherical and the system an exotic type of Cassegrain. An 18 inch Tinsley cassegrain is in a private observatory in Idyllwild, California, as of the 1980's. The Mt. Cuba Observatory, (Greenville, Delaware) 24 inch Tinsley Cassegrain is from 1964, and has f/16 and f/32 secondaries. A Baker corrector lens for prime focus astrophotography yields a 7 degree field, but requires the primary be stopped down to 20 inches, using a built in aperture ring in the mirror cover.

Most of the blueprints are copies of those for the U. Virginia 30 inch telescope. The 'Richard B. Herr Memorial Telescope' is in active use to this day. (From Emil Volcheck) Brigham Young U. owns a 24 inch Tinsley. Robinson Observatory of the Central Florida Astronomical Society owns a 26 inch Tinsley cassegrain, with a small hole in the back of the secondary, used to align the secondary with the focuser by inserting a laser pointer or a flashlight, to project a beam to the focuser. This telescope can be seen at their web site: www.cfas.org. University of Virginia's McCormick Observatory, Fan Mountain station, has a 30 inch Tinsley Cassegrain with a 5 inch Tinsley Maksutov as a finder scope. A source at U.V. is quoted that the mirror is 32 inches, but for prime focus work is stopped down to 30 inches, because the Baker corrector lens shows distortion at full aperture. U.V. has a student observatory on campus, that circa 1970 apparently housed a Tinsley 8 inch telescope that is now replaced.

The Fernbank Science Center, Atlanta, Georgia, has a 36 inch Tinsley. The 1 meter Ritchey-Chretien telescope at USNO Flagstaff was designed & built by George W. Ritchey, and completed in 1934. The Pyrex optics were replaced with Corning fused quartz in 1969, and Tinsley figured the primary to a modified concave hyperboloid, and the secondary to a modified convex hyperboloid. The Air Force Research Lab, Maui Space Surveillance Site, uses pair of Tinsley 1.2 meter open tube classical Cassegrains (parabolic primary and hyperbolic secondary), mounted on opposite sides of a single polar axis and fixed to a common declination axis.

See: http://ulua.mhpcc.af.mil/AMOS/gallery.html

U. Michigan's 1.3 meter (52 inch) Tinsley reflector, installed 1969 at the Portage Lake Observatory in Michigan, and was moved in the early 1970s to MDM Observatory on Kitt Peak. Tinsley was the prime contractor, and figured the optics from Cer-Vit (f/2.6 primary, secondaries, and two Coude flats). The secondary rotates to switch between f/13.5 and f/7.6 Cassegrain optics, and a third secondary is gimballed in place for f/33.5 Coude. The primary rests on an 18 point cell, with radial support from six teflon coated steel straps, each wrapping around 120 degrees of the mirror's circumference. The two pier English mounting and major mechanical parts were done by L and F Machine Co., Huntington Park, Calif. The telescope is still in use every clear night. See Sky & Telescope, Feb 1971, page 72. (from Patrick Seitzer)

A circa 1972 booklet notes the 34,000 square foot factory at 2448 Sixth St., Berkeley, built in 1961. Products included: A window for Skylab, 23 by 19 by 1 5/8 inches, transmitted wavefront lambda over 20 peak to peak; parallelism to 0.004 inch. Aluminum mirror, nickel plated, 23 feet diameter, f/1.9, spherical, weight 14 tons, for Martin Marietta, 2 made. Beryllium mirrors, nickel plated, 10 inch, polished to lambda over 10 peak to peak. In 1972, Tinsley ceased production of telescopes, in favor of precision optical systems and components, especially manufacture of aspheric optics.

By the 1990s, Tinsley was owned and operated by the Silicon Valley Group http://www.asphere.com/ Tinsley made COSTAR (Corrective Optics Space Telescope Axial Replacement) for the Space Telescope circa 1992. These were five pairs of mirrors placed over the focal planes of the telescope instruments. Wavefront error was better than 1/100 wave rms, and surface roughness was 4 to 5 Angstroms rms. ------ Sources: Tinsley catalogs & advertisements from Sky & Telescope. Email from various sources. 'Historical Notes About Tinsley', email from the Tinsley Corp., 1992.