Schlesinger's Telescope: A History of the Yale 26-inch Refractor in The Commonwealth

1. Schlesinger's Telescope:A History of theYale 26-inch Refractor in The Commonwealth William van Altena and Dorrit Hoffleit Yale University(IAU Commission 8 - July 16, 2003)

2. Frank Schlesinger (1871-1943) • Yerkes (1903-1905) • 40-inch refractor and the first modern parallax program. • Allegheny (1905-1920) • 30-inch refractor - design, construction and parallax program. • Yale (1920-1943) • 26-inch refractor - design, construction and parallax program.

3. Schlesinger at Allegheny • Develops astrometric methods for most of the 20th century. • Designs and builds the first large refractor for astrometry. • Establishes first large-scale parallax program. Schlesinger with optician James McDowell and the Allegheny 30-inch objective (1914) .

4. Schlesinger moves to Yale • Begins planning for a Southern Station even before moving in 1920. • Plans a southern extension of the Allegheny program. • Site survey in New Zealand is promising, but did not match image quality of US west. • Invited to explore sites in South Africa • Adopted Univ. Witwatersrand in Johannesburg.

5. Johannesburg is selected!

6. Site preparation for 26-inch • Foundation work begins in Feb. 1925. • The South Pier of the English-type mounting is constructed.

7. Telescope in Mason Lab. • Constructed at Yale in New Haven • Design by Schlesinger with Roland Sellew • Cross-axis English-type Mounting • Forced-air cooling of objective lenses

8. Schlesinger leaves for the South December 1924

9. Telescope is installed • Schlesinger ensures that only on-meridian observations will be made! • Yale Cottage and the “Dome”

10. The HRH Prince of Wales Dedicates Telescopes! • 26-inch with F. Schlesinger (June 22, 1925) • Jodrell Bank with B. Lovell & A. Lyne (April 28, 2003)

11. Harold Alden is the first director • Director of the Southern Station from 1925-1945. • Implemented the extension of Schlesinger’s Allegheny parallax program to the south. • Returned to US to direct McCormick Observatory in 1945.

12. Open house in April 1936

13. Parallax errors

14. Yale-Columbia Southern Station • Financial and logistical strains of operating the 26-inch begin to arise in 1943. • Talks start with Columbia University. • Columbia joined Yale in 1946 in the first of three ten-year agreements. • Columbia was interested primarily in photometry of stars and clusters. • Dirk Brouwer assumes Yale directorship following Schlesinger’s death in 1943.

15. The move to Australia in 1952 • In 1948 increasing light and smog pollution leads Brouwer to look at other sites for the YCSO. • R. v. d. R. Wooley invites YCSO to Australia, Brouwer visits the Commonwealth Obs. in 1950. • Affiliation with the ANU an important factor in the move.

16. Mt. Stromlo Observatory

17. Changing research interests • Fully operational in 1958 after many delays. • Disillusioned by small percentage of clear nights on Mt. Stromlo. • Brouwer was more interested in proper motions and fundamental systems than parallaxes. • After extensive site surveys Brouwer selected a site in Argentina for the new YCSO. • Last plate taken with the 26-inch under the auspices of the YCSO was on May 28, 1963 - #69,950. • 26-inch refractor donated to the Australian National University.

18. Schlesinger’s Legacy • Cape and Yale provided all of the parallaxes in the Southern Hemisphere until the Hipparcos Catalog was published in 1997. • Schlesinger started two of the four major parallax programs (Allegheny & Yale) and he trained the director of the third program (McCormick). • About 2000 parallaxes and many stellar masses were determined with the 26-inch refractor. • Schlesinger’s analysis methods were used until the 1960s, when computers became generally available.

19. Telescope use after 1963 • P. A. Ianna and collaborators (Univ. of Virginia) extend the McCormick parallax program to the southern hemisphere (1977-1992). • Second-epoch photographs taken of star clusters for membership determinations using proper motions. • Amateur astronomer projects. • In the final years the building was used as a night club and meeting hall after the dome became too fragile to turn. • Plans were being made to replace the dome so that the telescope could be used by the amateur astronomers.

20. Mt. Stromlo Observatory is Destroyed by a Firestorm • On January 18, 2003 a firestorm destroyed all telescopes on Mount Stromlo, the workshop, library and many of the residences. • Nearly 500 homes in the Canberra were also destroyed. • Previously, on February 5, 1952 a fire destroyed the workshop and the machine tools, but almost everything else in the complex was saved.

21. Dome exterior 2003

22. Dome interior 2003

23. Acknowledgements • We are grateful to The Commonwealth for hosting the Schlesinger 26-inch refractor during its many productive years in South Africa and Australia under the evolving auspices of: • The University of Witwatersrand • The Yale Southern Station • The Yale-Columbia Southern Station • The Commonwealth Observatory, Mt. Stromlo Observatory and the Research School of Natural Sciences of the Australian National University. • The Yale-Columbia Southern Station