The Mt. Wilson Solar Photographic Archive Digitization Project

1. The Mt. Wilson Solar Photographic Archive Digitization Project Sponsored by NSF – ATM, AST and NASA - LWS Roger K. Ulrich, Larry Webster, Ferenc Varadi, Liz Werden, Javaraiah Javaraiah, Sandrine Lefebvre, and John Boyden

2. Objectives • Preserve the original plate material. • Provide a web-based digital archive with incorporated logbook parameters. • Calibrate the images as much as possible. • Measure solar rotation over the past century. • Measure the solar magnetic field strength over the past century.

3. Plates are now in archival 4-flap housings in inert boxes without glue. Plate Management • Prior envelopes have glue seams and higher acid content. • Wooden storage cases outgas harmful chemicals.

4. Web Site Development • Main Page: http://www.astro.ucla.edu/~ulrich/MW_SPADP/ • Thumbnails: http://www.astro.ucla.edu/~ulrich/MW_SPADP/Archive_Pages/Webpages/Thumbnailpage • Fits files: • http://www.astro.ucla.edu/~ulrich/MW_SPADP/CaK_fits/

5. Calcium Spectroheliograms • We have started with the Calcium spectro-heliograms. • These provide an indication of the magnetic field strength. • The chromospheric network visible in these spectroheliograms can be used to detect solar rotation using the technique of feature tracking. • Our question: Does rotation depend on the level of activity?

6. Was Rotation Different During the Maunder Minimum? • The absence of sunspots during the Maunder Minimum period from 1645 to 1710 is well established. • The sun was observed regularly during this period. • The sunspot positions were the primary observable parameter. • Data from Helvius and La Hire shows that the rotation rate was probably altered during this period.

7. Beginning and End of the Maunder Minimum Rotation Adapted from Beck (1999)

8. Measuring Magnetic Fields

9. The Ca II H and K Line Profiles • The broad wings are called the K1 lines. • The red emission wing is called K2R. • The violet emission wing is called K2V. • The central absorption core is called K3. K1 K2 K3

10. Comparison of Ca II K Images to Magnetograms

11. The Early Years • Hale began his solar observations with the Kenwood Observatory in Chicago. • The Snow Telescope in the background was the first solar telescope on Mt. Wilson. • The 60 foot Tower was the first tower configuration on Mt. Wilson.

12. A-Series spectro-heliograms – 13000 plates, 1905 to 1928 Broadband directs – 43000 plates, 1905 to present Solar Photographic Collections Kenwood Ca H spectroheliograms – 3600 plates, 1891 to 1895

13. Coverage of the Ca Spectroheliograms

14. Solar Observations 1930 Film Clip featuring: Robert S. Richardson, Solar Observer, 1930 – 1958

15. 13-foot Spectro-heliograph

16. Available Spectroscopic Gratings 1911 Replaced in 1924 by the Jacomini Earthquake grating. An earthquake induced grating discontinuity led to the development of the Wood-Anderson seismograph.

17. Vignetting of Early Images

18. Sample Images 1920

19. Sample Images 1915 1918 1921 1924 1927 1930

20. Can We See Rotation at High Latitudes?

21. Conclusions • As of December 2004, 11,571 Ca K images spanning the period 1915 to May, 1940 have been scanned, identified with logbook entries, analyzed for radius and image center and placed on the project web page as fits files. • Vignetting and plate sensitivity functions are under investigation. • Image roll angle needs to be determined. • Scattered light needs to be corrected. • The Web Address is: http://www.astro.ucla.edu/~ulrich/MW_SPADP