1. Mount Wilson Solar Photographic Archive Digitization Project The 60-foot Solar Tower in 1914.

2. Project Personnel Roger Ulrich, P.I. Ferenc Varadi, Geophysicist John Boyden, Programmer J. Javaraiah, Post Doc, Data Analyst Sandrine Lefebvre, Post Doc, Data Analyst Liz Werden, Archivist Roger Ulrich, P.I. Ferenc Varadi, Geophysicist John Boyden, Programmer J. Javaraiah, Post Doc, Data Analyst Sandrine Lefebvre, Post Doc, Data Analyst Liz Werden, Archivist

3. Why Study Old Solar Images? The level of solar activity is measured by the brightness of the Ca II K line.The level of solar activity is measured by the brightness of the Ca II K line. Rotation of solar features can be measured at high latitudes using the Ca K images.Rotation of solar features can be measured at high latitudes using the Ca K images. The level of solar activity is measured by the brightness of the Ca II K line.The level of solar activity is measured by the brightness of the Ca II K line. Rotation of solar features can be measured at high latitudes using the Ca K images.Rotation of solar features can be measured at high latitudes using the Ca K images.

4. Variability of the Solar Cycle The Sunspot Number has systematically increased during the 20 th Century. The period of no sunspots is called the Maunder Minimum

5. Variability of the Solar Rotation Rate The rotation rate can be determined by tracking the traversal of features across the solar disk At the end of the Maunder Minimum the sunspot rotation rate was reduced.

6. The Mount Wilson Solar Photographic Archive George Ellery Hale Established the Mount Wilson Solar Observatory in 1906. Starting in 1915 spectroheliograms in the light of the Ca II K line were taken twice per day. Also about the same time “White Light” Direct images were taken once per day. There are approximately 45,000 images in the K line and approximately 30,000 images in white light. These images will be digitized and posted for distribution on the web. George Ellery Hale Established the Mount Wilson Solar Observatory in 1906. Starting in 1915 spectroheliograms in the light of the Ca II K line were taken twice per day. Also about the same time “White Light” Direct images were taken once per day. There are approximately 45,000 images in the K line and approximately 30,000 images in white light. These images will be digitized and posted for distribution on the web.

7. A Full Deck Scan The large-bed scanner can scan 5 plates simultaneously. Presently only 3 plates can be accommodated. The full-deck scan is 300 Mbytes in size. Details of this image are shown in the next few slides. The large-bed scanner can scan 5 plates simultaneously. Presently only 3 plates can be accommodated. The full-deck scan is 300 Mbytes in size. Details of this image are shown in the next few slides. July 1, 1925 June 20, 1921 June 30, 1921

8. One Solar Image This shows more detail.

9. The Image with the Clear Plate Enhanced

10. Aug. 17, 1915 to Aug. 21, 1915

11. A Sequence of Images Showing Solar Rotation