Editing Mount Wilson Observatory (section)

===150-foot Solar Tower===

The {{convert|150|ft|m|adj=on}} focal length solar tower expanded on the solar tower design with its tower-in-a-tower design. (The tower is actually {{convert|176|ft|m}} tall.) An inner tower supports the optics above, while an outer tower, which completely surrounds the inner tower, supports the dome and floors around the optics. This design allowed complete isolation of the optics from the effect of wind swaying the tower. Two mirrors feed sunlight to a {{convert|12|in|cm|adj=on}} lens which focuses light down at the ground floor. It was first completed in 1910, but unsatisfactory optics caused a two-year delay before a suitable doublet lens was installed. Research included solar rotation, sunspot polarities, daily [[sunspot drawing]]s, and many magnetic field studies. The solar telescope would be the world's largest for 50 years until the [[McMath–Pierce solar telescope]] was completed at [[Kitt Peak]] in Arizona in 1962. In 1985, UCLA took over operation of the solar tower from the Carnegie Observatories after they decided to stop funding the observatory.<ref>{{cite web |last=Gilman |first=Pam |title=The 150-Foot Solar Tower: History |url=http://obs.astro.ucla.edu/150_hist.html |publisher=[[University of California, Los Angeles]] |date=2003 |access-date=21 September 2020}}</ref>