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  • The Mt Wilson Observatory

    Reggie Jones

    The Mt Wilson Observatory just above Los Angeles was originally started at the turn of the 19th and 20th centuries as a location for solar observation and research, established by its founder, George Ellory Hale.   Hale was the driving force to build Mt Wilson as a major center for astronomical research and the first scientific enterprise built on an industrial model.  Everything needed to support astronomical research such as laboratories, tools and instruments, and living and working spaces for the scientists and astronomers was provided at this site so that they could develop and expand our knowledge of the universe.  The site originally included:

    The Snow Solar Telescope which was the first to gauge the cooler temperatures of sunspots and the first to see the hydrogen in our star.

    The 60 ft Solar Tower Telescope that saw magnetism outside of our planet.

    The 150 ft Solar Tower which discovered the the cycle of inversions of magnetic polarity in our star and the 22 year solar cycle.

    Just as these devices were operational, Hale commissioned the building of a 60 inch reflective mirror to be put into a telescope designed by George Willis Ritchey (yes, the Ritchey in Ritchey-Chretien) for astronomical observing.  The telescope became operational in December 1908 and observations (imaging via photographic plates) began shortly afterwards.  The telescope has a 24,000 mm focal length, and a focal ratio of f/16 in the Cassegrain configuration.  Using this telescope, astronomer and scientist Harlow Shapley found and used Cephid variable stars to determine the size of our galaxy and our star’s position within the galaxy.  Shapley proved what Nicholas Copernicus had shown almost 500 years before which is that we are not at the center of the galaxy, much less the center of the universe.

    In November 1917, the 100 inch Hooker Telescope became operational.  This telescope has a 32,000 mm focal length with a general focal ratio around f/12.  Using this telescope, astronomer Edwin Hubble was able to resolve individual Cephid variable stars inside of what was then known as a spiral nebulae which was theorized as very distant clouds of stars.  Using the process Harlow Shapley developed to determine distances within our galaxy, Hubble would show not only that these distant clouds of stars were “extragalactic stellar systems”, but he could also determine how far away they were.  Hubble was only able to do this using Leavitt’s Law, a rule developed by Henrietta Swan Leavitt that allowed you to calculate the distances to Cephid variable stars based on the period of these particular stars’ variable brightnesses.  Based on Hubble’s distance calculations of Cephid variables in the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33), the universe became a great deal larger than just our galaxy.   Today, the James Webb Space Telescope and the soon to be operational Giant Magellan Telescope, still use Leavitt's principles to determine the size of the universe.


    If you’re in the Los Angeles area or you plan to be, I highly recommend taking the detailed engineering tour of the Mt Wilson Observatory and it’s inner workings.  You can also spend a night with group of friends or strangers observing through either the 60 inch or 100 inch telescopes.  Simply go to - https://www.mtwilson.edu

    To learn the whole fascinating story of the history of Mt Wilson and how we developed the base of knowledge that we still rely on today, grab a copy of The Day We Found the Universe by Marcia Bartusiak. 


    Mt Wilson Observatory photos taken by Reggie Jones.







    Mt Wilson 100%22 Hooker Telescope - 1.jpeg

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