Astronomy Picture of the Day

   [1]Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2019 August 17
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                      1901 Photograph: The Orion Nebula
     Image Credit: [3]George Ritchey, Yerkes Observatory - Digitization
                             Project: W. Cerny,
   R. Kron, Y. Liang, J. Lin, M. Martinez, E. Medina, B. Moss, B. Ogonor,
                  M. Ransom, J. Sanchez (Univ. of Chicago)

   Explanation: By the turn of the 20th century advances in photography
   contributed an important [4]tool for astronomers. Improving
   photographic materials, long exposures, and new telescope designs
   produced astronomical images with details not visible at [5]the
   telescopic eyepiece alone. Remarkably [6]recognizable to
   astrophotographers today, this stunning image of the star forming Orion
   Nebula was captured in 1901 by American astronomer and telescope
   designer [7]George Ritchey. The original glass photographic plate,
   sensitive to green and blue wavelengths, has been digitized and
   light-to-dark inverted to produce a positive image. His hand written
   notes indicate a 50 minute long exposure that ended at dawn and a
   reflecting telescope [8]aperture of 24 inches masked to 18 inches to
   improve the sharpness of the recorded image. Ritchey's plates from
   [9]over a hundred years ago preserve astronomical data and can still be
   used for [10]exploring astrophysical processes.

                     Tomorrow's picture: human spaceship
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    Authors & editors: [22]Robert Nemiroff ([23]MTU) & [24]Jerry Bonnell
                                 ([25]UMCP)
          NASA Official: Phillip Newman [26]Specific rights apply.
              [27]NASA Web Privacy Policy and Important Notices
                A service of: [28]ASD at [29]NASA / [30]GSFC
                           & [31]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/1908/orion1901_ritchey.jpg
   3. http://photoarchive.lib.uchicago.edu/db.xqy?show=browse9.xml|12921
   4. https://en.wikipedia.org/wiki/Astrophotography
   5. https://web.archive.org/web/20090110170500/http://encyclopedia.jrank.org/articles/pages/1115/Astrophotography.html
   6. https://apod.nasa.gov/apod/ap090826.html
   7. https://history.aip.org/history/exhibits/cosmology/tools/tools-ritchey.htm
   8. https://en.wikipedia.org/wiki/George_Willis_Ritchey#/media/ File:RitcheyTelescope.jpg
   9. https://en.wikipedia.org/wiki/Astrophotography#/edia/File:18551_07_28_Berkowski.jpg
  10. https://www.nasa.gov/feature/goddard/2017/messier-42-the-orion-nebula
  11. https://apod.nasa.gov/apod/ap190816.html
  12. https://apod.nasa.gov/apod/archivepix.html
  13. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  14. https://apod.nasa.gov/apod/lib/aptree.html
  15. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  16. https://apod.nasa.gov/apod/calendar/allyears.html
  17. https://apod.nasa.gov/apod.rss
  18. https://apod.nasa.gov/apod/lib/edlinks.html
  19. https://apod.nasa.gov/apod/lib/about_apod.html
  20. http://asterisk.apod.com/discuss_apod.php?date=190817
  21. https://apod.nasa.gov/apod/ap190818.html
  22. http://www.phy.mtu.edu/faculty/Nemiroff.html
  23. http://www.phy.mtu.edu/
  24. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  25. http://www.astro.umd.edu/
  26. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  27. https://www.nasa.gov/about/highlights/HP_Privacy.html
  28. https://astrophysics.gsfc.nasa.gov/
  29. https://www.nasa.gov/
  30. https://www.nasa.gov/centers/goddard/
  31. http://www.mtu.edu/