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.

                              2023 September 23
   [2]See Explanation. Clicking on the picture will download and animated
                                    gif.

                             Afternoon Analemma
        Image Credit & [3]Copyright: [4]Ian Griffin ([5]Otago Museum)

   Explanation: [6]An analemma is that figure-8 curve you get when you
   mark the position of the Sun at the same time each day for one year. To
   make this one, a 4x5 [7]pinhole camera was set up looking north in
   [8]southern New Zealand skies. The shutter was briefly opened each
   clear day in the afternoon at 4pm local time exposing the same
   [9]photosensitized glass plate for the year spanning September 23, 2022
   to September 19, 2023. On two days, the winter and summer solstices,
   the shutter was opened again 15 minutes after the main exposure and
   remained open until sunset to create the sun trails at the bottom and
   top of the curve. The equinox dates correspond to positions in the
   middle of the curve, not the crossover point. [10]Of course, the curve
   itself is inverted compared to an analemma traced from the northern
   hemisphere. [11]And while fall begins today at the Autumnal Equinox for
   the northern hemisphere, it's the Spring Equinox in the south.

                  Tomorrow's picture: sunrise solar eclipse
     __________________________________________________________________

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    Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell
                                 ([26]UMCP)
          NASA Official: Phillip Newman [27]Specific rights apply.
              [28]NASA Web Privacy Policy and Important Notices
                A service of: [29]ASD at [30]NASA / [31]GSFC,
                         [32]NASA Science Activation
                           & [33]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2309/4pm-analemma-nz.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.instagram.com/portobellopictures/
   5. https://otagomuseum.nz/
   6. https://en.wikipedia.org/wiki/Analemma#As_seen_from_Earth
   7. https://apod.nasa.gov/apod/ap220702.html
   8. https://apod.nasa.gov/apod/ap221021.html
   9. https://apod.nasa.gov/apod/ap210102.html
  10. https://en.wikipedia.org/wiki/Analemma#Seen_from_other_planets
  11. https://solarsystem.nasa.gov/resources/749/seeing-equinoxes-and-solstices-from-space/
  12. https://apod.nasa.gov/apod/ap230922.html
  13. https://apod.nasa.gov/apod/archivepix.html
  14. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  15. https://apod.nasa.gov/apod/lib/aptree.html
  16. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  17. https://apod.nasa.gov/apod/calendar/allyears.html
  18. https://apod.nasa.gov/apod.rss
  19. https://apod.nasa.gov/apod/lib/edlinks.html
  20. https://apod.nasa.gov/apod/lib/about_apod.html
  21. http://asterisk.apod.com/discuss_apod.php?date=230923
  22. https://apod.nasa.gov/apod/ap230924.html
  23. http://www.phy.mtu.edu/faculty/Nemiroff.html
  24. http://www.phy.mtu.edu/
  25. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  26. http://www.astro.umd.edu/
  27. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  28. https://www.nasa.gov/about/highlights/HP_Privacy.html
  29. https://astrophysics.gsfc.nasa.gov/
  30. https://www.nasa.gov/
  31. https://www.nasa.gov/centers/goddard/
  32. https://science.nasa.gov/learners
  33. http://www.mtu.edu/