Lunar X

For the Google-sponsored competition, see Google Lunar X Prize.

The Lunar X (also known as the Werner X) is a clair-obscur effect in which light and shadow creates the appearance of a letter 'X' on the rim of the Blanchinus, La Caille and Purbach craters of the Moon.^[1]

Lunar X formation taken January 30, 2012, the formation is off the center towards the right

Lunar X and Lunar V recorded on a Skywatcher 150/750 with a ASI294MC Pro on May 29, 2020, in Mainz, Germany

The X is visible only for a few hours before the first quarter,^[2][3] slightly below the lunar terminator. Near to the X, the Lunar V is also visible, formed by Ukert crater and several other small craters.^[2]

Half waxing moon with inset closeup of Lunar X, used by a 60mm refractor telescope

References

1. Rice, Tony. "X marks the moon on Thursday night". WRAL.
2. Harrington, Philip S. (2010). Cosmic challenge : the ultimate observing list for amateurs. Cambridge: Cambridge University Press. p. 1999. ISBN 978-0-521-89936-9.
3. Chapman, David M.F. "The Lunar X Files: a fleeting vision near the crater Werner" (PDF). Willingboro Astronomical Society.

External links

• LPOD articles:
  • Wood, Chuck (August 29, 2004). "X Marks the Spot". Lunar Photo of the Day.
  • Wood, Chuck (December 12, 2013). "X Marks the Spot". Lunar Photo of the Day.
  • Wood, Chuck (March 9, 2014). "Xquisite". Lunar Photo of the Day.
• APOD articles:
  • Nemiroff, R.; Bonnell, J. (eds.). "Lunar X". Astronomy Picture of the Day. NASA.
  • Nemiroff, Robert; Bonnell, Jerry (December 10, 2016). "The Lunar X". Astronomy Photo of the Day (APOD). - also includes the Lunar V