Watch Regulus disappear behind the Moon Sunday morning

E HOR REGULUS OCCUL DISAPPEAR 15 OCT 17

One of the observing activities I find most fascinating and beautiful is watching an occultation of one celestial body by another.

My Merriam-Webster dictionary defines “occultation” as “the state of being hidden from view or lost to notice”.

Stars are occulted by asteroids almost daily and occasionally stars and the planets of our solar system hide briefly behind the Moon.

Occultations of first magnitude stars along the ecliptic are fairly rare and worthy of note.

North American observers will be treated to an early morning occultation of Regulus (Leo A) on Sunday, October 15th. Regulus shines at magnitude 1.3 and is the “front paw” of constellation Leo.

E HOR REGULUS DISAPPEAR 15 OCT 17

Timing on the disappearance of Regulus will favor observers from the east coast to Rockie Mountains. For observers to the east reappearance will be in bright pre-dawn or at dawn. Observers west of the intermountain region will just catch the reappearance with the Moon and Regulus very low above the eastern horizon.

This occultation will be an especially beautiful one since the waning crescent Moon will be illuminated only 19.1%. If you plan on observing with a telescope use a blue filter at your eyepiece to bring out the star.

The star will disappear behind the sunlit western limb of the Moon and reappear about an hour later on Luna’s dark limb.

E HORIZ REGULUS REAPPEAR 15 OCT 17

Here at my location in Southern Indiana disappearance is predicted for 9:30:47 UT (5:30:47 am EDT) with the Moon 22 degrees above the east horizon on a bearing of 92 degrees and reappearance one hour, one minute and 29 seconds later (10:31:16 UT) 34 degrees off the horizon at a bearing of 102 degrees.

Charts prepared using Stellarium software.

For disappearance and reappearance timings at hundreds of locations including location of the Moon visit the International Occultation Timing Association’s prediction page for this occultation

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