Saturday’s first quarter moon appears in the zodiacal constellation Pisces. It gets a lot more attention in the nights ahead, especially Tuesday night, when the gibbous moon occults one of the brightest stars in the night sky.

The moon will pass over the bright star Aldebaran, the principal star in the zodiacal constellation Taurus. You don’t need binoculars, but they obviously will help.

Astronomers across the United States will point their telescopes at this event while holding a stop watch. Following the tradition of their ancient brethren, they’ll be using their clocks to time the actual moment when the star disappears. Comparing this measurement around the globe will help them establish further understanding about their location on the Earth, the distance between the moon and the Earth, and the width of the moon. After all there are three players in this occultation: a star, the moon and the Earth. This information is already known more precisely, but for some there is joy in going over the data again.

Depending on where you are, the occultation will take place at different times. But it occurs here after 9 p.m. EST.

Aiding in this observation is the darkened side of the moon. There will be a clear distinction between the side of the moon that is in shadow, crossing over the distant star.

Aldebaran will reappear about an hour and 10 minutes later on the other side. Reappearance of Aldebaran will be harder to observe because it is happening on the considerably brighter side of the moon. It will be a bit of a challenge to see without an instrument. Binoculars and a telescope will be needed to see that final moment.

Whether you have a telescope or not, you will eventually see the bright star as the moon leaves it behind.

If you’ve got relatives across the country, consider sharing in real time, on a cell phone, that precise moment when the star disappears. Depending on location, the event will take place at a different time. Across the United States, the time difference can be over an hour.
 

                                                                                          *melted precipitation