This week in What’s Up are a few more events you should be on the lookout for in the next month.
First off, the Moon will be in the first quarter next week on October 3, which along with the third quarter, is the best time to observe the Moon’s features because the angle of the Sun provides the most contrast on the surface. You can tease out fine details easier this way.
Just before the formal first quarter is this year’s International Observe The Moon Night on Saturday, October 1. This is the twelfth edition of this event, which features public star parties all around the world dedicated to observing the Moon. As of press time, there were over 800 events scheduled. You can find more information on local events at the link in our show notes on DailySpace.org.
Of course, you don’t need to go to one of these to view the Moon; you can do it by yourself. Simply go outside and look up. Binoculars or a small telescope will help you tease out some of those details.
Next up, Mercury will make its next greatest western elongation on October 8. This is one end of the furthest angular separation it gets from the Sun, which still isn’t far as Mercury orbits so close. The western elongation is the best time to see Mercury just before sunrise in the Northern Hemisphere.
Finally, later in October, there will be a rare phenomenon that will actually take place three times: a double moon transit on Jupiter. While Jupiter has 80 moons that we know about, the four Galilean moons – Europa, Callisto, Io, and Ganymede – pass in front of the disc of Jupiter fairly often, and you can usually see their shadows on Jupiter as they’re crossing. Most of the time, you only get one shadow at a time and maybe a second right after the first one finishes its transit; it’s quite rare to have two moons transiting at the same time… let alone three of these events over the course of a couple of weeks.
The first of these double transits is on October 12, the second on October 19, and the last on October 25. Be sure to catch Jupiter before it heads below the horizon for the winter.
NASA press release
Weird Ways to Observe the Moon (NASA JPL)