September 1, 2019 – In this month’s sky, look for lovely crescent Moons at the start and end of the month. The September equinox brings the beginning of fall in the Northern Hemisphere. And Mars is at solar conjunction, meaning it has disappeared from night skies! (When will it return?) More info at

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What’s Up for September? Following the crescent Moon, the September equinox and – wait – where did Mars go?

We’re in a several-month period right now when the new moon falls right around the end of each month. This means we get to enjoy lovely waning crescent moons at dusk for the first few days of each month, and delightful waxing crescents in the predawn sky near the end of each month.

This month, look low in the west about half an hour after sunset to enjoy the crescent moon on September 1st through the 4th, with the Moon appearing a bit higher in the sky each night. By the 5th, the first-quarter (that is, half-full) Moon winds up here, just a couple of degrees to the right of Jupiter.

At the end of the month, from September 23rd to the 27th, look east half an hour before dawn for an increasingly slimmer crescent, that appears lower in the sky each day.

As you make your lunar observations, remember that for many thousands of years, the cycles of the Moon and Sun were the basis of human timekeeping. And many traditional cultures still rely on these cycles to mark special events.

A few months ago, it seemed like the Red Planet, Mars, was a constant companion in the evening sky. But as our two planets moved along in their orbits this summer, Mars has drifted further into the glare of the Sun, finally disappearing from our skies altogether in July. (Did you notice?)

In late August and early September this year, Mars is more or less behind the Sun as seen from Earth. This has implications for spacecraft at Mars, like NASA’s Insight lander and Curiosity rover.

This event, called solar conjunction, happens about every two years. During this time, mission controllers on Earth stop sending commands to our spacecraft, in order to avoid potential radio interference from the Sun. A few weeks later, when Mars has moved farther apart from the Sun as seen from Earth, normal communications can resume.

For those of us eager for a peek at Mars with our own eyes once again, it’ll return to our pre-dawn skies in early November.

September 23rd marks the equinox, with day and night being of equal length. This marks the beginning of fall in the Northern Hemisphere. And although this means it’s time to bid farewell to those long summer days, the upshot for stargazers is longer nights, meaning more time to look up!

Here are the phases of the Moon for September.

You can catch up on all of NASA’s current and future missions at

I’m Preston Dyches from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.