The chart above is for Saturday morning, April 7, 2018.
This weekend, in the morning sky, the waning moon joins up with the planets Saturn and Mars. These three worlds climb over the southeast horizon very late Friday and Saturday nights (April 6 and 7), then soar highest up for the night just before dawn Saturday and Sunday (April 7 and 8). At northerly latitudes, the moon, Saturn and Mars move southeast to south before dawn; meanwhile, at southerly latitudes in the Southern Hemisphere, this trio of celestial lights soars to high overhead before dawn.
On Saturday morning, you can distinguish Saturn from Mars because Saturn will be the closer of these two planets to the moon (see chart above). Mars will be closer to the moon on Sunday (see chart below). Meanwhile, both mornings, Mars will be brighter than Saturn. Plus Saturn exhibits a golden color while Mars shines reddish. If you have difficulty seeing color in the moon’s glare with the eye alone, try viewing these colorful gems through binoculars. Or look at Saturn and Mars later this month, after the moon has moved away from this section of sky.
Another way to tell Saturn from Mars is to set up your telescope. Even a modest backyard telescope will show you Saturn’s rings.
Red Mars and golden Saturn were in conjunction earlier this week, on Monday morning, April 2. They were only 1.3 degrees apart that day, about the width of your finger at arm’s length. And they’re still very close together. In fact, as seen from North America on the morning of April 7, Saturn, Mars and the moon might all fit (or nearly fit) into the same binocular field.
By the way, there’s an even brighter starlike object in the western half of the predawn sky. That’s the king planet Jupiter, which easily outshines Saturn or Mars. Jupiter is now about 12 times brighter than Mars and nearly 14 times brighter than Saturn.
All these planets – Mars, Jupiter and Saturn – are brightening in our sky day by day. Each one of these superior planets will be at its brightest for the year on the day that it reaches opposition – that is, shining opposite the sun in Earth’s sky – soon. Opposition happens around the time Earth is moving between an outer planet and the sun, for this year; it’s when we gain a lap on each planet, each year. Jupiter will reach opposition on May 9, while Saturn will sweep to opposition on June 27 and Mars will swing to opposition on July 27.
Mars’ opposition will bring it closer to Earth and brighter in our skies than it’s been since 2003. And it was closer and brighter then than it had been in some 60,000 years! At its opposition on July 27, Mars will be nearly 16 times brighter than the red planet is at present. Thus 2018 is a very, very good year to see Mars.
So take a good look at bright Jupiter in the sky near Mars this weekend. Mars at opposition this July will be brighter than Jupiter is now!
Bottom line: On the mornings of April 7 and 8, 2018, watch for the waning moon to join up with the ringed planet Saturn and the red planet Mars in the morning sky.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.