06/04/2019 – Ephemeris – The night sky previews summer

Ephemeris for Tuesday, June 4th. Today the Sun will be up for 15 hours and 24 minutes, setting at 9:23, and it will rise tomorrow at 5:58. The Moon, 1 day past new, will set at 10:51 this evening.

The Moon will be visible early this evening. By early I mean by 10 p.m. since the Sun sets so late now. By the time you see it it will be a day and a half old and a thin sliver. Closer inspection will reveal the the whole Moon will be visible due to Earth shine. That’s due to the nearly full Earth shining on the night side of the Moon.

Even though Summer is 17 days away the three bright stars of the Summer Triangle are visible in the eastern sky at 11 p.m. The three stars are Vega highest in the east. Deneb is lower in the northeast. Altair is lower close to the horizon in east. They will rise higher throughout the summer season. Looking close to the horizon in the southeast that bright star at that hour is the planet Jupiter.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The eastern skies at 11 p.m. June 4, 2019. Click on the image to enlarge. Created using Stellarium and GIMP.

03/11/2019 – Ephemeris – The Moon: Dark side, far side, which is it?

Ephemeris for Monday, March 11th. Today the Sun will be up for 11 hours and 40 minutes, setting at 7:43, and it will rise tomorrow at 8:01. The Moon, 3 days before first quarter, will set at 12:54 tomorrow morning.

Tonight the Moon is at its crescent phase, meaning it is slightly closer to the Sun than the Earth is. Most of the Moon we see is in night. Some earth shine may be seen on its night side due to the big nearly full Earth shining on it. I get ticked sometimes when someone who knows better, especially in the media, mentions the dark side of the Moon when they should use the term far side, the part of the Moon that permanently faces away from the Earth. When the Chinese Chang’e 4 spacecraft landed on the far side of the Moon recently many headlines proclaimed that it landed on the dark side of the Moon. The Moon has a night side, as does the Earth, but that changes as the Moon rotates in the sunlight.  And the Moon does rotate.  It happens to be in sync with its revolution about the Earth.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The crescent Moon tonight at 9 p.m. EDT, March 11, 2019. Created using Stellarium.

Demonstration of the Moon’s crescent phase with the Styrofoam moon ball we use for Project Astro held up to a light off frame to the right. The night side of the ball is illuminated a bit by the translucency of the ball, and the reflection off my hand. Note the roughness of the ball is visible only at the terminator.

The Earth and Moon if seen as a crescent, near side, far side, sunlit side and earth shine. Credit: me.

09/11/2018 – Ephemeris – Earth shine on the Moon

Ephemeris for Tuesday, September 11th. The Sun will rise at 7:16. It’ll be up for 12 hours and 43 minutes, setting at 8:00. The Moon, 2 days past new, will set at 9:27 this evening.

At around 8:30 this evening Venus will be in the southwest only 9 degrees above the horizon, about the width of a fist held at arm’s length. While viewing Venus the Moon will be to the right and above our evening star. It will be a thin sliver of a crescent and in the twilight there will be the suggestion that there is more than the thin sliver of the Moon visible. Binoculars will confirm that the entire disk of the Moon will be visible. The effect is called earth shine. The nearly full Earth is illuminating the Moon to a much greater degree than the full Moon illuminates the Earth. The Earth is about 4 times the Moons diameter and its surface is about twice as bright and the Moon’s. The ancients called it: “The old Moon in the new Moon’s arms.”

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Venus, the Moon and Jupiter at 8:30 p.m. September 11, 2018. Created using Stellarium.

An overly colored Moon to bring out Earth shine on thye evening of September 11, 2018. Created by Stellarium. Overly processed in GIMP.

11/25/2016 – Ephemeris – The Moon is near Jupiter this morning

Ephemeris for Friday, November 25th. The Sun will rise at 7:53. It’ll be up for 9 hours and 12 minutes, setting at 5:06. The Moon, half way from last quarter to new, will rise at 4:53 tomorrow morning.

The Moon passed Jupiter about 9 last night, and so this morning is to the left and a bit below the bright planet. The Moon is a waning crescent a bit less than 10% illuminated by the Sun from our vantage point. Or maybe it’s more proper to say we see less than 10% of its day lit side. The Earth is the only close object to it that can illuminate it’s night side, and that might be visible this morning as Earth shine. For the Moon the Earth is 90% illuminated by the Sun, exactly opposite its phase to us. It’s area in the Moon’s sky is 16 times the Moon’s area in our sky. On top of that the Earth is much more reflective than the Moon, which is dirty gray. So Earth light in the Moon is much brighter than moonlight on the Earth.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter, the Moon, and the star Spica at 6:30 this morning, November 25, 2016. The Moon is shown twice actual size. Created using Stellarium.

The Moon with Earth shine with a confluence of planets (Venus, Jupiter, Mars) on June 15, 1991). Credit Bob Moler.