2021, April 17: Evening, Crescent Moon, Mars, Star Cluster

April 17, 2021: During the early evening, the crescent moon is above Mars in the western sky.  Use a binocular to spot the star cluster M35 near the moon.  Mars is above the Bull’s horns.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:07 a.m. CDT; Sunset, 7:34 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

In a few evenings, Venus makes its first evening appearance without the aid of a binocular or telescope. This evening Venus sets 27 minutes after sunset.

As the sky darkens after sundown, locate the moon, that is 28% illuminated, over halfway up in the west.  It is in front of the stars of Gemini.

The crescent moon is 0.6° to the upper right of a star cluster known as Messier 35 (M35). 

Mars is 5.8° to the lower right of the lunar slice.  The planet is above the Bull’s horns, Elnath and Zeta Tauri (ζ Tau on the chart).  It is 4.0° to the upper right of Zeta Tauri and 5.4° to the upper left of Elnath.

M35 is like the Pleiades star cluster and the Hyades star cluster, except it is farther away and dimmer.  Use a binocular to view the cluster, the lunar crescent, and Mars in the same starfield.

Make nightly observations of the separation of Mars and the star cluster.  Each night Mars is closer.  The Red Planet passes M35 on April 26.

Here’s more about Mars during 2021.

Read about Mars during April.

Detailed Note: One hour before sunrise, Saturn is over 17° above the southeast horizon.  Saturn slowly crawls eastward compared to the starry background.  This morning, it is 1.6° to the upper right of θ Cap.  Brighter Jupiter – over 12° in altitude above the east-southeast horizon – is 13.7° to the lower left of Saturn.  The Jovian Giant moves to the east faster and continues to widen the gap to Saturn.  Its motion compared to the starry background is a little easier to observe. Jupiter is 3.0° to the upper left of Deneb Algiedi and 0.1° to the lower left of μ Cap.  One hour after sunset, the waxing crescent moon (6.0d, 28%) is over halfway up in the west in front of the stars of Gemini.  While not in an ideal location or dark sky, the moon is 0.6° to the upper right of star cluster Messier 35 (NGC 2168).  Use a binocular to see the moon with the cluster. If the binocular has a wide field, then place the moon and star cluster to the upper left of the field and fit Mars into the lower right.  Use the binocular each evening to track Mars as it approaches the star cluster.  Mars passes M35 on April 26, but the moon is very bright on that evening. This evening as the sky darkens and the celestial sphere turns westward, better views might be possible of the lunar slice and the cluster together.  Mars is 5.8° to the lower right of the moon, 4.0° to the upper right of ζ Tau and 5.4° to the upper left of Elnath.

Read more about the planets during April 2021.