As the sun sets this week, its latest of the year at 8:35, Saturn and Mars appear in the darkening skies, Mars high in the southwest and Saturn trailing 25 degrees at due south. Mars sets at midnight, with Saturn following 90 minutes later.     Our neighbor isn’t called the red planet for nothing: its orange hue is quite distinct and a real contrast to golden Saturn, although both shine at around first magnitude and are as bright as any star.

The nascent crescent moon emerges from the glow of sunset low in the west-northwest Thursday evening. Above the moon is Mercury with the Gemini twins Pollux and Castor higher still. Sunset Friday finds the waxing crescent a little higher in the west with Mercury, Pollux, and Castor farther to its right.

The waning crescent moon heralds the coming sun in pre-dawn eastern skies through week’s end. So close to the sun’s glow, there’s more to this moon than meets the eye. While the crescent appears clearly aglow, the supposedly missing face appears as a dark notch. This is a result of earthshine, sunlight reflected off our planet that casts a shadowy glow over the rest of the moon’s visible face.

Look for Mars high above the southwest horizon at the feet of Leo the lion, with blue-white Regulus well to the west. Saturn is high in the south, with equally bright Spica five degrees below. Mars and Saturn both shine at first magnitude, as bright as a typical star, but Mars fades noticeably over the month. Right now they are more than 30 degrees apart, but through summer they draw closer together until Mars passes the ringed planet in mid-August.

This is the final countdown to one of the rarest sights in the heavens, a transit of Venus. Venus crosses the face of the sun in eight-year pairings, each cycle separated by 115 years. The last transit of Venus was in 2004. The next is Tuesday, June 5. After that, there won’t be another until December of 2117!

Thursday the crescent moon appears high in the south at sunset, forming a line with the Gemini twins Pollux and Castor above. The three are still aligned Friday, but this time the moon is much farther below the two planets — closer actually to Cancer, the dimmest of the zodiac’s 13 constellations.

The moon wanes before reaching new phase on the 20th, when its visage is bleached out by the glare of the sun. The moon is still there, right in front of our eyes — and right in front of the sun. For people on the west coast and beyond, this is a special new moon, as it crosses directly in front of the Sun, causing an annular solar eclipse. Alas,  here on the east coast, the sun will have set before this happens, so we’ll miss out.

Sunset reveals Venus ablaze high in the west, shining as bright as she gets at magnitude –4.7. And while the light of a planet is usually steady, but as the Evening Star nears the horizon, she begins to shimmer and dance as her light is refracted by Earth’s atmosphere. The planet is so dazzling that at first glance you could easily mistake her for a passing jetliner or even a UFO. Venus is in fact the Number 1 culprit behind reported sightings.

Saturday’s full moon is commonly called the Flower Moon the Corn Planting Moon and the Milk Moon. But you can call it Super Moon. Not only does this full moon coincide with perigee — its nearest monthly approach to earth — but this is the closest perigee of the year. As a result, the full moon  will appear almost 10 percent bigger and brighter than normal.

Join the party Saturday, April 28, as people around the globe take aim at the heavens for Astronomy Day. This annual event was begun in 1973 by California astronomer Doug Berger, who organized a drive to set up telescopes along city sidewalks and other public spaces so that ordinary people could better appreciate the night sky. With four of the five naked-eye planets visible along with the near-first-quarter moon, the evening shouldn’t disappoint.