The sky this week from 14 to 23 September

Monday September 17th

The gibbous moon rising rises 4 ° from the upper left of Saturn tonight. Although the moonlight hinders the planet's ring observation, wait a day or two for it to move away and bring Saturn back to its glory. The planet is almost to the south and at its highest altitude, while darkness falls this week. It shines at a magnitude of 0.4, brighter than any of the background stars of its host constellation, Sagittarius. If you own a telescope, there is no better target than Saturn. Even the smallest instrument shows Saturn's 17 "disc surrounded by a spectacular 38" ring system and tilted 27 ° from our line of sight.

Tuesday September 18th

Asteroid hunters have an excellent opportunity to spot Vesta this week near one of the brightest areas of the Milky Way. The minor planet of magnitude 7 lies in Western Sagittarius, a region that currently hosts the largest planet Saturn. Vesta is a few degrees southwest of Saturn. More interestingly, the asteroid is located less than 2 ° southwest on the lagoon nebula (M8) tonight. Friday night, Vesta will slide 1 ° south of the lagoon.

Although autumn arrives with the equinox next weekend, the Summer Triangle remains prominently in the evening sky. Look high in the west after dark and your eyes will fall on the bright star Vega in the constellation Lyra the Harp. Of magnitude 0.0, Vega is the brightest member of the Triangle. The second brightest star, the 0.8 Altair magnitude at Aquila the Eagle, is about 35 degrees southeast of Vega. The darkest member of the asterism, of magnitude 1.3 Deneb at Cygnus the Swan, is about 25 degrees east-northeast of Vega. For observers from northern latitudes, Deneb goes to the zenith around 22h. local time, nearly 90 minutes after the disappearance of the last vestiges of twilight.

Wednesday, September 19th

The increasing Gibbous Moon is 4 degrees above Mars in the sky tonight. The two make beautiful companions from dusk until they go to bed around 2 am local time.

The Moon reaches the apogee, the farthest point of its orbit around the Earth, at 20:53. EDT. It is then 404 876 kilometers from the center of the Earth.

Thursday 20th September

Saturn and its rings are still wonderful using a telescope, but tonight offers an excellent opportunity to target the moons of the planet through an instrument of 8 inches or more. Two inner moons – the Enceladus of magnitude 12 and the Mimas of magnitude 13 – reach the greatest eastern elongation in the following hour and appear in good observing conditions. (The bright glow of the rings normally masks these moons when they are closer to the planet.) Both are just beyond the edge of the rings halfway between the Dione and Tethys 10-magnitude satellites.

Mercury reaches a conjunction greater than 22 hours EDT. This means that the deepest planet is on the opposite side of the Sun from the Earth and remains hidden in the reflections of our star. He will return to the evening sky, but hardly at the end of October.