In the second half of October, Mars shows off its volcanic and desert regions around 12 A.M. EDT. Elysium Mons is visible as a bright spot for those attempting video capture, or visually with a large, high-quality refractor. To the volcano’s south, the broad, dark feature of Mare Cimmerium spans much of the disk. The Tharsis ridge and Olympus Mons are rotating off, but appear centrally on the disk around October 25, along with Mare Sirenum to the south. Early evening observing presents the chance to view Valles Marineris and the dark Solis Lacus. At the end of October, these features are centered on the disk at 12 A.M. EDT. Can you spot the leftover ice from the south polar cap? Watch also for rare clouds or hazes near the limb, as high-elevation features such as the Tharsis ridge volcanoes rotate onto the planet. A blue filter will aid with their detection.
The Full Moon shares the sky with Mars for the second time this month on the 29th. You’ll find the planet less than 5° northwest of the Moon an hour after sunset.
Uranus reaches opposition on the 31st in a sparse region of the sky in southern Aries. A bright gibbous Moon rises nearby on October 3, and by 2 A.M. EDT on October 4, the planet is 4.3° north of our satellite, appearing as a magnitude 5.7 starlike object.
When the Moon is gone, the best way to catch the planet is to scan with binoculars between Hamal, the brightest star in Aries, and Menkar (Alpha [α] Ceti). Uranus lies 10.5° from Hamal along this line. There are no bright stars nearby; the closest is 6th-magnitude 29 Arietis. Uranus lies 1.2° southwest of this star on October 1. The planet moves westward along its retrograde path and is 2.3° from the star by October 31. It’s the best time to spy the distant planet through a telescope, as it is visible all night. High magnification reveals a 4"-wide disk.
Venus rises around 4:00 A.M. local time on October 1, alongside Regulus in Leo. The pair stand 1.8° apart. Venus shines at a brilliant magnitude –4.1, 145 times brighter than Regulus at magnitude 1.3. At 5 A.M. EDT on October 2 and 3, you’ll find the planet 41" and 30" from the star, respectively.
Venus progresses across southern Leo during October, passing 2.7° south of the galaxy M95 on October 10. A crescent Moon joins the planet on the 14th. Venus crosses into Virgo on the 23rd, ending October within 1° of 4th-magnitude Zaniah (Eta [η] Virginis).Telescopic views show the planet changing from a 72 percent-lit disk on October 1 to 81-percent illuminated on October 31st, its diameter simultaneously diminishing from 16" to 13", owing to its increasing distance from Earth.