Astronomy Guide for the cottage this week.
Monday, April 30
• Now Jupiter shines to the right or upper right of the Moon after nightfall.
Tuesday, May 1
• May has sprung, but wintry Sirius still twinkles very low in the west-southwest toward the end of twilight — far to the left of much brighter Venus. How much longer into the spring can you keep Sirius in view? In other words, what will be its date of “heliacal setting” as seen by you?
Wednesday, May 2
• Arcturus is the brightest star high in the east these evenings. Spica shines about three fists at arm’s length to its lower right. To the right of Spica by half that distance is the distinctive four-star constellation of Corvus, the Crow.
Far below Arcturus and Spica, Jupiter glares.
Thursday, May 3
• These spring nights, the long, dim sea serpent Hydra snakes level far across the southern sky. Find his head, a rather dim asterism about the width of your thumb at arm’s length, in the southwest. (It’s lower right of Regulus by about two fists at arm’s length. Also, a line from Castor through Pollux points to it about 2½ fists away.) Lower left of this is Hydra’s heart, orange Alphard. Hydra’s tail stretches all the way to Libra in the southeast. Hydra’s actual star pattern, from forehead to tail-tip, is 95° long.
• Now that the Moon is gone from the sky after dark, try for the Ghost of Jupiter planetary nebula, magnitude 7.7, in mid-Hydra (NGC 3242). At that brightness it’s a potential binocular target about as easy or difficult as Neptune; it’s so tiny that at low power it’s easily mistaken for a star.
In a telescope at medium or high power, it does looks sort of like Jupiter’s weak ghost dimly haunting the dark.
• Back at the real Jupiter, Europa slips into eclipse by Jupiter’s shadow around 11:55 p.m. EDT. A telescope will show Europa gradually disappearing barely off Jupiter’s western edge — since the planet is barely 5 days before opposition.
Jupiter’s Great Red Spot crosses the planet’s central meridian around 10:18 p.m. EDT. This timing is good for the Eastern and Atlantic time zones. Farther west, Jupiter is still low or hasn’t risen yet.
Friday, May 4
• Summer is seven weeks away, but the Summer Triangle is beginning to make its appearance in the east, one star after another. The first in view is Vega. It’s already shining low in the northeast as twilight fades away.
Next up is Deneb, lower left of Vega by two or three fists at arm’s length. Deneb takes about an hour to appear after Vega does, depending on your latitude.
The third is Altair, which shows up far to their lower right by midnight.
• As dawn begins on Saturday morning May 5th, the waning gibbous Moon shines between Saturn and Mars. Saturn is to the Moon’s right, and Mars to the Moon’s lower left.
Saturday, May 5
• Jupiter’s Great Red Spot crosses the planet’s central meridian around 11:56 p.m. Eastern Daylight Time.
• The Eta Aquariid meteor shower should be active before the first light of dawn Sunday morning. It’s usually the best shower of the year for the Southern Hemisphere, but northerners have a poorer view of it. Moreover, the light of the waning gibbous Moon will interfere.