This Week's Sky at a Glance for October 15 – 23

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This Week's Sky at a Glance
Some daily events in the changing sky for October 15 – 23
by Alan M. MacRobert
Rolando Ligustri photographed 103P/Comet Hartley 2 on September 6th. Since then the round coma has grown larger, but the central condensation remains weak.
Rolando Ligustri
Periodic Comet Hartley 2 remains about 6th magnitude, appearing big, round, and dim in binoculars. This week it's crossing Auriga and passing its closest to Earth (on October 20th). But moonlight is returning; the waxing Moon sets later each night. You can have a Moon-free view through about the morning of the 19th if you observe in the pre-dawn hours; find your local moonset time using ouronline almanac. What you'll see of the comet, if anything, depends strongly on the quality of your sky. See our articleComet Hartley 2 At Its Best, with finder charts.
 
Friday, October 15
Look just upper right of the Moon this evening (as seen from most of North America) for the 3rd-magnitude stars Beta and Alpha Capricorni, in that order counting up. Alpha is a double star that, with good or well-corrected vision, you can barely resolve with the unaided eye. Binoculars resolve it easily into a golden-yellow pair — and also show that Beta too is a wide double.
 
Now at naked-eye visibility, Mira in Cetus climbs the eastern sky in late evening — in this case, over hills in Iran.
Babak A. Tafreshi
Mira, the brightest long-period red variable star, is having an unusually bright maximum! As of October 14th observers were reporting it at about magnitude 3.0, very plainly visible to the naked eye. Will it grow any brighter? It's up in good view in the east-southeast by about 10 p.m. daylight saving time. Use the comparison-star chart in the SeptemberSky & Telescope, page 58.
 
Saturday, October 16
 
Jupiter's Great Red Spot should cross Jupiter's central meridian (the imaginary line down the center of the planet's disk from pole to pole) around 8:19 p.m. Eastern Daylight Time. The "red" spot appears very pale orange-tan. It should be visible for about an hour before and after in a good 4-inch telescope if the seeing is sharp and steady. A light blue or green filter helps. (For all of the Red Spot's transit times, good worldwide, use ourRed Spot calculator or print out our list ofall Red Spot transit times for the rest of this observing season.)
 
Sunday, October 17
 
This week the big Summer Triangle is still nearly overhead after dark. Look for Deneb close to the zenith (if you're in the north temperate latitudes). Brighter Vega shines to Deneb's west. And Altair is less high toward the south-southwest (with little Gamma Aquilae, or Tarazed, just to its upper right).
 
 
Jupiter's Red Spot should transit around 9:57 p.m. EDT.
 
Monday, October 18
 
Jupiter shines lower left of the waxing gibbous Moon early this evening, and directly left of it later in the night.
 
Tuesday, October 19
 
Jupiter's Red Spot should transit around 11:35 p.m. EDT.
 
 
Jupiter shines straight under the Moon this evening, as shown below.
 
As the Moon waxes toward full night by night, it draws away from Jupiter a month past its own opposition.
Sky & Telescope diagram
 
Wednesday, October 20
 
The Moon is now to Jupiter's left, as shown above.
 
Thursday, October 21
 
The Great Square of Pegasus is straight above the bright Moon this evening after dark (not shown above). It's tipped on one corner and somewhat larger than your fist held at arm's length.
 
Friday, October 22
 
Full Moon (exact at 9:37 p.m. Eastern Daylight Time).
 
 
This week the Big Dipper lies level in the north-northwest after dusk, quite low, far below the bowl of the much dimmer Little Dipper.
 
Saturday, October 23
 
Jupiter's Red Spot should transit around 9:05 p.m. EDT.
 
 
Not long after, the tiny black shadows of both Ganymede and Europa fall on Jupiter, from 9:40 to 11:04 p.m. EDT.
 
 
And by the time the double shadow transit ends on Jupiter, Algol is just about at its minimum light (mid-eclipse around 12:10 a.m. Sunday morning Eastern Daylight Time).