Skywatch Line for Wednesday and Thursday, July 26 and 27, 2023
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday,
July 26 and 27, written by Alan French.
The Sun rises at 5:40 A.M. on Wednesday and sets at 8:23 P.M. On
Thursday it rises at 5:41 and sets at 8:22. This Thursday has a little
over13 minutes less daylight than last Thursday.
The Moon was at first quarter Tuesday and is now moving toward full. As
darkness falls Wednesday night, look for a gibbous Moon, 62%
illuminated, low in the south southwest. By Thursday night, just after
sunset, the Moon will be farther toward the south and 72% of its visible
face will be in sunlight. The Moon will be full on Tuesday, August 1.
The ISS (International Space Station) will be visible in our evening sky
on Wednesday and Thursday nights. We see satellites in the hours just
after sunset and just before dawn because they are still in sunlight
while we are in darkness. The view of the ISS will be described as seen
from Schenectady, but will be similar for the surrounding region.
On Wednesday evening you can see the ISS twice. The first pass will be
during twilight and the space station will pass low across the northern
sky. Look for it 9 degrees above the northwestern horizon at 9:02 P.M.
It will be due north and 28 degrees above the horizon at 9:04:25
(HH:MM:SS). Its path will continue toward the east, taking it 27 ½
degrees above the northeastern horizon at 21:05:41. it will move into
the Earth’s shadow and vanish just after 9:08 above the eastern horizon.
The second pass of the ISS on Wednesday evening will be against dark
skies with the station crossing the western skies and moving into the
Earth’s shadow when well above the horizon. Look for the ISS low in the
west northwest at 10:39 P.M. It will be moving higher and toward the
south (left when facing west). Just after 10:41 it will pass closely
above Arcturus, the brightest star in Boötes and the brightest star
toward the west. (Arcturus is 37 degrees above the western horizon and
appears reddish.) Just after passing by Arcturus the ISS will enter our
Earth’s shadow and fade from view.
Thursday night’s pass of the ISS will be high in the sky and the space
station will reach magnitude -3.8 when near its highest. Look for the
ISS coming straight up from the west southwestern horizon between 9:50
and 9:51. When low in the sky the ISS is fainter and its motion is
mostly toward us, so it appears to move slowly and can be hard to spot.
As it moves higher it grows brighter and its apparent motion is faster
and more obvious.
Just before 9:53 P.M. it will pass close to the end of the Big Dipper’s
handle, which should be visible against the remaining twilight. The
station will be highest at 9:53:27 when essentially overhead and headed
toward the northeast. At 9:54:30 the it will pass close by Altair, the
brightest star in Aquila, the Eagle. Soon after it will enter the
Earth’s shadow and disappear, when still 30 degrees above the
southeastern horizon.