This is the Dudley Observatory Skywatch Line for Wednesday, July 25th, and Thursday, July 26th, written by Louis Suarato.
With the 97% illuminated, waxing crescent Moon rising at 6:57 p.m. in Sagittarius, set your sights on the brighter celestial objects these nights. After sunset, look for Venus about 15 degrees over the western horizon, shining at magnitude -4.3. Continue to look toward the western horizon at 9:14 p.m., when the -1.7 magnitude International Space Station emerges from below Venus. Follow the ISS as it continues on a northerly trek through Leo, and continues past Ursa Major, before crossing through Cassiopeia, and disappearing into the northeast. The third brightest object on this night is Mars, shining at magnitude -2.77. Mars rises in the southeast at 9 p.m. in the constellation Capricornus. Mars reaches opposition Thursday, and will be at its peak visibility for the year, and at its brightest since 2003. While Mars is rising, look for Jupiter about 20 degrees over the southwestern horizon in the constellation Libra. On this night of bright objects, look for Saturn, shining at magnitude 0.16, 10 degrees to the south of the Moon. Thursday night, the nearly Full Moon, will rise about an hour earlier than Mars, and the two will be separated by 10 degrees.
A surprisingly bright comet is now passing the constellation Auriga. After a second outburst in two weeks, Comet c/2017 S3 (PanSTARRS) is now a binocular target. This 8th magnitude comet may be as bright as 3rd magnitude in August, when it reaches perihelion. Auriga’s brightest star, Capella, rises in the northeast around 2 a.m., signaling the appearance of its host constellation. Look for Comet C/2017 S3 (PanSTARRS) 10 degrees to the lower left of Capella. Future positions for this comet can be found on the website www.heavens-above.com at https://www.heavens-above.com/comet.aspx?cid=C%2F2017%20S3&.