Neptune: star fields, and its moons

Event Date: August 24th

Time: 1:15(.22) AM


Brief

   Yesterday I showed Neptune on the rise.  Although at opposition this week, it is only slightly brighter than when near conjunction with the Sun.  While showing it rise in Aquarius, among the water bearer's dim stars, I also picked a time that even a powerful telescope would have to battle atmospheric pollution.  This time, I will show the planet at transit during the wee hours of the morning, when a powerful enough telescope can more easily pick up the methane-blue color.  The first shows a zoom-out of Neptune's position in the sky, with a decent altitude (41º), yet just barely good enough to be out of atmospheric pollution.

Detailed

   One other thing that I mentioned yesterday is that Neptune is near the star Iota (Aq)uarii: a 4th magnitude star that Neptune will get a little closer to over the next two months as it completes its retrograde motion.  Once it starts in prograde again, Neptune pulls a little further from the star each year.  As it does, spending the next decade-plus within the water-bearer's boundaries, it will pass by more stars, although very few matching the brightness of Iota Aq.
The second image is a 1º field (about 50x to show the stars surrounding the planet.  With Neptune about magnitude 8, the brightness of the other stars can be compared; those just barely bright enough to see are closer to 12-13th magnitude, while some are slightly brighter, between 5-7th magnitude.  Using Neptune as a guide, can you tell which stars bare brighter?
  Finally, I included a rare 3rd image, for which magnifying the planet to about 200x.  Although a smaller field, the planet may appear more disc-like instead of pinpoint-ish.  This magnification of 200 or more also reveals Neptune's largest--and therefore brightest--Moon Triton, which is nearly as dim as the dwarf planet Pluto, at 13th magnitude.  A telescope of 6" or larger can pick up stars and Moons at this dim magnitude on very clear, dark nights.  Out of Neptune's 8 Moons, only two are large enough to find with powerful telescopes (Nereid being the other yet extremely dim at 18th magnitude).  The voyager 2 mission discovered the other 6 back in the late 1980's during a close fly-by.  Unlike Triton also, for which those 6 other Moons have orbits smaller than, Nereid has the most eccentric orbit in the solar system, as, shown in that 3rd image with Triton's.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.