While I was playing around with the moon, I had remembered that the ice giants were up this time of year. I didn’t have my planetary equipment installed, so I didn’t try for any detail on them. Instead, I took some long exposures on them to reveal their satellites.
Neptune is currently 2.7 billion miles away. It’s apparent diameter would be only 2.35 arcseconds, making it only about four pixels wide at this image scale. Only it’s largest moon and probable dwarf planet, Triton, was visible beyond the glow of the planet. Triton is just about as far away from Neptune as the moon is from us, but it is about three quarters the diameter of the moon. Light from Neptune takes about four hours to reach my telescope. If you were standing on Triton, Neptune would appear about 5 degrees wide in the sky, or about six times larger than our moon.
Uranus is currently 1.8 billion miles away from us and appears slightly larger at 3.75 arcseconds wide. I was able to resolve 4 of its satellites. The four moons would all appear about 0.1 arcseconds wide and have magnitudes between 14 and 15. The light from these objects takes about two and a half hours to reach us.
