This article includes a JavaScript utility to help you identify Neptune's largest moon, Triton, in your telescope's eyepiece. You'll find instructions for its use below.

Neptune, at magnitude 8, is the beyond the reach of the naked eye and even some binoculars. Locating the most distant planet can be a bit daunting on its own. But if you are up for a serious challenge, you can go further and try spotting its largest moon, Triton.

Triton is tricky. It shines at only ~13.5 magnitude, nearly as dim as Pluto. But with our interactive Triton Tracker, you can try to join the exclusive club of amateurs who have spotted it. our JavaScript tool, and learn where to look for the dim satellite.

Our JavaScript tool can be set to match the view in your telescope's optical system, whether it shows a correct image with north up or south up, or a mirror-reversed image. The display has several parts. At right is a diagram showing the position of Triton (T) with respect to Neptune. Below the graphic are three buttons you can use to change the orientation of the diagram to match the view in your telescope. "Direct view" puts celestial north up and celestial east to the left; the routine opens in this orientation, the correct view used in most star atlases. "Inverted view" puts south up and west to the left, still correct but upside down. This matches the view seen in a Newtonian reflector in the Northern Hemisphere. "Mirror reversed" puts north up and west to the left, matching the view in most catadioptric (mirror-lens) and refractor telescopes used with a star diagonal in the Northern Hemisphere.

Next comes the date and time; when the routine opens, it is initialized to the present (as determined from your computer's clock). Change the date and time by entering new values in the corresponding boxes and clicking the dark gray Recalculate button on the next row. Or click on the adjacent buttons to step backward or forward in increments of 1 day or 1 hour.

Our Triton Tracker uses Universal Time (UT, the same as Greenwich Mean Time), and underneath the day- and hour-increment buttons it shows what we think is the offset between UT and your local time, based on your computer's current settings. When changing the time manually using the Time input box, enter the Universal Time that corresponds to the local time when you will be observing.