Saturn With and Without Moons
Saturn's moons are much fainter than the planet itself. A short exposure (left) captures only the planet and its rings, whereas an exposure long enough to record the moons (right) drastically overexposes Saturn. At the time these images were made, Saturn's brightest moon, Titan, was several ring diameters to the west (right) and outside the field.
S&T: Richard Tresch Fienberg

Anyone who looks at Saturn through a telescope will notice at least one and possibly several pinpoints of light glimmering near the planet. Even a 60-millimeter (2-inch) telescope will show Saturn's brightest moon, Titan, which shines around 8th magnitude and has a smoggy atmosphere that gives it an orange cast. A 15- or 20-centimeter (6- or 8-inch) scope may reveal up to four fainter satellites closer to the planet.
But how can you distinguish them from background stars, and how can you tell which moon is which?
That's where our interactive observing tool comes in! For any date and time between 1900 and 2100, it shows the positions of Titan and four other bright moons: 10th-magnitude Rhea, Tethys, and Dione, and 12th-magnitude Enceladus. Moreover, the tool can match the view through your telescope's optical system whether it shows the sky with north up or south up, and either correct-imaged or mirror-reversed.
SaturnMoons iconIf you enjoy using Saturn's Moons and own an Apple device, check out our mobile app. SaturnMoons is an up-to-the-moment guide to the ringed planet and its family of satellites, showing the locations of Saturn's nine largest moons at any date and time. Available on the iTunes App Store for $2.99.


Sky & Telescope's Saturn's Moons observing tool, which will open in a new browser window, shows the positions of the planet's brightest satellites, Titan, Rhea, Dione, Tethys, and Enceladus, for any date and time from January 1900 to December 2100.At upper left is the date and time; when it opens, these are initialized to the present (as determined from your computer's clock). Change the date and time by entering new values in the boxes and clicking the dark gray Recalculate button. Or click on the buttons in the next row to step backward or forward in increments of 1 day or 1 hour. Our Saturn's Moons uses Universal Time (UT). Beneath the time buttons, it shows what we think is the offset between UT and your local time, based on your computer's current settings. At upper right is a diagram showing the positions of Titan, Rhea, Dione, Tethys, and Enceladus with respect to Saturn and its rings. Below the time buttons and 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, which is the one used in star atlases. "Inverted view" puts south up and west to the left, matching the view seen in a Newtonian reflector in the Northern Hemisphere. "Mirror reversed" puts north up and west to the left, matching the mirror-image view in most catadioptric (mirror-lens) and refractor telescopes used with a star diagonal. Launch S&T's Saturn's Moons observing tool. If you see any problems with this tool, or any of our interactive tools, please send an email to Find more information about observing Saturn here: An Observing Guide to Saturn.

No comments:

Powered by Blogger.