Image Credit & Copyright: NASA Voyager 2.
Saturn fans rejoice; well now through mid-June will be the best time to observe the Ringed Planet until June, 2016. Though not a naked eye event, even small telescopes will reveal the brilliant rings and they will “wow” you every time. Currently in the constellation Libra, Saturn reaches opposition on May 23, 2015 at precisely 01:22 UTC (21:22 EDT on the 22nd though the exact time isn’t important). This means that Saturn will be directly opposite the Sun from our vantage point here on Earth, thus we will see it as a full planetary disk with rings tilted at +24.4 degrees as it passes high overhead around midnight at 77 degrees in altitude (90 degrees is straight overhead). That day the disk of Saturn will be an apparent size of 18.5” arcseconds (42.1” including rings) on the night sky while shining at a magnitude of about 0.1 at a distance of 9 AU from Earth which equates to roughly about 827,306,685 mi. (827 million mi.).
Let’s take a quick look at definitions for a moment just to clarify a couple of points. Opposition is when the Earth is placed exactly between the Sun and a given superior planet (planets beyond Earth’s orbit). Because planetary orbits aren’t perfect circles, opposition doesn’t truly mean “closest point” to Earth. The term “perigee” still applies here and they indeed happen at different times though very close. For example, opposition (opposite the Sun/full disk view of the planet) occurs on the 23rd while it will reach perigee (closest point to Earth but slightly less than a full planetary disk) also on the 23rd. Truth be told, it’s one in the same. Saturn is so far away (9 times further than the sun) that you won’t notice the difference between opposition and perigee.
The Moon will be cooperating with us this time as well (fist bumps for everyone). On opposition night the Moon will be a young waxing crescent having just come out of lunation 1143 (New Moon), 4 days old and only about 20% illuminated. It will be setting pretty early in the night as young Moon’s do so it shouldn’t impact your Saturn observations at all.
NOTE: I didn’t list Sun, Moon & Saturn set times because those times are local for your individual area but I did place links below for you to locate your own. Rise & set time isn’t a single “one moment” event it’s continuously happening so different individual locations will have different rise/set times but instead of the west coast of the US being exactly 3 hr. behind the east coast (as in calculating time zones) it will actually be pretty similar to your actual clock time but slightly off. It’s a little bit of a different approach and way of thinking than simple time zone calculations but that’s what they make calculation programs for.
Also, during the surrounding few hours of opposition look for a phenomenon known as the Seeliger Effect. You may also know this as “Opposition Surge”, “Opposition Effect” or even “Opposition Spike.” This is a sudden brightening of the planet; or in this case Saturn’s rings just before and just after opposition. You may notice that the disk of the planet doesn’t brighten; just the rings. The brightening is from the sunlight being reflected off the ice crystals in the rings as they are illuminated from almost the same direction in which we are viewing them from. This also happens with other celestial bodies including the Moon when full vs. its other phases but for slightly different reasons that include shadows etc.
Saturn oppositions occur every 12.5 months or 378 days or 13 days later every year. Although Saturn’s opposition cycle is currently taking it further from Earth each year as it reaches aphelion (furthest pint from the Sun) on 2018 it’s apparent magnitude is actually brightening because of the greater ring tilt (details of recent & upcoming oppositions below).
Opposition 2014: size 18.7” arcseconds with a magnitude of 0.2 & ring tilt of +21.7. Opposition 2015: size 18.5” arcseconds with a magnitude of 0.1 & ring tilt of +24.4. Opposition 2016: size 18.4” arcseconds with a magnitude of 0.1 & ring tilt of +26.0. Opposition 2017: size 18.4” arcseconds with a magnitude of 0.0 & ring tilt of +26.6.
“In-The-Sky” page for this event: https://in-the-sky.org/news.php?id=20150523_13_100
“Naked Eye Planets” Saturn page: http://www.nakedeyeplanets.com/saturn.htm
“Ice in Space” page for Planet Oppositions: http://www.iceinspace.com.au/planetopp.html
“Heavens-Above” Planet Summary w’ Rise & Set times: http://www.heavens-above.com/PlanetSummary.aspx?lat=0&lng=0&loc=Unspecified&alt=0&tz=UCT
Sun, Moon & Planets RISE & SET times: http://www.almanac.com/astronomy/rise/MA/Boston/2015-03-23
Sun, Moon & Planets RISE & SET times: http://aa.usno.navy.mil/data/docs/mrst.php
“Heavens-Above” current solar system positions: http://www.heavens-above.com/planets.aspx?lat=0&lng=0&loc=Unspecified&alt=0&tz=UCT
NASA Solar System Simulator: http://space.jpl.nasa.gov/
NASA Eyes on the Solar System: http://eyes.nasa.gov/download.html
The Planets Today: http://www.theplanetstoday.com/
Solar System Scope: http://www.solarsystemscope.com/