SATURN

   .  . 

1999.11.11 (left), 2001.11.15 (middle) and 2002.01.16 (right).   These photos illustrate the changing aspect of Saturn as it moves through its orbit (providing different apparent inclinations of the ring system), as well as the more subtle changes caused by the Earth moving through its orbit.  In 1999 the rings had an apparent tilt of 20 degrees, whereas in 2001/2002 the tilt is close to its maximum value of 28 degrees. All images show shadows cast slightly downward, caused by the sun illuminating Saturn from slightly above (and behind the Earth).  During the several months of each year's "opposition" the illumination geometry is seen to shift from shadows being cast rightward to leftward.  This is shown by the right two images, one taken from BEFORE opposition and the other taken AFTER opposition.

Most aspects Saturn images are unchanging, such as a brighter inner ring separated from the outer ring by Cassini's Division.  The equatorial region is always brighter than the mid-latitude region, and the polar region is even darker.  The brownish color of the mid-latitude and polar region is also a persistent feature.  [All images are with a Meade LX-200, 10-inch Schmidt-Cassegrain, f/6.2, eyepiece projection with a 1/2-inch FL eyepiece, digital camera - usually a Nikon Coolpix 990. The right-most image is an average of 6 images, each exposed 1/15 second, unsharp mask hard, Gamma 0.9, using MaxIm DL processing program.  The observing location is my Santa Barbara,CA residence.]

_________________  IMAGES BELOW THIS LINE ARE IN TEMPORAL SEQUENCE (MOST RECENT AT THE TOP)  __________________

The following sections are devoted to "oppositions," or the 6-month interval when Saturn passes from a morning object, to a midnight object (closest appraoch and best viewing) to an evening object.  Each opposition, starting with that of 1999, is shown by representative photos taken during that year's "observing season."  Changes in Saturn's appearance occur because the Sun-Saturn-Earth angle goes from -6 degrees to +6 degrees during this time.  Earth-based views therefore see a globe that shadows the ring system on the right side before opposition, and on the left afterwards.  Different oppositions have different ring inclinations, so each year's observing season has something different to see.

The image at the top can serve as a "reference" for the others.  Since it was taken at the time of the 1999 opposition, the rings were inclined a nice 20 degrees and the globe did not cast a shadow on the rings.  However, since Saturn was above the ecliptic plane the rings on the near side did cast a shadow on the globe.  This will always be true for about 14 years in a row since Saturn's period of revolution is a long 29.5 years (for half of those years Saturn is above the ecliptic plane, and for the other half Saturn is below).

____________________________________  PHASE SEQUENCE FOR 2001/02 OPPOSITION STARTS HERE  ___________________________________________

This is the first two images of a sequence for the 2001/02 opposition.  For the first image the sun is "behind us" to the left, causing shadows to be cast rightward and slightly downward.  Cassini's Division is especially apparent on the left and right sides.  Note also the greater brightness of the inner ring.  The second image was taken AFTER opposition, January 16, 2002, when the sun was illuminating Saturn from behind us and to the right - causing shadows to be cast to the left.  Note that the globe has decreased slightly in size due to the greater distance of Saturn from the Earth.  The glode has a bright equatorial band, is brownish at midlatitudes, and is noticeably darker near the south pole.  Compared to 2 oppositions ago, in 1999, the ring system is more "open" - or inclined.  The rings are inclined to near their maximum of 28 degrees.  [Meade LX-200 10-inch SCT, 1/2-inch eyepiece projection to a Nikon Coolpix 990 digital color camera set to 4x zoom; left image is a single image (no averaging of images), 1/15 second, ISO 100; 2001.11.15, 5:45 UT.  Second image is an average of 6 images, each 1/15 second, 2002.01.17, 5:50 UT.]

 ____________________________________  PHASE SEQUENCE FOR 2000/01 OPPOSITION STARTS HERE  ___________________________________________

2001.01.20, 9 PM.  62 days after "opposition" and the Sun-Earth-Saturn angle (elongation) is 113 degrees, and the "phase angle" (i.e., the Sun-Saturn-Earth angle) is 5.7 degrees.  At this phase angle the globe casts a shadow on the LEFT side of the rings, behind the globe.  The Earth is slightly below the plane of Saturn's orbit, which causes the near-ring region to cast a shadow on the globe toward the center of the globe.  Cassini's Division is easily discernible on both sides.  [Meade LX-200 Schmidt-Cassegrain 10-inch, f/6.2, with the aperture masked to 4.2-inches; eyepiece projection using a 1/2-inch focal length eyepiece; Coolpix 990 CCD digital camera set for ISO 200, 46.8 mm focal length (x2.0), each exposure 1/8-second long; average of 5 images.]

2000.12.29, Midnight.  40 days after "opposition" and the Sun-Earth-Saturn angle (elongation) is 135.7 degrees, and the "phase angle" (i.e., the Sun-Saturn-Earth angle) is 4.3 degrees.  The globe casts a shadow on the left side of the rings, behind the globe.  The Earth is slightly below the plane of Saturn's orbit, which causes the near-ring region to cast a shadow on the globe toward the center of the globe.  Cassini's Division is easily discernible on the right side.  [Meade LX-200 Schmidt-Cassegrain 10-inch, f/6.2, with the aperture masked to 4.2-inches; eyepiece projection using a 1/2-inch focal length eyepiece; Coolpix 990 CCD digital camera set for ISO 400, 46.8 mm focal length (x2.0), each exposure 1/8-second long; average of 5 images.]

2000.12.16, Midnight.  27 days after "opposition" and the Sun-Earth-Saturn angle (elongation) is 149.6 degrees, and the "phase angle" (i.e., the Sun-Saturn-Earth angle) is 3.13 degrees.  At this phase angle the globe casts a shadow on the LEFT side of the rings, behing the globe.  The Earth is slightly below the plane of Saturn's orbit, which causes the near-ring region to cast a shadow on the globe toward the center of the globe.  [Meade LX-200 Schmidt-Cassegrain 10-inch, f/6.2, with the aperture unmasked (i.e., a full 10-inch diameter aperture); eyepiece projection using a 1/2-inch focal length eyepiece; Coolpix 990 CCD digital camera set for ISO 400, 70.2 mm focal length, each exposure 1/30-second long; average of 4 images.]
 

2000.12.02, 10 PM.  13 days after "opposition" and the Sun-Earth-Saturn angle (elongation) is 164.8 degrees, and the "phase angle" (i.e., the Sun-Saturn-Earth angle) is 1.62 degrees.  The rings are tilted about 25 degrees.  Cassini's Division is apparent on the left and right sides of the rings.  The Earth is slightly below the plane of Saturn's orbit, which causes the near-ring region to cast a shadow on the globe toward the center of the globe; it also causes the globe's shadow to fall upon the far side ring region.  [Meade LX-200 Schmidt-Cassegrain 10-inch, f/6.2, with the aperture unmasked (i.e., a full 10-inch diameter aperture); eyepiece projection using a 5/9-inch focal length eyepiece; Coolpix 990 CCD digital camera set for ISO 400, 70.2 mm focal length, each exposure 1/30-second long; average of ~10 images.]
 

2000.11.17, 11 PM.  Just 4 days before "opposition" and the Sun-Earth-Saturn angle (elongation) is 177.3 degrees, and the "phase angle" (the Sun-Saturn-Earth angle) is 0.3 degrees.  Because the phase angle is small (compared to the largest it ever gets each year, 6.3 degrees) there is no discernible shadow of Saturn's globe upon the rings on the far side.  Since Saturn is slightly above the ecliptic plane we can see a slight shadow of the near-side rings upon the globe.  Saturn's globe has an apparent equatorial diameter of 20.3 "arc.  The "atmospheric seeing" never did settle down, so this image is sub-optimum. [Meade LX-200 Schmidt-Cassegrain 10-inch, f/6.2, with the aperture masked to the equivalent of 4.5-inches diameter; eyepiece projection using a 1/2-inch focal length eyepiece and a 2x Barlow lens; Coolpix 990 CCD digital camera set for ISO 400, 37.4 mm focal length, each exposure 1/4-second long; average of ~10 images.]
 

2000.11.03, 2 AM.  On this date the Sun-Earth-Saturn angle (elongation) was 163 degrees, or 17 degrees before "opposition."  The Earth-Saturn-Sun angle (phase) was 1.9 degrees, hence the smaller shadow of the globe upon the rings on the back side.  The "A" and "B" rings are distintly visible, but not the Cassini Division.  Visually, Cassini's Division was discernable "all the way around."  The globe had an equatorial diameter of 20.25 "arc.  [Meade LX-200 10-inch Schmidt-Cassegrain (full aperture used), Nikon Coolpix 990 CCD color camera, 1/4-inch FL eyepiece and Barlow lens projection, 1/4-second exposure, average of 4 images.]

2000.10.22/23.  The Earth-Sun line is now 151 degrees, and the globe's shadow on the rings is diminishing.  The apparent equatorial diameter of the globe is 20.07 arc seconds.  Combination of two images, one of which had seeing that permitted a good view of the left ring system and the other which had good seeing for the right side.  Cassini's Division is barely visible on both sides of this combined image (the color was added during processing; the original image was black-and-white). [Meade LX-200 10-inch Schmidt-Cassegrain, Pictor 416XTE, 1/4-inch FL eyepiece and Barlow lens projection, 1/10-second exposure, black and white CCD image with 16-bit pixel brightness depth.]

2000.10.02, 0032 AM, PDST.  This is "early in the season" for Saturn's opposition, with the Sun-Earth-Saturn angle being 128 degrees (and Saturn was low in the eastern sky when this image was taken).  Because the Earth is to the "right" of the Sun-Saturn line, the globe of Saturn casts a shadow to our right, seen clearly on the far side rings.  The southern hemisphere is darker than the equatorial region, as usual.  Although Cassini's division cannot be seen in this image, the boundary between the A- and B-rings is apparent.  Notice that the rings are more open than a year ago, being inclined 24 degrees (instead of 20 degrees).  [Meade LX-200, 10-inch Schmidt-Cassegrain, f/6.2, 1/2-inch FL eyepiece, Nikon Coolpix 990 digital camera; averge of two images.]
 

 ____________________________________  PHASE SEQUENCE FOR 1999/2000 OPPOSITION STARTS HERE  _________________________________
 

2000.02.02.  And a couple months later, the shadow of the globe on the left side of the background rings is slightly more pronounced due to the earth having revolved to location farther along in its orbit, and is closer to the farthest distance away from the Sun/Saturn line.

1999.12.05.  Note that the shadow of the globe upon the rings is on left side.  This is because the earth passed the Sun/Saturn line a month earlier, i.e., Saturn's opposition was 1999.11.05, a month before this image was taken.
 

1999.11.11, 0420 UT.   This is the same "reference" photo at the top of this web page.  It was taken a day after the photo below.  The date is within a week of opposition, so the globe does not cast a shadow on the rings. Since the Earth is slightly below the Sun/Saturn line, the rings in the foreground cast a slight shadow on the globe.  Ring tilt is 20 degrees from being edge on.  Visually, it was possible to see Cassini's Division between the rings at all times.  [Meade LX-200, 10-inch Schmidt-Cassegrain, f/6.2, 1/4-inch FL eyepiece with 2x Barlow (500 power), Canon CCD color camera.  Average of 4 images.]

1999.11.10, 0930 UT.  Note Cassini's Division separating the bright inner A-ring from the dimmer outer B-ring.  Note also the globe's equatorial bright band, a darker mid-latitude brownish region, and a dim south polar latitude region.  Since Saturn is near "opposition" the globe doesn't cast a shadow on the rings, as it did in the photo taken a month earlier (below).  The upper foreground rings cast a shadow on the globe.  More detail is seen visually.  [Canon CCD color camera positioned close to 1/4-inch FL eyepiece with 2x Barlow (500 power), Meade LX200 10-inch Schmidt-Cassegrain.]

_________________________  MISCELLANEOUS SATURN IMAGES  _________________________
 

1958.08.10.  University of Michigan's 12-inch refractor, Tri-X film, 5/8-inch eyepiece projection to SLR camera, 1-second exposure.  I was a Freshman in college when I took this picture.

.Uncredited picture from the web.

Spacecraft Voyagwer 2 picture (from JPL's PhotoJournal web site), before encounter, August, 1981.  The ring inclination appears different from Earth, due to the trajectory of the encounter.  North is at the top.  Two satellites are visible in the foreground.

Voyager 2 closeup (from JPL's PhotoJournal web page).

Return to AstroPhotos page.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This site opened:  August 26, 1998.  Last Update:  July 2, 2003