Observing Jupiter

1
Observing Jupiter
2
Why observe Jupiter?

• Shows the greatest amount of detail in amateur
  telescopes of all the planets.
• Constantly changing.
• Can be followed for most of the year.
• Easy to observe even with smaller telescopes.
• Can be observed even from the city.

3
Jupiter is like a miniature Solar System

• Planet is 88,000 miles in diameter (11x Earth).
• Composed of mainly gas (Hydrogen, Helium, and
  trace amounts of Methane and Ammonia).
• Planet rotates once every 10 hours.
• 50 moons.
• 4 large moons (probably formed with Jupiter).
• Many smaller moons which may be captured
  asteroids or comets.

4
Equipment for Observing Jupiter

• 3 to 12 inch telescope (6 inch best).
• Good eyepieces and barlows that will give 40x per
  inch of aperture (Plossls, Radians, etc.).
• Good telescope mount (with a drive, optional).
• Filters Light Blue or Light Green (optional).
• Sketch pad and pencils.
• Watch (accurately set to UT).

5
Features on Jupiter
6
What to look for

• Major Belts (NEB and SEB).
• Minor Belts (NTB, STB, etc.).
• Festoons in EZ.
• Great Red Spot (GRS).
• Smaller White and Red ovals.
• Atmospheric Disturbances.

7
(No Transcript)
8
Timing Atmospheric Features

• Jupiters atmosphere actually has more than one
  rotation rate.
• The EZ rotates once every 9h 50m.
• The rest of the planet rotates once every 9h 55m.
• Other features like the GRS and smaller ovals
  drift slowly relative to the rest of the planet

9

• To time a feature, watch Jupiter until the
  feature appears centered on a North-South line
  bisecting the planet.
• Note the time to the nearest minute.
• For large features like the GRS, the leading and
  following edges can also be timed.
• Use a planetarium program or almanac to find the
  longitude at the times you measured (be sure to
  use System I longitudes for EZ features and
  System II longitudes for the rest of the planet).
• Changes in longitude can be seen in as little as
  a couple of weeks for some features.

10
(No Transcript)
11
Sketching Jupiter

• On a good night, Jupiter can show a wealth of
  detail. At such times, making a drawing of the
  planet is a simple and satisfying way to make a
  record of what you see.
• Using a small sketch pad and pencil quickly draw
  a rough sketch just showing the outlines of
  features. Label each feature with a number from
  0 to 10 to describe how light or dark a feature
  is (0 black, 10 white). Also note any
  obvious colors or other interesting details.

12

• Write down the time (to the nearest minute), the
  telescope and magnification, plus any other
  relevant information.
• Later or the next day indoors, the rough sketch
  can be filled in and shaded using the intensity
  estimates that were made at the eyepiece.
• For the best results, use pencils with soft lead.
• An eraser can also be used to gently blend the
  lead.

13
Observing Jupiters Moons

• The four largest moons of Jupiter (the Galilean
  moons) can be seen even with binoculars.
• These moons all lie in the plane of Jupiters
  equator which means they pass in front of and
  behind Jupiter as seen from Earth.
• When the moons pass in front of Jupiter, they
  cast their shadows on the planet. The shadows
  look like bullet holes and take about an hour or
  so to cross the planet.

14

• When the moons pass behind Jupiter, they are
  occulted by the planet. These occultations
  usually take 5 to 10 minutes for the moon to
  completely disappear or reappear.
• The moons can also be eclipsed by Jupiters
  shadow. When watching one of these, the moon
  will start to fade (or brighten) very gradually
  then more rapidly until the moon is completely
  faded from view (or fully brightened in the case
  of a reappearance). The disappearances (or
  reappearances) last about 5 to 10 minutes.

15
Resources

• Sky Telescope magazines Jupiter Observing
  Guide http//www.skyandtelescope.com/observing/ob
  jects/planets/3304326.html?page1cy
• Association of Lunar and Planetary Observers
  http//www.lpl.arizona.edu/alpo
• Christopher Gos Jupiter images
  http//www.christone.net/astro/