ANSWER: JUPITER'S OBLATENESS
Measurements with a Ruler on My Monitor (Using the Enlarged Image):
Equatorial Diameter = 14.5 mm Polar Diameter = 13.5 mm Oblateness = (Equatorial Diameter - Polar Diameter)/Equatorial Diameter = (14.5 mm -13.5 mm)/14.5 mm = 1 mm/14.5 mm = 1/15 (rounded)* Published Value = 1/15! So Jupiter's polar diameter is about 1/15 (abt. 7%) smaller than the equatorial diameter.
(Compare this value with Earth's oblateness, 1/298, which makes Earth very spherical!)
*Note: Oblateness is often expressed as a fraction: 1/x.
WHAT DID YOU GET?