Jupiter at Quadrature

Wednesday evening, July 5, around 9:40:17 p.m. CDT, Jupiter reaches east quadrature, which means it is 90° east of the Sun.  In other words, the Sun-Earth-Jupiter line most nearly forms a right angle.

The best time to attempt daytime viewing of a superior planet like Jupiter is when it is at quadrature.  Then, we are looking at it through a region of the sky where reflected sunlight is most strongly polarized.  By using a polarizing filter with a telescope eyepiece, and properly rotating it, the sky background can be significantly darkened, allowing surprisingly good views of the planet during twilight and even daylight.

Jupiter reaches its most favorable viewing position when it crosses the celestial meridian, where it reaches its highest altitude, due south.  Wednesday evening, that occurs at 6:58:18 p.m. (Dodgeville) when the Sun is 16° above the horizon, 1h44m before sunset.  Use a polarizing filter for the best view of our solar system’s largest planet around this time on Wednesday, July 5—or the closest date that affords you clear skies.

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