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The gas giants at opposition

Clear summer nights in July should be used for observing the large gas planets Jupiter and Saturn, as both are at opposition to the Sun in the middle of the month. For us in central Europe this creates optimal conditions as both planets will reach their greatest apparent magnitudes and their highest positions above the horizon.

Unfortunately, the planets are usually found very close to the horizon, impairing observation due to strong air turbulence (so-called “seeing”). Furthermore, a position close to the horizon also results in a restricted field of vision due to buildings, mountains or trees. The atmospheric turbulence can be counteracted using an ADC (“Atmospheric Dispersion Corrector”).

At the time of opposition, both planets are located towards the south, in the constellation of Sagittarius, around 21° above the horizon which makes observation considerably easier. Due to their maximum apparent magnitude at this time, the gas giants are very easy to locate.  A star chart can offer good guidance.

Stellarium

The gas giants are also great viewing targets for newcomers or children with their parents’ support!

Jupiter will shine at up to magnitude -2.7, Saturn at around magnitude +0.1. Additionally, the giants will converge in the sky at a distance of around 7°. Both will, therefore, be able to be observed together over an extendedperiod of time, even during the short summer nights. In the case of Jupiter, smaller telescopes can also detect its four Galilean moons, Europa, Ganymede, Io and Callisto, as well as enabling examination of the planet’s main cloud bands. To increase contrast on the cloud bands, a suitable filter, such as a polarising or colour filter is often used.

Jupiter in March 2015 (Photo: Berns Gährken, Munich in March 2015 using a C11)

The much more distant Saturn will show us its impressive ring system and, in larger optics, also its Cassini division as well as the largest four or five of its total 82 moons.

Saturn surrounded by the moons Enceladus, Tethys, Dione, Rhea and Titan (Photo: James Bates, Berlin August 2019, C8, 2x Barlow, ADC, UV/IR band-elimination filter, ZWO ASI 224MC)

The precise opposition dates are 14 July for Jupiter and 20 July for Saturn. The months of July and August are generally ideal for observations – also in the periods directly before and after the opposition dates.

Those who subsequently have not had enough of planet watching can look forward to the commencing Mars opposition from September. The red planet is much closer to us, but also much smaller than the giants Jupiter and Saturn…

You can also show your enthusiasm for the planets with a suitable summer outfit.

We wish you a clear sky, success and fun when observing!

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13.08.2020
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