A Guide to Observing Jupiter

SkyNews is pleased to provide a primer on how to identify surface details on Jupiter and when the Great Red Spot will be visible.

Planetary observing requires good seeing conditions, patience and a telescope that has been correctly collimated and reached thermal equilibrium. Each of these conditions are essential in order to achieve excellent views of the planets.

Collimation may be intimidating at first, but with practice can soon become an easy task and should be checked each observing session (note: owners of refractors generally need not worry about collimation).

Instructions on how to collimate your telescope can be found here.

Before observing, ensure that your telescope has acclimatized to the outdoor temperature. If a telescope is taken from a warm storage area, such as a house, to cooler outdoor temperatures, heat currents inside the telescope will cause distorted views. Depending on the temperature variance, it may be necessary to set your telescope up an hour or more before observing to ensure proper cool down.

Other tips for using your telescope can be found here.

Seeing conditions can vary greatly from night to night. The more steady the air, the better the seeing conditions. Rapidly twinkling stars often indicates an unstable atmosphere, resulting in poor seeing, however it is advisable to still view through the telescope to confirm the actual conditions.

Remember to be patient while observing. Brief glimpses of subtle detail may pop into view for only a fraction of a second, but that moment may provide you with a wealth of visible detail. Seeing detail on the planets requires an observer to spend time at the eyepiece. Your eye will become trained to see more detail after a few observing sessions and remember that the more you look, the more you'll see.

Observing Jupiter

A 4-inch or larger telescope can provide fantastic views of Jupiter. Start your session off by identifying both the north and south equatorial bands. Good seeing may allow for the temperate bands at each pole to be seen. The Great Red Spot, a storm the size of the Earth, can be seen if it positioned facing the Earth. A list of times that the G.R.S. can be observed can be found here. With experience, observers may be able to discern festoons, barges and ovals upon the surface of Jupiter.

Shadow transits, eclipses of the Sun upon the surface of Jupiter by Io, Europa, Ganymede and Callisto, the four largest moons of Jupiter, can also occasionally be seen. This set of images, taken by Darryl Archer, shows how to recognize a shadow transit.

Some coloured filters may enhance planetary details. Light blue (80A), very light blue (82A) and light green (56) often accentuate surface features of Jupiter. Remember that detail will not magically appear with the use of a coloured filter and that using one which is too dark for your telescope can reduce the amount of visible detail. If the Great Red Spot cannot be seen without a filter, it will not prominently pop into view once a filter is used.

Owners of achromatic telescopes may benefit from the use of a minus-violet filter. These filters attach to the bottom of an eyepiece or to the telescope's diagonal, reducing the amount of chromatic abberation while increasing contrast and detail.

Click on the image below for a labelled diagram showing Jupiter's main features.