As a visual and photographic spectacle, in my opinion Jupiter comes a close second to Saturn among the planets.  The so-called ‘King of the Planets’, Jupiter is more than twice as massive as all the others combined. Notwithstanding its size, Jupiter has the shortest ‘day’ of any planet, rotating fully in just 9-hours and 50 minutes – as a result creating a significant equatorial bulge that measures 88,760 miles in diameter and 83,082 miles from pole-to-pole.  However, as a gas giant the planet does not rotate en masse, with the outer regions moving slower than the equatorial region leading to a series of distinctive belts and zones, most notable of which is the Great Red Spot – a massive storm on the edge of the South Equatorial Belt.

Partly because of its vast size and resulting gravitational field, Jupiter is thought to have played a dominant role in shaping the present Solar System.  The planet we see today is not alone, with 67 moons so far identified, the four largest discovered by Galileo 400 years ago being easily visible from Earth.  In order of distance from Jupiter the moons of Io, Europa, Ganymede and Callisto are extremely diverse in nature – ranging from the highly volcanic Io to the frozen world of Europa, whilst Ganymede and Callisto may have sub-surface oceans and are bigger than the planet Mercury.

Despite being by far the largest planet in the Solar System and the fourth brightest object after the Sun, Moon and Venus, my attempts to image Jupiter and its Jovian neighbours have so far met with only mixed success.

Most people’s first view of Jupiter is likely to be through binoculars or a basic telescope, which will   show the very bright planet accompanied by a number of its Gallilean moons, depending on their orbital position i.e. when located behind the planet they will, of course, not be visible.  Having viewed Jupiter a few times like this, my first attempt to image the planet and its moons was just such a view simply using the William Optics 81mm refractor, a x2 Barlow and my Canon 700D DSLR.  Compared to Jupiter the moons are not as bright and to capture their presence it is necessary to boost either the ISO or exposure time, which then overexposes the bright planet resulting in loss of detail – in this case the distinctive coloured gas bands. Conversely, with a lower ISO or exposure this detail once again becomes apparent but some or all of the moons are then lost in the image.  The way round is to combine two sets of images taken at different camera settings, thus obtaining the best of both worlds, literally.  For the moment however this remains work in progress.

January 2014, Jupiter – overexposed but shows all four Gallilean moons | 1 sec @ ISO 400

Jupiter – lower exposure shows the gas belts but the moons, though there, are now very difficult to see. 1/3rd sec @ ISO 800

Personally I like the wider view of Jupiter and its moons but inevitably the holy grail has to be a close-up image showing details of the planet’s characteristic gas belts, which requires the use of a CCD video, in my case a ZWO ASI 120MC camera.  Having mostly concentrated on DSO photography to-date using a DSLR, my use of the ZWO camera is limited and with mixed success.  Using this camera and the Skywatcher 150PL reflector telescope I have previously managed images of Saturn, Mars and the Moon but this time I used the William Optics refractor instead.

CCD imaging is a very different technique to DSLR and it’s fair to say that I still have much to learn. Notwithstanding, using Registax for processing I obtained some reasonable first-time Jupiter images but will need more practice to improve the detail; the quality might also be improved using WinJUPOS software during processing, which applies a de-rotational programme to the fast moving planet thus reducing blur – however, I have yet to understand let alone master this software.  Also, whilst the quality of the William Optics telescope is far superior to the Skywatcher 150PL, it is obvious that its relatively short focal length is not really adequate for good planetary imaging.

21st February 2015. Jupiter up close
WO 81GT81 | ZWO 120 MC

So far this year Jupiter had already provided a number of different opportunities for imaging.  Between February and April the planet moved across the southern sky in all its glory, whilst more recently it moved into close conjunction with Venus at the end of June and there’s more to come.

On 26^th August from our vantage point on the Earth, Jupiter will appear very close to the Sun in the sky as it passes around the far side of the solar system from the Earth.  At closest approach, Jupiter and the Sun will appear at a separation of only 0°52′, making Jupiter totally unobservable for several weeks while it is lost in the Sun’s glare.  At around the same time, Jupiter will also be at its most distant from the Earth – receding to a distance of 6.40 AU – since the two planets will lie on opposite sides of the solar system.  Over following weeks and months, Jupiter will re-emerge to the west of the Sun, gradually becoming visible for ever-longer periods in the pre-dawn sky. After around six months, it will reach opposition, when it will be visible for virtually the whole night, by which time I have hopefully mastered some new techniques for imaging this Jovian King of the Planets.