Planetary Section Report; December 2017 and January 2018

As with the last reporting period the outer ‘ice-giant’ planets of Uranus and Neptune were the main objects available to view during evening skies however Mars and Jupiter started to make early-morning appearances. It must be said, however, that observing opportunities were relatively few given the poor weather over the Christmas and early New-Year period.

I will therefore start with a number of observations of the spectacular planetary conjunction between Jupiter and Mars. The pair were seen rising close together from mid-December onwards but on the 7th of January they were, visually, only one fifth of a degree apart; close enough to be seen together in a moderately-powered eyepiece in most amateur telescopes. Mike Feist observed the conjunction from 0430 to 0825 UT with a range of binoculars and spotting telescopes and noted the striking colour difference between them, with Mars obviously red and brighter Jupiter showing varying shades from brown to grey. He was able to follow Jupiter into daylight, something that is relatively easy to do as long as suitable precautions are taken to keep the Sun well away from the field of view. Mike observed the conjunction on a number of days either side of closest approach including the 11th of January when the waning crescent Moon joined the pair to form a tight triangle in the south-eastern sky.

Steve Norrie also observed the pairing on the 7th and took a number of images, both wide and narrow field, from his home in Fife Scotland. The narrow field view exaggerates the apparent separation between the two bodies but gives an excellent idea of the telescopic view available on that morning.

Dave Eagle took images of the two planets and combined them into one frame, compressing their separation but showing obvious banding on Jupiter (as does Steve’s image) as well as the positions of the Galilean moons and the striking colour of Mars. Incidentally there have been recent reports of a major outbreak of storm activity within the South Equatorial Band of Jupiter so I look forward to more detailed observation to attempt to corroborate this outbreak.
In the period Mike Hezzlewood made a series of observational drawings of Mars to try and pick out detail on the red planet relatively early in its current apparition. He reports that it was at times painfully difficult and a major struggle fighting the low altitude of the target, its small apparent size and the vagaries of our own atmosphere. Perhaps not surprisingly his later drawings capture slightly more albedo variation as the apparent size grew towards 5 arc-seconds. In early December Simon Kidd managed to image Mars in good seeing conditions and he may have caught some indications of cloud forming over the Elysium plateau. In December the Areocentric longitude of the Sun from Mars passed 90 degrees; that is the Summer Solstice for its northern hemisphere. At this time the large amount of gas released by melting water and carbon-dioxide ice at the North Pole means there is plenty available for cloud formation and it is common to see orographic cloud as gas is forced up and over high points in the Martian terrain, including Elysium and the volcanic peaks along the Tharsis bulge. 

Additionally the season is such that observations of cyclonic cloud or obviously curved fronts of cloud may start to be seen on the morning side of the northern hemisphere; particularly at high latitudes near 60 North and 60 West, over Mare Boreum and, perhaps in the coming months, over Utopia at 60 North and 60 to 120 degrees East.

As with Jupiter, Mars is steadily improving in visibility and will certainly repay detailed observation in the next reporting Period. On the other hand the outer ice-giant planets are slowly declining in visibility. Uranus was still well placed mid-evening but Neptune was starting to sink lower into the western evening sky. Martin Lewis did exceptionally well to capture both Neptune and Uranus in mid-December and while detail on Neptune was illusive, the atmospheric shading of Uranus was beautifully caught along with the positions of the surrounding major moons; Umbriel, Ariel, Miranda, Titania and Oberon. Martin is currently trying to capture an image of the faint rings of Uranus and is hoping to get suitable weather conditions before the planet sinks too low to effectively photograph. He hopes to use an infra-red pass filter and relatively long exposures to pick up the faint ring system outside the glare of the planet itself. This is an interesting and very challenging project which few amateurs have achieved convincingly and then with very large aperture telescopes. The section wishes him well with this work and will report further on its progress, ‘though time is running out for the right weather conditions in the current apparition.

I will finish by remarking that most UK planetary observation of the major targets over the next year is going to be done at relatively low altitude and this may put-off some observers in the section; I hope this will not be the case. With careful planning useful observation can still be made. In the case of Mars, for example, the planet reaches opposition in late July but its very low declination, more than 25 degrees south, means it will be extremely low in UK skies. Mars can be better observed in the months leading up to opposition when the ecliptic is better placed, so it is best to start observing from now, rather than waiting until closer to opposition. The ‘rainbow’ problems of atmospheric dispersion with low altitude targets can be mitigated by observing with coloured filters or by using an atmospheric dispersion corrector, available at the cost of a mid-range eyepiece. I hope the section members will continue to report on their excellent work in the next reporting period and beyond.