Popular Astronomy

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Section Report for October and November 2016

 In this period the section membership mostly confined itself to reporting observations of the outer ‘ice-giant’ planets, Uranus and Neptune, and to the planet Jupiter as it began its glorious return to our early morning skies. Mars, however, does get a brief walk-on part in the play.

Uranus has been well-placed throughout the period but Neptune was beginning to decline to the south-west as darkness fell so presenting less opportunities for observation. Nonetheless Geoff Elston took wide-field images of the area around the planet at the very end of September and on the 5th of October. As well as capturing the small blue planetary disc of Neptune, he also caught, on both occasions, what appeared to be a tiny background ‘field star’ very close to the planet. Thinking this was an unlikely coincidence he researched the fields of view of his images by comparing the positions of the background stars using the software Carte du Ciel; he discovered that he had also caught Neptune’s moon Triton in both images. Considering he used a relatively short focal-length lens on a DSLR camera rather than a telescope, giving nearly one-and-a-half degrees of field, and that Triton was separated form Neptune by just 16 seconds of arc, Geoff did extremely well to capture such a tiny target.
Martin Lewis also imaged Neptune and Triton but by using his 444mm Dobsonian telescope as his cameras lens he was able to get somewhat more detail! The image shows a clear disc with some mottling within the upper atmosphere of the planet and three low-contrast cloud patches forming a rough clover-leaf shape; cloud activity on Neptune is extremely difficult to resolve so Martin is to be congratulated. In his image triton is very well resolved showing the quality of his optical imaging train.
Simon Kidd Imaged Uranus on the 4th of November.  Like Martin he used an ASI224MC camera and a Baader 610Nm long-pass filter; that is a filter that passes light from the red end of the spectrum and up into the infra-red. He collected around 25 minutes’ worth of video files at 25 frames per second to produce his image which reveals distinct banding and a lightening of cloud intensity in the northern hemisphere of Uranus. My own attempts at Uranus were much less successful. On the 28th of November I collected nearly 30 minutes worth of video and was unable to extract a single useful image from it! Seeing conditions may have contributed but it looks like I may have over-exposed the video by setting too high a gain within the camera, thus ‘burning-out’ any detail that may have been visible on the planetary disc. We live and learn and I am grateful to Martin Lewis for the advice he has offered on imaging this difficult target.
Dave Finnigan also managed to capture Uranus towards the end of November. He used an interesting technique of mixing colour images from an ASI 120MC camera,  taken through a UV and IR blocking filter, with monochrome images from an ASI120MM camera fitted with a Baader 610Nm long-pass filter; this filter seems to be fairly ubiquitous amongst the best imagers looking to capture atmospheric detail in the ‘ice giants’. Dave’s pictures from mid-evening on the 28th and 29th of November show the characteristic faint banding in the southern hemisphere along with a lightening of the northern hemisphere, all the way up to the pole.
Similar results were achieved by Richard Bosman who sent in images from the 27th and 29th of November; the latter showing the banding and shading effects most clearly of the pair. Martin Lewis was also out on the 29th imaging Uranus, clearly capturing the available atmospheric features and, remarkably, isolating and enhancing three moons of the planet. He has caught Ariel, Miranda and Umbriel, with only Titania and Oberon out of the field of view. On the same night Martin imaged what has become a rather neglected target; Mars! Surprisingly the eastern (prograde) motion of Mars against the background stars, combined with its slow but steady rise in the evening sky, means that the red planet is better placed for observation now than it was a month or so ago, despite being regarded as at the end of its current apparition. At around 6 arc-seconds from pole to pole it is both significantly larger and much brighter than either of the ice-giants and should be observable for some months to come. Martin has caught the region of the Valis Marineris on the central meridian and the South Pole shines like a beacon as the remaining polar ice reflects the sunlight.
But now we must move on to Jupiter; on the 19th of October Dr Glenn Orton from the Juno-probe team used NASA’s IR telescope on Hawaii to observe this giant planet as it emerged into the morning twilight. He found that while Jupiter had been in conjunction with the Sun there had been the start of a breakout of the North Temperate Belt (NTB) visible as bright plumes and dark blue-grey spots riding on the super-fast atmospheric jet-stream that rings the planet around temperate latitudes. Since then the progression of the breakout seems to be that the bright plumes have faded out leaving rapidly evolving dark spots and smears that may join into a complete belt soon; in fact this may have already happened by mid November. This type of outbreak in the northern hemisphere has followed a, very roughly, five year cycle since 1970 with the last being in 2012. If it continues as per previous cycles we should have a clearly defined NTB by Christmas, possibly in vivid orange / brown hues.
Simon Kidd took a wide-field view of the narrow crescent Moon, of Jupiter and of the star Porrima on the 16th of October; just before the current outbreak was discovered.  Then Steve Norrie began a series of early morning observations of Jupiter in mid-November while the planet was still at low altitude. With images from the 15th, 18th, 24th and 25th of November it is possible to see that the whole of the northern hemisphere is substantially darker than the southern hemisphere with a distinct NTB and that the northern hemispheric zones are narrow and relatively indistinct.
Using a monochrome DMK21 camera on his Celestron C9.25 telescope and by mixing both red and infra-red filters combined with green and blue, Steve has also caught two isolated red spots (possibly three) on the southern edge of the North Equatorial Belt (NEB),  and also the position of Oval BA which is south and a little prograde of the Great Red Spot.  My own One-Shot-Colour image from the morning of the 19th of November is a little less distinct but may show some of the same features. My methane-band image, taken slightly later shows no bright plumes in the northern hemisphere and no distinct dark spots in the NTB, suggesting it may have become contiguous by that date.
Jupiter will only improve in visibility during the next reporting period and I hope the section membership is able to follow the evolution of its atmospheric changes and report them to the SPA. I would also remind the section that the Juno Team are anxious to receive images of Jupiter to help them plan imaging runs by the probe as it makes its low-altitude passes across the cloud tops of Jupiter. Details as to how this may be done can be downloaded from the SPA website at:-
Alan Clitherow.