Planetary Section Report; October and November 2018

This was an interesting reporting period in which Mars received significant attention as it slowly rose, night on night, from its lowly altitude when at opposition back in late July. Despite steadily reducing in apparent size and brightness, the settling out of dust following the summer storm in the Martian atmosphere meant that major surface details were, once again, on view and ready to be observed.

In mid-October amateurs were notified of a new storm feature now visible at distant Uranus and a few of us have tried to capture an image of it so that the rotation rate of this feature can be analysed and predicted; so far without success by an SPA member, but there is plenty of time left to observe Uranus, and Mars for that matter, in full darkness so I am hopeful of better results before the New Year! Neptune, Venus and Saturn were also observed but having started this article with Mars I will continue with it for the moment.

The first observation came from Mark Beveridge from the evening of the 6th of October. Mark uses a One-Shot-Colour camera (OSC) but one that also has excellent sensitivity in the infrared; this means he can take both normal colour images and also IR filtered images that help cut through our own turbulent atmosphere. His colour image shows Xanthe Terra (Aurora Sinus) on the central meridian with Argyre Planitia just visible above the obvious south-polar ice cap. Martin Lewis then submitted a purely IR filtered image from the 9th of October with very obvious Sinus Sabaeus, Mare Acidalium, Axia Pallas and Aurora Sinus areas straddling the central meridian.

Following these came images from Dave Tyler and Dave Finnigan both taken on the 10th of October and another from Mark Beveridge from the same night. All described the local seeing conditions as poor, with Mark saying Mars looked like a “boiling blob”, however their results all capture some detail with Dave Tyler’s perhaps being the sharpest and showing a hint of a very bright Hellas basin on the limb.

Next came images from Dave Finnigan and Martin Lewis from the 18th of October showing that Hellas and Syrtis Major had rotated into view. Both Dave’s colour and Martin’s infrared monochrome images show these features clearly. Hellas is particularly bright; early October represented mid-summer for the southern hemisphere of Mars so the pale dust and sand that fill this deep basin would be almost directly under the Sun and reflecting strongly. In contrast the southern polar ice-cap is significantly shrunken with much of its water and carbon-dioxide given off into the atmosphere due to the southern summer heat; it is easy to see how Hellas might be confused for a polar ice-cap under certain circumstances.

Moving into November, Dave Finnigan sent an image from the first of the month showing the relatively empty northern and central stretch between Elysium and Olympus Mons, then Robin Scagell sent a very similar scene from the following night taken with a small, 130mm aperture Newtonian reflector. This shows softer detail, largely due to the reduced image scale from a short focal-length telescope, but does show that small instruments can contribute to planetary imaging observations. Poor seeing was reported for both images and a really steady night would have noticeably sharpened detail.

Dave Tyler sent in an image on the 17th of November when Mars had fallen to just over 10 arc-seconds in apparent size. This shows a view one full rotation on from images taken in mid-October with Hellas, once again very prominent, dwarfing the southern ice-cap and with dark Syrtis Major and Sinus Sabaeus clearly on view. My own images, taken from the 24th of November show a similar, if less defined, view of the same region. I used both a OSC camera, in this case an AS224MC, and monochrome camera, ASI290MM, to make images some 7 minutes apart with the monochrome camera taking infrared then blue filtered images, subsequently combined to make a false colour view; The larger image scale for the false colour image comes from the smaller capture pixels on that camera. Seeing for both images was only moderate and with Mars now below 10 arc-seconds in size I will hope for better seeing to continue to capture detail as Mars rises higher in the winter evenings.

Well, I mentioned the new storm discovery on Uranus. This was made by American Blake Estes in late October using a large aperture semi-professional telescope and has been followed up with a number of amateur observations, one using an aperture of 200mm (8 inches). Ephemeris data for this storm has been published on the SPA website and a number of section members are actively trying to image it. On the 6th of October Richard Boseman imaged Uranus using an ASI224MC colour camera fitted with an infrared pass filter. Despite being a colour camera the 224 chip is very sensitive to infrared light and this set-up has been used successfully in the past in capturing storms on both Uranus and Neptune. In this case, sadly, no storm feature is obvious in Richard’s image otherwise he would have stolen a march on Blake and been named as the discoverer!

Since the announcement of the discovery the race is on for an SPA member to image the storm but, so far (early December), with no success. My own attempts have been thwarted by either poor seeing or the position of the Moon but Martin Lewis managed to observe on the 17th of November and clearly caught the dividing line between the darker temperate and equatorial regions and the brighter north-polar region. The image is being studied carefully for any trace of the storm but sadly it is not obviously on view. You will note that Martin deliberately took a wide enough field of view to show the position of Uranus’s satellites as the positions of these is vital for determining the exact time of the image and hence the exact position of any storm feature on view.

Martin also managed to take images of Neptune, on both the 9th and 20th of October. The same infrared band filters that work well on Uranus have also shown storm features on Neptune but none have been seen by amateurs during this observing season. Saturn was also observed with a single image being submitted by Larry Todd, taken on the 3rd of October. The ring system and cloud-top banding are obvious but Saturn was a difficult, low-altitude target in the period, reaching the end of its apparition and no other effort was taken to observe it. Venus was also reaching the end of its eastern evening apparition, moving into inferior conjunction between the Earth and the Sun on the 26th of October however, just 5 days before that Martin Lewis managed to capture its thin, elegant crescent in an image similar to the one that won him a prize recently; overall winner in the Planets, Comets & Asteroids section of the Insight Investment Astrophotographer of the Year competion 2018: Very well done indeed Martin.

Thanks to all contributors during this period and may I wish you clear skies and steady seeing for the next reporting period.

Alan Clitherow