Section Report for August and September 2016
High summer into early autumn was an unhappy period for planetary observation from the UK with long, light evenings, short periods of true darkness and a dearth of bright targets to view. The outer planets, Uranus and Neptune were certainly on show but these 'ice-giant' worlds do not always receive the attention they deserve with many visual observers considering them too small and lacking in obvious detail to be worth observing. On the other hand the planetary imaging community has made great strides in extracting atmospheric detail from them over the last couple of years. It is still true that there is little point in trying to image such distant targets unless the seeing conditions are very steady, as I found to my own cost with multiple attempts leading to no worthwhile result; fortunately others were more successful as I will report! However I will describe the observations sent to me in August and September in strict chronological order, and that means beginning with Venus:-
On the 12th of August Carl Bowron managed to capture Venus in full daylight, around 1536 UT, using a 15 cm (6 inch) aperture refractor at F18 and a NexImage planetary camera. At that time Venus was just 18 degrees from the Sun and I have compared his image to the one he took in July at an even more impressive, and perhaps slightly risky, 10 degrees of separation. Carl is an experienced solar imager so is well aware of the dangers of using optical equipment so close to the Sun and his results show the slight change in phase and growth in size of Venus over this time very clearly. Venus will improve in visibility for the rest of the year so, hopefully, I will have more images to add showing the evolution of this fascinating planet.
On the 12th
of August Venus, Mercury and Jupiter were all spread out in a ragged line pointing eastwards, away
from the Sun. At 1818 UT, still in daylight, Simon Kidd managed to capture an image of Mercury, some 10 degrees east and at the same elevation as Venus, that shows bright albedo features correlating with known surface features. The image shown here includes a simulation made using the Winjupos software for the time of the image and which makes the correlation somewhat clearer. The low elevation and small apparent size of Mercury, especially as seen from the UK, makes this image a notable achievement, especially as Simon described the seeing conditions at that time as “precarious”.
On the 15th
of August Dave Tyler managed to capture a remarkable Saturn image. During what was, as he described it, the best evening seeing conditions that he had had in the last six weeks, he used a Celestron C14 telescope with an ASI 120M camera and an ASI Atmospheric Dispersion Corrector (ADC) to capture an image showing the full Cassini division and a hint of the Enke division in the rings as well as structure in the bright B ring, a sharp shadow of the planet falling on the ring system behind it and a pale yellow equatorial band with a soft pink temperate region and a pale green band surrounding the north pole. Please note this was an image taken with the planet at barely 17 degrees of elevation above the horizon.
What is particularly remarkable about this image is that, at around the same time, the well-known European amateur, Marc Del Croix, was also imaging Saturn from the Pic du Midi observatory; this is at over 9000 ft. of altitude in the Pyrenees Mountains of southern France; Marc used a professional 106 cm cassegrain telescope of 17.5 metre focal length. Dave, on the other hand, took his image from his back yard in England using a stock commercial amateur telescope. On this occasion there is little to mark an obvious difference between the two images. This is not to belittle the work of Marc del Croix which is often quite exceptional, rather it shows that, on the right night, really good things can be achieved from our own back gardens and that unless the seeing conditions match the resolution available for large telescopes they will not produce a significantly better image. On the 29th of August Dave produced another excellent image of Saturn again despite its low elevation as seen from the UK.
Shortly afterwards, on the 30th
of August, Martin Lewis managed to capture detail on the planet of Neptune. He
uses a Dobsonian telescope on a tilting platform that allows this equipment to follow a target as if it was equatorially mounted and, on this occasion, he used an ASI224MC colour camera fitted with a Baader 610 nm 'long-pass' filter; one that only allows deep-red and infrared light to reach the sensor. I featured his image on the SPA website as it shows a clover-leaf shaped collection of clouds in the south polar regions of Neptune that has also been tracked by a few other amateurs and professionals. Images like this add data-points for those studying the atmospheres of these frigid outer worlds and therefore add directly to our understanding of them.
I know my ten inch aperture (250mm) Newtonian telescope should be able to resolve these features and I have been trying to reproduce Martin's success but with absolutely no success, mostly as a result of poor seeing at my location. On the 15th of September I was, for once, not working late and the night was forecast to be clear with little or no wind through a great depth of the atmosphere and therefore promised excellent seeing conditions at my home. Unfortunately the full Moon sat midway between Uranus and Neptune and, combined with a thin atmospheric haze, its light caused all sorts of internal reflection and glare problems with my equipment and made it almost impossible to find tiny Neptune; when I eventually did, it was just moving behind the branches of my neighbour's tree; my wife eventually came outside to tell me to stop swearing. To add insult to injury, Martin had taken another excellent image showing the evolution of these cloud features on Neptune only the night before.
Steve Norrie had slightly better luck than me in that he has recently managed to repair the malfunctioning motors on one of his telescope mounts. He celebrated by checking out the alignment accuracy with a small 127mm Makzutov telescope and managed to 'GoTo' directly to Neptune and studied its disc. This brings me, in a roundabout way to, taking planetary images with smaller aperture telescopes. Steve Anderson emailed to ask for more details of how Robin Scagill obtained his images of Mars and Saturn using a five inch aperture (130 mm) Newtonian telescope as he thought this might inspire others with similar equipment to try out imaging. I will try to get full details from Robin but I know he used an ASI120MC one-shot-colour camera, which is one of the many readily available planetary imaging video cameras, combined with a laptop computer and free-ware image-sorting and stacking software such as Autostakert or Registax to produce his images. I covered the basic techniques of planetary imaging over the course of three articles in this magazine two years ago and I intend to get an updated version put on the SPA website within the planetary reference section before too long.
Suffice to say that the brighter and larger planetary targets are easily imaged with all apertures of telescopes and scientifically useful results can be obtained without having to own the largest 'light-bucket' available. Ultimately the highest resolution images will come from the largest apertures but only when our back-yard seeing conditions match the theoretical resolutions available; which is rarely in the UK. If you don't own a large aperture telescope, please don't be put off from attempting planetary imaging as you may be surprised by the results you can obtain.
Finally I will mention the planetary globes created by Eddie Carpenter. He sent me some images of his home-made globes that may be of interest to others. I was lucky enough to see the collection of planetary globes owned by Sir Patrick Moore and always wanted something similar. A few such globes are available for sale over the internet, particularly of Mars, but at rather high prices. Eddie decided to make a set of his own using repainted classroom style globes and he painted Mars according to his own observations. His wide collection of other globes even includes Enceladus, Titan, Pluto and Charon, taken from available images, and I was surprised to find from him that there are even accurate inflatable 'beach-ball' globes of Mars available from Japan; I can now buy one as an excuse for my grandson to play with.
As always, thank you for all your comments and observations and I hope you all have clear skies during the autumn and winter viewing season.