Orwell Astronomical Society (Ipswich)
Planetary & Lunar Groupings, 01 June 1980 - 23 February 2023
A close grouping of planets, with or without the Moon, can provide an interesting spectacle, with multiple bodies appearing in the field of view of binoculars or a low power telescope.
Observations of planetary and lunar alignments by members of OASI are presented below.
On 23 February 2023, there was a very photogenic alignment of the waxing crescent Moon, Jupiter and Venus. The following image was taken at approximately 18:45 UT in a clear sky.
In late April - early May 2022, all five naked eye planets were in an interesting configuration: in the evening sky, Mercury and the Moon passed close to the Pleiades while, in the morning sky, Venus, Mars, Jupiter and Saturn were in close proximity. The gathering in the morning sky was sufficiently noteworthy to receive a mention in the national press.
The morning gathering offered a particular highlight on 01 May, with Venus appearing very close to Jupiter but, unfortunately, visibility from the UK was poor with Venus at an altitude of only 9° at sunrise! By good fortune, I was on La Palma in the Canary Islands at the time: at latitude 29° north, it offered much improved observing prospects, with Venus at an altitude of 25° at sunrise on 01 May.
I spent my first night on the island in Santa Cruz on the east coast. The location offered an excellent horizon over the sea. But I awoke early in the morning to see nothing but cloud!
Moving on from Santa Cruz, I spent the bulk of my stay in a rural house on the west side of the island. I was uncertain whether all four planets would clear the eastern horizon before dawn. The following image, taken with a Sony A7S, shows the view eastward on the morning of 30 April: Venus and Jupiter do clear the treeline but are ascending into a rapidly brightening sky.
For the following morning's observations, I decided to ascend the mountain to my usual pitch which offers excellent views to the south. I did not anticipate how poor would be the view to the east, and I was equally unprepared for the freezing gale that was blowing. I pressed on to a location further east that provided both a fantastic view of the eastern horizon and absolutely motionless air. The following image, taken with a Sony A7S, captures the view in a dark sky, showing the four planets in proximity (Venus, Mars, Jupiter and Saturn) together with Neptune, a couple of the brighter asteroids and, faintly, the Helix Nebula.
Close proximity of Venus and Jupiter begs for a group photo, so I duly obliged! I used cotton thread across the front of the objective to create diffraction spikes around the planets. Image below, again taken with a Sony A7S.
I used a Meade ETX90 with the A7S to capture an image of the two planets at higher magnification (below). It shows them at a separation of 24 arcminutes, together with three of the Galilean satellites (Io is off the disk of Jupiter but is overwhelmed by glare from the planet).
The following morning, Venus and Jupiter were visibly further apart. The following image, taken with a Sony A7S, shows the planets at a separation of 77 arcseconds.
Meanwhile, in the evening sky, Mercury attained greatest elongation east (GEE) of 21° on 29 April. The planet was easily visible as it was nearly 20° distant from the Sun and almost vertically above it (less than 2°shift in azimuth) as the ecliptic at this time of year is almost vertical. At GEE, the planet appeared against an interesting area of the sky, close to the Pleiades. See the below image, taken with a Sony A7S camera. I used a thread across the lens to add diffraction spikes to Mercury. Unfortunately, I was only able to stack a limited number of frames to form the final image.
Three days later, the young Moon entered the field of view. See the following two images. (Framing of the upper image, with the 500 mm lens, could have been better so as to include all of the Hyades!)
The following evening, the Moon had moved, but the below image is a better-framed view of the Hyades, the Pleiades and Mercury.
Images of a very young Moon (one day old) taken during my stay on La Palma.
On 21 December 2020, the planets Jupiter and Saturn appeared at their closest together in the night sky since 1623, in an event dubbed the great conjunction. Viewed from Orwell Park Observatory, closest approach occurred at approximately 17:30 UT, just before the planets set, with a separation of just over 6 arcminutes. (Times and other circumstances differ very slightly depending on the location of the observer.)
Unfortunately, skies were largely overcast throughout 21 December, and only one observation was reported that day. However, in the days either side of the great conjunction, several members of OASI observed the planets on approach to and receding from the event.
On 06 November, Jupiter and Saturn were low on the southern horizon. Trees and the lower lip of the observatory aperture hampered observing, so I took the photo below from elsewhere in the garden.
The image shows Jupiter and Saturn and some of the main moons of each planet. The planets are at an angular separation of 4.7°.
Jupiter and Saturn continue to close towards the "Great Conjunction" on 21 December. On the evening of 19 November they were only 3.5° apart and the Moon was less than 4° distant.
The Moon, at five days old, was dazzling, even at an altitude of only 11°, so I used a Moon filter to reduce the lunar glare.
On 06 December, Jupiter and Saturn were less than 2° apart and closing.
By 15 December, Jupiter and Saturn were just over 40 arcmins apart. This is still too wide a separation for my Celestron Edge HD, so the below photograph was taken with a Sony A7S camera and 500 mm lens. The Galilean moons Io, Europa and Ganymede are visible in line with Jupiter's equator, but Callisto was in the shadow of Jupiter, thus invisible.
The great conjunction would not be visible from my garden so, for this rather special event, I decided to remove the Celestron Edge HD from the observatory and put it on a portable mount (indeed the one I used before the observatory was built) and travel to a site out of town with a good south-western horizon, near Capel St Mary.
The forecast for Thursday 17 December was not promising but I decided to proceed with the plan. As I reached the observing site, Jupiter and Saturn were visible and, with a nearby three-day old crescent Moon, there was a photo opportunity. However, I could see a difficulty about to arise: would the sky become dark enough before the cirrus clouds advancing from the south-west obscured the three bodies? I quickly assembled the mount and was forced to skip proper polar alignment, as Polaris was not visible through the clouds. I managed to focus on the Moon, then took a few photos of Jupiter and Saturn.
The clouds soon made their presence known. Both Jupiter and Saturn faded from naked-eye visibility and the Moon was largely obscured. To the naked eye, only an orange slab of cloud was visible, illuminated by the street lights of Colchester. However, in the camera viewfinder I could still see two bright spots: Jupiter and Saturn had not been completely obscured.
Over the next half hour or so I patiently waited for the clouds to move on, or for Jupiter and Saturn to re-emerge from the lower side of the cloud bank into a clear patch of sky. I took photos, more in hope than anything else. Eventually Jupiter and Saturn emerged from under the clouds which had steadfastly stayed still. While the view was now clearer and satellites of Jupiter could be seen, additional problems emerged, including atmospheric extinction caused by the altitude of the bodies, chromatic dispersion starting to stretch the images, and an increase in the wind. There was no avoiding the latter as it blew in from the south-west, making the images dance about. Eventually I called it a day.
The following image shows the grim view towards Colchester. Jupiter and Saturn were invisible to the naked eye, even though they are captured on camera.
The following image, taken just over half-an-hour later, shows Jupiter, Saturn and the Moon through a clearer area of sky, closer to the horizon. I am not convinced that the nearby sky was free of cloud or haze, it was just less well illuminated.
The next five images were taken through the telescope.
The following image captures just the planets. Both appear rather featureless, but at least Saturn is the correct shape! The planetary disks lack the detail that can be revealed by a planetary webcam. Exposure time three seconds.
The following image shows Jupiter’s Galilean satellites, an overexposed image of the planetary disk and a better image of Saturn. Europa had passed only 3 arcseconds north of Ganymede some 20 minutes earlier, so the two bodies appear as one. Exposure time 15 seconds.
An exposure of 58 seconds through the most dense cloud shows no stars. (Had it not been such a rare event, I would not have taken pictures through cloud!)
A 39 second exposure in a clearer sky shows the Galilean moons of Jupiter, as well as Titan and some field stars (with their magnitudes expressed without decimal points).
With Saturn less than 4° above the horizon, chromatic dispersion is evident in a 1.5 second exposure.
On 19 December, conditions looked much more promising than they were on 17 December. When I arrived at my site outside Capel St Mary, I found another observer from Ipswich already there with his telescope. Fortunately there was room for both of us!
Although the sky was much clearer than two days previously, there was now a different problem - a cold wind blowing from the south-west, not particularly strong, but ever-present. As it blew from approximately the same direction in which the planets were located, it was impossible to shield from it. I persevered, hoping that by taking lots of photos, some would come out OK.
The following brief video illustrates the problems caused by the wind.
Many still exposures were so badly blurred that I had to discard them before stacking the remainder. The following image is a stack of 1/90 s exposures where Saturn is not overexposed.
The following image is a stack of 0.1 s exposures, but does not show much more detail.
On 20 December, the day before minimum separation, a clear south-western horizon was visible just after sunset at my out-of-town location outside Capel St Mary. There was a touch of wind at first but this died away. There was ample opportunity to record Jupiter and Saturn under a variety of exposures through the Celestron 8 Edge HD with a Sony A7S camera.
The following short video shows the improvement in conditions compared with the video for the previous day (above).
The following image is a (nearly) full frame view, showing Jupiter and Saturn (both overexposed) just over 9 arcminutes apart, at an altitude of just under 8°. Closer inspection of the planetary disks reveals colour fringing - this is atmospheric chromatic dispersion that becomes more pronounced closer to the horizon.
I do not possess an atmospheric dispersion corrector so, to remove the unsightly dispersion, I adopted a zero-cost approach:
Note that the above approach cannot make the stars appear round because, within each monochrome layer, there is a range of wavelengths that are dispersed, creating an elliptical profile. Nevertheless the approach has been applied to all subsequent images.
Below, an exposure of 1/30 second shows the four Galilean satellites of Jupiter. The planet itself appears saturated, but Saturn is OK.
A lower ISO is needed to record detail on Jupiter, e.g. the below stack of 1/125 s frames. But please note that the A7S is not a planetary camera, so the image does not show the Cassini Division or Great Red Spot!
The following image corresponds to the first presented above for the day, with the emphasis now on the satellites of Saturn: Titan, Rhea and Tethys are clear, but Dione has marginal visibility due to glare from the rings.
As can be seen below, increasing the cumulative exposure time to 61 seconds brings out another of Saturn’s moons, Iapetus. Io is now lost in the glare of Jupiter. It is not often that one can capture seven planetary satellites in one picture!
Clouds arrived, forcing a termination of photography. By this time, there was condensation on the corrector plate of the telescope.
The weather was predictably awful on the day of closest approach, 21 December, and on the next two days. Around sunset on 24 December, it was clear for a while and I could see Jupiter and Saturn from outside my house. There was no time to set up the Celestron Edge HD, so instead I used the Sony A7S with a 500 mm lens. I captured the following image, showing Jupiter and Saturn a mere 21 arcminutes apart. The dark area at bottom right is a long finger of cloud passing eastwards below Jupiter.
The following day, Christmas Day, was also clear around sunset. With the Celestron Edge HD relocated directly below an illuminated street lamp in the freezing cold, there was insufficient time for an accurate polar alignment. Jupiter and Saturn, now some 27 arcminutes apart, still fitted into the field-of-view. Ganymede was occulted by Jupiter and hence invisible.
Below, a deeper exposure brings out three the satellites of Saturn, Titan, Rhea and Dione, with another two, Iapetus and Tethys, at the limit of detection.
Arriving home from work on 17 December, the crescent Moon was visible but Jupiter and Saturn were low down in the south-west, occasionally hidden by high cloud and moving ever closer to being obscured by a neighbour's house. I quickly opened up my observatory, powered up the Skywatcher 200p, inserted a 25 mm eyepiece, plugged in the handset (software always takes longer to load when I'm in a hurry!) and lined up on the two planets.
The planets appeared together in the field of view, but would I have time to photograph them before they were obscured? Running indoors, I grabbed my camera (Canon 1100d), telescope adapter and an Android tablet and, to save time, switched on the tablet as I walked back to the observatory. I attached the camera to the telescope and connected the tablet to the camera via a USB lead. Turning on the camera caused the DSLR controller app to activate. The app enables control of a Canon camera, providing a much better image than the viewfinder screen on the latter, and facilitates quickly changing parameters (exposure, aperture, ISO, etc.) without requiring contortions to reach the camera controls at the end of the telescope.
Jupiter and Saturn easily fitted into the field of view of the camera and, by 16:55 UT, I was taking photographs with different exposure settings of this rare spectacle. The planets soon were obscured by the neighbour's house, terminating further observations. (Indeed, had the conjunction occurred one week later, thanks to said house, I would not have been able to observe it from my back garden!)
I also took photos on 19, 20 and 24 December. Below, the photos are cropped to the same area of the sky to show the movement of the bodies. The times of the photos are as follows:
The forecast for 21 December was for unremitting cloud and rain. However, at around 18:00 on the day, a few limited breaks in the cloud cover appeared and I ventured into the back garden. I looked SW and saw nothing. Moving to the far back of the garden I could see, just clearing the neighbouring roof tops, a bright disc that I knew to be Jupiter. I could also, with an eye of faith, see a faint darker brown spot just above Jupiter which, after a quick check via Google, was the right distance and position for Saturn.
Time was short and the task now was to capture an image! I grabbed the nearest camera and a light-weight tripod and returned to the garden. My view of the planets was across the sky above central Chelmsford: not a good start. However the biggest problem was that the low altitude of the bodies meant that I was viewing them through branches of trees on the border of the garden. Not only did this offer a changing obstacle to their visibility, it also made focussing somewhat fraught. Finally, I managed to capture the below image, which has the best focus of those that I took. (Camera settings: manual, 15 second exposure.)
The image has been subject to an extreme contrast boost to reveal the branches of trees which so nearly prevented the photo from being taken, and show how lucky Neil was!
We saw the conjunction on 20 December but, on 21 December, the day of closest approach, it was cloudy. We looked out every 10 minutes or so between 16:00 and 18:00 UT and didn't find a clear sky.
I began my observations of the conjunction on Wednesday 16 December. From an upstairs room in my house, Jupiter and Saturn were both visible in the same field of view of my 10x42 binoculars. The following day was also clear, so I attempted to observe with my telescope in my back garden, hoping to start observations before sunset, while the planets were relatively high in the sky. Unfortunately, my view was obscured by houses and trees.
The next clear evening was Saturday 19 December. I decided to walk 50 metres from my house and set up my camera and tripod in Bourne Park, as this offered a much better view of the south/south-west horizon.
It was clear again on Sunday 20 December. I again set up my camera and tripod in Bourne Park and took the below image at 16.45 UT. It shows Jupiter and two of the Galilean moons, Ganymede and Callisto, the other faint point of light above and left of Callisto is the star HIP99314. I used a Canon 1200D and a Sigma 70-300 lens at 300 mm with a 2 second exposure at ISO 200.
I took the below image on 20 December from Foxhall Heath. It shows two of Jupiter's moons. I put in some foreground to give the picture some scale but the whole thing is a little over exposed.
I took advantage of the clear sky on 20 December. The below image was taken with a 300 mm lens on a Nikon D3200 camera at f/5.6, 1/3 s exposure at ISO 3200.
I took the below images on 19 and 20 December using a fixed Canon 6D Mk II with Canon 300 mm lens at f/5.6. (LH: ISO 1000, 0.8 s exposure; RH: ISO 10,000, 1.0 s exposure.) The field star H99314 is visible (only just visible in the LH pane!) and provides a fixed point against which to judge the motion of the planets.
The morning of 14 September 2020 presented an opportunity to observe the Moon and Venus in close proximity to M44 (the Beehive Cluster, Praesepe). From the front garden I could see all three, low in the northwest, from just past 02:30 UT, having cleared a neighbour's roof.
The still is a composite of two frames taken 90 minutes apart. It shows the motion of the Moon and that of Venus. I used two cotton threads across the front of the telephoto lens to produce the diffraction spikes.
The first part of the video shows the motion of the Moon past M44 and Venus. The second half is a 1620x1080 px crop from the first, at the original resolution, showing the Moon passing under the star Asellus Borealis.
It was humid and longer exposures longer than a few seconds produced a halo around the Moon. I let the camera run until morning twilight, by which time the legs of the tripod were dripping with condensation. Fortunately, the telephoto lens had its hood on, so remained dry.
The image below, taken on the morning of 06 September 2020, shows Mars only 51 arcminutes distant from the Moon: the two bodies were still closing, but closest approach would be in daylight. Mars had an apparent diameter of 20 arcseconds. The image was captures through cirrus clouds.
I missed out on the recent Mercury-Venus conjunction due to the weather, but on 24 May 2020 the sky cleared and another photo opportunity beckoned: Venus, Mercury and a young crescent Moon. The bodies were too low to see from the garden or the street, so I had to take to an upstairs window. Mercury was some 20° from the Sun and Venus only 15°. It is on occasions like this, where there is another bright "marker" object nearby, that it is possible to find and Mercury easily with the naked eye. I have only seen the planet with the naked eye on a handful of occasions previously.
It's not often that three planets are visible close together in the sky, but on the morning of 07 April 2020, Mars, Jupiter and Saturn came within a 10° field of view. They were poorly placed for observers in northern latitudes, all at low altitude close to the SE horizon which meant that, unfortunately, due to various obstructions, they were not visible from my house or garden. The ban due to COVID-19 on non-essential travel meant that I could not drive to find a clear horizon, so I crept under cover of darkness into the middle of the cul-de-sac where I live to find a suitable vantage point from which to observe.
Mars, Jupiter and Saturn were at altitudes respectively 7°, 10° and 9°, with the Sun at -10°. My photograph of the planets is below. To my amazement, the photograph also shows two Galilean satellites of Jupiter and Saturn's largest satellite, Titan, at the limit of detection. Fainter objects could be found in the darker sky at higher altitude. Dwarf planet Pluto was also in the frame, some 46 arc-minutes south of Jupiter but, at magnitude 14, was well out of range!
In 2020, Venus passed through the Pleiades. In fact, this happens every eight years - it is a product of the eight-year periodicity between the motions of the Earth and Venus that also produced the pair of transits in 2004 and 2012.
The closest approach of Venus to the Pleiades was on 03 April 2020. The weather was overcast in the days before the event but there were some breaks in the clouds, enabling images to be captured. OASI members Martin Cook, Nigel Evans and Mike Harlow captured images; their best shots are below.
During October 2015, the planets Venus, Mars and Jupiter performed a merry dance in the morning skies! Mars and Jupiter made their closest approach on Saturday 17 October, coming within 0.22° of one another. Just over a week, later, on Sunday 25 October, Venus and Jupiter came within just over 1° of one another. On 26 October, Venus attained Greatest Elongation West (GEW), shining at a spectacular magnitude -5.1. On 28 October, the three planets lay within 1° of one another.
David Murton captured images 1-3 below from his home observatory at Bucklesham, south-east of Ipswich, in the early morning of 29 October 2015, shortly after the planets were at their closest. All photos were taken with a Canon 60da camera body and Canon lenses as follows:
Neil Short captured figure 4 from his home in Chelmsford. His report of the observation is as follows:
At 04:15 on the morning of 29 October, looking due east out of the window I made out two bright "stars" shining through the trees and bushes in our garden in central Chelmsford. I was instantly reminded of the coverage on the BBC that a three-planet alignment was due so went into the garden to determine if the two bright objects were indeed Venus and Jupiter, and whether Mars was also visible. Fortunately a gap in the trees allowed a clear view of the three planets. Back inside for my camera and the results are below, taken with a Canon 50HS (hand-held) set on auto. The inset was taken at higher zoom to confirm the unmistakable red colour of Mars.
On 30 June 2015, an appulse of Venus and Jupiter occurred in the evening twilight sky. At their closest, the planets came within 20 arc-minutes of one another. Images of the appulse, taken from a balcony at Orwell Park Observatory, are below as follows.
Prior to the appulse, in late May - early June, James had tracked the motion of the planets. Throughout the period, they were in the neighbourhood of Castor and Pollux, which provided convenient reference points against which to judge motion. During the three days 21 – 24 May, the crescent Moon passed the pair, the conjunction forming a very photogenic grouping.
On each clear evening during 21 May – 10 June, James photographed the western sky after sunset. (The project was terminated when the planets disappeared in the evening twilight behind a neighbour's house.) He adjusted the images to a common scale and alignment (using the fixed stars Castor and Pollux as markers), highlighted Castor, Pollux, the Moon, Venus and Jupiter as foreground objects and set everything else as transparent background and overlaid the images. Adding as background the terrestrial landscape looking west produced the composite figure 4, below. In the figure, the numbers below the Moon and planets represent dates in May and June. The position of Jupiter is shown for the same dates as Venus, and in the same sequence (numbers are not given for Jupiter as they would be too squashed together). Castor and Pollux are marked. Note that the images of the stars and planets have been slightly retouched to enhance visibility: the image covers an area of approximately 600 square degrees and the objects un-retouched would appear as tiny dots.
The Moon clearly shows the largest apparent daily movement, followed by Venus, then Jupiter. The motion of Venus appears approximately linear and prograde over the period shown, with daily increments in RA slightly reducing over time; this is in line with theory. The path of Jupiter also appears prograde, but notably less regular; this is due to its increased apparent distance from Castor and Pollux, magnifying the effect of alignment errors in composing the image.
Table 1 lists the apparent daily motions of the planets over the period in question, calculated using the NASA ephemeris DE-430. As expected, the dominant motion of the bodies is in RA.
|Body||RA (°)||Dec (°)|
Table 1. Average daily planetary motions, 21 May - 10 June 2015.
To the naked eye, the motion of Venus was apparent each night as it sped towards and then away from Pollux. Greatest eastern elongation occurred on 06 June. The daily motion of Jupiter, however, was not obvious.
Fig. 4. Motion of the Moon, Venus and Jupiter.
Mercury is a relatively small planet, only about the size of Earth's Moon and, because it orbits close to the Sun, is always difficult to observe. However, in summer 2005, the planet Venus, much easier to find because it is physically larger, can be nearer to Earth and is intrinsically brighter, came within 0.07° of Mercury. To put this figure in perspective, consider that the Moon has an apparent diameter of approximately 0.5°; so, Mercury and Venus were apart in the sky approximately 14% of the diameter of the Moon. Of course, this was just an effect of perspective: although the planets appeared close together, it was a line-of-sight-alignment and they in fact were situated at vastly different distances from Earth.
The epoch of appulse was 19:00 UT on 27 June 2005. Mercury was emerging from superior conjunction on 03 June and approaching greatest elongation east (26°) on 09 July; Venus had emerged from superior conjunction on 31 March and also was heading towards greatest elongation east. Within a few days of closest approach, the planets did not appear to move so very far, so I hatched a plan to attempt to observe them each evening from 22 June to 29 June inclusive, in the hope of seeing them at least once.
An effective method for finding an object in the sky that is invisible to the naked eye is to point the telescope first at something that is visible and then move it by the appropriate offsets in right ascension (RA) and declination (dec) to find the object of interest. In the case of Mercury, I was able to download from the Internet a table published by Jonathan Shanklin (Director of the BAA Comet Section), listing offsets in RA and dec between the Sun, Mercury and Venus. My plan therefore was to open the Observatory at 18:00 UT each evening, point the Tomline Refractor at the Sun, then swing it round by the tabulated offset in RA, search in dec for Venus and, once located, search for Mercury in close proximity.
Below is a summary of each evening's observations:
So, in summary: I planned eight nights of observing, made five trips to Orwell Park, and recorded two successful observations. Not a bad score! I would like to thank Jonathan Shanklin for making his positional figures available. The observers were (in alphabetic order): James Appleton, Garry Coleman, Nicky Gillard, Ken Goward, Mike Harlow, Gerry Pilling, Pete Richards, Ted Sampson, Mike Whybray.
From late April until mid-May 2002, all five of the classical planets (Mercury, Venus, Mars, Jupiter and Saturn) appeared together in the western sky after sunset. The minimum separation was 33° on 13 May. Several members of OASI photographed the spectacle, among them Nigel Evans and Roy Gooding. On every clear evening in late April and early May, Nigel attempted to photograph the five planets together. Generally, he limited the exposure to that given by the 500 / focal length (mm) rule. Only when the Moon was present did he use a driven mount. Roy captured three of the planets in a photograph taken at Orwell Park Observatory on 01 May. A selection of the images is below.
A close conjunction of the two day old crescent Moon, Saturn, Mars and Jupiter occurred on 06 April 2000, low in the western horizon, shortly after sunset. I took the following photograph from East Ipswich at 20:00 UT on 06 April 2000 using a 80 mm zoom lens with 1000 ASA print film. The conjunction preceded a spectacular auroral display later in the evening.
Tuesday 23 February 1999 saw the closest apparent approach of Venus and Jupiter for many years. The weather was reasonably favourable in the few days beforehand, offering naked eye observers the opportunity to view the spectacle evolve over successive evenings in the western sky shortly after sunset.
Monday 22 February. The weather was cold and clear. I observed Venus and Jupiter between 18:30 and 19:00 UT. At this time, the Sun had set and the planets shone brightly against a darkening western sky, approximately 1° apart, at an altitude of about 10°. Venus was at a slightly lower altitude and noticeably brighter than Jupiter (magnitudes were respectively -4.0 and -2.1). The planets also exhibited a marked colour contrast: Venus appeared pure white, whereas Jupiter appeared yellow-white. 10x50 binoculars showed the two planets in the same field of view, and also revealed Jupiter's Galilean satellites. Io and Callisto appeared as a single point of light to the east of Jupiter (the binoculars could not separate them) and Ganymede appeared to the west while the planetary disc occulted Europa.
Tuesday 23 February. The evening of apparent closest approach suffered from very hazy conditions affecting the whole sky. Only the Moon, planets and the brighter stars were visible. The haze created a very prominent halo surrounding the Moon at a distance of some 10 lunar diameters. The following diagram shows the general orientation of the sky at 18:30 UT. Despite the poor observing conditions, Jupiter and Venus were visibly very close together, presenting an unusual spectacle as they sank towards the western horizon. At 18:30 UT, the planets were at a separation of 514 arc-seconds (approximately one quarter of a lunar diameter) decreasing to only 481 arc-seconds as they set on the western horizon.
Sky on 23 February 1999.
Martin Cook, Garry Coleman and Mike Harlow observed the apparent close approach from Orwell Park Observatory using the 26 cm refractor with a wide-field eyepiece giving a magnification of approximately 50x. Both planets were visible in the field of view. Venus exhibited a slight phase, while the belts of Jupiter were very prominent. An image taken with an SLR camera body at the prime focus of the refractor is below. It shows Jupiter's flattened, brownish globe contrasting strongly with the brilliant white, gibbous Venus.
Venus and Jupiter through the Orwell Park refractor, 18.20 UT on 23 February 1999, ½ s exposure on 400 ASA slide film. (North up.)
Wednesday 24 February. The evening after closest apparent approach offered the best viewing conditions, with a very transparent sky. Around 18:30 UT, Jupiter and Venus shone against a dark blue background, this time with Venus at the higher altitude. Mercury was visible, just above the rooftops, and, further east along the ecliptic were Saturn and the Moon. The first magnitude star Aldebaran was close to the Moon (in fact, parts of China had witnessed a lunar occultation of Aldebaran a few hours earlier).
An appulse of Mercury and Venus was predicted to occur at 18:88 UT on 01 June 1980, the two planets coming within ⅓° of one another, Mercury at magnitude -0.5 and Venus at magnitude -4.4.
Alerted to the appulse by the OASI Newsletter, we aimed to observe the event. Cloud persisted early in the evening and it did not, initially, look as if we had much chance. Then, just before 21:00 UT, while watering the garden, we suddenly realised that the sky was clear and rushed to the front of the house to see if the area of the sky around the setting Sun was clear.
It did not take us long to find Venus and then, after a little while, Catherine thought that she spotted Mercury with the naked eye. Quite a feat to be sure, but yes, on looking through a 5.6 cm handheld refractor at 40x magnification, there it was. We took it in turns to watch for over a quarter of an hour and made the following drawing of the position of the planets.
Venus was at low altitude and its disk therefore appeared distinctly reddish and devoid of its excessive glare! Indeed, at the end of our observation, the planet was only a couple of degrees above the horizon.