The New Full Moon Illusion?

The full Moon on 14 November 2016 is the perigee-syzygy full Moon for 2016. This is a term used to describe the full Moon which occurs nearest to when the Moon is at the closest point in its orbit to the Earth. Perigee is achieved on average once every 27.55455 days (an anomalistic month) but this doesn’t always coincide with when the Moon appears full in the sky. The period between the same phase of the Moon occurring – e.g. full Moon to full Moon – is known as a synodic month and is equal to 29.53059 days.

Syzygy is a term describing a situation when three bodies in a gravitational system appear in a line. This is the case when the Moon is full; the Moon, Sun and Earth being the bodies in alignment. Most of the time the alignment isn’t precisely perfect – if it were, we’d get a lunar eclipse during every full Moon, but it’s close enough.

A perigee full Moon will, in theory, appear at its largest and brightest in the sky, something the popular press and websites exploit for attention and a few extra clicks. Indeed, in the run up to November 14, there are many articles appearing which describe the upcoming perigee-syzygy full Moon. Many of these articles use the term ‘Supermoon’ to describe this event, a misleading and unnecessary term which fails to tell you very much about what it happening.

The 14 November perigee-syzygy Moon will be the largest to appear in our sky since 1948 and you’ll need to make sure you catch sight of it because you won’t see another full Moon this large until November 25th, 2034. Exciting stuff, except that it isn’t true.

The apparent size of the Moon depends on how far away it is from you. Different location on Earth experience different apparent diameters. Imagine a full Moon directly above your head. A line from the centre of the Earth to the centre of the Moon would pass through you and, consequently, the distance between your location on the surface of our planet and the centre of the Moon would be at a minimum. Now consider a superhero, say SuperMan (…sigh…) standing on precisely the other side of the Earth to you, so a line from him to the centre of the Moon would also pass through the centre of the Earth and you. He’s got super-vision (make it stop!) which can see the Moon through the body of the Earth. So how big does the Moon look to him? Well it looks smaller than if does to you because it’s further away, an Earth diameter further away to be precise.

Your average non-super being wouldn’t be able to see the Moon because the Earth’s bulk would block the view, but as the Earth rotated on its axis, it would eventually bring it into view. Ignoring the natural variation in distance caused by the Moon’s non-circular orbit, etc., as the Moon rises it will be getting closer to you until, when it’s on the meridian line (the imaginary line passing from north to south on the horizon which also passes though your zenith or overhead point) it will appear closest to you.

When you do factor in the variability caused by the Moon’s orbital shape, and the fact that the Moon doesn’t orbit the centre of the Earth – but rather the barycentre of the Earth-Moon system – things get a bit more complex.

Let me give you an example using my own location in the UK. Full Moon in November 2016 occurs on the 14^th at 13:53 UT, 3 hours after perigee. From where I live, the Moon will be below the horizon at this time. If I had super-powers allowing me to see through  the Earth, I would see the Moon with an apparent diameter of 1997.2 arcseconds and its centre would be 358,869.9 km from my location.

As the Earth turns on its axis the distance between my location on the Earth’s surface and the centre of the Moon changes. The Moon is moving away from perigee as it rises so it’s becoming more distant but the rotation compensates for this as it brings the Moon closer to me personally. So much so, that the Moon will appear to have an apparent diamter of 2038.2 arcseconds at 23:45 UT on 14 November. At this time the distance between me and the Moon’s centre will have reduced to 351,652.8 km. In other words, the rotation of the Earth has moved my location on the Earth’s surface so that I’m now 7,217.1 km closer to the Moon’s centre than when the Moon was full at 13:52 UT. My closest approach is around 00:15 on November 15, 2016 when the distance between me and the Moon’s centre will have shrink to just 351,633.6 km.

Okay, this is just pedantry, lighten up – it’ll still be huge and the largest full Moon until 25 November 2034! Well, not exactly.

The full Moon which occurs on 2 January 2018 will be the perigee-syzygy Moon for 2018. However, the timing is much better for my location.  Full Moon occurs at 02:25 on 2 January, and the Moon will appear 2036.9 arcseconds across and be 351,873.2 km away – wow, that’s just 239.6 km further than when it was closest to my location at 00:15 UT on November 15th, 2016!

But it gets better. At 23:45 UT on 1 January 2018 the Moon’s disc will appear 2041.3 arcseconds across and lie 351,113.9 km away from my location. And at 00:00 UT on 2 January 2018 it will appear 2041.4 arcseconds across and be 351,108.3 km away. All of these figures beat those for the November 14th, 2016 perigee-syzygy Moon that many articles said would be the record holder until 25 November 2034. Awkward!

Of course this is all rather nonsensical because the size difference between the perigee-syzygy full Moons and others which occur slightly further away from perigee (e.g. the October and December 2016 full Moons) will be so tiny that you’d wouldn’t notice it.

During the late autumn and early winter, full Moons for northern hemisphere observers, arc high across the sky. Contrast this with the full Moons of summer which appear low down. This situation, combined with the hype which will accompany the November 14th perigee-syzygy, will lead people to perceive the Moon to be much larger than it actually is normally. Perhaps this should be called the New Full Moon Illusion?

First NLC display of 2015 – for me anyway!

The night sky in June and July is a somewhat troublesome affair because there’s not much of it. For an astronomer in the UK, it’s a difficult time of the year because the background sky never gets truly dark. The standard used to indicate when things have got dark enough to do proper night time astronomy is astronomical twilight. The period between astronomical twilight ending and beginning is that time when the sky is truly dark because the Sun’s altitude below the horizon is equal to or greater than 18 degrees. During the UK’s summer, this never happens, so the sky never gets properly dark.

All is not lost though because there are still lots of interesting things to look out for. One of these is a phenomenon that bridges the gap between astronomy and meteorology – Noctilucent Clouds.

Noctilucent Clouds, or NLC’s, are formed in a thin layer at an altitude of 76-85km altitude. This is located within the atmospheric layer known as the mesosphere. Getting particles up into this layer around which water ice crystals can form was always something of a mystery. However, recent research has shown that the tiny specks left behind after a sand grain sized particle vapourises in the atmosphere to create a meteor,  are a prime source for NLC seeding.

Getting water vapour up that high is also a problem and the complex chemistry involved has potential uses as an indicator for climate change. The beautiful NLC displays which result may turn out to be a double-edged sword!

NLC displays used to be considered quite a rare phenomenon, typically occurring in the period between late May and early August. This is when the temperature of the mesosphere in the Northern Hemisphere drops low enough for NLC’s to form. It’s also when the altitude of the Sun can drop to within 6-16 degrees below the horizon. This allows the sky to get reasonably dark but also is able to illuminate the high altitude NLC cloud layer. So although we are in darkness, the NLC’s shine with reflected light from the below the horizon Sun.

Consequently, NLC’s appear to hug the twilight arc, and shine against the darker sky of night; hence the name – noctilucent which roughly means ‘night shining’.

A display, if present, will typically be visible 90-120 minutes after sunset low in the northwest or a similar time before sunrise low in the northeastern part of the sky. A bright display may be seen starting in low in the northwest but appearing to move through north and into the northeastern position as the reflected light follows the position of the Sun below the horizon.

From my location in Selsey, NLC’s can be tricky things to see. During the Northern Hemisphere’s summer months, they are typically seen from latitudes between 50° and 70° north. My latitude is 50.75° north, which puts me close to the edge of visibility.

A clear(ish) night on 16/17 June 2015 meant I was still up at the appropriate time to spot NLC’s low in the northeast before the dawn kicked in. Actually, I had seen that there was a display happening that night from the excellent IAP camera network. Unfortunately, a thin band of cloud had passed through in the early part of the night and this rendered the northern part of the sky out of action, so I concentrated on some other projects I’ve got going.

I headed down to Selsey Beach at around 03:00 BST (02:00 UT) and immediately spied a small, faint (type 1) patch of NLC under the bright star Capella in Auriga.

There were some other bright clouds passing through the region too, but these were most probably high altitude aircraft vapour trails, posing as fake NLC’s! As the twilight arc grew, so did the brightness of the patch (type 2).

A magnified image of the patch showed the characteristic network structure of NLC’s, giving me my first display of the 2015 season.

The patch had faded to nothing by 02:15 UT. Hints of a lower and brighter display were seen, but from my latitude these were lost to the horizon and low cloud that persisted there.

Fingers crossed that the 2015 display begins to build.

I mentioned NLC’s, as well as two comets which may be visible in the coming weeks, in my Star Guide in the June 2015, BBC Sky at Night broadcast. Click here watch this clip.

Europa transits Jupiter and Callisto…

Jupiter has recently undergone an equinox which means that it’s equatorial plane appears pretty much edge on to us here on Earth at the moment. The four big moons of Jupiter, the so called Galilean moons, all orbit more-or-less in Jupiter’s equatorial plane, so around the time of a Jovian equinox, they can appear to interact with one another.

They’re not physically interacting of course but they can appear to pass in front of one another, partially hide bits of each other and even cast shadows on one another. Collectively, these line of sight interactions are known as “mutual events”.

On the night of April 8th 2015, I sat outside watching Jupiter under reasonable seeing conditions. The sky was actually a bit wobbly but after a recent run of jelly seeing what was delivered on the 8th  was very welcome. The Great Red Spot was on disc as was the second Galilean moon, Europa. You can see Europa in this red-filtered image I took; it’s the dark dot in the centre of the planet.

As the minutes clicked by, Europa headed towards the edge of Jupiter’s disc. As the disc naturally darkens close to the limb, the more constant brightness of Europa switches it’s appearance from a dark dot to a bright one. The black dot you can see coming in from the left is Europa’s shadow.

The video has been constructed from 90 separate movie files (approximately 70Gb of component files were captured for this sequence) each distilled into a still frame. The frames have then been individually processed and the whole lot compiled into a single AVI movie file.

It’s still a work in progress and there are bits about it that need to be addressed. The ‘disturbance’ off Jupiter’s limb close to Europa, isn’t real – it’s an imaging artifact (seriously conspiracy theorists, it’s not of alien origin nor it is a sign that Jupiter’s about to explode!). Also, there is some noise from the individual frame edges which I’ll clean up at a later date.

The frames have had an artificial gamma boost which renders the planet looking a bit washed out. This was necessary to brighten the rather dark disc of Callisto which can be seen off to the right of Jupiter.

As Europa heads off disc, it heads over towards Callisto before passing right in front of it in a moon-moon transit, mutual event.

>>> Click here to watch the movie sequence <<<

Eclipse Day, March 20th, 2015

This is an account of my personal experience on the day of the March 20th 2015 total eclipse of the Sun…

Decisions, decisions

The best place to start is really on the evening of March 19th, when myself and my travelling companions were sitting down to dinner aboard the Fred. Olsen cruise ship MS Boudicca. The WiFi reception on board had been a little temperamental but during a pre-dinner drink in the aptly named Observatory Lounge, I had managed to get connected and downloaded the latest weather data for region we were headed. You can take weather models with a pinch of salt when they’re predicting relatively fine detail many days ahead but now it was possible to see what was being predicted for just  a few hours ahead. I was a little concerned at what I saw.

For a number of days, the model had been predicting a broken cloud area with its southern edge just south of the point of greatest eclipse – our intended location. A thin precipitation band was also forecast running east west, through the Faroe Islands to the south of us. The new model forecast showed that the broken cloud area had become smaller and that the precipitation band had widened in latitude. The northern edge of the band was full of snow and now covered our location.

This is one of those tricky situations where you need to take a calm, rational decision. It might seem obvious what to do given the model forecast, but what if this was wrong? What would happen if I gave advice which took us out of a good position and into cloud? I’d been referring to the model during the previous days of the cruise and had been making predictions as to what would happen based on it. The predictions had been pretty accurate (to the hour!) giving me enough confidence to bother the bridge with the new information.

We’d had a meeting with Captain Lars Kjeldsen a few days earlier and had discovered that he was extremely open to discussion about our final viewing position. So I sent an email from reception to the bridge explaining what I’d seen and suggesting it would be prudent to head further north.

An early start

At 03:25 UT I woke up – a full 95 minutes before my alarm was set to go off, due to pitching action of the ship. To be honest, it felt like someone had put their foot on the accelerator and we were cutting through the waves at a fair pace. At 05:00 my alarm did its thing and I got up. I decided to take a tripod bag out on deck and grab my observing spot. As it happened my eagerness was unnecessary because it was snowing heavily and the deck was deserted.

I’d worked out a good location with plenty of visibility earlier in the trip. There are lots of factors to take on board including vibration from the engines which affected the upper decks. I dropped my tripod bag in my chosen location and for some reason which escapes me now, stood there getting wetter and wetter. My colleague, Dr Paul Abel, joined me soon after and had the good sense to stand under a cover rather than out on deck! I think at this point we were both a little numb.

The run up to the eclipse had us all imagining what eclipse day would actually be like. For me, I’d been working on this one for over 2 years. The reality of the day really hit home – I don’t think any of my imaginings had heavy snow falling! I hoped that the positional adjustment request I’d sent up to the bridge was being enacted as Bouddica continued to slice through the waves.

Misery

A few others joined us looking as miserable as we felt. One chap touched me on my shoulder and said not to worry, as it wasn’t really my fault. Having been an observational astronomer for more years than I care to remember, I knew that it was imperative to get a handle on what the conditions were actually like. Sunrise occurred behind a thick wall of cloud and the sky simply got an overcast shade of grey brighter.

As my wife joined us around 06:30, the snow had stopped. This was a good sign. I’d figured that if we were trying to punch through the precipitation band, this would be the first sign we’d succeeded. We looked hard for evidence of structure in the overcast blanket. Both Paul and I could see it faintly speeding across the sky.  It was at this point I knew we had a good chance of seeing something.

Things started looking brighter

Others joined us as the minutes passed and at 08:00 I got a call to head up to the bridge. Captain was there (of course!) and showed me the charts and location Boudicca was heading for. The weather wasn’t great but he’d seen some thinning cloud ahead and was now heading for that. During our previous meetings I’d requested that, weather permitting, the ship be orientated to point northeast so the starboard (right) side of the ship and the aft decks had the best view. This also gave the largest deck area for the 800+ passengers on board. Captain was aware of this request but pointed out that the weather might mean the ship may have to change heading. In the event, he skillfully managed to maintain the same course throughout the eclipse.

I gave a surprisingly chirpy commentary to the ship – or so I was told afterwards. This coincided with fleeting bright patches in the cloud where the approximate position of the Sun could be seen. While giving my commentary, I remember seeing the bridge crew all excitedly looking out the starboard window. Captain took a look too and signalled back with a thumbs up. Things were improving and spirits were cautiously lifting.

A busy first contact

I returned to the deck with a radio handset. I’d agreed I would do a number of further bridge announcements. In the lead up stages to the cruise, the question had been raised as to whether I’d give a running commentary of the event. I’d declined to do this on the grounds that an eclipse is a very emotional and personal event to witness. The last thing you need under such circumstances is someone jabbering away and ruining the mood. I would guess that all Boudicca’s passengers would now understand why I made that decision now.

The clouds were noticeably thinning and the crowds were starting to grow, both in number and in excitement. After the wet start and with decreasing deck space, I decided to reduce my original rather ambitious equipment set up and simply go for a DSLR with a 500mm lens.

I just had enough time to set this up before I got another call to the bridge at 08:30. First contact was due around 08:42 and the variable cloud cover didn’t give me any time to focus or correctly adjust my camera. Rather cruelly, I passed this task over to my wife Tessa who, at the time, wasn’t that familiar with DSLR cameras!

I headed up to the bridge and gave another even more excited commentary. First contact started while I was up there waiting to assist Captain who was giving a radio interview. In the end, they kept the interview short and I wasn’t needed. However, the bridge crew confirmed that the first dent could be seen out of the right side of the Sun’s disc.

It’s perhaps not that much of a surprise that this piece of celestial clockwork could be seen just as anticipated. Modern predictions are very accurate and we were inside the path of totality, actually very close to the centreline.

Despite this, for this guide astronomer at least, there’s always a great sense of relief knowing that the thing which you’ve been promoting and presenting is actually happening exactly as predicted!

Blue sky appears

After the 08:30 commentary, I made it back to my camera kit in time to take some pictures. Tessa had done well getting the camera set up. The partial phase was now well under way and could be seen through thick cloud without glasses (naughty but inevitable!) and with glasses when the cloud thinned sufficiently.

   

Blue sky started to appear ahead and Captain kept our heading northeast. It was great having some of our immediate party of friends – Kevin McNulty and Jon Culshaw in our bit of crowd. Although they may not have realised it, the nerves required to make some of the positional decisions were greatly assisted by their kind words of confidence in my ability.

I got another call to the bridge as the Sun’s crescent was thinning. At this time the photography started to get trickier and I was grateful that my colleague, Paul Abel stepped in to do next bridge announcement instead.

As he returned, totality was getting very close. A peculiar light started to enshroud the ship and all eyes were straining to see what the weather gods had arranged for us. Ahead of the ship there was a huge patch of blue sky!

Totality approaches

As the horns of the crescent Sun closed at an ever accelerating rate, the light levels dropped in a way that I imagine you’d experience if you were falling down a well. As this happened the big patch of blue sky was in front of the Sun – we were going to see totality!

One of my cameras was pointing to the southwest as the Moon’s shadow approached. Here’s what it saw (time runs from upper-left, upper-right, lower-left and lower-right).

The first diamond ring

The first diamond ring appeared and filters came off cameras and eclipse glasses were removed. An eerie but beautiful darkness engulfed us. It wasn’t total darkness but just odd. The Sun hung in the sky with the inky black disc of the Moon in front of it. The solar corona appeared and glowed with awe and majesty around the edge of the eclipsed Sun. The sky turned an incredible turquoise blue. The scene looked like we had fallen out of reality into a painting. Then, the thing that eclipses do to you happened – emotion took over.

Tears rolled down the cheeks of many eclipse chasers. The realisation that we were witnessing something so, so special took hold. This was an eclipse that on paper at least, had a very low probability of success. With skill, tenacity and luck we’d made it and we were finally standing under the shadow of the Moon and witnessing probably the most special event in all of nature.

Totality!

The pink chromosphere and equally pink prominences appeared around the leading edge of the Moon as the first diamond ring faded.

One of these had a small detached portion which many claimed to have seen visually.

Totality lasted for a full 2 minutes 46 seconds because we were so close to the point of greatest eclipse duration. Actually, this is a technical measure of totality determined by the amount of time between second and third contact. In reality, the first diamond ring to the second lasts for longer than this period because the diamond rings occur seconds before and after technical totality. From the first diamond ring to the second, as measured by my camera, the spectacle was over 3 minutes long.

The corona during totality was as beautiful as ever and no camera can ever do it justice. Below is a high dynamic range composite to try and emulate its visual appearance.

The second diamond ring

Being such an unusual event to actually see, time appears to speed up during totality. So it was for this eclipse as the second diamond ring started to appear. Some thin clouds had crept back across the sky which only seemed to enhance the view.

For the third contact diamond ring, I switched my camera into video mode. The resulting movie can be seen below (the voices are mainly Paul Able and Tessa Lawrence). We were at sea as this was taken and the ship was moving about considerably. This is reflected in the movement of the eclipse image around the frame – I did my best to keep it contained!

>> Watch the third contact diamond ring movie here <<

And then, it was over.

I headed up to the bridge for one last commentary and to assist Captain with another radio interview. Everyone was elated up there. The whole ship became alive with smiling faces – some appeared to be in a state of astonished disbelief that we’d actually seen the eclipse at all. But we had, and it felt like we’d pulled a rabbit out of the hat.

I’ve seen eclipses in clear blue skies, and through cloud. Clear blue versions are beautiful and fulfilling but the risk factor of cloud, when it clears at the right moment, delivers something really special. It feels as if you’ve had to work for the experience – which in this case we certainly did!

The close of the day

As a final treat, as we headed towards the Faroe Islands on the evening of the 20th, an aurora was active to the north. This was a low, but bright green glow embedded within the clouds. A fitting end to what had been a fantastic adventure.

The future

There’s another total eclipse visible from Indonesia in 2016, but my next venture will be the 2017 eclipse visible from the USA. I’ll be over there with Omega, the company that engaged me this time round. I’ve worked with them since 2005, mostly taking people up to see the aurora and eclipses.

We had a magnificent eclipse success in 2006 with 1,600 people being transported to Turkey to get a superb view of totality in pristine blue skies. In 2009 we took a party over to China to see the longest period of totality of the 21st century. Weather was poor along much of the eclipse track for that one, but again with good planning, we saw the whole event.

I can’t wait!

I’d like to dedicate this article to my wife Tessa, and good friends Peter and Jen Truman, Paul Abel, Kevin McNulty and Jon Culshaw.

All images are copyright Pete and Tessa Lawrence and may not be used without permission.

Update: Never happy to leave things alone – here’s my latest process on the solar corona. This is a tricky thing to tease out from results obtained from a moving platform – i.e. the deck of MS Boudicca – but not impossible…

March 20th 2015 – Solar Totality!

Solar totality as seen from the deck of the Fred Olsen cruise ship MS Boudicca on the morning of March 20th 2015. Despite walking out into a heavy snow storm at 5am, a bit of tenacity, positional adjustment and plain old luck brought MS Boudicca into a patch of sea 230 miles north of the Faroe Islands, which had blue skies! A more detailed report will follow but for the moment here are a few shots of the event…

Finding Comet C/2014 Q2 Lovejoy (Feb 8-13, 2015)

Now the Moon’s heading out of the way, it’s worth having a look for comet C/2014 Q2 Lovejoy once again. The come is currently passing through the eastern part of Andromeda, heading north towards the border with Perseus and then into Cassiopeia.

The W-shaped constellation of Cassiopeia is the key to finding Lovejoy at the moment. Look for the W a little over half way up the sky in the northwest around 21:00. The W will appear on its side as shown in the chart below.

Look at the line between Caph and Schedar and extend this line for 4x the distance again to locate Almach which is in Andromeda. Almach, or Gamma Andromedae, is of similar brightness to both Caph and Schedar. Once located, look above Almach for about 0.5x the Caph-Schedar distance to locate the fainter star 60 Andromedae. The head of the comet sort of completes an equilateral triangle with 60 and Almach on the night of the 8th.

Here’s what it looked like on the night of the 6th using a camera. The bright star at the bottom of the image is Almach and the fainter but still prominent one at the upper left is 60 Andromedae.

Update – Feb 8th

Here are some images from Feb 8th…

Near Miss Asteroid Chasing

The night of 26 Jan into the morning of 27 Jan presents an opportunity to spot asteroid 2004 BL86, a 0.5km diameter lump of rock destined to pass just 1,191,000 km from Earth. Actually, that’s not really anything to worry about as it’s just over 3x the distance of the Moon!

So, assuming the UK’s skies clear on the night of 26/27 January, what’s the best way to go about spotting the asteroid?

First let’s look at its brightness. As the sky darkens on 26 January, the asteroid will appear as a small dot of magnitude +9.7 – that’s doable with an average pair of binoculars given a clear dark sky but if your visual limit is around mag. +5.0 you’re going to struggle.

As the night, or rather morning, draws on, so the asteroid will brighten. It reaches its peak brightness of mag. +9.0 at 04:30 UT. This is when the asteroid is passing up through Cancer the Crab, heading towards the eastern side of the magnificent binocular object, M44 or the Beehive Cluster. In fact, this object is very useful because it gives you a means to calibrate your binoculars in terms of how deep they can go. Using a pair of binoculars, if you can see stars which are the same brightness or dimmer than the asteroid then you know you’re in with a shot of spotting it. The graphic below shows the Beehive Cluster and identifies the main pattern within it – the bit I always think looks like a beehive, albeit, an upside down one! It should be relatively easy to pick this out with binoculars. Once you’ve done this, jump to the first arrowed pattern and then, once you’re used to the view, see how faint you can go. If you’re not familiar with magnitudes, the larger the number, the fainter the object.

Assuming you’re able to see stars equal to or dimmer than the asteroid, the next job is to locate it. This is trickier as it’ll appear exactly like a star. However, it’s presence will be given away by the fact that it’ll move noticeably over the space of a few minutes. The downside is that there are a lot of stars around the mag. +9.0 to +10.0 range in that part of Cancer. The chart below gives the location for a given time. The asteroid will be at mag. +9.3 at 00:00 UT on Jan 27 and +9.2 at 01:00, +9.2 at 02:00, +9.1 at 03:00, +9.0 at 04:00, +9.0 at 05:00 and +9.2 at 06:00. At 06:00 the Beehive Cluster will have an altitude of 19 degrees in the west.

The position of the asteroid will vary very slightly with your location due to parallax but the chart below should allow you to find it. This chart doesn’t sugar coat the situation and shows it how it is. The stars picked out go down to mag. +10.0 which means that these are will be slightly fainter than the asteroid.

When trying to locate something like this, identify patterns that stand out to you which lie near to where the asteroid is supposed to be. Use these patterns as your navigational beacons, and use them to home in on the position of 2004 BL86.

Good luck and clear skies!

Update – Here’s a 60s exposure of the field containing the asteroid. 2004 BL86 is shown as a streak in this relatively short exposure.

A Wobbly View of the Rare Triple Shadow Transit on Jupiter

I returned from an exhausting set of Northern Lights flights on the afternoon of 23 Jan 2015. An early night followed both because I was so tired and also because the weather forecast was favourable for the early hours of 24 Jan. Between 06:23 and 06:58 the planet Jupiter would be crossed by no less than 3 dark moon shadows, cast by the Galilean moons Io, Europa and Callisto. This is an event I’d been looking forward to for some time and had promoted via my writings in the Sky at Night Magazine and also the Star Guide I present on the Sky at Night TV show. Here’s the simulated view at 06:40 UT I created…

The reason for pushing the event is that this was the last opportunity to see a triple shadow transit until 2032. Such events tend to come in small bursts with up to 3 triple shadow transits occurring within a relatively compact timescale. This batch started with a triple shadow transit which occurred on the morning of 12 October 2013, one for which I was clouded out! The next one occurred when the Sun was still up on 3 June 2014. That one I managed to observe and image through ever thickening cloud despite the bright sky. Consequently the images weren’t amazing but at least I got it! It took a lot of patience though.

The final triple shadow transit on 24 January 2015 should have been much better but as it turned out it too was rather tricky to view and image. For me the first problem I had was due to fatigue from the Northern Lights flights. I was so tired that I had my doubts as to whether I would actually be able to get up. I set a wake up alarm on my old trusty Blackberry Torch 9800 (I’ve found my iPhone 5’s alarm function to be unreliable and I don’t trust it anymore!) for 04:00 on the 24th and went to bed at 22:00. Before going to bed, my weather apps indicated that rain would pass through the area before the sky cleared. I put my C-14 outside but under cover of my observing cabin’s porch.

Amazingly, I managed to wake up quite naturally at 03:50, before the alarm sounded (how does that happen?!) and headed downstairs. I needed to move the mount for my C-14 across to the east boundary of my garden so I could see the transit which occurred at low altitude in the west. Unfortunately, this meant setting up on a wet lawn. The resulting mud bath at the end of the session was quite impressive! When I went to collect the C-14 from its sheltered location – now properly cooled to match the outside air – I discovered that the rain that fell must have come in sideways across the porch because the scope was wet through.

A quick check inside showed that the main mirror was about 50% dewed up. So I mounted the scope and made the executive decision to remove the corrector plate so I could dry the mirror with a hair dryer. This shows why it’s a good idea to give yourself plenty of time to prepare for events such as this. Of course, the hair drying exercise destabilised the internal temperature of the telescope but there was still time for it to cool properly.

When I finally got a view of Jupiter it was clear that the seeing was pretty awful – some of the worst I’d seen to be honest. Click here to see a video of just how bad it was! The reason for this was mostly down to a raging northerly jet stream.

I decided to image at prime focus with my ASI 120MM mono high frame rate camera. This still allowed me to see detail but removed some of the nastiness that the poor seeing was pouring down my scope. To make matters worse, the event was due to occur in a location that would position Jupiter above the central heating vent of a neighbour’s house. No matter where I went in my garden, the vent remained in a problem position. It reminded me of a portrait in oils and the way the eyes appear to follow you around the room!

The end result was less than impressive compared to what the C-14 is capable of with this fantastic planet. However, there was a feeling of satisfaction that I’d made the effort and overcome a few unexpected hurdles. In the end, I figured the best way to present the results was to add the 60 separate images I took through a 742nm IR filter (this helps stabilise bad seeing – but there’s a limit!) and animate them together.  Here’s the result (click on the animation to load a larger version)…

What you’re seeing here are the dark shadows of Io and Callisto off to the right. Look carefully and you might be able to see Io as a slightly brighter dot moving from Callisto’s shadow (the left hand one of the pair). These are joined by two further dark dots on the left of the disc. The upper one is the moon Callisto transiting across Jupiter’s disc – a fairly rare sight in itself. The lower dark spot is the shadow of Europa. The moon Europa can be seen off to the left of Jupiter.

Aurora Flights and Time Shuffling

Every year from November to March I’m employed as an expert guide on a number of aurora expeditions. Most of these don’t land but rather take people to the edge of British airspace in a totally darkened plane to look out in hope of spotting the elusive aurora. The big advantage here is that at a height of 36,000 feet, it’s extremely unusual to get any weather in the way which would otherwise spoil the view.

I’ve been doing this for 10 years, together with a team which works extremely well together. The format of each flight is exactly the same. Passengers gather in a predefined location beforehand in anticipation of a live presentation given by two astronomers, one of which tends to be me. The period before the presentation start time is covered by a multi-media pre-presentation, presentation (PPP) which addresses many of the questions we used to get after each flight. It also introduces the passengers to the team.

I used to write computer software for a living and wrote the scripting language for the PPP. This gives me a lot of flexibility when putting the PPP together. It also allows for problems that sometimes occur when we can’t start the PPP rolling on time. The current version can auto-scale itself to start at any time before the main presentation. Music and graphics always stop at the correct time just before the main, live-presentation. The biggest benefit though, is that I have total control over the PPP’s content and can customised for each flight beforehand. All I need to do is turn up, activate the program and relax – well sort of! The PPP counts down to the start of the main presentations and it’s atomic clock accurate!

What follows is a brief introduction from an Omega Holidays representative – typically Peter Truman, who initially came up with the idea – and then into the main presentations. Both run for 30 minutes each. The first covers some of the procedures of the flight and a guide to the main patterns of stars that passengers will see outside. The second, describes the aurora; where it comes from, what it looks like and a forecast for our chances of seeing it on the flight.

After this, the next stage is getting on-board the plane. After take off, a short food service normally occurs and then, approximately 40 minutes in, the astronomers attempt to get the cabin as dark as possible. Once this has been done, passengers normally have 20-30 minutes in darkness before we arrive on ‘station’. This is the term used to describe our location, typically between 58 and 61 degrees north, and to the west of the Shetland Islands (out of light pollution range from the islands). Here, the plane takes up an east-west and west-east circuit allowing each side of the aircraft a look towards the north where hopefully the aurora will be putting on a show.

Out of the 250+ flights I’ve now done we’ve not seen any hint of the aurora on just 8 of them. However, in fairness, some of the sightings have been extremely weak displays but the Northern Lights all the same.

The January 2015 season started with a flight from Glasgow Airport. I live on the UK’s south coast and Glasgow is a long drive for me. When we got on board, an operational issue with flight path planning meant we took off 90 minutes late. As it happened this worked to our favour because we got a lovely display of the Northern Lights which we may not have seen had we taken off on time!

The next night was from Edinburgh which had a weak display. Unusually for us, the following displays from Newcastle, Stansted and Bristol were also rather weak, the Bristol display being virtually non existent! However, the aurora sorted itself out for the last two flights in January from East Midlands Airport and Leeds-Bradford. Both were nail-biters in that the aurora remained misty and indistinct until right up to the last minute when suddenly it burst into life. Fortunately, the Jet2 crews we had on these flights were very understanding and made extra circuits so everyone could get a look. Lots of happy faces leaving the aircraft after those two.

The flights are pretty exhausting to do for the team. In this instance they were arranged as three on (Glasgow, Edinburgh and Newcastle), a one day gap before Stansted and another rest day before the final three (Bristol, East Midlands and Leeds-Bradford). My typically complicated diary meant that the rest day between Stansted and Bristol needed to be be used for my Sky at Night filming duties. I drove straight from Stansted to the Winchester Science Centre, filmed during the afternoon and returned home at 20:30.

It was clear when I got back so after a bit of internal negotiation between my brain and body, I managed to set up my kit to take some shots of the beautiful comet C/2014 Q2 Lovejoy. Of course, finding the time to process these results is the next hurdle to overcome!

You can see scheduling information and previous flight photos from my Aurora Flights website.

My last astro image of 2014

What with poor weather and generally poor seeing, it was great to have a restbite on 30 December 2014 and grab some decent results of Jupiter. The conditions for this shot were reasonable but by no means the best I’ve seen from my observing location. A slight northerly component to the wind direction messes up my seeing, air having to pass across land rather than sea, as is the case for me when the wind is from the southeast, south or southwest.

The image is the result of taking a number of movie sequences, sorting and stacking the frames held within each sequence and combining all of these into a final result.

Here, four 90s red filtered mono images were combined with two 90s green filtered images and two 90s blues to produce a final RGB colour result.

As Jupiter is a fast rotator, spinning once on its axis in less than 10 hours, an imaging period of this length would normally result in a blurred RGB. However, using the wonderful WinJupos software it is possible to derotate each result back to a common time.

The net result is a final RGB that looks sharp, detailed and unblurred by Jupiter’s rapid rotation.