Shunbun no Hi: Solargraph

My latest hobby is making pinhole cameras from household waste, recording images on film or photosensitive paper. I don't know anyone in person who is into pinhole photography, but thanks to social media (mostly Facebook groups), I've connected with, and gotten a lot of advice and tips from, the very helpful worldwide community of pinhole photographers.

A few months ago, when I was a total newbie, a photographer from Oaxaca, Mexico even offered to do a one-on-one Zoom session to answer some of my questions and show me her studio. At one point I said something like "I didn't understand this design, but as you know I'm a beginner..." She chuckled and said, "Yes but I can tell you're enthusiastic. By this time next year you'll have made at least ten pinhole cameras."

I laughed at the time, but I already have six, and I'm planning a seventh.

My latest pinhole camera is made from a beercan. The goal is to create a solargraph: an ultra-long exposure stretching over weeks, months or even years, capturing the Sun's trail across the sky.

I thought Spring Equinox would be a nice day to set it up, and accordingly I tied it to a betel-nut tree behind our flat. (I added arrows to show the pinhole in the first pic, and the camera in the second.)

My camera, as you can see, is made from a can of Kingfisher beer. A few hours after setting it up – coincidence of coincidences – I saw an actual kingfisher sitting on the wire just behind it. Perhaps it was the same bird which featured in my last Shunbun no hi post.

Happy equinox, everyone.

Three Views of the Milky Way

Three views of the Milky Way, shot over two nights in the Mojave Desert, California.

1. Still photo



Move your cursor over the image (or touch on mobile) to see labels: constellations are in blue and planets are in pink. Click on the image for a high-res version, where you can make out some of the amazing deep-sky objects in Sagittarius, including star clusters and nebulae (interstellar clouds of dust and gas hundreds of light years wide, where new stars are being born). Though it cannot be seen in the photo, the frame also includes the galactic centre – the theorised location of a supermassive black hole known as Sagittarius A*.

2. Star trails

These star trails were shot over 65 minutes. I like how it really brings out the variation in star colours. The stars moved from left to right, and the brightest streak is Jupiter.

3. Timelapse

The video above opens in a new window (I recommend setting the quality to 1080p as YouTube sometimes picks a lower resolution). 2.5 hours of diurnal motion are compressed into 20 seconds: an effective speed of 450x. The "star" rising around 0:08 is Mars. The sky lighting up at the end of the video is not daybreak, but the Moon rising in the east.

+ Show tech info

Nikon D-5200 digital SLR camera, Nikkor-NC f/2.8 24mm manual-focus lens
Still photo
f/2.8, 20 sec, ISO 4000
27 panoramic stills, stitched together with Image Composite Editor
Star trails
f/2.8, 30 sec, ISO 800
120 stills at 3-sec intervals, stacked using Startrails
Timelapse
f/2.8, 15 sec, ISO 4000
500 stills at 3-sec intervals, played at 25 fps (effective speed 450x), compiled using Shotcut

Calcutta, 5:52 pm

There was a supermoon on 2 January, though this post is so late it's almost new moon time. I was in Calcutta, and my mother and I went up to the roof terrace of our building to watch the Moon rise. For is it not written: "The term 'supermoon' may be mostly hype, but it's as good an excuse as any to go out and look up."

This photo was taken from the same chilchhad – and features the same coconut tree – as the photo of the sunrise taken nearly five years ago.

The Milky Way Over Teide National Park

If you were in one of the best stargazing locations in the world for just one night and could spend it either stargazing or doing astrophotography, which would you pick? Stargazing seems like the obvious choice, unless, like me, you've spent months dreaming up cool astrophotography projects, all the while stuck in a cloudy, light-polluted metropolis.

When Anasua and I went to the island of Tenerife last spring, we booked a parador (a government hotel halfway up Mount Teide, in the middle of the otherwise uninhabited Teide National Park) for not one but two nights, thereby avoiding this dilemma. Or so we thought.

We spent the first night stargazing. Orion set over the Roques de Garcia in a cloudless, moonless sky. At midnight, Jupiter, not long past opposition, shone like a miniature sun. A few straggling Lyrid meteors crisscrossed the heavens, like a curtain-raiser for the Milky Way which filled the southern sky before dawn.

The Milky Way, for my money, is by far the most dramatic naked-eye object in the night sky. But we were lucky enough to have the hotel's Dobsonian telescope all to ourselves, which gave us a closer look at Jupiter, Saturn and a couple of deep-sky objects.

The second night, which I had earmarked for astrophotography, turned out to be cloudy – something that's apparently uncommon in Tenerife, especially at high altitudes. I did not get a single good photo that night. But if I had to do it all over again, I think I would still spend the first night stargazing. Besides, just before we packed up and went to sleep at 6 am, I did sneakily take one single shot of the Milky Way.



Move your cursor over the image (or long-touch on mobile) to see labels: constellations are in blue; planets and deep-sky objects are in pink. Click for a high-res version.

Slightly-Larger-than-Average Moon

The term 'supermoon' may be mostly hype, but it's as good an excuse as any to go out and look up.

Of late my posting has been even more irregular than usual. I have however been writing about bees on the LSE Bees blog, and book reviews for the LSE Review of Books. On the off chance that either of those interest you, go take a look!

London vs Cambridgeshire

This week the Widescreen Centre, the last surviving telescope shop in Central London, announced that they are relocating to Cambridgeshire. The reasons they cited for the move are "[t]he current economic climate, changing retail patterns, and critically a major rent review due imminently".

I only visited their shop once, to buy a solar filter to observe the transit of Mercury. The Widescreen Centre folk graciously answered some questions I had about telescopes, although I'd made it clear that I wasn't looking to buy one. They are also among the core members of my astronomy club (their announcement says they will continue to come for our monthly meets in London).

Rent is not the only thing that makes Cambridgeshire more conducive to astronomy than London. I took this photo last month when my friend Rohini and I went stargazing in Hampstead Heath in London. If you hover over the image, you can see the names of major constellations as well as two Messier objects: the Pleiades Star Cluster and the Andromeda Galaxy.

Try as we might, we could not see the Andromeda galaxy with the naked eye (the photo above was a 15-second exposure, so the camera captured about twice as many stars as our eyes could see).

For me, the most striking thing about the photo is the light pollution. Long after sunset on a clear night, the light from thousands of buildings and streetlamps gives the London sky an unsightly orange cast. Compare this with a photo I posted earlier this year of the International Space Station over Cambridgeshire (hover to see constellation labels):

Relatedly, the photographer Nicholas Buer has a wonderful video simulation of what London would look like if there were no light pollution.

Day Length and Decision Theory

I am in currently Copenhagen where, 15 days after the solstice, there is no such thing as night. Daytime gives way to civil twilight, then nautical twilight – and that is the darkest it gets.

Growing up in Calcutta, I experienced relatively little seasonal variation in day-length. As far as I remember, it affected my life in only one respect: I was allowed to play in the streets in the afternoon on condition that I'd be back before dark, which meant I could stay out a little later in summer.

The longest day of the year in Calcutta is less than 3 hours longer than the shortest day. In London, where I now live, the difference is almost 9 hours. I sometimes wonder: if I had to choose between Calcutta and London based on day-length alone, which would I pick?

Graph made using data from ptaff.ca

Other things being equal, I prefer longer days. By moving to London, I gained about 350 daylight hours in summer, but gave up the same amount in winter.¹ The question is, does the loss offset the gain?

Most people are thought to be loss averse: the pain we experience if we lose £100 is more than the pleasure of winning £100, and in general, bad things have more impact than good things. The psychologist Paul Rozin illustrated this beautifully: "a single cockroach will completely wreck the appeal of a bowl of cherries, but a cherry will do nothing at all for a bowl of cockroaches."²

But when it comes to day length, I am not quite sure what I prefer. Sometimes I lean towards more variation, sometimes towards less. Perhaps this means I am indifferent!

A question for the reader: How much variation seems optimal to you? No variation (12-hour days all year, like at the equator), extreme variation (6 months of darkness and 6 months of light, like at the poles), or somewhere in between?

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1.	In reality the gain is not exactly equal to the loss, but let's pretend it is, for the sake of simplicity.
2.	As quoted in Thinking, Fast and Slow by Daniel Kahneman.

ISS in ♋️

This evening I photographed the International Space Station streaking through the constellation of Cancer (my zodiacal sign, as it happens). The two lighter streaks to the left are airplanes.

The sighting lasted only about 3 minutes: look how much it moved during a 15-second exposure! But for those few minutes, with the sunlight glinting off its solar arrays, it was the brightest "star" in the sky.

This was my first attempt at photographing the ISS. Next time I want to try and capture a longer streak (with a longer exposure), and maybe have some interesting object in the foreground – not just a Cambridgeshire meadow.

If you're interested in spotting the ISS, NASA has a helpful page. Spotting – and especially photographing – the ISS requires a bit of planning, but it's fun. And of course, standing around in the cold setting up the shot helps build character.

The Spider Parable

Tintin readers may be familiar with Araneus diadematus: it was the spider which sat on Professor Phostle's telescope, leading him to think there was an enormous spider travelling through space.

This line made an impression on me when I read it as a kid, so although Araneus diadematus is not found in India, when I saw spiders in our house, I would often mutter to myself, "It's an Araneus diadematus! An enormous Araneus diadematus!"

Now that I am in Cambridgeshire, a beautiful specimen lives in our back garden.

She likes to spin her web across the garden gate, which unfortunately means that each time I take out my bicycle, I have no option but to tear the web down. For over a month now, I have been – reluctantly – destroying her web on an almost daily basis, but the next morning I find it has been rebuilt.

If I were Robert the Bruce, I might have drawn some sort of life lesson from this.

Astronomical Inaccuracy

A quick housekeeping announcement: you can now follow this blog via email if you are so inclined. There is a new field in the sidebar where you can enter your email address. Once your subscription is active, you will receive email notifications about new posts. Of course, you can unsubscribe at any time.

Edit: No more subscribe option, sorry!

* * *

I was in London yesterday on some work, and I saw this poster on a tube station wall.

I was idly scrutinising the night sky in the poster, trying to see if I could recognise any constellations, when I noticed a curious thing. Not only is the depiction of the sky inaccurate (which alone would be bad enough, this being an advert for an observatory of all things!), it actually repeats horizontally.

You can see this clearly in the image below, where I have circled three of the asterisms* for easy identification (you have to make some allowances for the distortion caused by the camera lens and the curvature of the wall).

I think this is rather lazy design; contrast it with Randall Munroe's obsessive attention to astronomical detail.

Happy equinox, everyone!

*

An asterism is a pattern of stars smaller than a constellation, like the Big Dipper which is part of the constellation Ursa Major. It is also the name for one of my favourite typographical symbols: ⁂. You may have known these facts already; I basically inserted the footnote because the temptation to put an asterisk next to asterisms was irresistible.

Jupiter–Venus Conjunction

Venus and Jupiter, the two brightest objects in the night sky (excluding of course the Moon), were very close tonight – just a third of a degree apart (for reference, the full Moon is about half a degree in diameter). We will not see a closer Jupiter–Venus conjunction until 2039.

I positioned myself at a spot whence, I calculated, I would see the two planets set over the Shard. But my trigonometric efforts were in vain; clouds obscured the view while the sky was still quite bright and the planets some distance above the horizon (at the upper left in the photo below). Oh well, I'll try again tomorrow.

Whenever I see Venus in the evening sky, I think of these lines from Terrapin Station by the Grateful Dead:

Counting stars by candlelight / All are dim but one is bright / The spiral light of Venus / Rising first and shining best...

Shunbun no Hi: Solar Eclipse

This year's Shunbun no Hi post is four days late, for which I apologise.

This year the equinox coincided with a solar eclipse, though the UK only experienced a partial eclipse. The weather forecast said (correctly, as it turned out) that there would be a thick cloud cover over London, so Anasua and I took an early morning coach to Oxford, which had clearer skies.

Here are two photos: the first taken shortly after the eclipse began, and the second just a few minutes after the maximum point, when about 85% of the Sun was occulted by the Moon.

The Moon and Saturn

The night after I took the photo of the Milky Way, I photographed Saturn and the first quarter Moon through Tommy's home-made Newtonian telescope.

That night the Moon and Saturn were in different parts of the sky (here is a hi-res photo of the Moon on its own). For a sense of (apparent) scale, I used image-editing software to merge two photos taken at the same magnification, thus bringing the Moon and Saturn together in a single frame. The result is similar to what you might see during an occultation.

In the photo you can see some of the craters, mountains and "seas" of the Moon, which are cool enough in their own right. But of all the objects that can be seen in the night sky with an amateur telescope, there are few, if any, which are cooler than the rings of Saturn.

The Milky Way over Lone Pine

In my blog CQA I wrote that one of the reasons I continue to blog is because through blogging, I've come to know some people I would not know otherwise. This summer I visited one such person in his desert lair at Lone Pine, California.

On the first night of our stay, the moon set early behind the Sierra Nevada. The skies were clear, and the remote desert location meant that there was minimal light pollution. When I ventured outside at around 2 am, I was treated to one of the most beautiful night skies I have ever seen.

The photograph I took captures only a small section of the vista that stretched out above us, but it has a number of interesting objects. The dominant feature is, of course, the Milky Way. You can also see (parts of) eight constellations, binary stars, a red supergiant whose diameter is nearly 900 times that of the Sun, and a number of deep-sky objects (star clusters, and nebulae – interstellar clouds of dust and gas hundreds of light years wide, where new stars are being born). The deep-sky objects have exotic names like the Wild Duck Cluster and the Eagle Nebula (and sometimes non-exotic names like NGC 6441). You can also see a star cluster 87,400 light years away in another galaxy, and a dark nebula in the shape of a black horse galloping through the heavens.

Perhaps coolest of all, the photo includes the galactic centre – the theorised location of a supermassive black hole known as Sagittarius A* whose mass is over 4 million times that of the Sun. Sagittarius A* cannot be seen in the photo – or even through astronomical instruments from Earth, at least not at visible wavelengths – because of interstellar extinction by dust and gas. We know its location because it is detectable as a source of strong radio waves.

You want to know where all these cool objects are, don't you? Click on the photo for an interactive guide.

I would have unveiled this photo long ago, but Anasua coaxed me into making the guide, which took weeks of research and coding. "Reach for the stars," she said.

Bellingham, 12:53 pm

On the drive down from Mount Baker, I saw a good example of a 22º halo, an optical phenomenon caused by the refraction of sunlight by hexagonal ice crystals in a layer of cirrostratus nebulosus cloud. The inner edge of the halo is red and the outer edge bluish, though this could be seen more clearly with the naked eye than in the photo.

The 22º halo is actually a fairly common phenomenon, occurring up to 100 days a year in temperate latitudes. If you haven't seen it, it's probably because you are wise enough not to stare at the sun.

Waxing Crescent

Six-day-old moon over London, photographed through a 300mm lens
(click on the image to see names of some lunar features)

Porthgain, 9:06 am

Porthgain is a coastal village in Wales. This photo of a ruined cottage was taken near our campsite, a short way from the village.

Being from Calcutta (22.57° N, 88.37° E), it took me some time to get used to the fact that in London, the sun is never directly overhead. The closest it gets is a solar elevation angle (the angle between the horizon and the centre of the sun's disc) of about 62° (where 90° is directly overhead).

Yesterday I was speaking to a friend (also from India) who has just moved into a new flat. She said, "My flat faces west, but it doesn't get direct sunlight in the afternoon. And we observed that even at noon, the sun is not overhead. Do you know why?"

At this latitude, this is just about the worst time of the year for someone who likes the sun directly overhead. The solar elevation angle in London at noon today will be just over 15°.

Happy solstice, everyone.

Chasing the Lights

“Looking for the northern lights,” said our bus driver, as we left the outskirts of Reykjavík and hit Route 41, “is like fishing.”

She did not elaborate, because Icelanders like their sermons short, and because she was simultaneously driving a bus, scanning the sky for northern lights and keeping up a running commentary – activities which left her with little or no leisure for explaining metaphors. But this is what I understood it to mean: Having invested in a fishing-rod and tackle and a day’s outing, if you catch no fish at all, you may be tempted to call it a waste of a day. And this can cloud your appreciation of the sunshine, the smell of grass and the music of the river.

February is not the most popular time to visit Iceland. The days are short, many roads are still impassable, there is limited public transport, and it is – as you might expect – fairly cold. But the Quaker and I wanted, if possible, to see the northern lights. In an earlier post, I wrote briefly about our quest, and promised to apprise you of further developments. The time for a fuller account is now come.

First, of course, you need a project name.

We take our trip-planning seriously, and I enjoy it nearly as much as the trip itself. Occasionally, we get carried away: to plan our Edinburgh trip, for instance, we booked a meeting room in Prakruthi’s swanky condominium.

Needless to say, we have project names for our trips, which are chosen early on in the planning process. Edinburgh was Project Kilt. Iceland, of course, was Project Aurora.

Being sensible people, we knew, project name notwithstanding, that a glimpse of the northern lights is by no means assured. By going in February and spending eight nights in Iceland, we were improving our chances. But aurora displays depend on the interaction between solar wind and the earth’s magnetic field and atmosphere, and even when they do occur, you may miss it because of an overcast sky, or the glare of city lights, or simply because you are not in the right place at the right time.

We based ourselves in Reykjavík and Akureyri, but within city limits, chances of seeing the lights are slim. So we signed up for ‘northern lights tours’ – nightly bus trips into the countryside run by tour operators, using weather information, aurora forecasts and their own considerable experience at chasing the lights. Conveniently, they offer you a free second trip if you did not see the lights on your first. We were able to take advantage of this and make two trips from Reykjavík and two from Akureyri.

Trip 1 was from Reykjavík, on a partially overcast night. We went south-east, all the way to the south coast of Iceland, where the sky was supposed to be clearer. We saw the North Atlantic Ocean by night, but although we made several stops – by the ocean, on a deserted side-road outside Selfoss and, of all places, at a KFC – we saw no aurora. Then, around 1 am, just when we had given up hope, we stopped in the middle of a snowfield and spied a faint glow overhead. Behind a veil of cloud, the lights faintly flickered and moved, and vanished after a few minutes. The tour operators were, nevertheless, kind enough to offer us a free second trip.

Trip 2 was from Akureyri. There were not many tourists in the whole town, and only eight of us went on the tour. So we had a van, which was much cosier than a large bus. We were better prepared too, with biscuits, water and more warm clothing than we wore in Reykjavík.

I think it was on this trip that I really started enjoying the whole experience. Seeing the lights was still the main objective, but I began to appreciate other things: the vastness of the scenery, the incredible clarity of the stars, the icy crispness of the night air, the warmth inside the van and the sense of common purpose – something almost akin to the thrill of the chase.

To occupy ourselves during the long hours of standing around in the cold, the Quaker and I would play around with the settings on our cameras and take practice shots, so that when the aurora finally made an appearance, it would not find us unprepared. We have compact cameras and no tripods, but in our efforts to make the best of our limited resources, we left no technique untried. By the end of it, we could have written A Cheapskate’s Guide to Photographing the Northern Lights.

A Cheapskate’s Guide to Photographing the Northern Lights

(condensed version)

•	Switch to Manual mode.
•	Set a long shutter speed (on my camera, the longest possible is 15 seconds).
•	Set the widest possible aperture (f/2.8 on my camera).
•	Select a high ISO speed, but not so high that the grain is unacceptable (I opted for ISO 800).
•	Set a 2-second timer, to eliminate camera shake caused by depressing the shutter.
•	Find a horizontal surface, or failing that, put your backpack on the ground and balance your camera on it.
•	Learn to do all of the above with gloves on, unless you want to lose a few fingers to frostbite.

It was an almost cloudless night; still we saw no aurora. But we saw the glimmering lights of Akureyri reflected on the waters of Eyjafjörður, and we got another free trip.

Trip 3 was also from Akureyri. There was a thick cloud cover over northern Iceland, and we knew from the start that we stood almost no chance of an aurora sighting. But by this time, it mattered less to us. We drove north, right up to Siglufjörður.

Our guide and van-driver was Inga Svavarsdóttir – a sheep-farmer and part-time tour guide. She kept up a stream of cheerful conversation, telling us about scientific explanations for the aurora, local folklore, the Siglufjörður fish industry, hiking in the surrounding hills, and Icelandic farming techniques. (Long-time readers may recall that this is not the first time I have been lectured on farming techniques.)

In case you’re wondering what an Icelandic farm looks like, here is a photo of one in the daytime.

At one point, after we had stood outside for a while vainly scrutinising an opaque sky and shivering in our shoes, Inga revealed homemade kleiner and thermos flasks full of hot chocolate. I doubt if even a sudden and dramatic appearance of the northern lights could have delighted me so.

Trip 4 was on my last night in Reykjavík. We had briefly wondered whether we should quit chasing the lights and do something else, but we decided we may as well avail of our remaining free trip. It was another cloudless night, but we had learnt not to expect too much. We drove west of Reykjavík, towards the Keflavík peninsula.

Around 9:30 pm, we made our first stop near a church. Excited tourists on their first northern lights tour piled out of the bus, quivering with anticipation and excitedly discussing our chances. The Quaker and I also disembarked, but with a dignity befitting four-trip veterans, with an indulgent smile or two at the over-enthusiasm of the first-time tourists: what did they know of disappointment and of long waits in the bitter cold?

Then the aurora lit up the sky, just like that.

People madly took photos. One dude, for reasons best known to him, pointed a red laser at the aurora. Having finely honed our photographic technique on the preceding nights, the Quaker and I reeled off a few quick shots, which left us with some time to forget our cameras and gaze at the sky.

The display lasted almost an hour. A vivid green streak formed in the northern sky, then a second streak curved into a horseshoe shape.

Some Aurora Myths

A Finnish folktale says that the aurora is caused by an arctic fox flinging fire into the sky with its tail. Some Scandinavians believed that the lights are the celestial reflection of a giant school of herring. Inuits thought they are the souls of dead children. Icelanders, typically, eschewed such romantic notions, holding only that if a pregnant woman gazed at the northern lights, her child would be born cross-eyed.

The Koyukuk Indians in northwest Alaska banged on metal pans to attract aurora – I know not to what end. In Lapland, people were warned not to mock or whistle at the aurora, though I must confess that the one time I saw the lights, it did not occur to me to do either of these things.

The next day, I was back in London.

Icelandair offers Northern Lights City Breaks. Our dispreference for package tours meant that we did not consider it an option, but I still read their disclaimer, because I am sad like that. It says:

Please Note: The Northern Lights are a natural phenomena and therefore their appearance cannot be predicted. [...] If the weather conditions on the evening of your tour are not favourable for searching for the Northern Lights, the tour will be cancelled and you will be given the option of going on the tour the following night. Please note that no refunds will be offered for the tour portion of the package.

How much nicer was the disclaimer we got from our bus driver: chasing the lights is, indeed, like fishing.