One of my favorite regions of sky to image is around the constellation of Orion. Hiding within one of the most recognisable asterisms are: an ancient supernova remnant written large across ten degrees of the sky, dusty regions sculpted by stellar winds and radiation pressure and a plethora of star-forming regions.
This first image shows the constellation Orion below the Milky Way, which runs from middle left to the upper right corner. The Rosette nebula is on the left while the Hyades cluster is on the right, with the orange giant Aldebaran in front of them. It was taken with a kit lens at 18mm/f5.0 on a modded Canon 1100D camera. It's a slight crop, the field of view is about 40 by 55 degrees. The plate-solved image below shows Orion in relation to its neighbouring constellations.
A 50mm lens gives a closer view of the busiest region of Orion, including the seven bright stars recognisable to even the most casual stargazer.
The bright star at upper left is the red supergiant Betelgeuse. If placed at the centre of our solar system Mercury, Venus, Earth, Mars and perhaps Jupiter would be inside it. Yet despite its vast size its mass is only 10-15 that of the Sun, its tenuous outer layers being no more than hot near-vacuum.
The contrasting star at lower right is the blue supergiant Rigel, over 100,000 times brighter than the Sun. It is responsible for lighting up the dust cloud to its right known as the Witch's Head nebula, although in this orientation I think it looks like a leaping dolphin.
The nebula at the head of Orion is sometimes known as the Angelfish. Intense UV radiation from the star Meissa ionizes a could or largely hydrogen gas, causing it to glow a characteristic deep red colour.
Finally, the enormous nebula on the left of frame is Barnard's Loop. It's thought to be the result of a 2 million year old supernova, the explosion swept gas and dust into a roughly spherical shape. From our vantage point we see the left hand edge of the sphere because we are looking through a greater depth of materiel. The other side of the arc may be invisible because there was less material to be swept up in that direction, or because there are no hot stars in that vicinity to light it up. These superbubbles are fairly common, our own solar system is passing through one.
A 200mm lens gives a closer view of Orion's Belt and Sword, home to some of the most famous objects in the night sky.
Rotated 90 degrees anticlockwise from the other images, the bright star at lower left is Alnitak, the leftmost star of Orion's belt. Scattered across the frame are a collection of star-forming regions, in different stages of evolution.
The Flame Nebula on the left has a unique yellow colouration, I haven't been able to find an explanation of this. I suspect it has something to do with scattering of light by foreground dust. To its right lies the famous Horsehead Nebula, readily visible silhouetted against the bright emission nebula IC434. The Horsehead is at any early stage of star formation, a cloud of gas and dust is collapsing under gravity to form new stars which are obscured in visible wavelengths by the concentration of dust. Infra-red light is attenuated less, making it possible to peer inside the Horsehead and see these newly formed stars.
On the right of the image lie two bright nebulae, embedded in a wider dusty region. On the left is the Running Man, a reflection nebula. To its right is the Great Nebula in Orion, M42, the closest star-forming region to Earth and easily visible to the naked eye. (I like to think of it as a great engine of possibilities, a few hundred stars are in the process of forming inside it along with associated planetary systems. Our own Sun would have been birthed in a similar nebula about 4.5 billion years ago.) M42 is in at a much later stage of evolution than the Horsehead. Intense radiation and stellar winds from the hot young stars at its core are expelling gas and dust into space, giving it the appearance of an open rose. This will bring an end to star formation in the near future, leaving behind a bright open cluster.
These images show what is possible at the budget end of astrophotography. The first two were taken with cheap kit and 50mm lenses, a modded DSLR and a basic tracking mount. The final image was taken with a fairly expensive lens, a second hand Canon L 200mm f2.8, and a borrowed, more sturdy mount. However, similar results could have been achieved with a much cheaper optic, using a longer exposure time.
Got up at 3:30 this morning to image Comet Catalina passing close to M101 (the Pinwheel Galaxy). First light for my kit in a while due to the terrible run of whether we've been having, and first legs for my astronomical longjohns, which did their job of keeping my legs warm. The above image was taken using a vintage 135mm lens and modded Canon 1100D camera, it's 14 minutes exposure time in total.
The comet is displaying two distinct tails, a wide dust trail pointing up and a fainter, narrower ion tail to the left. The dust is left behind in the wake of the comet's orbit, while the ion tail points away from the Sun as it more strongly affected by the solar wind. M101 is a spiral galaxy similar in size to our own Milky Way. Above and to its right a faint smudge is visible. This is another galaxy, a satellite of the Pinwheel that has been disrupted by its gravity, NGC 5474.
Comet Catalina C/2013 US10 makes its closest approach to Earth tomorrow, the 17th January. By coincidence it also makes its closest pass to M101 on the same date. Hopefully the weather will be kind and some astrophotographers will be able to capture it at higher magnification than I could manage with my mid-telephoto lens. There will never be another opportunity to image this particular comet. After making its closest approach to the Sun on the 15th November it is heading back out of the solar system and will escape into interstellar space.
This image of the Orion Nebula was taken, not with a telescope, but with a camera lens older than myself attached to an entry-level modded DSLR camera. The lens in question is a 200mm SMC Takumar f4. It was manufactured sometime in the early 1970s and I picked it up off eBay for £22. The total exposure time is about 40 minutes, enough to show hints of structure in the larger dust lane the nebula is embedded in. The internal lens iris was used to stop the lens down to f5.6, which gives better star shapes in the corners. However, this has resulted in large diffraction spikes on the bright stars, for this particular shot I’d have preferred to use a step-down ring as a front aperture mask, a cheap and simple way of producing circular stars.
Vintage lenses like this can provide a very cost-effective route into astrophotography. I’ve used a number of different ones of between 24mm and 200mm focal length for a variety of shots. By shopping around carefully I’ve amassed quite a collection, my cheapest cost me £18 while the most I’ve spent was £65. Below are some of the better images I've taken with them.
This slightly wider shot was taken with an SMC Takumar 135mm f2.5 lens (cost £50) at f4, it’s also just over 40 minutes of data. On the left are the three bright stars of Orion’s Belt. Nothing quite divides astrophotographers like diffraction spikes but in this particular shot I quite like them – they highlight the naked eye visible stars which helps place the scene in context. This particular lens has an eight bladed iris, giving eight tight diffraction spikes. On the left are the aptly named Flame and Horsehead nebulae, while the Orion Nebula is on the right. The Horsehead and Orion nebulae are both star-forming regions but the former is at a much earlier stage of evolution. In the Horsehead newly formed stars are hidden by the concentrated dust clouds, while fast stellar winds and radiation pressure the hot blue stars in the Orion Nebula are in the process of expelling most of the gas and dust back into space. Shooting at f4 rather than f5.6 has doubled the amount of light reaching the camera sensor, as a result more structure is visible in the background dust.
Prior to upgrading to the f2.5 lens I was using an even older and cheaper 135mm lens - an f3.5 Super-Takumar from the mid 1960s - which cost me just £18.
This is just 30 minutes of data showing the Heart & Soul Nebulae along with the Double Cluster, in the constellation Perseus. The field of view with this lens on an APS-C camera is about 9 by 6 degrees, for scale each component of the Double has about the same apparent size as a full Moon. There are a few enormous nebulae like this hiding just out of sight.
The image was taken with the lens aperture wide open, at f3.5, giving circular stars but increasing distortion in the corners (it’s more apparent when viewing the image at a larger size). Shooting at f4.5 gives better results but requires longer exposure times to reach the same depth.
For a wider view of the same region I used a borrowed Carl-Zeiss 35mm f2.4 lens at f5.6.
The view is centred on the w-shaped constellation of Cassiopeia, the diffraction spikes help it stand out from the mass of stars in the Milky Way. Also visible near the centre of frame is the Pacman nebula, at this scale its name is merited.
I’ve heard only good things about the Carl-Zeiss lenses but they are quite expensive on the second-hand market. The Takumar lenses by Asahi Optics tend to offer better value for money. Here’s another shot taken with another Takumar lens, a 50mm f1.4 at f4.
This image is about 1h30m on the busy region of the constellation Cygnus. The bright star on the left is Deneb, a distant blue giant about 100,000 times brighter than our Sun. Numerous nebulae are in view, including the North America, Pelican and the Veil supernova remnant.
There are many versions of the 50mm f1.4 Takumar, they are popular as portrait lenses. Mine is a fairly late model, an SMC from the 1970s with 8 aperture blades, which cost me £65. At the other end of the scale, I’ve also had some success using it as a macro lens with the help of an extension tube.
Prior to getting the 50mm Takumar lens I used a new 50mm f1.8 Canon lens, which cost about the same amount. It’s not quite as good as the vintage glass for AP, bright stars produce larger artefacts as can be seen in the shot of Orion below and the corner stars are not quite as good at f4, but it has the advantage of auto-focus for daytime shots.
Another family of cheap lenses worth mentioning are the family of kit lenses commonly supplied with new cameras. While not ideal tools for AP they are still capable of producing good results, as this wider view of Cygnus shows.
This particular shot is just 20 minutes of data taken with an STM lens at 18mm focal length and f5.0.
Vintage lenses giving a wide field of view are rare, making the kit lens the best budget option for Milky Way shots, but I have used a Vivitar 24mm f2.8 lens that was gifted to me.
Shot at f5.6, this view shows the Hyades star cluster at left with the prominent red giant Aldebaran in front of them, the Pleiades and the California nebula. On close examination the lens appears to be heavily infested with fungus and has since been placed in quarantine. We really don’t know if life is common or scarce in cosmic vistas such as the one shown above, but it is certainly present in the optic used to take it.
All these images were taken using a cheap tracking mount, an EQ3-2, from a dark sky site.
Vintage Lens Tips
Vintage lenses can offer good image quality for AP at affordable prices, and also offer some ergonomic advantages compared to modern auto-focus lenses. The focus rings are larger and offer more resistance making them less fiddly to adjust - with my Canon lenses I have to tape or blu-tac the focus ring to stop it creeping out of position. However, there are a few things to watch out for if you are considering buying one.
The lenses I’ve used all have either a M42 (42mm threaded) or Pentax-K (bayonet) mount. These are common types but there are many others, you’d need to check if an adaptor is available for the camera body you own. To muddy the waters slightly, even with an adaptor not all types will reach infinity focus. For example, M42 lenses can be fitted to Nikon bodies but will not focus anywhere near infinity as the element-to-sensor distance is incorrect (Nikon M42 adaptors with a correcting glass element are available but looking at example images this appears to kill the image quality). Here are some combinations that I know to work:
Another thing to be aware of is that if you have a modded camera it may not reach infinity with camera lenses. Mine was modified by Cheap Astrophotography and the sensor was re-shimmed to prevent this issue, but many self modded cameras suffer from this.
Not all vintage lenses are suitable for AP, some will suffer from chromatic aberration where the red and blue light focusses at a different point. Searching online to see if a particular lens has been successfully used is advisable. Prime, fixed focal-length lenses will typically give better results than zoom lenses. Optical design is a compromise and the extra elements in zoom lenses can reduce light transmission and increase distortions. Finally, a small number lenses won’t quite reach infinity even with the correct adaptor, and might need adjustment of the actual lens itself.
If there are any lenses you’ve used for AP please comment below, I’d be interested to hear from you. There are plenty of good optics out there languishing in attics, boxes and the back of cupboards waiting to be claimed. My vintage lenses hail from the 1960s and 1970s, it would be fun to get hold of a really old one just to see what could be done with it.
When it comes to imaging galaxies it's natural to think that a large telescope is required, we picture of Hubble orbiting in space or giant domes on Hawaii or in the Chilean desert. And for the majority this is true due to the vast distances involved. However, there are a handful both large and close enough that they can be imaged with a small camera lens. Conveniently the two with the largest apparent size, that are visible from the northern hemisphere, are close enough in the sky that they can be imaged together.
Shown above are the Andromeda and Triangulum galaxies, our two nearest large neighbours. Andromeda is slightly larger than our own Milky Way and is thought to contain a trillion stars, while Triangulum has a relatively modest 40 billion. The bright star in the middle is Mirach, a red giant roughly a hundred times larger than out Sun. While they are relatively faint objects - the core of Andromeda can see seen through moderate light pollution while Triangulum is only visible from the darkest sites - they occupy considerable real-estate in the sky. Here's the Moon pasted in to give a sense of scale.
The image above was taken with a cheap 50mm lens at f4.5, using an entry-level DSLR camera and a simple tracking mount as shown below. It's about an hours worth of 210 seconds exposures, combined in Deep Sky Stacker and then processed in my usual erratic manner.
For a closer look at Andromeda I used a 200mm lens to take the image below, quadrupling the magnification. The image below has also been cropped for an even closer view.
The yellow core indicates a population of older stars while the bluer spiral arms are a sign of recent star formation. There are two other small galaxies in this image, M32 and M110, both satellites of Andromeda. Our own galaxy also has two prominent satellites, the Magellanic Clouds, that are visible from the Southern Hemisphere. The larger of the two has an apparent size of almost 11 by 9 degrees, twenty times the width of the full Moon. Hopefully someday I'll get a chance to image them on a trip south of the equator.
Finally, here's a wide angle shot taken with a kit lens, showing Andromeda Triangulum relative to the Milky Way. The W-shaped constellation of Cassiopeia is in the centre of the frame but it's quite difficult to spot against the dense starfield.
Kit lenses, commonly bundled with DSLR cameras, offer a natural entry point into astrophotography due to availability and their wide field of view, allowing reasonable exposure times from a fixed tripod. The difficulties for the first time user are finding the correct camera settings and focussing on infinity. This guide offers a few tips based on my own experiences and blunders.
This was one of my first attempts at shooting the Milky Way, taken while on holiday in Menorca. I didn’t have a tripod with me so I simply laid the camera down on the patio, pointing straight up. It’s a 30 second exposure at 18mm focal length with the camera iris wide open, giving a focal ratio of f3.5.
Camera and Lens Settings
It’s worth experimenting with these settings before heading out, to help avoid the frustration of fighting the camera in the dark.
When shooting from a fixed tripod it’s important to gather as much light as possible. Typically this means shooting with the lens wide open by selecting the lowest aperture setting available.
When shooting the image above I’d forgotten to open up the aperture and it was shot at f5.6. As a result less light is reaching the sensor, giving a dim and grainy image dominated by electronic noise. Despite this I managed to accidently capture the Andromeda galaxy at lower right. The aperture setting is something of a compromise, shooting wide open will result in distorted stars in the corners (coma) but this is preferable to a noisy image. (If shooting with a faster lens or a particularly low-noise camera it may be worth stopping down slightly to improve the star shapes.)
At 18mm focal length, giving the widest field of view, exposure lengths of roughly 20-30 seconds are possible before star trailing becomes apparent. The maximum exposure time varies slightly depending on where the camera is pointed. Close to the north and south celestial poles the apparent motion of the stars is slower, so longer exposures can be used. I usually take 30 second shots regardless when imaging the Milky Way, trading a little bit of star trailing for a brighter image.
Users of entry and mid-level cameras will probably get the best results between ISO 800 and 3200. ISO 3200 will show up the Milky Way much more clearly but at the expense of a noisier image; however, this can be greatly reduced in post-processing.
Selecting 2 second timer mode helps prevent any vibration when releasing the shutter, to avoid producing streaky stars in the final image.
Lens Switches and Zoom
Manual focus must be selected on the lens. Also, some lens models have an image stabilisation/vibration reduction switch which may need to be disabled, depending on the model – some are not suitable for shooting from a tripod with this turned on. The zoom barrel should be set to the widest setting, typically 18mm focal length.
The next step is to take the camera outside, preferably somewhere dark. Finding a sharp focus with a kit lens can be challenging as they are quite slow lenses. Optical design is a compromise and the handy zoom ability results in lower light transmittance compared to a fixed focal length prime lens at the same focal ratio. Even at f3.5 only the brightest stars will be visible through the viewfinder or on liveview.
The first step is to find a rough infinity focus. Auto-focus lenses need to be able to focus past infinity so this won’t be quite at the limit of travel of the focus ring. It’s worth checking in daylight which way the focus ring needs to be turned to reach infinity. For a rough focus turn it to the stop and then back a very small amount.
Fine focussing is best achieved using the liveview feature if the camera supports it; I boost the ISO level to 3200 or 6400 after turning the display on to increase the number of visible stars. The next step is to find an object bright enough to focus on, which may not be in the same area of sky as that you wish to image. This is where some familiarity with the sky helps. A software planetarium such as Stellarium (a free download) will allow you to check what is visible from your location at any given time. Here are some suggested targets in order of brightness:
• The Moon. If the Moon is up you can even use auto-focus then click the lens back into manual mode, however this may not give the best possible focus for reasons given below. Also, if the Moon is too bright the sky will be washed out and fewer stars will be visible.
• The planets. Venus, Jupiter, Saturn and usually Mars are brighter than any stars and easier to focus on.
• Failing that, a bright star. Here’s a list of the brightest visible stars, if you aren’t sure where they are located in the sky you can check using Stellarium.
Depending on your location, a light on the horizon may be easier to focus on.
When focussing on liveview it’s better to place the object a third of the way from the edge of frame rather than in the centre, this gives a better focus across the whole frame. This trick appears to work with all lenses. Make small adjustments back and forth, the goal is to make the star as small and round as possible. Another approach is the ‘disappearing star’ trick. Find a star that is barely visible, as the focus ring is tweaked it will pop in and out of view.
Depending on the model the focus ring on kit lenses can slip slightly out of position while shooting, a piece of micropore tape or a blob of astronomical blu-tack can be used to fix it in place.
Framing the Shot
Once the lens is focussed you’re ready to go. The Milky Way is the most obvious target but familiar constellations or asterisms also make pleasing images.
Adding a foreground object can add interest. For the shot below of the Hurlers, an ancient stone circle in Cornwall, I used light-painting to make the stones visible by flicking a torch around the scene for a few seconds. The more distant stones needed to be illuminated for longer.
To speed things up I usually use high ISO ten-second exposures for framing, it can take a few attempts to line everything up correctly. It’s important to tighten all the controls on the tripod as the action of the shutters can shake the camera and produce streaky stars if it’s not secure. For the final shot I typically reduce the ISO level to 1600 or 3200 and increase the exposure time to 25 or 30 seconds.
Shooting from a dark site will help but moderate levels of light pollution can be incorporated into a composition. The glow of street lighting in this image masquerades somewhat as a sunset.
Some simple tweaks in an image processing program to brightness, contrast and colour saturation can greatly enhance an image. For high ISO shots applying a de-noise filter can clean up a background considerably.
I usually present or print my kit-lens images at a fairly small size to hide any defects in the image.
With a little imagination the kit lens has plenty more to give. For example, multiple shots can be stitched together to make a panorama; Microsoft ICE is a free download that does this. It is also suitable for making star-trail images, something I haven’t yet experimented with.
A better lens, such as the Samyang 14mm f2.8, would yield better results due to its superior light-gathering ability. Compare this shot of the Hurlers with the one at the top of the article:
Full-frame cameras produce very little noise and can be used at higher ISO levels, making them the best solution for fixed-tripod shooting, but are expensive. However, an entry-level modded camera on an equatorial tracking mount can easily out-perform them even using the kit lens, as the image below shows.
The image above is just 8 two-and-a-half minute exposures combined using Deep Sky Stacker, using a kit lens on a modded Canon 1100D (EOS Rebel T3 in North America) on an EQ3 mount. The mount can also be used with much longer lenses, bringing smaller deep sky objects into view.
All images by myself, any typos by myself and any trespassing cats.
Here's an image I took of the Veil Nebula in Cygnus, using a 200mm lens. It’s a supernova remnant, the remains of a star that exploded perhaps 5,000 years ago. This event would not have escaped the notice of our ancestors, shining more brightly than Venus for a few weeks and visible during the daytime. We can only wonder what they made of it. (I can't really do the Veil justice with a camera lens, this deep hydrogen alpha image by Sara Wager shows its structure in intricate detail.)
Today the expanding nebula spans 3 degrees of the sky, six times the apparent diameter of the full Moon. The red colour is mostly hydrogen while the blue indicates an abundance of oxygen, glowing at a temperature of several thousand degrees. Most of the visible material is interstellar gas swept up by the supernova shock-wave, but mixed in is a sprinkling of heavier elements such as iron, cobalt and nickel from the core of the progenitor star. If you jangle your keys you’re handling materiel cooked up in an explosion like this.
The rightmost component of the Veil is often referred to as the Witch’s Broom for obvious reasons (astronomer see, astronomer say). Above it lies a dust lane, obscuring the stars behind it. The Witch’s Broom is aptly named, as the Veil expands it's sweeping this dust away and revealing - or unveiling - more stars, making it a functional as well as figurative broom.
Eventually the products of the supernova become mixed into the interstellar medium, where they can be incorporated into the next generation of stars and planets.
A simulated view of the winter constellation Orion to show the difference that observing from a dark site makes, and what long exposure photography can reveal.
From town only the seven brightest stars are visible through the murk of light pollution - if you see more in the left hand pane then your screen, like mine, could probably do with a clean. From a truly dark site a plethora of stars pop into view and the Orion Nebula is clearly visible at lower middle. The long exposure reveals thousands of stars, several nebulae and dust lanes in the Milky Way.
Another advantage of a video like this is that it gives a better sense of the relative brightness between objects. Deep images of the sky are both revealing and subtly misleading - due to the limitations of human vision objects of greatly differing luminosity must be presented at a similar level. With the video the brighter objects appear first.
The source image was taken using a 50mm lens on a modded Canon 1100D camera, with a total exposure time of roughly 75 minutes.
Here's an image of the recent Venus & Jupiter conjunction I shot with a 250mm lens. I then pasted in an image of the Moon taken previously to show their relative apparent sizes. At the time the shot was taken Jupiter was about 11 times further from Earth than Venus but being 11 times larger they appear as roughly the same size. Venus, on the left, appears as a crescent due to the angle of illumination by the Sun. Jupiter on the other hand always shows a full disc as it is outside our orbit. The only way to view Jupiter as a crescent is to go there, as the New Horizons probe did on the way to Jupiter.
Planetary imaging requires a seriously high level of magnification. If my maths is correct - something that can never be taken for granted - Jupiter is about as big as the tip of your finger from 200 feet away. The image below was taken with a 12" newtonian telescope fitted with a 4x barlow lens, giving an effective focal length of 6 metres. The mark to the left is the shadow of one of its moons, Io. The famous red spot was on the far side of the planet at the time it was taken.
DSLR cameras provide a cost-effective route into astronomical imaging, especially as the entry-level models are often just as capable as mid-level ones as far as astrophotography is concerned. However, their Achilles heel is poor sensitivity to deep reds. While not a problem when imaging galaxies and star clusters this greatly limits their ability to image emission nebula, whose light mostly comes from clouds of ionised hydrogen. The glowing hydrogen emits in a specific wavelength with a deep red colouration, and as much as 75% of this light can be blocked by the camera’s infra-red filter.
The solution is to remove or replace this filter. For the brave, there are various online guides for performing camera surgery yourself. Alternatively there are individuals who will perform this service for you. I had my Canon 1100D modded by Cheap Astrophotography and am very pleased with the result.
Here’s two images that show the difference that removal of the filter makes. The first shows Comet Jacques and the Double Cluster in Perseus, taken with the 1100D before modification, using a 135mm lens.
Comet Jacques is the green streak at the lower left, with the Double Cluster right of centre. Above and below the comet some nebulosity is faintly visible. The next image shows a very similar field of view taken using the same lens fitted to a modded camera.
Using the modded camera the Heart & Soul nebulae are clearly visible. The comparison is not an entirely fair one as the second image was taken at a site with very little light pollution, but in other experiments I've found it difficult to get much colour from an unmodded camera even from the darkest site.
While summer isn't the best time for astronomy - hindered by short nights and a lack of full astronomical darkness – there is at least one compensation. For observers at high latitudes in the northern hemisphere the season of noctilucent (night-shining) clouds is almost upon us. These tenuous ultra high-altitude clouds are only visible during deep twilight, being lit directly by the Sun while the observer stands in darkness. They are too insubstantial to be seen when standing directly underneath.
Last Summer I was lucky enough to observe and photograph this rare phenomena, only a week or two after learning of their existence. It took me some time to realise what I was seeing, at first I assumed it was a low and near cloud lit-up by light pollution, but eventually I realised it didn't appear to be moving.
This image, taken at about 1:30AM, was featured on the BBC News website. It’s an 8 second exposure taken with a Canon 1100D DSLR fitted with a 50mm lens.
I was curious as to how far away the clouds were, so I plate-solved the image to identify the visible stars and used a software planetarium to find their angles above the horizon. Noctilucent clouds form at an altitude of about 50 miles, so with a quick bit of trigonometry I was able to work out that they were several hundred miles away. From a location a few miles north of London I was looking at clouds somewhere off the west coast of Norway!
Plate-solved image shows the constellation Auriga on the horizon, with the bright star Canopus at upper right.
So if you find yourself at a dark site between June and August it’s well worth taking a moment to scan your northern horizon. A bright display like the one pictured above is clearly visible even from a moderately light-polluted site, while fainter ones may only show up on long exposure photographs.