The Secret to Great Astronomical Photography
Copyright: Mark Gee/National Maritime Museum
Traveling through capital cities is always a stressful occasion and this time was no exception. I had left myself a whole hour to get from the train station to the Royal Observatory Greenwich in London for The Astronomy Photographer of the Year 2013, and it seems an hour was only just enough! But once I'd arrived, I settled back in the very comfortable seats of the Peter Harrison Planetarium and the lights dimmed as the winning photographs were presented to the excited audience. There was a tangible buzz as the images appeared right over our heads on the inside of the planetarium dome against a beautiful background of glittering stars.
This years winners did not disappoint, there was a wide range of skills and techniques on show from the stunning "Deep Space" category where the photos had taken literally days to capture and process to the simple yet enigmatically beautiful "People and Space" category. As I watched the beautiful images appearing above me it reminded me just how powerful images of space can be in communicating the wonder of the Universe. The shortlisted photographs entered into the competition came from 49 countries. The overall winning image was taken by Mark Gee from Australia and was titled 'Guiding Light to the Stars' (shown here), depicting the stunning sight of the Milky Way with a glowing beacon of a lighthouse to the right of the scene. The composition reflects the way the stars used to be employed as a way of navigation in contrast to modern navigation techniques. Mark's image also won the "Earth and Space" category.
Copyright: Adam Block/National Maritime Museum
Adam Block from the United States won the Deep Space category with his image called "Celestial Impasto." The picture beautifully captures the delicate shades in the dust and dark nebulae of Sh2-239 in the Taurus molecular cloud about 450 light-years away.
Copyright: Man-To Hui/National Maritime Museum
The winner of the "Solar System" category was Man-To Hui from China with this beautifully captured image of the Australian solar eclipse of 2012. Phenomenal levels of detail can be seen in the usually hidden solar corona which can only be seen at the moment of totality during a solar eclipse.
Copyright: Jacob Marchio/National Maritime Museum
Jacob Marchio from the United States was the winner of the Young Astronomy Photographer of the Year and at the age of 14 was able to capture this beautiful image captioned simply "The Milky Way." The image is a beautiful reminder of our place in the Universe as the stars from our galaxy shine with a lovely warm glow.
Copyright: Mark Gee/National Maritime Museum
There were three special categories too this year, the first "People and Space" was won by Mark Gee with this beautifully composed image of an observation platform silhouetted against the moon. Mark took this picture from a distance of about 3 kilometers and used a zoom lens to get the shot.
Copyright: Sam Cornwell/National Maritime Museum
The winner of the Sir Patrick Moore Prize for Best Newcomer was Sam Cornwell form the UK who managed, against the odds of the British weather, to capture a glimpse of the 2012 Venus transit just before it finished. The cloud really adds atmosphere to the picture and wonderfully represents the challenges facing astronomers suffering adverse weather conditions.
Copyright: László Francsics/National Maritime Museum
The Robotic Scope Image of the Year was picked up by László Francsics from Hungary with an amazing picture of the famous Trapezium Cluster in the Orion Nebula.
Copyright: Fredrik Broms/National Maritime Museum
The shifting lights of the Aurora Borealis can take on many shapes and forms as they are molded by the Earth’s complex magnetic field. Sheets and planes of glowing gas appear to be twisted into a giant vortex above Grøtfjord in Norway.
Copyright: Dani Caxete/National Maritime Museum
All of the light which reaches the ground from space must first travel through the Earth’s atmosphere. During its journey the light can be altered by all sorts of atmospheric phenomena. Tiny ice crystals high above the ground refract the moonlight diverting it into a number of beautiful halos.
Copyright: Fredrik Broms/National Maritime Museum
Like the snowy mountains in the foreground, the nucleus of Comet Panstarrs is composed largely of ice and rock. The nucleus itself is just a few kilometers across but as it neared the Sun in early 2013, ice evaporating from the surface formed a tail of gas and dust hundreds of thousands of kilometers long.
Copyright: David Kingham/National Maritime Museum
A great deal of careful planning, a long night of photography and hours of painstaking image processing have gone into creating this startling composite image of the Perseid meteor shower. The Perseid meteors get their name from the constellation of Perseus from where they appear to come. However, even at the peak of the shower it is impossible to predict exactly when or where the next meteor will appear. The photographer has combined 23 individual stills to convey the excitement and dynamism of this natural firework display.
Copyright: Tom O’Donoghue/National Maritime Museum
The smoky appearance of the dust clouds in this image is fitting, since the grains of dust which make up the nebula are similar in size to particles of smoke here on Earth. The dust can reflect the light of nearby stars, as seen in the blue and yellow regions. It can also block and absorb the light of more distant stars, appearing brown and black in this image. To the right a bright star is ionizing a cloud of hydrogen gas, causing it to glow red, while below it far in the distance, is a globular cluster containing thousands of stars.
Copyright: Michael Sidonio/National Maritime Museum
First discovered by astronomer Caroline Herschel in 1783, NGC 253 is a rare example of a ‘starburst galaxy’ with new stars being formed at many times the rate in our own galaxy, the Milky Way. Its mottled appearance comes from extensive lanes of dust which thread through the galactic disk. These are studded with many red clouds of ionized hydrogen gas, marking the sites where new stars are being born.
Copyright: Ivan Eder/National Maritime Museum
Lying at a distance of twelve million light years from Earth, M81 and M82 are galaxies with a difference. Close encounters between the two objects have forced gas down into their central regions. In M81 this influx of gas is being devoured by a supermassive black hole. In neighboring M82 the gas is fueling a burst of new star formation which in turn is blasting clouds of hydrogen (shown in red) back out into space.
Copyright: Diaz Bobillo/National Maritime Museum
Omega Centauri is a globular cluster, a spherical cloud containing several million stars. As this image shows, the stars are more densely clustered towards the center. The pronounced red color of several of the stars gives away the cluster’s great age: it is thought to have been formed billions of years ago. The cluster was first noted by the astronomer Ptolemy almost 2000 years ago and cataloged by Astronomer Royal Edmond Halley in 1677.
Copyright: Ariana Bernal/National Maritime Museum
The awesome scale presented in this image depicts what as far as we’re concerned, are the three most significant objects in the Universe. The Sun and Moon each play an important role to us on Earth, and both are seen here, reddened by our vital atmosphere, presiding over the horizon. The third object is the Earth itself, and here its land, sea and sky meet around an amazing human megastructure, San Francisco’s Golden Gate Bridge.
Copyright: Samuel Copley/National Maritime Museum
The Great Nebula, also referred to as The Orion Nebula and M42 is found in the well-known constellation of Orion, just below the hunter’s belt. To the naked eye the nebula looks like another star in Orion’s sword. However, this skilful young photographer has shown there is more to it than meets the eye by producing this beautiful image that not only shows the stunning formation of this popularly observed nebula but also it diffuse nature.
Copyright: Jacob Marchio/National Maritime Museum
The Moon seems to be emerging from the interplanetary darkness, and the young photographer has captured the contrast been the dark lava-filled lunar ‘seas’ and the mountainous southern highlands.
Copyright: Eric Dewar/National Maritime Museum
By keeping the camera shutter open this young photographer gathers precious light, making the desert scenery seem as bright as day. But the stars in the blue sky give the game away, showing that this dramatic photograph was actually taken in the middle of the night.
Copyright: Ben Canales/National Maritime Museum
Appearing like a column of smoke rising from the horizon, a dark lane of dust marks the plane of the Milky Way in this photograph. This dust plays a vital role in the life story of our galaxy. Formed from the ashes of dead and dying stars, the dust clouds are also the regions in which new stars will form.
Copyright: Alan Friedman/National Maritime Museum
The darkest patches or ‘umbrae’ in this image are each about the size of Earth, with the entire region of magnetic turmoil spanning the diameter of ten Earths. This image captures rich details directly around the sunspots, and further out in the so-called ‘quiet’ Sun where simmering hot plasma rises, cools and falls back. This produces a patchwork surface like a pot of boiling water, but on an epic scale – each bubbling granule is about the size of France.
Copyright: Ignacio Diaz Bobillo/National Maritime Museum
At a glance, this image may seem like a post-processed montage of objects from three separate images. However the truth is that they were all captured together providing the viewer with an amazing view of the Solar System, galaxy and Universe. Comet Lemmon only comes into our neighborhood every 11,000 years, racing around our Sun and back out to the far reaches of the Solar System. The light from the globular cluster in the center of this image took a journey of over 16,000 years to reach Earth. The furthest object in the image is a dwarf galaxy called the Small Magellanic Cloud whose starlight takes 200,000 years to reach us.
Copyright: Jia Hao/National Maritime Museum
The Moon’s orbit about the Earth is not perfectly circular, so that at different times the Moon can be slightly closer or further away than usual. If the Moon passes in front of the Sun when it is at its furthest point, it will appear to be too small to entirely cover the solar disc. This is an ‘annular eclipse’ in which a ring, or annulus, of the Sun remains visible. This composite shot shows the progress of an annular eclipse in May 2013. Close to the horizon the distorting effects of Earth’s atmosphere can also be seen.
Copyright: Damian Peach/National Maritime Museum
This incredibly sharp portrait brilliantly captures the jewel of our solar system, revealing the subtle banding around the orb that results from the planet’s weather. It also shows the exquisite gradation of brightness and color in the planet’s rings. The ultra-faint inner ‘D-Ring’ and outermost Encke gap are clearly visible. The hexagonal storm at the North Pole – a scientific curiosity – shows off three of its angular kinks. Images with this much clarity challenge our ideas of what can be achieved with amateur telescopes.
Full resolution versions of these photographs can be found on the National Maritime Museum (www.rmg.co.uk/astrophoto). All photographs are credited to the respective photographers and the National Maritime Museum. Photo captions for the winning entries are written by Mark Thompson; captions for runners up and highly commended entries are courtesy of the National Maritime Museum and Astronomical Photographer of the Year 2013.
We are constantly being wowed by stunning space imagery from amateur and professional astronomers alike. There is clearly a lot of skill in acquiring these pictures and a great knowledge of image processing is critical for success. However, the one task that is key to master is that of "polar alignment."
I remember when I was new to astronomy and the thought of polar alignment struck fear into my heart, but getting an accurate alignment of your telescope to the axis of rotation of the Earth is actually quite simple and essential for excellent astronomical images.
Getting good polar alignment is a two stage process:
Step 1: Get it Rough
The object of rough polar alignment is to get the mount set up so that it is approximately aligned; this will generally be enough for visual work but is also a necessary step to make the precise polar alignment phase easier.
Identify your telescopes declination axis and take a close look to find the scale around it from 0 to 90 degrees. Rotate the telescope about this axis until it’s at 90 degrees. It should now be roughly pointing along the polar axis.
Now you need to adjust the angle of the whole mount so it is the same as the latitude at your location and for that, equatorial mounts have a latitude scale. So, the next step is to adjust the latitude scale to equal the latitude of your observing site. Your telescope mount should now be pointing roughly in the right direction.
Next, wait for nightfall and identify Polaris, the Pole Star. Polaris is easy to find in the night sky -- follow the two pointer stars in the bowl of the Plough (part of the constellation Ursa Major). Now move the entire telescope mount so the telescope tube is pointing toward Polaris.
If you have set the mount up correctly, then Polaris should be visible in the field of view of the finder telescope. Now you just need to make minor adjustments to the mount by adjusting its left-right position and your latitude setting to center Polaris. Assuming your finder telescope is aligned well, then you should now see Polaris in the field of view of an eyepiece. Your telescope is now roughly polar aligned and that will be enough for visual observing.
Step 2: Accurate Alignment
Assuming your goal is long exposure imaging, then it is worth spending time getting your mount precisely polar aligned. The first time you do this, expect to spend an hour or two fiddling around, but you will soon get it down to a fine art. Time spent here is worth while and the benefits will be gained in the quality of your final images.
The technique relies on observing the drift of stars through the eyepiece and slowly fine tuning your polar alignment.
You need an extra piece of equipment to perform this task, an "illuminated reticule eyepiece." This is an eyepiece that has either a cross etched into the lens or thin wires forming a cross. These are illuminated by a faint bulb inside the eyepiece. They can be bought from most astronomical suppliers.
To start, identify a star that is roughly due south, or preferably a little to the left of due south and within 5 degrees of declination from the celestial equator (the celestial equator is the extension onto the sky of our own equator). Center this star in the field of view of the telescope so that it lies on the illuminated cross. Now, using the slow motion controls of the telescope, move it east and west in right ascension. Adjust the illuminated eyepiece so one axis of the cross follows that line and the star moves slowly back and forth along it. With the motor running, observe how the star moves, ignoring any left-right movement, just looking at up and down.
If it moves down, the polar axis of the telescope is too far to the west (or to the left of Polaris). If it moves up, the polar axis of the telescope is too far to the east (or to the right of Polaris).
Using the mount’s azimuth adjustments, make appropriate changes to correct. Now re-center the star and perform the same step again. It will take a few attempts but eventually there will be zero drift up or down for a good 5 minutes or more.
Now find a star near the eastern horizon, ideally it should be 20 degrees above the horizon, no more and fairly close to the celestial equator. Center it on the cross like before and align the cross so that east-west right ascension movement takes the star along one axis of the cross. Now monitor the star (with the motor still running).
If it drifts down, the polar axis of the telescope is too low. If it drifts up, the polar axis of the telescope is too high. (Note: if you don’t have a good eastern horizon, a star in the western horizon will work fine but the notes above regarding adjustments required will need to be swapped.)
Make adjustments to the elevation of the polar axis as appropriate, re-center the star and check the drift again. Once drift is eliminated, go back and check with the star due south and once that has been rechecked, your telescope will be very accurately polar aligned and objects will stay in the center of the eyepiece or more importantly your camera.
Take the time to really nail this and get it accurately polar aligned and with some practice you will achieve alignment with incredible accuracy. If you want to increase your accuracy and the speed of the process, insert a Barlow lens (which usually doubles or triples the magnification of the eyepiece) so drift will be noticeable much quicker. You will also be able to polar align to a greater accuracy. With my telescope, I can get a star centered with a magnification of about x200 and it stays there for about 10 minutes! That's good enough for me.