APEX Insight: Yesterday, Alaska Airlines adjusted its Anchorage – Honolulu flight plan to allow “umbraphiles” and “eclipse chasers” to view the solar eclipse. There is a growing interest in astronomical tourism – where passengers take a flight specifically to witness events such as eclipses and meteor showers from a vantage point at 30,000 feet above the Earth’s surface. Astrophotographer Colin Legg shares his passion for the skies, and what it’s like to capture striking images through a cabin window.
I have been fascinated with the night sky as long as I can remember. Observing and photographing Halley’s Comet 30 years ago from our backyard in Melbourne is a still a memorable event. In those days there were no fancy digital single-lens reflex cameras; we used film and needed the patience to develop it to see what nuances the pictures revealed that the naked eye could not otherwise see.
Comets are of particular interest as they are one of the origins of meteors. They leave in their wake a stream of debris which is largely made up of particles finer than sand. When the Earth passes through such a trail, the fast speed of the particles imparts a lot of energy as they collide with the atmosphere. We see this as a flash of light as they burn up – what many of us call shooting stars, but are in fact meteors. (If a larger particle happens to make it to the Earth’s surface then it’s called a meteorite). The bigger the particle, the bigger the flash. Occasionally they are even bright enough to be seen in daylight, as evidenced recently in Russia.
Since the orbit of the comet is well known, it is possible to predict in advance when it will intersect the Earth’s orbit. All meteors radiate from this intersection, known as the radiant. You are more likely to see meteors in the quadrant of sky surrounding the radiant, so it is a good place to point your camera.
Capturing meteors in a photograph is like imaging lightning; the shutter need only be open long enough to capture the event. How much meteor light your camera captures is determined by its aperture and ISO. Pupils dilating at night to improve night vision work exactly like aperture blades in your lens: The wider the opening, the better. The second factor, ISO, is a measure of how sensitive the camera sensor is to photons of light. The higher the number, the more sensitive and the more photons captured. Increased sensitivity, however, has a downside, as it’s more sensitive to random noise, which can overwhelm what you are trying to capture.
ESCAPING THE CLOUDS
Digital cameras are becoming so sensitive that now astrophotographers are able to take photos at ISO settings never dreamt of in the days of film. Add help from noise-reduction software and even the amateur can produce spectacular pictures of the night sky. But this all depends on having a cloud-free sky. Clouds are the bane of an astrophotographer’s life. I’ve lost count of the number of times I’ve driven hundreds of kilometers to escape the light pollution of the city for a celestial event, only to be thwarted at the last minute by wispy clouds or smoke haze from bush fires. The best planning is still prone to the whims of Mother Nature.
Escaping clouds is one reason to consider airborne astrophotography. Another is less absorption of starlight across the electromagnetic spectrum as you climb towards thinner air. NASA was onto this in the 1970s with the Kuiper Airborne Observatory (KAO). The KAO, a modified Lockheed Starlifter, was responsible for several important discoveries. Airborne observations continue today, although the KAO has been superseded.
Escaping clouds is one reason to consider airborne astrophotography. Another is less absorption of starlight.
Being airborne also provides a totally different perspective for events like total solar eclipses. Over the years there have been many flights specifically for eclipse observation. It’s reported that in 1887 Dmitri Mendeleev used a hydrogen balloon to get a better view of a solar eclipse on a cloudy day. On June 30, 1973, Concorde 001 intercepted the path of the eclipse over Africa. The scientists on board were party to a rare and grand perspective of the moon’s shadow racing across the Earth’s surface. Only a supersonic jet could keep pace with the shadow and it allowed them to view for over an hour what lasts a mere few minutes on Earth. Chasing eclipses from private or commercial jets is very popular to this day.
While there are viewing advantages from an airplane, capturing a star-filled sky with sharp landscape is still quite challenging. Moon-free starscapes from the ground usually require exposures of 10–30 seconds, but in flight, air turbulence and plane motion typically limit you to one second or less. Only very recently have camera/lens combinations become sensitive enough to achieve this.
On a recent flight from Melbourne to Perth I had the opportunity to try my hand at in-flight meteor photography. The Alpha Centaurid meteor shower was active and the moon was new. I booked an overnight flight home and chose a south-facing window seat near the back of the airplane. While good planning is essential, there are some things besides the weather that you cannot control. Compliant fellow passengers are one. You don’t want to be next to the ones that insist on kneeing your seat or jostling for position on the armrest. Fortunately, I had three seats to myself so I could spread out.
Prior to the flight I fashioned a hood from black felt to block as much interior light as possible. Once onboard, I mounted the camera on a small tripod, placed the hood over it, cut a small hole to reveal the screen and taped the edges to the window frame. Strangely, no one asked me what I was doing. With the lens pushed firmly against the window and the tripod wedged beneath the armrest, I set the camera firing at one frame per second.
I had the camera pointed south toward the Small Magellanic Cloud with the Alpha Centaurid radiant out of frame to the left. In the 20 minutes of smooth flying, I captured four meteors that could be traced back to the radiant. I also captured three others with random orientations, a number of satellites, some green-banded airglow and hundreds of stars. Had the other passengers been aware of what was out their window, perhaps they too could have appreciated the wonder of a meteor.
“Astro Boy” was originally published in The Design Issue of APEX Experience magazine.