Photographing Star Trails Part-2

The first part of the series ‘Photographing Star Trails’ dealt with an introduction and prerequisites of star trail photography. While the star trails photography looks amazingly easy to capture, there is a lot of planning that goes behind creating those stunning images that make everyone go “Wow!”.

What is a Star Trail?

Many people see a star trail image and wonder ‘Where on Earth can I see this phenomenon?’ To understand a star trail image some explanation is required. This is not some instantaneous phenomena which can be seen with your eyes. In a normal situation, you can’t see any of the stars in the sky moving, but all the stars are steadily moving across the sky. You see – the Earth is rotating, once in 24 hours!
A star trail is a type of photograph that uses long exposure times to capture the apparent motion of stars in the night sky due to Earth’s rotation. A star-trail photograph shows individual stars as streaks across the image, with longer exposures yielding longer arcs.

The travails and travels of star trail photos

A surprisingly satisfying amount of planning goes into making star trail images. I and my better mate in astrophotography, as well as life – Neelam Talwar, plan our star trail images sitting at home. Neelam goes on her flight duties to interesting cities of the world and comes back with a bucket full of sequential images, which then I process into star trail images. Let me explain with a couple of examples.

Prominent Locations

You should plan your star trails at prominent locations wherever it is possible for you to go. Neelam was on a flight duty to Sydney and the most famous icon is the Harbour Bridge. Sydney- siders call it ‘The Hangar’ because of the resemblance. Everyone in the world also knows about the Opera House nearby. We wanted to shoot the South Polar Trails in the sky along with these two icons on earth. What would be the possible location where we could capture all three in one image? Google Earth helped us and we identified the location of Luna (amusement) Park across the harbour, where the South Celestial Pole would be visible above the Hangar and the Opera House would be visible below. Neelam spent the entire cold night at Luna Park to collect the 650 images that went in to making this image.

Dark locations

Dark locations, i.e. places where you cannot see many city lights. Such places are getting rare by the day. Unfortunately, the Milky Way is becoming a mythical being just like the unicorn, due to omnipresent city lights. Western Indian Himalayas have many choice locations which are really dark, dry and conducive for astrophotography, especially the high altitude desert of Ladakh. But it is not always possible to travel long distances and you long for a nearby dark location. Here is an example of Milky Way and star trail image from a place called Saragthal in Haryana, which is 76 km northwards of my place in the middle of fully lit Gurugram.

How did I find the dark location of Saragthal? By using Google Earth and a special layer of Earth Lights provided by NASA. Here is how (see the screenshot of Google Earth). Neelam and I went on a one-night observation trip to Saragthal and came back with this fantastic image from a nearby dark location.

Kepler’s Observatory, the site of our Star Trail Workshop, is one such place which is really close- by to Delhi and Gurugram.

Vantage locations

Vantage locations, where the eye can see till far distances, are really conducive for stunning star trails. Inside the city, you can look for high rise buildings, where you will be allowed to photograph for long periods without interruptions. The foothills of the Himalayas offer many such locations where you can see till far off in the plains. Look for such locations to go and shoot star trails. Here is an example from Surkhanda Peak, which is near Dhanaulti and about 25 km from Mussoorie. Looking southwards from the peak you can see Dehradun, Shivalik Range, and Roorkee. Towards the north, you can see many snowcapped Himalayan peaks of Uttarakhand.

Neelam and I trekked up the steps leading to the peak one evening and made this image from the vantage location. It was the evening of the Holi Full Moon Night, this year. Here is the image.

Vintage locations

Since 1937, 82 years back. This is probably the most photographed bridge in the world, a vintage location. Need I say more?

When to go out? Weather, temperature, phase of Moon, do you want moon or don’t want moonlight?

Check the weather before you go out, In India the clear winter months after the monsoons have settled the dust, are best. The Himalayan skies are also clear and fully studded with stars. Deciding the phase of the Moon is important. A moonless night will have a dark sky, but if you are after a nightscape, i.e. a night landscape image, you better plan for a night when the Moon’s phase is half or less. The landscape would be beautifully lit by the natural moonlight. Here is an example from Narkanda on a full moon night. Neelam and I had especially traveled to the location in the month of January, after carefully watching for the weather. There was rain in the plains, and snowfall in the hills. Just as the snow and rain settled, we immediately made for Narkanda, even though the phase of Moon was full.

Star Trails in the city & Prominent Constellations

Photographing star trails in the city call for really short exposures to subdue the city lights below. Whereas at a dark location you would be shooting exposures of 20 seconds to 40 seconds or even more according to the ambient lights, but while shooting star trails at a city location you need to carefully manage the exposures. The length of the exposures needs to be short, as short as 2-3 seconds. Again the ambient light dictates the length of the individual exposures.

Plan to shoot city star trails in the direction of prominent constellations which feature bright stars. Orion is a very popular winter constellation, a region of the sky which contains bright stars. Another bright constellation to consider is Ursa Major towards the north, Sagittarius and Scorpius are bright summer constellations towards the south. Other bright constellations to consider are Cassiopeia & Perseus; Cygnus, Lyra, and Aquila; Taurus and Canis Major on either side of Orion are bright constellations.

How do you find these bright constellations in the sky, on a particular date, season and time of the night? Plan for these constellations using planetarium software. On your desktop, you can use Stellarium. On your smartphone, you could use Sky Safari app. You can set the location, date and time in the software. You can even run an animated sky motion at any speed and plan your shoot.

Here is an image showing the famous skyline of Manhattan on the Earth and the bright Hunter in the sky, i.e. the Orion constellation.

As I said before a surprisingly satisfying amount of planning goes into making star trail images.

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