A lone tree, a watcher and the Pleiades: reading a night sky photograph

A long, straight raised bank runs across the middle of the photograph. On it stand a single small tree and, a little to the left, a person with hands on hips, looking at the sky. Above them the sky is full of stars, with a few pale clouds drifting through. In the foreground, a still pool reflects all of it upside down: the person, the tree, the clouds, and even some of the brighter stars.

The image is simple, but it holds more than it first seems: a well-known star cluster, a star with a place in Indian astronomy, signs of Earth’s rotation, and several photography decisions that made the picture work. This article goes through each of them.

What is in the sky

The Pleiades: the small, bright cluster at upper right

The tight group of blue-white stars at the upper right is the Pleiades, also known as Messier 45 or the Seven Sisters. In Indian astronomy it is Krittika, one of the 27 nakshatras (lunar mansions).

The Pleiades is an open star cluster: a group of young stars that formed together from the same cloud of gas and dust. Most people can see six or seven stars with the naked eye. Binoculars show dozens, and the cluster contains many hundreds in total. NASA gives its distance as about 400 light-years, and other recent estimates are a little higher. The light in this photograph left the cluster centuries ago.

The blue-white colour in the photograph is real. The brightest Pleiades stars are hot, massive and young, astronomically speaking: only around 100 million years old, compared with about 4.6 billion years for our Sun.

The Hyades and Aldebaran: the V below

Below the Pleiades and slightly to the right is a looser group of stars arranged in a V shape. This is the Hyades, the nearest established open star cluster to Earth. NASA gives its distance as about 151 light-years.

The orange star at the tip of the V is Aldebaran, the eye of Taurus, the bull. Indian astronomy knows it as Rohini. Aldebaran looks as if it belongs to the Hyades, but it doesn’t. It lies along almost the same line of sight, at less than half the cluster’s distance. It is an orange giant: an older, cooler star that has swollen to many times the Sun’s size. That is why it looks orange next to the blue-white Pleiades.

What the positions tell us

The Pleiades and Hyades rise together in the east. As seen from northern India, when they are rising, the Pleiades sits higher and the Hyades lower and to the right. That is exactly their arrangement in this photograph, so the camera was facing roughly east, with Taurus climbing above the horizon.

Taurus rises in the east in the evening around October and November, and before dawn around July and August. The warm glow along the left horizon could be early dawn, or simply light from a nearby town. The photographer’s notes on the date and time would settle it.

Signs of movement

Look closely at the stars and you’ll see they are not perfect points. Most are short streaks, all slanting the same way. During the exposure, Earth turned slightly, and each star moved a little across the frame. This is the start of a star trail. The streaks are short enough to keep the stars looking like stars, but long enough to show that the exposure lasted several seconds or more.

The clouds have smooth, soft edges for the same reason. They drifted while the shutter was open, and their shapes blurred. The tree and the person are sharp, because they stayed still.

The reflection: why the water mirrors the stars

The pool in the foreground is the most unusual part of the picture. It reflects the tree, the figure, both clouds and many of the brighter stars, Aldebaran among them.

The water could only do this because there was no wind. Even a slight breeze breaks the surface into ripples, which scatter the reflection. Calm nights, often after rain, give the best mirror effect. The reflection is darker than the sky because water reflects only part of the light that falls on it. Fainter stars disappear in the reflection, and only the bright ones remain.

The reflection also does something for the composition. It doubles the subjects, gives the bottom of the frame a purpose, and makes the image feel balanced from top to bottom.

How the photograph is composed

The horizon sits a little below the middle. This leaves room for the sky above and for the reflection below. The bank creates a strong horizontal line that divides the image into sky, land and water.

Two silhouettes, not one. The tree is near the centre and the person stands to the left. The gap between them is wide enough that neither crowds the other. Together they form a small, quiet scene: one person standing on an open bank under a large sky.

The human figure gives scale. Without the person, the tree could be any size. With the person there, the viewer immediately understands how large the land and sky are.

Silhouettes against the brightest part of the sky. The figure and tree stand against the paler glow near the horizon, so their outlines stay clear. Against a dark part of the sky, they would almost vanish.

The clouds point towards the subjects. The line of clouds runs diagonally from the upper left down towards the tree, leading the eye to the centre of the picture.

How to take a similar photograph

The photographer’s camera settings are not available, so the following is general guidance for this kind of scene.

Equipment. A camera that allows manual settings, a wide-angle lens (about 14–24 mm on a full-frame camera), and a steady tripod. A lens with a wide aperture, f/2.8 or larger, helps a lot.

Choose the right night. Pick a night near the new moon, with little or no wind, ideally after rain has left standing water. Check where Taurus or another target will be using a free planetarium app such as Stellarium.

Suggested starting settings.

• Aperture: as wide as the lens allows (for example f/2.8)
• Shutter speed: 10–20 seconds with a wide lens. Longer exposures give more obvious streaks, as seen here.
• ISO: 1600–3200, adjusted after a test shot
• White balance: set manually, around 3800–4500 K, so the sky doesn’t turn too orange
• Format: RAW, so you can reduce noise and fix colour later

Focus. Switch to manual focus, zoom in on a bright star in live view, and adjust until the star is a small, sharp point.

Place the person. Ask the person to stand completely still for the whole exposure, against the brightest part of the sky. A clear outline, with hands on hips or a hand raised, reads better than a person with arms tight to the body.

Get the reflection. Set the camera low, close to the water’s surface. That makes the reflected area larger and keeps both the bank and its reflection in frame.

Deal with noise. High ISO and low light leave grain, which is visible in this photograph, especially in the sky. Use moderate noise reduction in editing. Too much will smear the fainter stars. Taking several frames and stacking them in software is another way to cut noise.

Safety at night

Water edges and embankments can be slippery and uneven in the dark. Take a head torch with a red light mode, go with a companion, tell someone where you are going, and watch out for snakes in grass near water, especially in warmer months.

Conclusion

The photograph has three layers: stars and clouds in the sky, a person and a tree on the land, and their reflection in still water. The stars include the Pleiades (Krittika), the Hyades, and Aldebaran (Rohini), and their positions show the camera faced east as Taurus rose. The short streaks of the stars show Earth’s rotation during the exposure. Calm air, a low camera position and a subject who stayed perfectly still made the reflection and silhouettes possible.