Star Trails over Cherrapunjee: How 250 Frames Captured a Night of Stars and Storms over Bangladesh

Most people know Cherrapunjee (Sohra) for rain. It has one of the highest average annual rainfalls on Earth, about 11,777 mm. On a clear monsoon night, though, the edge of the plateau is also one of the best viewpoints in Northeast India. It sits about 1,430 m above sea level and looks south over the Bangladesh plains.

This article explains how one photograph was made there. It is a star trail image built from 250 separate exposures. The stars sweep across the sky in arcs, a thunderstorm glows over Bangladesh, and town lights spread across the plains below. It covers why the photograph looks the way it does, the settings used, how the frame was composed, and how the 250 frames became one image. If you want to try star trails yourself, every step here can be repeated.

The two photographs: one frame and the finished image

It helps to compare the two images first.

The single frame is one 30-second exposure, straight from the camera’s RAW file. Even unedited, it holds a lot. The core of the Milky Way runs through the upper part of the frame. Thousands of stars appear as small points. A storm cloud rises on the right, lit from inside by lightning. Lights from the Bangladesh plains glow along the horizon. In this frame the stars look almost still, because Earth only turns a small amount in 30 seconds.

The finished star trail image combines 250 frames like that one. Together they cover more than two hours, and each star becomes an arc. The Milky Way’s soft glow fades into the trails because it moves too, and nothing in the image stays still except the land. The storm looks like a single large outburst of lightning. In fact it is many flashes from separate frames, added together.

Neither image works without the other. The single frame proves the exposure was right. The finished image shows the passing of time.

Why the stars draw arcs

Star trails show Earth’s rotation, not movement of the stars. Earth turns about 15 degrees an hour, so every star appears to circle the celestial poles. Here is the rough sum for this image:

• 250 frames × 30 seconds = 125 minutes of exposure
• 125 minutes × about 15° per hour ≈ 31° of rotation

Each trail in the image covers roughly that angle. The arcs are a little longer in real time, because the camera needs a moment to save each frame.

The direction of the arcs tells you where the camera faced. Bangladesh lies south of Cherrapunjee, so the lens pointed south. From about 25° north, the south celestial pole is below the horizon. The stars therefore trace wide, shallow curves that bend around a hidden centre below the ground. That explains the dome of arcs in this image. Facing north would produce the more familiar circles around Polaris. Facing east or west gives nearly straight diagonal lines.

The colours are real as well. Long exposures show star temperatures more clearly than the eye does. Blue-white trails come from hotter stars and orange-yellow trails from cooler ones.

The setting: why this night worked

Three things came together.

1. A dark, moonless sky. The photograph was taken on 18 July 2023, one day after the new moon on 17 July. The thin crescent set soon after the sun, so it did not wash out the stars. Moonless nights within about five days of the new moon are best for star trails.

2. A break in the monsoon. Clear July nights in Sohra are uncommon and usually short. The frame was recorded at 7:42 pm, just after twilight. That explains the slight blue in the lower sky of the single frame.

3. Night storms over Bangladesh. Thunderstorms over the plains south of the Meghalaya Plateau often peak at night. A study of the Sylhet region found that pre-monsoon rain was concentrated between 6 pm and 9 am. Large, deep storm systems built over northeast Bangladesh from around 9 pm. A photographer high on the plateau can watch these storms from above, while the sky overhead stays clear.

Camera and settings

Setting	Value	Why it works
Camera	Nikon Z6 II (full frame)	Low noise at medium-high ISO; good for long sequences
Lens	NIKKOR Z 24-70 mm f/4 S at 24 mm	Wide enough for sky, storm and plains in one frame
Aperture	f/4 (lens maximum)	Lets in as much starlight as possible
Shutter speed	30 seconds	Long enough for faint stars; short enough to control sky glow
ISO	1250	Bright stars without too much noise or overexposed town lights
Focus	Manual	Autofocus cannot lock on stars in the dark
Exposure mode	Manual	Keeps every frame identical, which is essential for stacking
Frames	250	About two hours of sky movement

Why ISO 1250 and not higher? A higher ISO would show more faint stars in each frame. But Bangladesh’s town lights and the bright storm clouds would have lost detail. In a stack, faint stars are not the main point anyway. The brightest stars make the strongest trails, and those were easily captured at ISO 1250.

What about the “500 rule”? Photographers often use 500 divided by the focal length to find the longest exposure before stars blur: 500 ÷ 24 ≈ 21 seconds. A 30-second exposure is a little longer than that, so if you zoom into the single frame the stars are very slightly stretched. For star trails this does not matter, because the stars are meant to move. What matters is that each frame follows straight on from the last.

Focusing in the dark

This is the step where most beginners go wrong. The lens was in manual focus. The usual method:

1. Switch on live view and zoom in on the brightest star or planet in the frame.
2. Turn the focus ring slowly until the star is as small and sharp as possible.
3. Take a test shot, then zoom in on it and check.
4. Once focus is right, don’t touch the lens ring again. Taping the ring in place is a good habit.

Focus peaking can help, but it is unreliable on stars. Zooming in on a bright star is more dependable.

How the scene was framed

The composition follows a few simple rules, and each one does a job.

Sky above, land below. The horizon sits in roughly the lower third of the frame. The sky, which is the main subject, gets most of the space, and the land still gives the picture a setting.

Two light sources, set against each other. The storm sits just right of centre. The town lights spread along the lower right. Together they stop the image from feeling empty below the trails. The warm orange of the storm and the town also contrasts with the blue trails.

A dark ridge as a frame. The hills on the left are almost black. They give the eye a resting area and push it towards the bright right-hand side.

Foreground plants for depth. The shrubs at the lower right show that the photographer is standing on a real cliff edge. That adds a sense of scale and place.

Facing south on purpose. As explained above, the camera direction sets the shape of the trails. South here meant both broad arcs and the view over Bangladesh. One composition decision gave the image its subject and its look.

The shooting process

Mount the camera on a sturdy tripod. The camera must not move for more than two hours. Hang your bag from the centre column if it’s windy, and avoid extending the thinnest leg sections.

Use the interval timer. The Z6 II has interval timer shooting built in. Set it to fire repeatedly with as little gap as possible between frames. Large gaps cause small breaks in each trail. Nikon’s manual warns that the exposure smoothing option can still allow brightness changes between frames. In fully manual mode with auto ISO off, the exposures stay locked.

Turn off long-exposure noise reduction. It takes a second “dark frame” after each shot, which doubles the time between frames and leaves gaps in every trail. In this RAW file, long-exposure noise reduction is recorded as Off, which is correct.

Consider silent (electronic shutter) shooting. It reduces vibration and saves wear on the mechanical shutter during long sequences. Nikon notes that some features are disabled in this mode.

Plan for power and dew. 250 frames of 30 seconds each, plus saving time, means more than two hours of running. Take a full battery, or use a USB power supply if your camera supports it. On a humid plateau like Sohra, dew forms on the front of the lens quickly. A lens heater strip, or wiping it now and then without disturbing the camera, saves the session.

Shoot RAW. RAW files keep the detail in the storm highlights and the dark sky. They also let you fix white balance consistently across all frames later.

Turning 250 frames into one image

Star trails are built in software using a “lighten” blend. For each pixel, the software keeps the brightest value it finds across all frames. A star that moves a little in every frame leaves a bright point in a new place each time. Combined, those points become a continuous line.

Common tools include:

• StarStaX (free, Windows and macOS), designed specifically for star trails
• Adobe Photoshop: load all frames as layers and set the blend mode to Lighten
• Sequator (free, Windows), mainly for stacking but also has a trail mode

A simple workflow:

1. Edit one RAW frame in Lightroom or Nikon NX Studio: white balance, exposure, noise and lens corrections.
2. Copy those settings to all 250 frames, so every frame matches.
3. Export all frames as high-quality JPEG or TIFF files.
4. Stack them in StarStaX or Photoshop using Lighten.
5. Make final adjustments to contrast and colour on the stacked image.

Why the lightning looks so strong: the lighten blend also explains the storm. Each lightning flash brightened the clouds in only a few frames. But the blend keeps the brightest version of every pixel, so every flash from the two hours ends up in the final image. The storm looks more intense than it would have to someone standing there at any one moment. That isn’t a fault. It is simply how stacking records time.

Other things the stack reveals: In the lower right, near the horizon, a curved dotted line of light shows an aircraft passing low over the plains. Short straight streaks may appear near the storm. Most often these come from aircraft or satellites. You can remove them in Photoshop with a mask, or keep them. Many photographers keep them as an honest record of the night.

Problems you will meet and how to deal with them

Foreground that moves. In the finished image the shrubs on the right look soft, because wind moved them during the two hours. A common fix is to stack only the sky. Then mask in a sharp foreground from a single frame, ideally one taken in calm conditions.

Light pollution. The glow from Bangladesh adds drama, but it also brightens the lower sky. Shooting in RAW and choosing a neutral white balance during editing keeps the glow natural rather than orange.

Clouds crossing the frame. On monsoon nights, clouds can appear without warning. With a stacking method, you can delete frames with heavy cloud. You only lose a short section of trail, not the whole image.

Gaps in trails. These come from pauses between frames: noise reduction left on, a slow memory card, or a long interval. Use a fast card and keep the interval as short as the camera allows.

Bonus: the same frames make a time-lapse

The same 250 frames, played as a video at 25 frames per second, make a time-lapse of about 10 seconds. It shows the stars turning and the storm flashing in motion. Many star trail photographers produce both from one session.

Responsible night photography in Meghalaya

Cherrapunjee’s viewpoints are on steep cliff edges. At night, carry a head torch with a red light setting, which does less harm to your night vision. Check the ground before setting up a tripod. Don’t go alone to remote points. Many viewpoints are on community-owned land, so respect local rules and access timings. Take all your rubbish home.

Conclusion

This photograph needed a dark, moonless sky; a clear gap in the monsoon; a south-facing viewpoint above the Bangladesh plains; and storms that tend to build at night. The technique is simple to describe: a fixed camera, identical manual exposures, 250 frames and a lighten blend. Doing it well takes planning, patience and a few hours on a cliff edge in the dark. The result shows two hours of Earth’s rotation in one picture, above a storm over Bangladesh, taken from one of the wettest places in the world.