Astrophotography with a phone

The steady mount

Taking photos of the night sky with a modern smartphone is surprisingly capable, but the absolute first rule is stability. Even a tiny hand tremor will turn a crisp star into a blurry streak. You do not need expensive tracking gear, but a basic plastic clamp that attaches your phone securely to a sturdy camera tripod is essential. If you are shooting through an eyepiece, a dedicated smartphone adapter that locks onto the plastic barrel will save hours of frustration. “Holding the phone by hand is a recipe for blurry failures,” says local amateur photographer Sarah Lin. Adjusting the clamp so the phone camera lens aligns perfectly with the glass of the eyepiece takes patience, but once locked down, it stays put.

Manual settings and focus

Autofocus is designed for daytime scenes and will fail completely in the dark. Switch your phone camera to its manual or pro mode to take full control of the sensor. Set the focus manually to infinity, which is often represented by a mountain icon on the slider, or pull it back just a fraction of a millimeter if the stars look slightly bloated on your screen. Set your sensitivity, or ISO, between 800 and 1600 to capture faint light without introducing too much digital noise that ruins the image. Your exposure time, or shutter speed, should be set between one and ten seconds depending on the brightness of your target.

If you are aiming your telescope at a bright target like the moon, a fast shutter speed of perhaps one-hundredth of a second is necessary to prevent washing out the surface details. For fainter targets, you might find yourself finding galaxies by taking longer exposures through the eyepiece, though tracking the sky’s movement becomes a factor during long shots. Using a two-second delay on the shutter timer prevents the vibration of your finger tapping the screen from ruining the shot… a simple trick that immediately improves image sharpness. You can also use a wired pair of headphones, using the volume button as a remote shutter release.

Aligning the optics

Before you even attach the phone, make sure your telescope is pointed exactly at your chosen target. Trying to locate a faint target on a small screen is incredibly difficult. It is much easier to align the target in a low-power eyepiece first using a red dot finder to get it dead center in your field of view. Once the target is perfectly centered, gently swap in the phone mount without bumping the telescope legs. If you are tracking a moving target, like a faint comet tail drifting across the field of view, make small, gentle adjustments to the mount controls rather than forceful shoves.

Processing your images

The raw photo straight from your phone is only the beginning of the creative process. Most modern smartphones allow you to shoot in RAW format, which preserves much more detail in the shadows and highlights. Transfer these files to a computer or use a mobile editing application to adjust the black levels and contrast — simple sliders found in most apps — to clean up the frame. By pulling the black point up slightly, you can darken the gray sky background and make the stars pop against the darkness. Do not over-process the image with heavy noise reduction, as this can wash out faint stars, turning them into soft smudges rather than sharp pinpoints of light.