Smartphone cameras have come a long way. Once upon a time, most astrophotographers considered deep-sky images of our galaxy to be off limits for the tiny sensors and optics that are packaged into the ubiquitous devices we all keep in our pockets. But slowly and steadily, the technology bundled into these portable cameras has developed and improved. An ongoing arms race, to meet the demands of consumers looking for better low-light photos from their phones, has led giants like Google and Apple to design systems that would have been hard to believe were possible at the dawn of the smartphone age.

With the release of the iPhone 12 range, Apple introduced the ProRAW image format, which retains exceptional quality in the image file. For serious photographers, this was a welcome addition. Two generations later, the iPhone 14 Pro series launched with a 48-megapixel sensor, offering resolutions comparable to that of a much larger camera. The iPhone 14 Pro employs a technique called binning, in which several pixels are combined, to achieve unprecedented low-light performance. The resulting data is easily good enough to withstand a traditional astrophotography workflow, allowing remarkable images to be made. This image of the Cygnus star clouds and surrounding areas of the Milky Way was created entirely from iPhone 14 Pro Max image data.

The image shows good sharpness at the edges of the field, which is quite an achievement for the fast, f/1.8 optics of the phone's main camera lens. It reveals many thousands of individual stars, and beyond them the faint light of billions more partly obscured by clouds of dusty in our galaxy's sweeping spiral arms. Sprinkled throughout the scene are a variety of constellations and deep sky objects. This area of sky, the vicinity of the famous Summer Triangle asterism, is rich with interesting objects, a few of which are visible to the eye. Binoculars or a small telescope will reveal the rest, including nebulae, galactic star clusters and globular clusters.

With such a wide angle of view (equivalent to a 24mm lens) these objects aren't resolved in fine detail, but it's a marvel that they are visible at all. The optics, sensors and electronics involved are minuscule in comparison to traditional DSLR or Mirrorless cameras, yet the iPhone has now become a capable low-light camera for those wishing to dip their toes into the world of astrophotography.

By default, even with ProRAW enabled at the longest exposure time of 30 seconds (composed of three 10-second exposures) the iPhone's images of the night sky show up aberrations in the optics (such as vignetting) and a great deal of noise. With such tiny pixels, even binned images will be subject to a high level of noise, and so for the cleanest result many calibration images must be taken. By using images which record just the noise, as well as the vignetting from the lens assembly, astrophotographers calibrate their images before processing them. The iPhone's ProRAW format is increasingly compatible with astrophotography processing software, allowing this workflow to be applied to data sets that are very convenient to collect.

The superb low-light performance of modern smartphones is a boon for astrophotography, which has traditionally demanded specialist equipment - sometimes bulky, often expensive. The multipurpose nature of the phone, and its compact size, make it a compelling option for would be astro-imagers. Undoubtedly future generations of smartphones will only improve on these capabilities, making astrophotography more accessible and widespread in years to come.

Image credits: Tom Kerss