It’s a common refrain, heard at many a modern star party. “Can I take a photo of that?” an eager viewer will say, pulling out their smartphone and activating their camera.
It’s a noble effort, though first-time smartphone astrophotographers soon learn the limits of their handheld cameras.
You can, with practice, simply shoot bright targets with your phone by simply hovering over your eyepiece using the afocal alignment method. The limits of the exit pupil size of your phone’s camera versus the eyepiece, however, quickly becomes apparent, as the view bobs around on the screen, in and out of focus.
While this will work for bright targets requiring short exposures such as the Moon or the (filtered) Sun, controlling the phone while holding it steady can be a tricky, three-handed operation. A phone clamp works great in this regard, and several models such those made by Orion, Antares and Gosky are targeted specifically toward astrophotographers. A good phone clamp will hold the phone steady, while allowing for minute positioning changes by the user.
Good targets for Smartphone Astrophotography
The Moon, of course, is an easy and obvious starter target. I’ve even seen some pretty decent shots of the Sun in hydrogen-alpha taken with a smartphone through a Meade Coronado Personal Solar Telescope. It is now possible to go after fainter targets such as planets – and even brighter Messier objects – with a smartphone and a telescope, and apps such as DeepSkyCamera for Android will make captures in RAW/DNG file format suitable for post-processing.
After focusing, image acquisition is the next critical key. An equatorial tracking mount with free you up from hand-guiding, though it is possible to capture images using an alt-azimuth mount. You’ll want to use the ‘Pro-mode’ to adjust the ISO/F-stop/and shutter settings down to an acceptable level of contrast.
‘Night mode’ and ‘astrophotography mode’ are becoming the latest ‘must have’ features on modern smartphones. I currently use an Android Samsung S9 Galaxy, which will take you down to an exposure of 10 seconds; the latest Android Samsung Galaxy S21 phone can do 20-second exposures. The newer Huawei phones also offer an astrophotography mode. Curiously, Google killed the touted ‘astrophotography mode’ for its Pixel 4/5 phones in late 2020.
‘Time exposure’ and ‘night mode’ applications open up another exciting option of using panorama mode – and the phone on its own – for astrophotography. These apps mean you’ll be mounting the phone on a tripod, and triggering the virtual shutter via timed release mode, to avoid shaking the camera during the exposure – much like using a cable release back in the film era.
This setup will allow for wide-field captures of aurorae, satellite passes and Milky Way versus foreground objects. A bright comet, such as last summer’s F3 NEOWISE, would also make for a fine smartphone capture. As with imaging with a DSLR camera, you’ll want to image from a dark-sky site and use as high an ISO as you can get away with, so as to not overexpose and ‘wash out’ the sky background.
Smartphones are changing quickly, and the market is keen on competing to bring users the very best in compact camera technology. Smartphone cameras have also evolved from gadgets of curiosity to serious cameras, and now offer amateur astronomers a great option for entry-level astrophotography.