I’m often asked how I am able to take high-quality images of the solar system using my iPhone. In short, the quality of today’s smartphone cameras makes it possible to take very respectable images of the Moon and planets through a telescope with your phone – but it takes some work.
While the end results may not match those taken with webcam or DSLR equipment, smartphone astrophotography can be a good starting point for budding astrophotographers. It can also be a useful alternative for experienced astronomers who wish to capture an image quickly with little equipment.
What You Need
1) A Smartphone Adapter
The simplest way to take a photo at the telescope is to simply hold your phone’s camera up to the eyepiece, but this approach rarely produces good results. Not only is it very difficult to centre the object properly, it can be tricky to ensure that the object is well exposed.
A simple adapter will improve your smartphone astrophotography immensely. An adapter will help you centre an object in the phone’s viewscreen, steady the camera, and ensure proper focus and exposure. A handful of companies are now producing adapters, including Orion whose adapter for iPhone 4s (no longer available) is pictured here. Orion also produces a Universal Smartphone Adapter (mobile-friendly link here) that is said to fit most phone brands and which is what I now use.
Here’s a video of the Orion Steadypix in action to give you a sense of how an adapter is used: http://youtu.be/ej9uj5fsbDo?t=5m
2) A Way to Dim the Object
While smartphone cameras have excellent resolution, many don’t yet have the manual exposure control settings needed to evenly expose the entire lunar disc or to capture subtle planetary features. You’ll often find Jupiter, Saturn, Venus, and Mars to be much too bright on the camera screen by default. iOS 8 has incorporated good exposure controls for the iPhone camera that I often find do the trick to dim the image and bring out the right amount of detail – but usually only in video mode. If you don’t want to record video and stack the frames to create images (more on that later) or if your smartphone doesn’t have powerful enough exposure control on its own, you’ll need to use eyepiece filters
(mobile-friendly link here) such as an a variable polarizing Moon filter (mobile-friendly link here) and/or a coloured filter to reduce the object’s brightness in the eyepiece.
The magnification you’re using – and the magnitude of the object itself – will
determine how bright or dim the object will appear to the camera. A nearly-full Moon through a low-powered eyepiece will require a dark filter, while a crescent Moon at dusk may not require a filter at all. If you don’t have an adjustable Moon filter, a coloured filter can sometimes work to reduce brightness just the right amount for a planet like Saturn.
By default, a smartphone will capture Jupiter or Venus as a bright, over-exposed blob. Using your phone camera or app’s exposure controls or a Moon filter, you can reduce the brightness of Jupiter’s disc and bring out important detail. In the example below, the addition of a 13% Transmission Moon filter to the eyepiece eliminated the light from the Galilean moons, but allowed Jupiter’s cloud belts to pop into view.
At high magnification, it’s sometimes possible to use a filter that allows more light transmission (such as a coloured filter) to image a planet. Below is an image of Saturn taken with a #80A Blue filter. While this filter gives Saturn an unnaturally blue hue, it brings out ring and cloud detail that would not be visible through an unfiltered shot. It also delivers a brighter view than would be obtained using a Moon filter.
3) Stacking & Editing Software
While it’s possible to take high-quality snapshots of the Moon with a smartphone, it’s difficult to take an individual planetary image that matches the view through the eyepiece. To tease the most detail out of a planet, it’s best to record a short video clip of the object using the camera’s video function or an app (I use FilMic Pro with my iPhone). You can then use freely available image stacking software to select and combine (stack) the best individual frames from the video.
The Stargazers Lounge tutorial on Stacking Planetary Images offers an excellent introduction to image stacking and editing. AutoStakkert, Registax and AviStack are popular, free stacking software tools, and Apple users can also import iPhone video directly into a shareware program called Keith’s Image Stacker to accomplish similar results.
As with most astronomical pursuits, your skills will improve with practice. Don’t be disappointed if your first images don’t match those you see online. Experiment with different eyepieces, filters, and software and understand that the image quality is only partially in your hands. Your success will also depend on the degree of atmospheric turbulence or “seeing” at the time you’re taking your images. The same techniques might produce dramatically better (or worse!) results from one night to the next.
Once you’ve obtained some images you’re happy with, be sure to Tweet them to me www.twitter.com/failedprotostar so that I can see your hard work!
It’s also possible to take photos of the brightest deep sky objects with a smartphone. Using the NightCap app, which mimics the long exposures of DSLR cameras, I was able to obtain a high-quality image of the Orion Nebula that was recently featured on the website io9!
No stacking was required to record the colour and detail found in this nebula. I simply brightened the original image with the Camera+ app.
Lastly, I’ve created a Flickr gallery that contains my most recent iPhone astrophotos.
Earlier in 2014 I took some of my best iPhone photos of Saturn and Mars using the techniques described above: