Smartphone Astrophotography has come a long way since I first began doing it 2007 with my then just released Apple iPhone. Today’s smartphones have amazing cameras and camera apps can take incredible (for a smartphone) images in low light. The simplest way to take a photograph of the Moon or bright planets using a telescope is to focus the object to your eye and then handhold the smartphone camera over the eyepiece and take a photograph. For such bright objects the shutter speed will be fast, reducing the chances of blurring the image by moving the smartphone. For fainter objects, and yes you can photograph stars, comets, nebulae, and galaxies using low-light camera apps, the smartphone should be physically attached to the eyepiece. But with most smartphone adapters that brings another challenge: getting the camera lens aligned properly over the eyepiece.
Using the right Adapter
Using a “universal” adapter that fits most smartphone models you can spend many minutes struggling to get the object into the camera field-of-view and then locking the various adapter knobs to keep it there. This is especially difficult with faint objects. This problem is eliminated with the Phone Skope Digiscoping Adapter. Unlike universal adapters, you purchase a Phone Skope case designed for your smartphone model. The case ensures that the eyepiece adapter is properly aligned with the location of your smartphone camera lens.
There are Phone Skope adapters for binoculars and spotting scopes and telescopes.
Of course, just mounting the smartphone on the eyepiece will not get you the best images.
Avoid Using Shutter Button
First, you need to avoid using the smartphone shutter button. Otherwise, you can easily create vibrations that will ruin your photograph. Image 2 shows the earbuds cable attached to an iPhone. The volume control on the cable acts as a “remote shutter release” for most camera apps to start and stop the exposure. You can also use a Bluetooth remote shutter release or even the Apple Watch with your iPhone as a remote shutter.
Use a Camera App to Capture Photos
Next, you need to use a camera app to take the photograph. This is where things get interesting.
Basic camera apps have auto-exposure and auto-focus. Some apps allow you to make some minimal exposure adjustments and even lock the exposure and focus settings. Locking the focus is helpful.
You first focus the object in the eyepiece using your eye. After mounting the camera to the eyepiece, a basic camera app may or may not be able to properly focus the object depending on how large and bright the object is. If the camera gets the object in focus, you lock the focus and then take a photograph. With a bright large object like a full or nearly full Moon, auto-exposure can take a properly exposed photograph. However, if there is a lot of black area surrounding the object, the camera will see that as a dimly illuminated part of the scene and try to properly expose the subject, usually resulting in an overexposed Moon or planet.
Using a camera app that provides full manual control of the exposure (shutter speed, ISO, focus, and even White Balance) will let you photograph bright and many faint objects with a proper exposure. Some apps will even “stack” (merge) multiple photographs on the smartphone to increase the effective exposure to minutes, which is really needed with faint nebulae and galaxies.
For example, I use NightCap Camera on my iPhone. This app has many special modes for astrophotography allowing you to photograph faint deep sky objects. A typical faint object exposure could be shutter speed 1/3sec, ISO 12800, 1 minute exposure. NightCap Camera is only available on Apple devices, but there are similar apps for Android devices.
Using the right lenses
Many of today’s smartphones have multiple lenses (wide-angle, normal, and telephoto). The wide-angle lens is useful for night sky photography, but otherwise is not normally used when photographing objects in the telescope. Some small objects (e.g., planets) can benefit from using the telephoto lens. However, for most objects and especially for faint objects, the normal lens is the best choice.
Aligned Tracking Mount
A properly aligned tracking mount to compensate for the Earth’s rotation is useful for two reasons. The first is that you do not have to deal with object movement while trying to align the object in the camera field-of-view and set the exposure. The second is that the object will not be trailed during long exposures.
Here are a few examples of Smartphone Astrophotography.
Bright objects like the Moon can be photographed using the camera app that comes pre-installed on the smartphone or you can use the Phone Skope app. Planets can also be photographed with these apps. Some camera apps have low-light modes that can take good photographs of bright nebula like the Great Orion Nebula. Special astrophotography apps like NightCap Camera will let you photograph nebulae like M8 (Lagoon Nebula) and NGC7662 (Blue Snowball Nebula), and galaxies like M82.
Some adapters have built-in tripod mounting holes that let you attach your smartphone to a camera tripod. Phone Skope has an optional adapter for their smartphone adapters. Mounting your smartphone on a tripod will let you take photographs of the night sky.
No matter what equipment you have, whether that is a pair of binoculars, a telescope, or just a camera tripod, give astrophotography a try with your smartphone. Initially you will be challenged to get good images but don’t give up. As you gain experience photographing objects in the night sky you will be surprised at what you can photograph with your smartphone.
For my in-depth review of the Phone Skope Digiscoping Adapter, see: http://www.weasner.com/co/Reviews/2019/PhoneSkope/index.html
Guest Blog by Mike Weasner, Cassiopeia Observatory