Learning never exhausts the mind
Home >  Astronomy > Astrophotography > Smartphone Astrophotography

Published 13th November 2019 by

As hobbies go, astrophotography can be quite an expensive one, however, your smartphone can be just as good as an expensive DSLR or CCD camera.

Although many smartphone cameras offer a reasonable number of sensor pixels, sensitivity and low noise are also needed for reduced light astrophotography and it's here that smartphone cameras can run out of steam. Bright objects such as sunsets, sunrise, the brighter planets and the Moon are a different matter and do presently viable targets.

Creating a decent scaled image to show detail on the Moon isn't easy with a smartphone camera because the lens has only a limited zoom capability. We can, however, use a technique called afocal coupling, which is when we point the camera down the eyepiece of a telescope, or even binoculars.

The theory is quite straightforward. Point the telescope at the Moon, focus it and then point the camera down the eyepiece. When the Moon's image is nicely framed on the phone's display, press the shutter button and that's the job done.

Of course, in practice, things aren't quite so straightforward, but the basic principle holds. First, you'll need to set your scope up with an eyepiece. Choose a low to medium power one to start with, a 25mm is normally a good choice. If your telescope is equatorial mounted, a drive is a great asset because it'll keep the telescope pointing directly at the Moon, giving you one less thing to worry about. Don't worry if you don't have a driven mount, because you can still get a shot. Without a drive to keep things centred, use a lowe power eyepiece as you can find. This will limit the apparent speed of the Moon.

Point the telescope at the Moon and focus through the eyepiece as best you can. If you wear glasses, it's a good idea to focus with them on so that the view the phone camera gets is as normally focused as possible.

Before you start, take a moment to identify where your camera lens is located on your phone. This may sound a bit obvious, but it's surprising how easy it is to mistake the lens for the small flash windows sometimes present.

Cheap smartphone holders can be found for as little as £5

Cheap smartphone holders can be found for as little as £5

Turn the camera on and with the Moon centred through the eyepiece, hold it up so that it's pointing straight down the barrel of the eyepiece. This is the important bit and the part which is the hardest to achieve. If your phone isn't pointing down the eyepiece, you won't see anything on the phone's screen.

You'll need to hold the camera quite close to the eyepiece initially, but once you've got the image in the frame, experiment with different distances until you get a comfortable view. Try not to touch the eyepiece itself. This may cause the telescope to move, meaning you might be trying to line up with an empty view.

Once you've got the Moon on the screen, double check the orientation of your phone so that the camera lens is looking straight down the eyepiece. This makes all the difference to the final shot because if you get it right, the light coming out of the eyepiece will be the brightest and evenly spread as it enters the phones camera lens. If you're slightly tilted, you'll get a gradual degradation of the brightness across the field of view.

When you're all lined up, the only thing left to do is take the shot. Here, one last hurdle appears to thwart you - as you press the shutter button you'll probably move the phone in the process. The easiest way around this is to be gentle. You can either use the timer function or if your phone supports it, you can use a hands-free headset and control the shutter with the volume button.

Most smartphone cameras don't offer much in the way of control when it comes to exposure. However, the Moon should be bright enough to trigger auto exposure functions so that the shot comes out correctly.

Leave a Reply

Fields marked with * are mandatory.

We respect your privacy, and will not make your email public. Hashed email address may be checked against Gravatar service to retrieve avatars. This site uses Akismet to reduce spam. Learn how your comment data is processed.