How to image lunar craters
Discover why it’s never been easier to photograph the Moon’s crater-ridden surface
he Moon is a pockmarked lump of rock – battle scarred from a multitude of past impacts. Some of these were so large that they deformed the lunar crust, depressing and cracking it so the resulting depressions infilled with lava. These huge basins form the lunar seas or maria – and they can be extensive in area.
TShooting the Moon
As well as the large basins, there are many craters of all shapes and sizes that make great imaging targets. The larger ones can be imaged with basic kit like a smartphone; all you need to do is to point the phone’s camera down the eyepiece of a telescope. Known as afocal imaging, this technique produces good results, often exceeding the results that used to be produced by coupling a DSLR to a scope.
As afocal imaging requires you to point your scope at the Moon, a tracking drive is recommended as it alleviates the need to continually shift the scope’s position to keep the Moon in view; you’ll have enough to do lining up the camera. Focus is critical and it needs to be done for corrected vision; if you wear glasses, focus with them on. Use a low- to mid-power eyepiece and centre the Moon in the field of view.
Next, activate your smartphone’s camera. Most camera apps have a pro or manual mode that allows you to control the camera settings, which is great if you’re feeling confident. If not, leave the camera on automatic. The Moon is bright enough to activate the camera app’s auto-settings and 75 per cent of the time the values selected will work just fine.
It helps to develop a lining-up technique. One way is to hold the phone’s camera some way off the eyepiece. You’ll need to be able to see the eyepiece with a bright light (the Moon) coming from it. Then, slowly but surely, move towards the eyepiece keeping the bright area in view. It can take a while to get this right, and bear in mind you need to a) keep the camera flat to the eyepiece and b) eventually press the shutter button. The second step is easier if you use a remote shutter release. A smartphone’s wired headphones often mimic this action; plug them in and press the volume up button.
The best crater images are obtained using a high frame rate planetary camera attached to the eyepiece end of a telescope. Here, there are certain techniques which will give you optimal results, and we’ve shown some of these in our step by step guide (opposite). How small you can go in terms of crater diameter is determined by the size of your scope; the greater the aperture, the smaller the feature you can resolve. The stability of the atmosphere will also have an effect, the best results being achieved when seeing is steady. Forward planning can help here (see opposite, Step 4).
With so many lunar craters to choose from, and the earlier phases of the Moon being well placed in the winter and spring sky, this month is a great time to get acquainted with our nearest neighbour in space using whatever equipment you have to hand.
Recommended equipment: Telescope on a tracking mount, smartphone for afocal-imaging, DSLR/ MILC camera, high frame rate planetary camera, optical amplifier, red or infrared pass filter
Send your images to: gallery@skyatnightmagazine.com