There is something undeniably awe-inspiring about seeing the Moon’s battered and scarred surface in a telescope. For my money, it’s as impressive as the grand vastness of the Rocky Mountains or the pounding rush of Niagara Falls. The Moon has something else in common with these famous terrestrial sights: It unfailingly triggers a desire to take a picture so that the experience can be enjoyed again later or shared with family and friends.
But unlike photographing the Rockies or Niagara Falls, getting a good snapshot of the Moon isn’t quite as simple as aiming your camera and pressing the shutter button. A modest amount of extra effort, preparation and equipment are part of the process. Although practically any camera-and-telescope combination will do, you’ll have to try your hand at some new techniques if you want to bring back a memorable lunar postcard.
Pointing And Shooting
The most direct way to photograph the Moon is simply to position your camera so that it’s looking into the eyepiece of your telescope and fire away. This is known as afocal photography, and it works well for point-and-shoot cameras, those with non- removable lenses and LCD viewscreens to frame the scene.
To give this method a try, first aim your telescope at the Moon and bring the view into sharp focus with a medium-power eyepiece. Next, set your camera’s white balance to daylight (usually the little Sun symbol) and to infinity focus (or leave it in auto-focus if no such mode is available), and carefully aim into the eyepiece while looking at the viewscreen. Zoom in with your camera until the eyepiece field fills the screen. It’ll probably take a few tries before you manage to line up the camera with the eyepiece correctly. Once you do, take a couple of test shots and see what you get.
Chances are, your first photos will show a featureless white disc, instead of a richly detailed lunar portrait. That’s because the black sky surrounding the Moon can trick your camera into over- exposing the scene. The first thing to try is to increase the magnification of your telescope by changing the eyepiece or (better) zooming in with your camera so that the lunar disc occupies more of the field of view. The less blackness the camera sees, the less likely its metering system will be fooled.
Various camera settings can also help you tame the Moon’s brightness. First, make sure the ISO is set to its lowest level. If that doesn’t yield the correct exposure, check to see whether your cam- era has a manual mode. If it does, this is where it comes in handy. Switch the camera off automatic, throttle down the exposure, and try again. If you don’t have manual exposure, dig out the instruction booklet, and look for a feature called “exposure compensation.” This allows you to reduce the camera’s sensitivity so that the Moon isn’t blown out. Experimentation is the key, but luckily, today’s memory cards easily hold loads of test exposures.
After a few pictures, you’ll probably find that lining up the camera with the telescope is a tedious hit-and-miss affair. To make it easier, mount your camera on a tripod so that you can aim into the eyepiece more precisely. And if you really want to get serious about shooting the Moon afocally, invest in a specialized bracket to couple your camera directly to the telescope. Suitable units are available from most Canadian telescope dealers. An adapter bracket will en- sure the best, most consistent results with the least amount of fuss.
The DSLR Moon
Compared with small point-and-shoot models, digital SLRs offer greater dynamic range and less picture “noise.” The result is high-quality lunar images bursting with an impressive amount of fine detail. You can use a DSLR with the afocal method, but to take full advantage of the camera’s potential, try prime-focus or eyepiece projection.
In prime-focus photography, the telescope essentially functions like a powerful telephoto lens. To make the prime-focus connection, you’ll need a T-ring adapter. This is a simple fitting with female T-threads in front and a bayonet flange on the rear to match your camera’s lens mount. T-rings are available for most popular camera brands and models. Some telescope focusers are threaded to accept T-adapters directly, but if the one on your scope isn’t, you’ll also need a prime-focus adapter tube. This piece screws into the T-ring and allows you to attach your camera to your telescope’s focuser like a preposterously oversized eyepiece.
In prime-focus photography, the size of the lunar image depends on the focal length of your telescope’s objective lens or mirror. A telescope with a focal length less than about 1,500mm will show the entire lunar disc on a standard DSLR camera. This is ideal for photos of the Moon’s phases and for lunar eclipses. If you want to get closer, you’ll need a teleconverter lens, which typically magnifies the image 1.4× to 3×, depending on the specific model. However, this gain in image scale requires a corresponding in- crease in exposure time. In other words, a 2× teleconverter will double the image size, but you’ll need to double the exposure time or the ISO setting.
Once your camera is attached, use the telescope’s focuser to get a sharp image. This task is made much simpler if your DSLR is equipped with “live view.” Most DSLRs manufactured after 2008 have this option. Generally, it’s easiest to focus on the limb of the Moon or some well-defined feature. As you adjust focus, you’ll probably notice that the image jiggles every time you touch the telescope or camera. This is why a cable release or a remote shutter trigger is essential. You don’t want the vibrations caused by the camera’s shutter firing to blur your Moon pictures. If you don’t have a remote for your camera, look for a shutter-delay setting buried in the menu system. This feature builds in a few seconds between when you push the shutter release and when the picture is actually taken, which gives vibrations time to die down. Another helpful option to guard against vibrations is “mirror lockup.” Check your camera’s instruction manual to see whether your DSLR has this. Anything you can do to avoid jiggling the camera and telescope will increase the sharpness of your images.
Prime-focus photography is great for whole-disc shots and for capturing large expanses of the lunar surface, but if you want to record individual features with your DSLR, “eyepiece projection” is the answer. This method works more or less as the name implies. A telescope eyepiece is inserted into an eyepiece-projection adapter, which is then slipped into your telescope focuser to mate to your camera’s T-ring. The eyepiece projects a magnified image of the Moon onto your camera’s CCD chip. With this setup, the size of the lunar image depends on the focal length of the eyepiece and the projection distance. You can really get in close, but these gains come with an important caveat: The bigger the image, the longer the required exposure, the more difficult it is achieve sharp focus and the more troublesome vibrations and atmospheric distortion become.
Furthermore, you will need to use a sturdy telescope mount that is equipped with a motor drive to compensate for the Earth’s rotation. With sufficient magnification, the Moon will move far enough even during a brief exposure to blur the image. An ordinary Dobsonian likely won’t do.
Eyepiece projection can be very challenging, but it is also very rewarding.
The Moon Up Close
Today, it’s possible for skilled astro-imagers to produce detailed shots of the Moon that rival spacecraft images. How? They use highly sensitive, digital video cameras or webcams, recording at 30 frames per second or faster. This rapid frame rate allows astro- imagers to “beat the seeing” and avoid the worst effects of atmospheric blurring. The nuts-and-bolts details of the technique are beyond the scope of this article, but if you’re determined to capture detailed close-up pictures of individual lunar features, video imaging is how it’s done.
Essentially, the procedure involves three main steps, beginning with image capture. You place a specialized CCD camera in your scope’s focuser and record the video output with a computer. Next, you use software to pick out the sharpest individual frames from the raw footage and digitally stack them together for maximum clarity and freedom from image “noise.” (Software such as RegiStax will perform both the sorting and the stacking more or less automatically.) And, finally, you use image-processing software to sharpen the stacked Moon picture and tweak the brightness and contrast levels. You may even choose to stitch several images together into a larger mosaic, since individual video image stacks tend to be quite small.
Each step in the process — from capture to final adjustment — must be performed with great care and will test your patience and skill. But the results! Knock-your-socks-off Moonscapes that push the boundaries of resolution to the limits of your telescope’s optics. This powerful technique is easily the most involved and difficult to master, but it is also the one with the greatest potential payoff.
No matter which techniques you try, experimentation is key. And don’t be discouraged if you shoot more duds than winners — most of us do. First-rate images of the Moon require you to control vibration, achieve tack-sharp focus and battle the effects of atmospheric turbulence, all at the same time. But when everything is working just right, the reward is a picture- perfect lunar postcard that you can share with others and enjoy for years to come.