Astrophotography for Beginners Step 2: How to Shoot the Moon
Close-ups of the Moon are rewarding, and an easy way to learn to shoot through your telescope. While good results are possible with a phone camera clamped to an eyepiece (as shown below), this tutorial concentrates on using a DSLR camera body, as a step toward shooting deep-sky images later..
Connecting a Camera
DSLR camera bodies (with the lens removed) can attach to the focusers of most telescopes using a specialized adapter tube that replaces the eyepiece.
We stock adapters for both 1.25-inch and 2-inch focusers, with most also requiring the purchase of a T-Ring to go from either the M42 or M48 diameter T-threads on the camera adapter to the lens mount specific to your camera, such as Canon or Nikon.
T-Rings made for mirrorless camera bodies are rare. Instead, you will have to use an additional adapter made by your camera manufacturer for attaching older DSLR lenses to your camera body. This goes between the T-Ring and your camera.
Schmidt-Cassegrain telescopes can be fitted with their own T-Adapter tubes that thread onto the telescope, replacing the Visual Back.
The Best Telescopes
Most refractors and all Maksutov- and Schmidt-Cassegrain telescopes will reach focus with a DSLR camera attached using such an adapter.
However, many Newtonian reflectors are designed just for visual use and will not reach focus with a DSLR camera. The focuser will not rack in far enough. A solution is to insert a 2X Barlow into the focuser, and then slide the camera adapter into the Barlow.
The Moon’s image will be double the size, but that might be an advantage. As we show above, it takes a whopping 1,500mm of focal length to fill a full-frame camera sensor with the Moon’s disk.
While a telescope with a non-tracking mount will work, you will have to keep re-centering the Moon every few seconds. A GoTo mount is preferable.
As with all astrophotography, focus is critical. Poor exposures can be fixed, to a point, later in processing. But not poor focus.
Use Live View to zoom in on the limb of the Moon or the rim of craters or mountain peaks along the line between light and dark, the “terminator.” Focus until the features look as sharp as possible.
Our wobbly atmosphere and vibration from touching the telescope will make it hard to nail the point of best focus, but practice makes perfect.
When shooting with a DSLR, try using Mirror Lockup (left), to avoid vibration from the reflex mirror blurring the image. With a mirrorless camera, use Silent Shooting or Electronic First Curtain Shutter (right), to avoid vibration from just the shutter itself.
Windy nights will be a challenge! After all, you are effectively shooting with a 500mm to 2000mm telephoto lens, so any vibration, even from nearby traffic, can spoil the image.
The Best Exposures and Settings
Despite its presence in our night sky, the Moon is surprisingly bright. It is essentially a sunlit rock, so exposures are snapshot length, just a fraction of a second.
Exact exposures will depend on the focal ratio of your telescope, the altitude of the Moon, and the clarity of the sky. Take a range of exposures to pick from later at the computer. Aim for images that don’t overexpose the bright areas toward the limb, while not underexposing the dark areas along the terminator.
Exposures need to shorten as the Moon waxes from crescent toward Full. But 1/8-second for a crescent Moon, 1/60-second for a quarter Moon, and 1/500-second for a Full Moon are typical.
Use a low ISO (100 to 400) for the least noise and highest dynamic range.
Take lots of images, as some will be sharper than others, those caught by chance when the air was steadiest (during moments of good “seeing”).
To frame just small areas of the Moon the best option is to employ a Barlow lens (perhaps up to a 4X model) between the camera and telescope, using a nosepiece style adapter to slide the camera into the Barlow.
Focusing will be tougher, and the image darker, requiring exposures much longer (perhaps a second or more), risking blurring from seeing turbulence and vibration.
The more common practice of lunar and planetary photographers is to use either a DSLR in movie mode or a dedicated planetary camera (such as models by ZWO) to capture a movie.
Free Windows software such as AstroStakkert! or Registax extracts the sharpest frames from the movie, then stacks and aligns them for a final still image. Multiple but overlapping closeup images of the Moon can be stitched into a high resolution full-disk image using Photoshop or the free panorama software Hugin.
Imaging the Planets
The sharpest images of planets require the same techniques outlined above for lunar closeups. A DSLR can be used, but achieving the results you see on the web demands good seeing and a specialized high-frame-rate camera.
For example, using a ZWO planetary camera (shown above), the little ZWO ASiair control computer can record a movie, and select, stack and sharpen frames right in the field, greatly simplifying post-processing.