How to Photograph the Lunar Eclipse

In this article Jonathan Green explains different ways to image the lunar eclipse, with a variety of equipment. 

Wide angle photography of the eclipse

The simplest way to photograph an eclipse is to use the Wide Angle technique. Any kind of camera can be used as long as it's capable of shooting long exposures of 5 seconds or more. If the camera accepts a cable release, this will help eliminate any vibrations that can blur your photo. Alternatively, you could use the camera's self timer to minimize vibrations.

Wide angle photo of lunar eclipseWith long exposures, it's best to attach the camera to a solid tripod (an Astronz tripod would do the trick ). With a DSLR use a focal length in the range of 18mm to 35mm. With a point and shoot camera, try setting the zoom at wide angle (shortest focal length).

The Moon appears quite small in a wide angle photo, so the idea behind this kind of picture is to capture the eclipse with an interesting foreground. It could be a building, a tower, a tree or even the horizon. This gives the photo some context by showing the eclipsed Moon in a familiar environment. 

Watching and photographing an eclipse of the Moon is a relaxing activity since it progresses at a leisurely pace. The eclipse begins as a small notch slowly appears along one edge of the Moon. During the next hour, the Moon gradually dips deeper into Earth's dark shadow. The last remaining minutes of the partial phases can be quite dramatic and beautiful. The crescent of the Moon grows thinner as darkness propagates through a night sky now deprived of moonlight. If you're away from city lights, the Milky Way becomes bright and beautiful as the total phase begins. It's a remarkable sight.

An ISO setting of 400-800 is a good choice. If your camera has a manual exposure mode, set the lens to its widest aperture (smallest numeric f/number) and use a range of exposures from 5 seconds to 30 seconds (eg, 5, 10, 20 and 30 seconds). Exposures longer than this will start to trail or streak because of Earth's rotation on its axis. A major advantage of digital cameras is that you can check your exposures to see which shutter speeds work best for your setup.

Create a moon trail image

A variation on the Wide Angle technique is to use very long exposures of a minute or more. This allows the Moon to slowly drift across the camera field of view as the Earth rotates. The Moon trail technique can be done with the same kind of camera and lens used for Wide Angle photos.

Eclipse moon trailIn this case, a tripod and a cable release are a must, and your camera also needs to have a manual bulb setting so that you can lock the shutter open. Choose a moderate ISO speed (ISO 200 or 400), and an aperture of f/8 or f/11. As the eclipse begins, place the Moon's image in one corner of your camera's viewfinder. Your camera should be oriented so that the Moon's image will move across the camera's field during a series of long exposures (1-2 minute exposures are best, again experimentation is key to finding the exposure that best suits your equipment, make sure your are not overexposing by taking test images before the eclipse starts ). The motion you will capture is caused by Earth's rotation on its axis. You can figure out the approximate orientation by trying it out on the Moon one or two nights before the eclipse. Just remember that the Moon rises about 50 minutes later each night.

To record all the partial and total phases of a lunar eclipse in one frame, you need to know the field of view of your camera lens as well as the the duration of the eclipse. The Moon appears to move across the sky at a rate of 15° per hour - its own diameter every two minutes. When done correctly it should take the Moon about two to three hours to traverse your field of view, so try to orient your camera so that the Moon moves in the correct direction.

After capturing the complete event you then use a star trail program to stack the images together to create your final image. Star trail programs can be found for free on the internet. Google "Star Trail Programs". StarStaX is one example and it's free to download.

Combine multiple exposures

 The Wide Angle technique captures one instant during an eclipse. The Moon Trail technique records several hours of an eclipse but the resulting image is rather abstract and doesn't resemble the naked-eye view of an eclipse. The Multiple Exposure technique combines the best of the Wide Angle and Moon Trail techniques by capturing a sequence of individual images that shows the eclipse through a large number of stages. The key technique for this kind of an image is to take a series of exposures that are shot during the eclipse and saved as separate image files. These are later stacked and combined into one image using a photo editing program like Adobe Photoshop.

The camera set up and orientation is identical to the Moon Trail method. The difference here is that you will take a series of short exposures at various stages of the eclipse instead of a series of minute long exposures, the idea is to keep the exposures short so that there is no trailing due to the Earths rotation, The resulting exposures will reveal a series of small Moon images each illustrating a different phase of the eclipse. An essential key to the success of this method is ensuring that your camera and tripod remain absolutely rigid and do not move throughout the eclipse.

Exposure times will depend on your setup and again experimentation is key to finding out what works best with your setup, since the Moon's brightness varies during the eclipse, you also need to change the exposures as the eclipse proceeds. But don't worry the eclipse takes plenty of time to happen so as long as you've got a decent image every five to ten minutes you'll be able to put together a nice image showing all the phases of the eclipse.

Once the event is finished download all the images to your computer. Use an image editing program like Photoshop or Photoshop Elements to add all the individual image files as separate layers in one new composite file. Finally, flatten the layers to combine the separate exposures into one.

Using a telescope or telephoto lens 

To achieve large images of the Moon, you need to use a long telephoto lens or a telescope. Point & Shoot cameras can be used if they have a powerful zoom lens. In this case, the longer the zoom's focal length, the better. Try shooting some photos of the Moon a few days before the eclipse to see how big the Moon's image will be using the maximum zoom setting.

Lunar eclipseThe big advantage of DSLR (digital) cameras is that they take interchangeable lenses. In this case, a lens with a long focal length is needed to get as large an image as possible.

Focal lengths in excess of 1000mm take you into the realm of the super telephoto lens. If you're in the market for such an item, you might consider a small telescope instead. The main advantage of a telescope is that you can also use it visually with variable power eyepieces. There are a number of telescopes available from Astronz that would be suitable for the task. These telescopes are available with equatorial mounts and electric clock drives which counteract the Earth's rotation and allow you to automatically track the Sun, Moon and stars.

Even if your're not using a telescope, the capability to track the Moon will make your life a lot easier because at long focal lengths the Moon will quickly move out of your frame, The iOptron Sky Tracker and Sky Guider both have Lunar tracking speeds that would be suitable for the task and are available through Astronz.

Don't worry if you don't have tracking, you can still image the eclipse. You will just have to keep adjusting your tripod and camera to keep putting the Moon back into the middle of your frame. With your telephoto lens or telescope, you can capture various stages of the eclipse. Again exposure times will depend on your setup and experimentation is key to finding out what works best with your setup but generally you will only need fractions of a second when the Moon is still bright. I usually keep the same exposure times until the Moon is in the total eclipse phase and at that point you can start taking slightly longer exposures and ramp up your ISO. Experimentation is key to getting the best results. Just remember that you can always delete any mistakes later on, and with digital cameras you can always check the results as you take your exposures.

SkyTracker Pro Mount To capture a good sequence of photos, you'll probably want to take a bracketed series of exposures, so experiment with opening or stopping down your lens. With a telescope you will need to either take longer or shorter exposures or ramp your ISO up or down depending on how bright the Moon is. With a lens you might even bracket plus or minus two stops. Weather conditions (fog, haze, thin clouds) may require an additional two or three stops to achieve a good exposure.

During a total eclipse, the Moon's colour and brightness can vary enormously. It can take on hues from bright orange, through deep red, dark brown or even dark grey as it's brilliance ranges from bright to dark to nearly invisible. Although the Moon is cut off from all direct sunlight while it is in Earth's shadow, the Moon receives indirect sunlight which is refracted through and modified by Earth's atmosphere. Our atmosphere contains varying amounts of water (clouds, mist, precipitation) and solid particles (dust, organic debris, volcanic ash).

This material filters and attenuates the sunlight before it's refracted into the Earth's shadow. For instance, large or frequent volcanic eruptions dumping huge quantities of ash into the atmosphere are often followed by very dark, brownish red eclipses for several years. Extensive cloud cover along Earth's limb also tends to darken the eclipse by blocking sunlight.

So to make sure you capture the colour of the total eclipse a bit of experimentation is required, you will want to take loads of images during totality making sure that your focus is sharp and that the results on your view screen are showing the kind of red hues you'd expect to see. Remember now that we are in the digital era it costs you nothing to take a lot of exposures and you can always delete mistakes later on.

Once the event is finished download all the images to your computer. Use an image editing program like Photoshop or Photoshop Elements to create a sequence on a black background layer, once your happy with the results flatten the layers to combine the separate exposures into one.

Good luck and clear skies 

I hope this article gives you a a few ideas for imaging the lunar eclipse and remember that lunar eclipse images will make great entries into the 2018 Harry Williams Astrophotography Solar System category, looking forward to seeing what you come up with.

Fingers crossed for clear skies where ever you are on the night of the eclipse.