CAPTURE
Photograph the Milky Way
Image the misty glow of our home Galaxy as it crosses the sky during the summer months
The Milky Way represents the plane of our home Galaxy. Its diffuse glow is caused by the light of billions of stars too distant to be seen individually with the naked eye. As our Galaxy is shaped like two fried eggs back-to-back, and the Sun sits within the ‘whites’, two-thirds of the way from the centre, the mistiness appears like a path in the sky; the plane where all the stars are found.
The path isn’t uniform, something very evident at this time of year from a dark sky site. From the UK, the Milky Way brightens as it passes south through the Northern Cross asterism. It’s made more dramatic by a dark dust cloud blocking some of the Milky Way’s light, known as the Cygnus Rift.
Dark swans
If your skies are good and dark, it’s obvious that as the Milky Way passes out of the southern end of Cygnus, interesting things are happening. However, from the UK, its low altitude makes seeing this quite difficult. Passing down into Sagittarius, we reach the bright core of our Galaxy. Here atmospheric extinction reduces its appearance but a camera can help restore at least some of its impact.
As it flows south through Cygnus, one portion meanders towards the northeast corner of Ophiuchus where it comes to an end. The main thread passes down through Aquila and into Scutum where there’s a bright feature, the Scutum Star Cloud. It then appears to widen, an effect caused by the core bulge. From locations further south where the core is able to climb high in the sky, it can be impressive, even casting blurry shadows under the right conditions.
From the UK, its low altitude means we see it through a thick layer of atmospheric haze. For the best views, you will need a location which is dark and free of light pollution. A flat southern horizon is highly recommended. These conditions are often met by south facing coasts, though they can be achieved inland.
Choose a moonless night, and time your session for when the Milky Way’s core region is high in the sky. The last week of July until 4 August and 20
August until the end of the month are good this year. The core can be photographed using a camera on a static mount, and even certain smartphones. However, the best results will come from a DSLR/MILC with a medium- to wide-angle lens on a tracking mount.
You’ll need to do some processing to get the best out of the results, and you need to consider shooting at low to mid-low ISO values. Go too high and the amplification nature of ISO will work against you, delivering shots that will degrade rapidly when pushed. However you do it, July and August are great months to capture the beauty of our galaxy.
Equipment: Tripod or tracking mount; DSLR, MILC or night-sky capable smartphone; remote release
Step by step
STEP 1
Choose a location with as low and flat a southern horizon as possible. The night sky will be relatively bright at the start of July, so you have plenty of time to find a suitable location. You’ll also need to get as far from light pollution as possible, avoiding direct lights in view. A south- to southwest-facing coast can be ideal.
STEP 2
A wide-field lens, say of 12-14mm focal length, will cover a large area in portrait orientation; the horizon to the Summer Triangle. Alternatively, choose a longer focal length to home in on specific bright regions such as the Scutum Star Cloud, useful if you have bad light pollution at low altitude.
STEP 3
Use a tripod for stability. If you have a star tracker, this is ideal. If you’re planning to use a smartphone, some have the capability to take night shots while handheld, but a cheap tripod mount will yield the best results. If you’re planning to set up on the coast, remember beach locations can get quite windy, so find a sheltered spot.
STEP 4
If using a static tripod, select a mid to high ISO value. If using a tracking mount, select a low to mid value. Fully open the lens (lowest f-number). If a test shot shows distortion at the frame edge, consider closing the lens by a stop or two. A remote shutter release is recommended to keep the camera still when activating the shutter.
STEP 5
Focus as accurately as possible. Using Live View on a bright star such as Altair (Alpha (α) Aquilae) or a planet should be fine for this. Take a 10-second test exposure and examine the result. If you use a tracking mount, aim for 30-60 second exposures, longer if your polar alignment is good enough to allow.
STEP 6
Download and select your best shot, then load them into a layer-based editor. For a quick image fix, use Levels, dragging the mid-slider so it’s under the main histogram peak. Apply a gentle Curves ‘S’ adjustment and apply ‘auto-colour’. Finish off with a tweak to the brightness and contrast adjustment settings.
Send your images to: gallery@skyatnightmagazine.com
Pete Lawrence is an expert astro-imager and a presenter on The Sky at Night