![\"Away](\"\/wp-content\/uploads\/2015\/03\/Milky-way.jpg\")
<\/a>\t\t\tAway from light pollution, shots of the Milky Way are possible in the UK<\/p>\n\t\t<\/div>\n\t\t\n
Like many branches of photography, the work that goes into a successful wide-field astro image starts before you leave the house. I\u2019m looking for scenes that let me convey the relationship between Earth and the stars. Researching and selecting locations based on local features and the quality of darkness is essential.<\/p>\n
The earthly element could be anything from celestially aligned megaliths to the skeletal form of a decaying tree. In fact, almost any feature that can be silhouetted (or gently illuminated) against the starry backdrop will suffice.<\/p>\n
The key to a purposeful image is gathering lots of starlight and that means using a wide aperture or high ISO settings \u2013 or both. While it\u2019s cheaper to buy an extra stop of light via a fast prime lens than to upgrade your camera body, there\u2019s no doubt that the high ISO performance of current models like the Sony Alpha 7S, which has a sensitivity range of ISO 40-409,600, is particularly well suited to low-light conditions. Such cameras provide a visible step up for low-light image quality, producing files with less noise and greater dynamic range for processing.<\/p>\n\t\t
<\/a>\t\t\tCameras with high ISO noise performance, like the Sony Alpha 7S, are well suited to astrophotography<\/p>\n\t\t<\/div>\n\t\t\n
Exposure time<\/h2>\n
With settings of, say, f\/2.8 and ISO 3200 to gather lots of starlight, the last factor of the exposure triangle is duration. Shutter speed controls the ambient light \u2013 the brightness of the sky \u2013 and it\u2019s the shutter speed that gives me the most flexibility to work in range of conditions.<\/p>\n
As the Earth rotates constantly, it doesn\u2019t take long for stars to begin streaking within an image. Unless I\u2019m specifically creating a star trail, I prefer to keep exposures as short as possible to retain the pinprick appearance of the stars. A wide aperture and a high ISO will always gather most starlight, but a scene that\u2019s truly dark will need a much longer exposure to help define the foreground \u2013 30secs or more than somewhere affected by light spill.<\/p>\n
It\u2019s not just streetlights that can brighten the scene. The moon also casts a lot of illumination, so it\u2019s best to shoot when the sky is moonless. Clouds are another hindrance, especially thanks to the void between a meteorologist\u2019s definition of clear skies and what we require as photographers.<\/p>\n
That said, a wisp of cloud can add focus to an otherwise overwhelmingly starry sky. Personal taste will help you determine how much cloud you can tolerate. With the UK\u2019s unpredictable climate, it already feels like a minor victory to be out beneath a clear sky. However, the challenges continue, as framing, focus and depth of field have yet to be overcome. At this point, a bright torch becomes an ally when shone towards the subject to give the camera\u2019s autofocus something to bite on. While autofocus is not flawless, I\u2019ve found that it\u2019s either spot on or miles out. This makes it easy to confirm on the camera\u2019s LCD, as opposed to manual focus, which can be slightly out and only becomes apparent when you look at an image on a big screen at home.<\/p>\n
Framing<\/h2>\n
Depth of field needs consideration, but thanks to hyperfocal distance it is possible to shoot with a wide aperture and have both your foreground subject and backdrop of stars in sharp focus. For this, and for star-filled vistas in general, a wideangle lens is preferable. I\u2019d suggest switching off any anti-shake systems as well.<\/p>\n
My torch also helps me locate the bottom corners of my frame and check the foreground for unsightly elements. I have to remind myself when composing an image that the vast area of negative space above the horizon will be brought into play by the appearance of countless stars. Finally, with everything locked down on the tripod and a quick double check that the camera is set to record raw files, I can click my cable release to start the exposure.<\/p>\n
I treat my first shot as a test. If it turns out well, it\u2019s a bonus. Wide-field astrophotography needs a lot of trial and error, some intuition and a bit of luck. If my test looks too bright, I\u2019ll shorten the exposure duration and reshoot. This dims the sky without drastically reducing the number of stars recorded, as I\u2019m not changing the light sensitivity. If the test is too dark, usually I\u2019ll push the ISO a little further to let in more light, without affecting depth of field or causing the stars to trail. At some point, though, a compromise is bound to arise. This is where it pays to know exactly what your camera is capable of, both on location and when its files reach the post-processing stage.<\/p>\n
Meanwhile, luck will manifest as catching a meteor or, on rare occasions, experiencing aurorae. Neither can be reliably predicted, but setting up with the most light sensitivity provides the best chance of catching either.<\/p>\n\t\t
<\/a>\t\t\tA meteor passes over Arundel Castle in West Sussex during a 30sec exposure<\/p>\n\t\t<\/div>\n\t\t\n
Star trails<\/h2>\n
I\u2019ve talked about keeping the stars as specks in the sky, but there are times when star trails can transform the shot. This is particularly the case if you\u2019re able to include Polaris to the north, around which the other stars seem to circle.<\/p>\n
For this effect, I set up with the same approach, but make sure continuous shooting mode is selected. It\u2019s then just a case of locking the cable release in bulb mode to keep it firing, shot after shot. I tend to shoot star trails for an hour or longer, batteries permitting. I step back from the tripod and avoid using incidental torchlight when the camera\u2019s running.<\/p>\n\t\t
<\/a>\t\t\t60x 20sec exposures (totalling 20mins) were \u2018stacked\u2019 to create this star-trail shot of the Seven Sisters in East Sussex<\/p>\n\t\t<\/div>\n\t\t\n
Back at my desk with a much-needed cup of tea, I load the files into Lightroom. Having spent time carefully setting up on location, most of my processing takes place via white balance, colour adjustments and a bit of noise reduction, though some shots need a little more work.<\/p>\n
My preference is for images with integrity to the original scene, so I avoid pushing the contrast and clarity sliders too far. While they can certainly add impact, it\u2019s often at the expense of image quality.<\/p>\n
Why darkness matters<\/h2>\n![\"Darkness\"](\"\/wp-content\/uploads\/2015\/03\/extended.jpg\")
<\/a>\nEvery doubling of exposure duration is a doubling of ambient brightness. If you expose for longer, the static parts of your picture become brighter. With each star being of fixed brightness (although some are brighter than others), dim stars are very easily overpowered by ambient light, such as light pollution from street lamps and stray security lights. To further complicate matters, stars move through the sky so their brightness in any one place is finite.<\/p>\n
The importance of ambient darkness is mirrored in the importance of choosing your settings. At the same location, an exposure at ISO 1600 and f\/4 for 30secs would give you an image the same brightness as ISO 200 (3 stops less sensitive) and f\/11 (3 further stops less sensitive) for 32mins (6 stops longer).<\/p>\n
Despite the light levels being comparable, the appearance and mood of the two images would be vastly different, with the first shot featuring the presence of many tiny stars and the latter showing just a handful of extended star trails.<\/p>\n
Why it works<\/h2>\n![\"Astrophotography](\"\/wp-content\/uploads\/2015\/03\/Astrophotography4.jpg\")
<\/a>\nA recent trip to Northumberland saw me well out of my local area, shooting with the Sony Alpha 7S. I\u2019d researched what I could online, but there\u2019s always the hope of stumbling upon something unexpected. A night watchman had steered me to this viewpoint, but rather than looking out over Kielder Water, I found the camper compelling.<\/p>\n
Even without actual people, it reveals a sign of human activity that\u2019s often absent from nocturnal images, while the scale of the camper versus the trees and night sky serves to highlight the part we play in the universe.<\/p>\n
I laid my torch on a rock way out to the left of the frame to gently illuminate the van. Light from the torch also brought detail into the background, with the subsequent fir-green of the trees contrasting against the orange glow in the lower sky. It took careful white balancing to introduce this palette, offsetting the colour temperature of the LED torch against the rest of the scene. I just wonder why the camper residents, clearly outdoor types, weren\u2019t alongside me, marvelling at the stars above?<\/p>\n
<\/a>\nA recent trip to Northumberland saw me well out of my local area, shooting with the Sony Alpha 7S. I\u2019d researched what I could online, but there\u2019s always the hope of stumbling upon something unexpected. A night watchman had steered me to this viewpoint, but rather than looking out over Kielder Water, I found the camper compelling.<\/p>\n
Even without actual people, it reveals a sign of human activity that\u2019s often absent from nocturnal images, while the scale of the camper versus the trees and night sky serves to highlight the part we play in the universe.<\/p>\n
I laid my torch on a rock way out to the left of the frame to gently illuminate the van. Light from the torch also brought detail into the background, with the subsequent fir-green of the trees contrasting against the orange glow in the lower sky. It took careful white balancing to introduce this palette, offsetting the colour temperature of the LED torch against the rest of the scene. I just wonder why the camper residents, clearly outdoor types, weren\u2019t alongside me, marvelling at the stars above?<\/p>\n