Nightscapes
Simple to take, these astro images are a great way to practise processing
What is a nightscape photo? It can be a landscape at night and it can also be a wide-angle photo of the night sky capturing the Milky May, noctilucent clouds, Moon sequences or the aurora. Nightscapes are often achieved using single, untracked images, meaning that you can capture these without using a mount that follows the apparent movement of the sky. Each of the above can be captured using basic equipment; either a DSLR with a lens, or a smartphone, and a tripod.
Depending on the equipment, exposure times can be up to 30 seconds before the stars start trailing noticeably. To find out the approximate exposure time before stars stop looking sharp, use the ‘500 Rule’. Dividing 500 by the focal length of your lens provides the longest exposure time for your setup.
Processing nightscapes (especially single, unstacked images) often requires just a minor stretch to the light curve in Adobe Lightroom or Photoshop, using the sliders rather than specific or niche settings.
A popular option for nightscapes, however, is to blend several side-by-side images into a panorama. Many Milky Way images are blended mosaics or panoramas, consisting of several images pasted together. Stitching images together requires software such as Microsoft Image Composite Editor (ICE) – a program that is simple to use. Simply open the software, click ‘New Panorama From Images’ and upload the exposures (see figures 1 and 2). The resulting image can then be saved and edited in Photoshop or Lightroom.
Once the image has been stitched together, we suggest adjusting it in Photoshop with the ‘Brightness/ Contrast’, ‘Hue/Saturation’ and ‘Selective Colour’ sliders. ‘Selective Colour’ is useful for removing sky glow (such as oranges and pinks) and magenta from a nightscape. These colours can diminish the impact of a Milky Way shot, so take your time on adjusting these (see figure 3).
Remember not to go too far – moving the sliders too much risks making the image noisy (revealing unwanted artefacts), particularly if it is a single image rather than multiple images ‘stacked’ together. Oversaturation or over-stretching, so that stars lose their colour or the sky appears too blue, can leave nightscapes looking artificial.
If you have a star tracker or a tracking mount that moves with the sky it’s also possible to do tracked nightscapes, which allow for longer exposures that capture fainter stars. Processing these images is largely the same, although if taking images to stack (which reduces noise), stacking software is needed before processing (see ‘Planets and Moon’ for more on this).