STEP BY STEP
STEP 1
A fast lens with a focal length shorter than 30mm is ideal for this shot. By fast we mean one with a low minimum f/number. Anything below f/4 will be fine; anything lower than f/2.8 will be very well-suited to the job. The 30mm figure quoted here is for non-full-frame DSLRs. If you’re using a full-frame model the figure is 20mm or shorter.
STEP 2
Choose a medium ISO. Set the lens to manual focus and focus at infinity. Set the lens aperture to its lowest f/stop and check whether this introduces distorted stars at the edge of the frame. If it does, close the aperture by a stop or two. As ever, your camera’s RAW format (use RAW + large JPG for convenience) will give the best results.
STEP 3
The exposure you use will be determined by your mount type and sky brightness. For fixed mounts, a maximum exposure in seconds of 500 divided by your lens focal length in mm will avoid trails. For a 30mm lens, this equates to 17s. Review your results. If too dark, lengthen the exposure or up the ISO. If too bright reduce exposure or lower ISO.
STEP 4
Noise in images can be further reduced by taking multiple dark frames and averaging them together. To take a dark frame simply cap the lens and take another shot using exactly the same exposure you used for the Milky Way shot – the ‘light’ frame. Apply the master dark to each light frame as described in the main text.
STEP 5
Take at least nine light frames. Register and stack them as described in the main text. Save the averaged master light frame as a flattened image. Load into your photo editor and duplicate the layer. The base layer should be left untouched with adjustments applied only to the upper layer. This allows you to compare your adjustments to the original.
STEP 6
Increase the brightness slightly, followed by an increase in contrast. Do not overdo this and make the view look unnatural. To reduce orange light pollution, open Levels and select the red channel. Reduce red until image shows a green hue. Repeat with the green channel until image looks slightly blue. Repeat with the blue channel until image looks balanced.