Eleven 20sec exposures were needed to capture tonight's pass of the International Space Station, from when it first appeared just above the horizon until it faded into the shadow of the earth.
I'd already fired off a few test shots before the spacecraft appeared, checking for focus (because it's pretty much pitch black this has to be done manually, but the focus-peaking system on the Sony helps with that) and that no shadows or highlights were clipped. When you're in the dark, and relying on checking an the shot on screen, what looks pretty evenly exposed can be a fair bit off if your eyes have adjusted for the lack of light. Using the histogram and any clipping warnings is a better bet. Glad I did that too, as I'd forgot to switch back to RAW capture after shooting some lower resolution JPGs for a task earlier in the day; less wriggle room for pulling out the shadows or holding in the highlights with those.
As the station flew over I used a remote control to fire each shot, trying to leave as little a gap as possible. But, when something's travelling over at 17500mph, there's going to be gaps.
To fix that, I set all the images to edit from Lightroom, opening them all as Layers in Photoshop. Masking off each layer then using a brush not much wider than the light trail, the track of the ISS can be brought back into view across the whole scene, albeit with the gaps from between frames.
Using Photoshop's Content-Aware Move tool I selected a small section of the trail, near each gap, and slid this over each missing section. PS does a good job of matching the direction of line as well as the colour and luminosity of the pixels, much better than would appear if, for example, you used just the Clone Stamp tool.
Layers are then all flattened to create a composite image, recording the near 3 minute pass in one single frame.