How are dramatic night-sky images made without star trails, and what does “hundreds of exposures” mean?

Question

I’m looking at award-winning astrophotography images where the scene shows a sharp foreground and a very detailed star field. In one case, an article says the image was made from “525 separate exposures,” but the photographer’s own notes seem to describe a single 30-second exposure at f/2.8, ISO 6400.

How are images like this typically produced? Specifically:
- Can a wide-field night image with a silhouetted person or landscape be done in a single exposure?
- If not, is it usually a composite of foreground and sky?
- When people mention hundreds of exposures, are they usually talking about stacking, mosaics, or tracked telescope shots?
- How do photographers avoid star trails while still getting so much detail?

user1375 · Answer

A little bit of research goes along way...

The image with the figure in the lower right that won the "people and space" category was not created from 525 separate exposures as the article claims, but one single relatively short exposure. From the photographer himself, via flickr:

The setup was pretty simple... I found the foreground hill where I could stand silhouetted against the night sky, I set the camera on 10 second self timer for a 30 second, f/2.8, ISO 6400 exposure, then I walked into the frame and stood still until I heard the shutter close.

I suspect the "525 images" got misplaced and belonged to one of the images from the "Robotic Scope" category. These are images of far away objects through proper telescopes with tracking mounts. Many exposures are needed due to the dimness of light reaching Earth from these distant structures.

How are dramatic night-sky images made without star trails, and what does “hundreds of exposures” mean?

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