A day is 24 hours — but 24 hours of what, exactly? A solar day is the time from one solar noon to the next: the Sun back in the same spot in your sky. But Earth is also orbiting the Sun, moving about 1° farther along its orbit every day. That means after Earth spins exactly 360° — enough to bring the stars back to the same position — it still has to turn a little bit further before the Sun lines up again, because the Sun has shifted too.
A sidereal day — the time for the stars to return to the same position — is about 23 hours, 56 minutes: roughly 4 minutes shorter than the familiar 24-hour solar day. That 4-minute gap is small enough to ignore on any single night. It is not small enough to ignore over a week.
Because a sidereal day is about 4 minutes shorter than a solar day, a star crosses your local meridian about 4 minutes earlier each night. Looked at another way: at the exact same clock time on two consecutive nights, a star has already shifted roughly 1° farther west than it was the night before — the same 1° per day that Earth gained on its orbit. Over a full week, that adds up to about 28 minutes of "earlier," or roughly 7° of westward shift, at a fixed clock time.
Drag to see how much a star shifts at the same clock time, after a given number of nights.
You observe a constellation at exactly 9:00 PM on Night 1. You plan to observe again at 9:00 PM every night for a full week (7 nights). Roughly how much will the constellation have shifted by the final night?
Nothing here is new physics — it's the two prior activities put to work. Each night, you're recording your constellation's altitude and azimuth (Activity 1.1.2) at your fixed clock time. Stack seven nights of those alt-az readings on the same horizon-dome chart, and the points should trace a short arc drifting westward and slightly downward — exactly the motion the sidereal/solar gap predicts above.
One thing worth double-checking as you log: if your constellation is circumpolar from your latitude (Activity 1.1.1), it never dips below the horizon regardless of the drift — you'll still see the same westward creep, just traced around the pole instead of toward a horizon. If it isn't circumpolar, watch for it rising later or setting earlier over the week, which is the same drift showing up as a change in visibility window rather than position alone.