On July 24, a waxing gibbous moon is expected to sit near red-orange Antares, the star marking the scorpion's heart, giving UK observers a bright marker for Scorpius low in the southern sky. [1]

The Guardian's chart shows the view from London at 11 p.m. BST, while noting that the constellation stays so low at UK latitudes that it never fully rises above the horizon and can be frustrating to trace; it remains in roughly the same region all week, but the moon pairing makes that night easier. [1]

That makes this a future service forecast published on July 20, not a report that the sky cleared, the full constellation rose or anybody completed a sighting four days later, and the guidance describes prospective observers rather than a count of successful viewers.

Local cloud, light pollution and the quality of a southern horizon will decide what any observer can see, and Antares may appear to twinkle because its light passes through thicker, more turbulent air close to the horizon rather than because the star changes.

The mythology can help memory: Scorpius was said to have killed Orion and the constellations occupy opposite sides of the sky, but the practical value lies in keeping date, time, direction and limits together so a chart remains guidance instead of becoming an observation, with no later weather admitted into the July 20 record.

-- KENJI NAKAMURA, Tokyo