Saturday, 4.39 am to 4.42 am. Calcutta’s tryst with a man-made celestial phenomenon. The International Space Station (ISS) will be visible to the naked eye for three full minutes on August 31.

“Many of us who have not yet seen the enigmatic, slow-moving, glowing-bright white object with copper-hued solar panels, will have their chance early in the morning, on the last day of August,” Piyush Pandey, assistant director of the M. P. Birla Planetarium, said on Thursday.

Pandey assured the common enthusiast that it would not be tough to identify the spaceship: “Though the ISS looks like any other bright star, it is eye-catching because of its movement and the glow it emanates.”

If the skies are clear, star-gazers will be treated to a three-minute show, as opposed to the ones earlier this month that often lasted less than 60 seconds. “If conditions are right, the ISS can be seen clearly from ground-level. The spacecraft will appear over the western horizon, move slowly across the sky and disappear over the eastern horizon. It will appear nearly as wide as the planet Jupiter,” said Pandey.

The ISS will rise on the south-western horizon of the morning sky at an elevation of 11 degrees and then soar to 80 degrees. It will finally disappear at a point “22.5 degrees to the north of the true east point”, at a height of 69 degrees.

The space station moves rapidly, at about 27,400 km per hour, as it circles the earth every 90 minutes. A typical meteor travels at around 160,000 km per hour and streaks across the sky in a few seconds.

Planetarium sources said satellites and spacecraft are clearly visible if the conditions are right and it helps that the ISS is now one of the most visible objects in the sky. In a typical sighting, the ISS appears first as a dim speck of light on the western horizon.

The space station brightens rapidly as it moves east, a splendid white sphere as it crosses the sky in a matter of a few minutes. At its best, the ISS is said to outshine every star and planet, except the sun and moon.

Mrinal Kanti Roy, a scientist of the Positional Astronomy Centre, however, added a rider: “Through a modest telescope of about eight inches, one can see this colourful spaceship more clearly. The details, like the copper-coloured solar panels, will not be visible to the naked eye.”