An astronomer in Shanghai has voiced his concerns over an exercise in an enrichment book that requires primary school students to document their observations of the moon.

According to the Xinmin Evening News, first-grade students are required to observe the shape of the moon between 7 pm and 9 pm for 28 consecutive nights in order to complete the task.

Tang Haiming, secretary general of the Shanghai Astronomical Society, was quoted as saying that the task is misleading because the moon rises at a different time every day. For example, people living in Shanghai were able to see the moon rise at 9:04 pm on July 12 and descend at 7:32 am the next day. On July 13, moonrise took place at 9:42 pm and moonset was at 8:32 am the next morning.

The difference in timing was greater on July 23 when moonrise was at 4:36 am. Moonset, on the other hand, was at 6:43 pm.

"It's a shame that the editors do not have enough knowledge about the science that led to such a mistake in a science book," said Tang.

He Qi in Shanghai contributed to this story.