Mahmoud Bey (1815-1885) was the official Astronomer to the Viceroy of Egypt. He was one of the leading intellectuals in Egypt in the middle to late nineteenth century. He was a scientist, engineer, mathematician, and astronomer.

In this work, the observations concerning the star Sirius’s apparent connection with the Great Pyramid are unique and valuable. Using the techniques which he describes in detail, Mahmoud was able to specify a date when he believed the Great Pyramid was constructed: in 3303 BC, with a margin of error of about 100 years either way. He calculated this date carefully from astronomical data which he explains clearly. He also concluded that the pyramids of Giza ‘were built with an astrological and religious intent based on the divine star Sirius.’ He noticed that at the equinox the importance of Sirius became evident in this way: ‘I was completely astonished when I saw that Sirius, when it reached its point of culmination, was shining down perpendicularly upon the southern faces of the pyramids.’ He further says that he became convinced ‘that Sirius held the key to our understanding of the age and purpose of the pyramids.’ As is well known, the heliacal rising of Sirius every year was regarded by the ancient Egyptians as their New Year’s Day, and the star Sirius, called Sepedet (written Spdt) in Egyptian and often referred to by Egyptologists by its Ptolemaic name of Sothis, was considered a female goddess and was identified with and considered as an aspect of the goddess Isis.