Although Western astrology is based on the seasons (tropical system), Chaldean numerology also explores connections with fixed stars and constellations. The development of Chaldean numerology was undoubtedly influenced by Egyptian sidereal astronomy (circa 3000 BCE) and later, during the Hellenistic period, by Egyptian sidereal astrology (ancient decans).

There is ongoing debate about whether an ancient Chaldean astrology (around the 5th to 4th century BCE), was based on sidereal or tropical astrology. My personal opinion is that the shared astro-numerological foundation was sidereal, although I won’t delve into proving this here. If true, Chaldean numerology is, in a way, closer to Indian astrology (which is sidereal) than to Western astrology (which is tropical).

The basic fixed stars in Chaldean numerology include the four so-called “royal stars,” associated with the following numbers:
• 23 – The Royal Star of the Lion, or Regulus
• 37 – The Royal Star of the Bull, or Aldebaran
• 51 – The Royal Star of Aquarius, or Markab (contrary to the common notion that Fomalhaut is the royal star in this sign)
• 65 – The Royal Star of Scorpio, or Antares

These four stars can also be combined with planets represented by specific numbers. For instance, 23 represents Mercury in conjunction with Regulus, 37 represents the Sun in conjunction with Aldebaran, and 51 represents Venus in conjunction with the star Markab. The conjunction between the Moon and Antares symbolizes the number 65.

Chaldean numerology can be used to designate additional stars. Various criteria exist for categorizing stars numerologically, and according to one criterion, the following fixed stars can be defined:
• 21 – Polaris
• 82 – Arcturus
• 91 – Sirius

Some constellations include:
• 11 – Virgo and Leo
• 17 – Andromeda
• 37 and 111– Pleiades
• 13 and 43 – Draco

Other interpretations are also possible.