Lat: 7.3°N, Long: 63.4°E, Diam: 56 km, Depth: 2.14 km, Rükl: 38
- AS11-42-6214 and AS11-42-6222 (made during the mission of Apollo 11 in july 1969) show orbital northwest-looking views of both Firmicus (foreground) and Mare Crisium in the distance. Note the dark streak of Lacus Perseverantiae nearby Firmicus.
- Apollonius N, the 9th item in C.A.Wood's list of Concentric Craters (1978), is noticeable on the Hi-Res scan of Lunar Orbiter 4's photograph LOIV-184-h1. Because of the oblique look at it (at the region of Apollonius and Apollonius N) it's rather difficult to locate both of them. But... once you have detected the dark-floored FIRMICUS, it will be an easy task to discover Apollonius N. In this online scan of LOIV-184-h1, we are looking "upside down" at the Apollonius region (north toward the bottom). The Concentric Crater Apollonius N is "just above" the dark-floored Firmicus (in reality it's SOUTH of Firmicus).
- Research Lunar Orbiter IV and orbital Apollo 11 photography: Danny Caes
(IAU Directions) FIRMICUS.--A somewhat larger, more regular, but, in other respects, very similar ring-plain, N.E. of Apollonius. Some distance on the E., Madler noted a number of dark-grey streaks which apparently undergo periodical changes, suggestive of something akin to vegetation. They are situated near a prominent mountain situated in a level region.
Depth data from Kurt Fisher database
- Pike, 1976: 2.14 km
- Westfall, 2000: 2.14 km
- Viscardy, 1985: 1.7 km
- Cherrington, 1969: 2.56 km
Julius Firmicus Maternus, (fl. A.D. 330-354) a writer and notable astrologer, who lived in the reign of Constantine I and his successors. Author of Matheseos Libri Octo ("Eight Books of Astrology", c. 330).
- Southeast of Mare Crisium (near Condorcet, Auzout, Firmicus, and Apollonius) runs the unofficially named North Valley/ Vallis North; or Vermiform Valley. These unofficial names are included in the Hitchhiker's Guide to Rukl 38.