Fernelius is a lunar

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 impact crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 located in the southern highlands just to the north of the walled plain Stöfler

Stöfler (crater)

Stöfler is a large lunar impact crater located in the crater-riddled southern highlands, named for Johannes Stöffler. It sits to the west of the crater Maurolycus. The distorted crater Fernelius is attached to the northern rim, and Miller and Nasireddin lie to the west...

. The crater Kaiser

Kaiser (lunar crater)

Kaiser is a lunar crater. It lies in the crater-riddled terrain in the southern part of the Moon's near side. The crater is nearly attached to the northeast rim the slightly larger crater Fernelius, and the two are separated by an irregular patch of ground only a few kilometers wide...

 is located next to the northwest rim of Fernelius. To the north-northwest are the craters Nonius

Nonius (crater)

Nonius is a lunar impact crater. It is located in the rugged southern highlands on the Moon's near side. The northwestern side and about half the interior floor are overlain by the rim and outer rampart of the walled plain Walther...

 and Walther

Walther (crater)

Walther is an ancient lunar impact crater located in the southern highland region of the Moon. It is joined along the western rim to the crater Deslandres...

. Southeast of Fernelius is the crater cluster of Miller

Miller (crater)

Miller is a lunar impact crater that lies amidst the rugged terrain in the southern part of the Moon. It is attached to the northern rim of the smaller crater Nasireddin, and the outer rampart of the latter reaches almost to the central peak formation at the mid-point of Miller's interior floor...

, Nasireddin

Nasireddin (crater)

Nasireddin is a lunar impact crater that lies in the rugged terrain in the southern part of the Moon's near side. This crater overlaps two older formations, intruding into the crater Miller to the north and Huggins to the west...

, Huggins

Huggins (lunar crater)

Huggins is a lunar crater that lies in the rugged southern highlands of the Moon's near side. This crater lies across the eastern rim of the larger crater Orontius. The eastern rim of Huggins is laid across in turn by the slightly smaller crater Nasireddin. Thus these three craters form a triplet...

, and Orontius

Orontius (crater)

Orontius is a lunar impact crater that lies in the heavily cratered southern highlands of the Moon's near side. It is located to the northwest of the prominent ray crater Tycho, and south and east of the large walled plain Deslandres...

.

In the past the floor of Fernelius has been resurfaced, leaving a relatively flat, featureless surface with no central peaks. The crater rim has been heavily worn and indented by impacts, the most prominent being Fernelius A which intrudes into the western rim.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Fernelius.

Fernelius	Latitude	Longitude	Diameter
A	38.3° S	3.5° E	30 km
B	37.4° S	4.1° E	10 km
C	38.9° S	4.4° E	7 km
D	38.2° S	6.2° E	7 km
E	38.3° S	6.6° E	6 km