Based on a recessional velocity of 4470 km/sec, NGC 2150 is about 210 million light years away. Given that and its apparent size of 1.1 by 0.9 arcmin, it is about 65 thousand light years across.

NGC 2158 is 10 to 15 thousand light years away. It is over a billion years old, so its hottest Main Sequence stars are spectral type F0, and it has many orange and red giants. Its thousands of stars are contained within a region about 5 arcmin across, or 15 to 20 light years in diameter. Because of this compact structure, it was once thought to be a small globular cluster, but the "youth" of its stellar population confirm that it is a galactic cluster (Milky Way globular clusters are over 10 billion years old).

In the image above, NGC 2158 is the smaller cluster at lower right. M35 is the larger one at upper left. However, the difference in apparent size is misleading, as it is primarily due to their different distances (NGC 2158 being 10 to 15 thousand light years away, and M35 only about 2800 light years away, or about four to five times closer).

M35 is about 2800 light years away. Its core is almost 20 arcmin across, and scattered outliers cover twice that distance (these apparent sizes correspond to about 15 and 30 light years). The cluster contains over 120 stars brighter than magnitude 13, and around 500 stars total. Its hottest stars are of spectral class B3, but it also contains some yellow and orange giants of type G and K. This indicates a probable age of 100 million years. Velocity studies indicate that there are about 2000 solar masses in the central 10 light years, and the entire cluster probably contains at least twice that mass.

In the image above, NGC 2158 is the smaller cluster at lower right. M35 is the larger one at upper left. However, the difference in apparent size is misleading, as it is primarily due to their different distances (NGC 2158 being 10 to 15 thousand light years away, and M35 only about 2800 light years away, or about four to five times closer).

(See the discussion of Hodierna for an explanation of why he was not credited with the discovery of any NGC object. In addition, although many of his discoveries can be definitely connected to specific NGC objects, the identification of NGC 2169 and 2175 with Hodierna's observations is very uncertain.) Just a few stars, scattered across a region about 6 arcmin across.

Per Dreyer, NGC 2174 (= Stephan's list IX (#7), 1860 RA 06 01 03, NPD 69 19.0) is "extremely faint, between 3 very faint stars". The position precesses to RA 06 09 23.9, Dec +20 39 56, dead center on the brightest portion of a group of stars and surrounding nebulosity located in the northwest portion of NGC 2175, so the identification is certain. The "knot in NGC 2175" (as described by Corwin), is about 3.5 by 2.0 arcmin in size. Note: Many (if not most) references assign NGC 2174 to the much larger nebula which should be actually be called NGC 2175 (as shown below). As a result, most images of "NGC 2174" are actually images of NGC 2175.

Per Dreyer, NGC 2175 (= Bruhns, 1860 RA 06 01 19, NPD 69 29.7) is an "8th-magnitude star in nebulosity" (the 8th-magnitude star being Auwers 21, or HD 42088). The second IC lists a corrected 1860 RA (per Bigourdan) of 06 01 32. Per Corwin, this correction is due to Bigourdan's mistaking a bright portion of the nebula as the object observed by Bruhns. However, Auwers' observation of the 8th-magnitude star and surrounding nebulosity, combined with Dreyer's description, makes it clear that it is the much larger nebula surrounding that star that is meant to be NGC 2175, and not the bright knot to its east measured by Bigourdan. Therefore, ignoring the "corrected" RA, the position precesses to RA 06 09 39.2, Dec +20 29 11, which is within 0.1 arcmin of HD 42088 (whose position is listed as the position of NGC 2175, above); so the identification is certain. Despite the certain identification, many (if not most) references incorrectly call this nebula NGC 2174, most so-called images of NGC 2174 are actually images of NGC 2175, and the positions and descriptions of the two are often mixed up, more or less randomly. The apparent size of NGC 2175 is about 40 by 30 arcmin. Aside from NGC 2174 (one of several knots in NGC 2175), the emission nebula contains IC 2159 and an open cluster (OCL 476) which has acquired the title NGC 2175, despite not being mentioned in the historical literature describing the nebula (but is therefore mentioned in the double description at the start of this entry).