Chacornac discovered NGC 1988 in Taurus at Paris Observatory with a 10" refractor. He described the object as a 11 mag star with nebulosity (seen again on January 27, 1856). On November 20, 1862 the nebula had disappeared. Jean Elias Benjamin Valz (1787-1867), the director of Marseille Observatory could not find the object in 1861, noting a false image of a star. Chacornac is kown for his Ecliptical Charts.
| D | N | NI | Y | M | D | Ap | I | T | Con | Type | S | Author | Title | Source |
| 1 | N | 1988 | 1855 | 10 | 19 | 10,0 | Rr | v | TAU | * | 9 | Chacornac | Nebuleuse variable de zeta Taureau | Comp. Rend. 56, 637 (1863) |
 |
 |
Chacornac's sketch of M 51, made 1862 at the 80 cm Foucault reflector of Paris Observatory
