Le Gentil 3 is named after the French observer Guillaume-Joseph-Hyacinthe-Jean-Baptiste Le Gentil de la Galaziere, who observed and
cataloged it in the 1700s.
Dark nebula are concentrations of obscuring dust and dark matter in space that are opaque
that don't let the stars behind them shine through. The other nebula are red because of the ionized hidrogen gases
in the structure.
You can easly see Le Gentil 3 from a location with dark-sky. Not so visible but very beautiful are the other smaller dark nebula, many of them
were cataloged by astronomer E. Barnard.