American astronomical computer & astrophotographer Mary R. Calvert was born #OTD in 1884.
She started as her uncle Edward Emerson Barnard's assistant & ended publishing his (and their) work that cataloged over 300 dark objects (dark nebulae) β primarily those that extinguish the most starlight reaching the Earth lie between the bulk (inward local sector, central bulge, and other sectors of the Milky Way) thus between the Local Arm (Orion Arm) & the Sagittarius Arm.