{Oberlin College [F. E. Carr; Emma L. Frank]; Sir Frederick O'Connor; J. Ogden; R. M. Ogden; Yngve Öhlman; Eleanor Olney; John Ohlsson; William Tyler Olcott [& G. H. Lutz]; Charles P. Olivier; P. Th. Oosterhoff; Earle L. Ovington}
[Douglas G. O'Brien {Corning Glass Center}; G. J. Odgers; Stephen O'Donnell {& Irving D. Hirschfield}; Ruth Oedin; Richard Ogden; Yngve öhman {c.ltr HWBabcock to Yö}; J. B. Oke; Frank O'Malley; Jan H. Oort {incl c.ltr JWB to JHO; c.ltr JHO to Henry T. Heald; c.ltr WCMiller to JHO}; P. Th. Oosterhoff; Optical Society of America {Wallace R. Brode}; Dwayne Orton {Think magazine}; Mabel Romero de Osnovikoff; Donald E. Osterbrock]
[Madeline Ochsé; G. J. Odgers {incl ltr RMPetrie to ISB; ltr GJO to OCWilson; c.ltr OCWilson to GJO}; John L. Odom; Office of Naval Research; Yngve öhman {incl c.ltr HWBabcock to Yö}; Jan H. Oort {incl c.ltr JHO to CPH}; P. Th. Oosterhoff; Ygnacio A. Ortiz {folded}; T. G. Ostrom]
[Claus Oesterwinter; Alfred Olmstead; Jan H. Oort {incl ltr OStruve to ISB; c.ltr OStruve to JHO}; P. Th. Oosterhoff {incl memos on project for a European observatory in southern hemisphere}; Donald E. Osterbrock{incl ltr ISB to MLHumason; ltr ISB to GOAbell}]
{Charles L. Limes; E. M. Lindsay; Charles B. Lipman; Charles G. Little; L. C. Lonyo; Rafael Obregon Loria; Los Angeles Board of Park Commissioners; Los Angeles Civic Bureau of Music and Art; Los Angeles Times [G. L. Goodmansen]; Hazel Marie Losh; Katheryn Lowe [incl ltr Irving M. Grey ? FHS]; Percival Lowell; Robert L. Lucas; --Luppo-Cramer; Lwow Astronomical Institute}
{Dorothy N. Davis; Dartmouth College, Baker Memorial Library; L. P. Delsasso; Denver Public Library; Debrecen University Physical Institute; Rev. C. E. Deppermann, S.J.; Detroit Public Library; Deutsche Physikalische Gesellschaft; Deutsches Museum; L. E. Dickson}
{L. Gabba; Galileo Portrait [Charles E. Lewis]; Joaquín Gallo; H. A. Garfield; Willard H. Garrett; G. N. Garrison; General Petroleum Corp. of California; Georgia Astrophysical Observatory; F. Louise Gianetti; Henry L. Giclas; Millicent Gilder}
