Astronomy on MSN

What is the origin of the letters used in star classification?

What is the origin of the letters used in star classification? Why didn't astronomers use ABCD? J. HaldimanChicago, Illinois ...
The Harvard Crimson

OBSERVATORY BEGINS TO EXTEND GUIDE TO STARS

Work has been begun at the University Observatory on the extension of the Henry Draper Catalogue, and immense compilation of the spectra of 225,000 stars in every part of the sky, made over a period ...
insider.si.edu

The Henry Draper catalog, by Annie J. Cannon and Edward C. Pickering

https://siris-libraries.si.edu/ipac20/ipac.jsp?&profile=liball&source=~!silibraries&uri=full=3100001~!176585~!0#focus ...
Nature

Our Astronomical Column

RELATION OF SPECTRAL TYPE TO MAGNITUDE.—The Henry Draper Catalogue of the Spectra of Stars, which is now completed but not yet fully published, contains as many as 225,000 stars. The classification is ...