Editing Stellar classification (section)

===Draper system===
{| class="wikitable" style="float: right"
|+ Classifications in the Draper Catalogue of Stellar Spectra<ref name="drapera"/><ref name="draperb"/>
|-
! Secchi || Draper || Comment
|-
|style="text-align:center;"| I
| '''A''', '''B''', C, D
| Hydrogen lines dominant
|-
|style="text-align:center;"| II
| E, '''F''', '''G''', H, I, '''K''', L
|
|-
|style="text-align:center;"| III
| '''M'''
|
|-
|style="text-align:center;"| IV
| N || Did not appear in the catalogue
|-
|style="text-align:center;"| V
| '''O'''
|style="max-width:25em;" | Included [[Wolf–Rayet star|Wolf–Rayet]] spectra with bright lines, sometimes classified separately as type W<ref>{{cite journal|bibcode=1930BHarO.878....1P|title=Classification of the O Stars|journal=Harvard College Observatory Bulletin|volume=878|pages=1|last1=Payne|first1=Cecilia H.|year=1930}}</ref>
|-
|style="text-align:center;"| V
| P || Planetary nebulae
|-
| &nbsp;
| Q || Other spectra
|-
|colspan="3" style="text-align:center;" | ''Classes carried through into the MK system are in '''bold'''.''
|}

In the 1880s, the astronomer [[Edward C. Pickering]] began to make a survey of stellar spectra at the [[Harvard College Observatory]], using the objective-prism method. A first result of this work was the ''[[Draper Catalogue of Stellar Spectra]]'', published in 1890. [[Williamina Fleming]] classified most of the spectra in this catalogue and was credited with classifying over 10,000 featured stars and discovering 10 novae and more than 200 variable stars.<ref name="Williamina Fleming">{{Cite web|title=Williamina Fleming|url=https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095823407|access-date=2020-06-10|website=Oxford Reference|language=en}}</ref> With the help of the [[Harvard Computers]], especially [[Williamina Fleming]], the first iteration of the Henry Draper catalogue was devised to replace the Roman-numeral scheme established by Angelo Secchi.<ref>{{Cite web|title=Williamina Paton Fleming -|url=http://www.projectcontinua.org/williamina-paton-fleming/|access-date=2020-06-10|website=www.projectcontinua.org|language=en-US}}</ref>

The catalogue used a scheme in which the previously used Secchi classes (I to V) were subdivided into more specific classes, given letters from A to P. Also, the letter Q was used for stars not fitting into any other class.<ref name="drapera">{{cite journal |bibcode=1890AnHar..27....1P |title=The Draper Catalogue of stellar spectra photographed with the 8-inch Bache telescope as a part of the Henry Draper memorial |journal=Annals of Harvard College Observatory |volume=27 |pages=1 |last1=Pickering |first1=Edward C. |year=1890}}</ref><ref name="draperb">pp. 106–108, Hearnshaw 1986.</ref> Fleming worked with Pickering to differentiate 17 different classes based on the intensity of hydrogen spectral lines, which causes variation in the wavelengths emanated from stars and results in variation in color appearance. The spectra in class A tended to produce the strongest hydrogen absorption lines while spectra in class O produced virtually no visible lines. The lettering system displayed the gradual decrease in hydrogen absorption in the spectral classes when moving down the alphabet. This classification system was later modified by Annie Jump Cannon and Antonia Maury to produce the Harvard spectral classification scheme.<ref name="Williamina Fleming"/><ref>{{Cite web|url=http://spiff.rit.edu/classes/phys301/lectures/class/class.html|title=Classification of stellar spectra | access-date=2020-06-10|website=spiff.rit.edu}}</ref>