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View Full Version : Happy birthday, redshifts!



ngc3314
2012-Sep-17, 03:06 PM
If I got my timing right, tonight marks the 100th anniversary of V.M Slipher's first galaxy spectra, which formed a key part of the realization that there is an overall redshift-distance relation (and initially stood out as showing larger red- and blue-shifts than met with in samples of nearby stars). For a book chapter, I once asked a colleague at Lowell for details - she went to the old observing logs and found that some of Slipher's spectra needed exposures as long as 35 hours spread over many nights. Slipher was using the 0.6m Lowell refractor; spectrograph design is pretty interesting when the primary optic has chromatic aberration to start with.

And look where that start has brought us...

antoniseb
2012-Sep-17, 03:38 PM
That's a very cool anniversary! I'm trying to think of a fun and appropriate way to celebrate...

StupendousMan
2012-Sep-17, 04:11 PM
Examples of spectra taken by Milton Humason with exposure times of 33 and 45 hours:

http://spiff.rit.edu/classes/phys443/lectures/expand/expand.html

The page contains links to discussions of the early spectroscopic work at Mount Wilson.

Squink
2012-Sep-18, 09:01 PM
http://spiff.rit.edu/classes/phys443/lectures/expand/expand.htmlThat's a very nice raisin bread recession velocity demo in there: http://spiff.rit.edu/classes/phys443/lectures/expand/RaisinBread.swf

George
2012-Sep-21, 05:25 PM
If I got my timing right, tonight marks the 100th anniversary of V.M Slipher's first galaxy spectra, which formed a key part of the realization that there is an overall redshift-distance relation (and initially stood out as showing larger red- and blue-shifts than met with in samples of nearby stars). For a book chapter, I once asked a colleague at Lowell for details - she went to the old observing logs and found that some of Slipher's spectra needed exposures as long as 35 hours spread over many nights. Slipher was using the 0.6m Lowell refractor; spectrograph design is pretty interesting when the primary optic has chromatic aberration to start with.
I vaguelly recall an odd account that he had to use his body to help the alignment in getting those spectra. Were there clock drive isssues back then?