Beta Lyrae (HD 174638) is ascribed visual magnitude 30.0 in the Henry Draper catalog. There are hundreds of other stars in the catalog also given magnitude 30.0. What was meant by these nominal magnitudes? Is there a resource in Vizier or elsewhere that provides corrected magnitudes?
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10$\begingroup$ If you click on the "Ptm" column header, you get a pop-up window including "Note (2) : codes used for the magnitudes:"; below that is a list of codes, including "30.0 = variable (var. in published catalog)". $\endgroup$– Peter ErwinMay 9, 2021 at 9:52
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2$\begingroup$ For up-to-date magnitudes, I'd try Simbad, e.g.: simbad.u-strasbg.fr/simbad/… $\endgroup$– Peter ErwinMay 9, 2021 at 9:53
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1$\begingroup$ You can also use Vizier’s photometry tool, vizier.u-strasbg.fr/vizier/sed . The results of a search are displayed as fluxes, but if you click on individual entries you can see the underlying catalog data, which are often in magnitudes. $\endgroup$– Eric JensenMay 9, 2021 at 13:27
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2 Answers
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30.0 mean "variable".
If you click on the "Ptm" column header, you get a pop-up window including "Note (2) : codes used for the magnitudes:"; below that is a list of codes, including "30.0 = variable (var. in published catalog)"
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I have a problem to believe, that the visual magnitude of beta lyrae changes from 3.51 to 30 mags. Maybe 3.0 mag. I looked into the new Gaia catalogue and I am wondering about a lot of measurements. In most cases you can read N unbelievable values for one astronomical star and so on. In my opinion the Hipparcos and Tess catalogue conform better to terrestrial measurements until 2010.
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2$\begingroup$ "30.0 = variable (var. in published catalog)". $\endgroup$– ProfRobMay 13, 2021 at 12:29