Talk:Gamma Draconis

Magnitude[edit]

I reverted the magnitude change; the current source is 2007, it was changed based on a 1991 source claiming "newer". Please explain before making the change again. Tarl.Neustaedter (talk) 18:13, 19 September 2015 (UTC)[reply]

Just to clarify, the Hipparcos catalogue does include Johnson V magnitudes. In the case of γ Dra, it is magnitude 2.24. The value usually quoted as a "Hipparcos magnitude", in this case 2.3617, is a special photometric V magnitude used by Hipparcos. The Hipparcos photmetric magnitude is extremely accurate, but it isn't directly comparable with anything except another Hipparcos photometric magnitude, although there are various conversions available. The 2007 paper often referenced as "Hipparcos" is the new reduction of parallaxes performed on the original Hipparcos data. The Hipparcos mission made measurements between 1989 and 1993. The Johnson V magnitudes from Hipparcos are not widely quoted since they are derived from a variety of sources includeing older ground-based observations. Simbad is a good guide to the most useful and recent photometry sources, in this case choosing the 1991 UBV photometry supplement. Lithopsian (talk) 19:57, 20 September 2015 (UTC)[reply]

Thank you. Tarl.Neustaedter (talk) 05:07, 21 September 2015 (UTC)[reply]

@Tarlneustaedter: @Lithopsian: Actually, the magnitude here apply to all stars. Photometric magnitudes are measured using standard filters (V), which mimic those of the human eye, stated as 'v.' These are derived and calibrated by using standard stars, like in the FK5, etc. Sigma Draconis is FK5 No. 676. Hp magnitudes use a different filter system at different wavelengths, where all the visual magnitude quoted are approximated but calculation of the stars energy distribution via their temperatures. They are more accurate in measure (and comparative measure), but vary significantly in value. The value in SIMBAD is 2.24. This is also in the Yale BSCV5 as 2.23V SIMBAD gives an additional 13 magnitudes made through the 20th Century, and these magnitudes range between 2.12V and 2.25V. None state 2.36V. This is why I changed and revert based on much of the available evidence, as I also did on the Sigma Draconis page. :::As to be accused me by User:Tarlneustaedter because of "personal animosity is causing damage to Wikipedia." [1] for this edit is both unfair and plainly wrong in this case.

Tarlneustaedter. Please get your facts straight before reverting any edits on magnitudes unless you understand the basics of other people's edits. Removal of the numbered order of the bright stars in the [List of bright stars] by User:Tarlneustaedter is obviously ill-informed based solely on questioning and not understanding why this current reverting was actually ecessary.

Comment: As only a few seems to appreciate the complexity of magnitudes in quoting values within articles, I think we need a standard set of guidelines on their usage. Arianewiki1 (talk) 08:08, 21 September 2015 (UTC)[reply]

That sounds like something you should pursue at WP:AST. Tarl.Neustaedter (talk) 18:38, 21 September 2015 (UTC)[reply]

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