Talk:Apparent magnitude

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Table of notable celestial objects - too extensive[edit]

It seems out of place to have such an extensive listing of objects. Perhaps this table should only include truly 'notable' objects, and have its own page (or just link to a website with a similar table) for the extended version? All Clues Key (talk) 02:20, 15 September 2012 (UTC)

Table modified in accordance with this suggestion. All Clues Key (talk) 17:30, 9 October 2012 (UTC)
I have reverted you severe castration of the list as unnecessary. If you do not like the long list you can simply ignore that section. I think it is useful to list sample objects at many apmags. -- Kheider (talk) 18:17, 9 October 2012 (UTC)
As I said above (and received no protests or disagreements to), the current list in unnecessarily extensive and detracted from the overall readability of the article. Hopefully other editors will voice their opinions, but it doesn't seem like this is the right place to include an exhaustive list of apparent magnitudes. The purpose of the article is simply to explain what 'apparent magnitude' means and is. That being the case, providing **some** common, important examples of apparent magnitude is very helpful. A list that contains entries such as, "Sun as seen from Eris at aphelion", "Callirrhoe (small ~8 km satellite of Jupiter)", and "Jupiter if it were located 5000AU from the Sun" seems completely subjective, excessive, irrelevant and unaesthetic. All Clues Key (talk) 18:51, 10 October 2012 (UTC)
You agreed with yourself, and I have protested the excessive removals. Your castrated version of the list included no object dimmer than Messier 33 @ apmag 5.7. How do you know people do not want examples of objects that require a telescope to actually see? Most objects simply are not visible without a telescope and obviously will not be as notable as naked eye objects. Many amateurs consider objects such as Uranus, Ceres, M81, Neptune, Titan, Pluto, Eris, the moons of Pluto, and Halley's comet as notable. -- Kheider (talk) 20:28, 10 October 2012 (UTC)
I agree with Kheider. The lengthy list is most interesting. Rothorpe (talk) 21:14, 10 October 2012 (UTC)

Photometric Reductions[edit]

How is this related, if at all, to photometric reductions? ~jp

Needs improvement[edit]

This article is quite poorly organised and in some places poorly explained. For a relatively important atronomy article it is a bit disappointing. 86.160.222.250 (talk) 21:04, 18 March 2013 (UTC)

Move large table down so that readers needn't scroll down many pages to find formulae[edit]

While the extensive table has its uses (discussed above), readers have to scroll down many pages to find formulae to calculate magnitude. As the table mainly provides examples, I think it's reasonable to move it to the bottom to detract from the rest of the page. cmɢʟee୯ ͡° ̮د ͡° ੭ 11:57, 13 August 2013 (UTC)

It might be useful to have a simpler set of examples of how magnitude relates to linear brightness. I've landed here as a rank amateur simply trying to find out what a magnitude difference (for a rotating asteroid lightcurve) of +/-0.4 means for actual luminance, and I'm still not entirely sure if I've got it right... in fact I've got two different answers, one around +/-0.832x the base figure, the other (more likely) of +/-0.692x. Something basic like what an 0.1 and 0.25 magnitude difference means alongside the 0.5, 1.0 and greater differences already noted (which don't seem to agree?!) as well as a straightforward method of working one to the other in both directions using a regular scientific calculator rather than some kind of advanced graphing model or scientific maths software package (how do you do log100 using Windows Calculator or a Casio FX-85? I've no idea... they just have basic "log" buttons that could mean anything) might do the trick...? This information is, after all, of use and interest to absolute beginners with an interest in astronomy, as well as doctors and professors of the art. 146.199.60.87 (talk) 18:29, 11 August 2019 (UTC)
Edit: or from a further reading of another part of the article, it could be simply described in terms of raising 2.512 to the power of the magnitude in question. EG, 2.512 ^ (-)0.4 = 1.445x (or 0.692x) ((to 3dp / 3.5sf, anyway)). For some reason that simple method isn't part of the discussion anywhere else. Though now I'm having difficulty figuring out how to reverse that to get a magnitude from the linear difference...?! 146.199.60.87 (talk) 19:08, 11 August 2019 (UTC)
Edit 2: Never mind, I'm being dumb / have a poor memory / may have had the calculator overlapping important parts of the screen. Simple terms, raise 100 to the power of (difference/5) to get the magnitude, and raise 2.511886... (ie, 100^0.2) to the power of the magnitude to get the difference. Sorted. Though it may still be worth putting that in such simple plain-English terms in the article because the formulae are rather offputting and not immediately comprehensible to the layman... 146.199.60.87 (talk) 19:16, 11 August 2019 (UTC)
2.512, or however many decimal points you want, is an approximation. You will certainly see it discussed in many places, but there are simple ways to calculate magnitude/brightness differences that don't need any approximations. Not to mention that raising 10 to the power of something has to be a better idea than raising 2.512(...) to the power of something. The article doesn't seem to do itself any favours with explanations that seem to favour factoids for maths geeks over simple explanations for the average reader. Lithopsian (talk) 19:40, 11 August 2019 (UTC)
BTW, in my in-my-head fashion, your calculation would be 10±0.4/2.5. Note that the result is not ± 0.692, but 0.692 or 1/0.692. Lithopsian (talk) 19:45, 11 August 2019 (UTC)

Superbolide[edit]

Since a superbolide, as in a very bright meteor, or a "superbolid meteor", is defined as a bolide of high apparent magnitude (see Wiktionary on "superbolide"), I wonder if anyone has a scholarly source for at what magnitude a bolide is no longer a bolide and becomes a superbolide? Need it be brighter than the Sun? (App. Mag. approx. equal to -26) Or what? N2e (talk) 04:40, 21 November 2013 (UTC)

Maybe far too late an update, but the actual superbolide page says "In astronomy, it refers to a fireball about as bright as the full moon, and it is generally considered a synonym for a fireball", and further down the lede says it's usually considered anything of Mag -17 or above, or about 100x as bright as the full moon. So you've still got a bit of a range there, but at least it's been tied down somewhat. 146.199.60.87 (talk) 18:31, 11 August 2019 (UTC)

TZP[edit]

I removed a messed up part of a sentence. One part of what I removed said, "and then switched to using tabulated zero points" but I could find nothing using a Google search but pages that quoted this Wikipedia article. No one but a specially trained astronomer knows what a "tabulated zero points" is. Another part of what I removed was an external http reference, that was a dead link, leading to a page with nothing on it. If you have a reference to "tabulated zero points" and can explain what they are, in plain, non-technical, English, please do. I am really curious. Nick Beeson (talk) 21:25, 24 February 2015 (UTC)

It looks a bit better now; at least, from what's written, although I don't understand the actual methods used or what they mean, I can at least understand that a different method based upon using a certain celestial object as the measurement benchmark for "zero" (so other measurements may come out positive or negative in relation to it) is now preferred in some cases because of how the colour of different objects / the colorimetry of the observing equipment may affect the results. 146.199.60.87 (talk) 19:20, 11 August 2019 (UTC)

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Relation to implied distance[edit]

If true, could we note somewhere that 5 magnitudes fainter implies 10 times further away (since it is used in distance modulus) ? - Rod57 (talk) 19:22, 16 January 2017 (UTC)

That would seem self evident given that the inverse square law itself implies something that appears 100x fainter is likely 10x as far away, but it may still be worthy of exposition? 146.199.60.87 (talk) 18:33, 11 August 2019 (UTC)

Faintest object seen by hubble[edit]

The cite seems to say limiting magnitude 31.2 - it would help to have a quote for the 31.5 in the footnote, a search of the paper for the number 31.5 turns up a blank. Is it a typo? Robert Walker (talk) 10:01, 20 May 2018 (UTC)

Main Article Problems[edit]

There are many problems with this article page that need significant improvements or update. Fixes include:

  • Magnitude is a unit of measure of relative brightness.
  • The value is not dependant by observations from Earth. e.g. Planets still can have a different apparent magnitudes when viewed, say from Mars. It is the observer perspective not necessiarily from Earth
  • Apparent magnitude often is taken to mean apparent visual magnitude - specifically visible light seen by the human eye.
  • Apparent visual magnitude uses 'v' e.g. 4.5v with instrumental means like photometry uses 4.5V, etc.
  • There is no mention of photometric magnitude (different from visual magnitude and notable requires conversion from on system to another) Nor under Magnitude (astronomy) or Photometric system
  • Various contradictions with Magnitude (astronomy) or Photometric system (Main Strömgren photometric system (related to stellar classification isn't mentioned.
  • Added text also showing positive magnitudes, and exampled range of possible magnitudes with cite.
  • Added the definition of unit of brightness, based on the apparent bolometric magnitude. This has a value of energy measure in watts per square metre (which is measured with a bolometer), where apparent standard is a 0.0 magnitude star. A source for this is "IAU 2015 Resolution B2 on Recommended Zero Points for the Absolute and Apparent Bolometric Magnitude" [1]

I have attempted an improvement in the Introduction, but from the fragmentary nature of the article's text is near impossible to repair.

History section

The History section is very confusing and is poorly cited. Various contradictions appear with Magnitude (astronomy)#History

  • Vega as a standard 0.0 magnitude is sometimes used for instrument calibrations (There are other ways e,g, Described here[2]) How is this used in the southern hemisphere where Vega isn't visible or has intinction problems?
  • It says "The brightest stars in the night sky were said to be of first magnitude" The link to brightest stars is irrelevant, and only refers to stars above 1.0 (or 1.25 in some sources or 1.5 magnitude under Magnitude (astronomy))
  • A second paragraph should have something written about visual estimates of the brightness of stars made with the naked eye. These appear in older text books/ Some of these in the early 19th Century used comparison photometry. Magnitudes of such stars have 'v' attached. I.e. 3.5v.
  • There is little explanation to why surface temperature is related magnitude (It should be linked to the article on luminosity) Most of the text around Vega should probably be removed. The last paragraph has been mostly superseded and might be rightfully removed.
  • Energy is related to Wien curves
  • Variable star observers can estimate magnitudes to 0.11 magnitude and visual observers to about 0.3 magnitude
  • There is no mention of atmospheric extinction

Absolute magnitude section

Most of this should be simplified, summarised and condensed. It should plainly mention that apparent magnitude is independent of distance, while absolute magnitude is based on an arbitrarily set distance of 10 parsec.

  • I could not find the source of this statement: "Indeed, some L and T class stars have an estimated magnitude of well over 100, because they emit extremely little visible light, but are strongest in infrared."
  • The article mentions photographic magnitude, but there is not mention how this related apparent magnitudes.
  • The part about the Milky Way absolute magnitudes and redshifts or there correction appears irrelevant to the article.

Table of examples

Most of this listing is theoretical and difficult to understand. Suggest making a shorter Table with atypical values for bright star and planets. he labels should b changed from "planet Mercury" to Mercury (planet) which would make this more readable. (or even a separate column?)

NOTE: @Lithopsian: There also needs to be an explanation of usage. Many articles have odd usage, like "magnitude 6.0" or or a " the components are magnitudes 4.0 and 5.1 respectively"[3] If magnitude is the unit measure of brightness, then the value must be followed by the unit measure. e.g, "6th magnitude' or "6.0v magnitude" or a "double star is 4.5v and 5.6v magnitude" must be correct. Using the plural of magnitude is also incorrect usage in this respect. Better usage would be "magnitude of 6.0" I find few examples of the reverse usage in the popular or astronomical literature. The claim "correct usage of magnitude as a unit," must be problematic? RfC??

This is explained here[4], where the IAU officially says: "5.17 Magnitude: The concept of apparent and absolute magnitude in connection with the brightness or luminosity of a star or other astronomical object will continue to be used in astronomy even though it is difficult to relate the scales of magnitude to photometric measures in the SI system. Magnitude, being the logarithm of a ratio, is to be regarded as a dimensionless quantity; the name may be abbreviated to mag without a full stop, and it should be written after the number.." Also it says: "The use of a superscript m is not recommended. The method of determination of a magnitude or its wavelength range may be indicated by appropriate letters in italic type as in U, B, V. The photometric system used should be clearly specified when precise magnitudes are given."

Arianewiki1 (talk) 08:27, 19 May 2019 (UTC)

Standard reference values section[edit]

The one thing that the Standard reference values section doesn't seem to discuss is standard reference values, although there is a table of standard fluxes in various passbands. The text of the section is just general chit-chat, very poorly-referenced. I can't think of a name for it. Should it just be dumped and written from scratch? Chopped up and farmed out to other places like the history section? Lithopsian (talk) 19:26, 7 June 2019 (UTC)

Agreed, it's a bit of a mess. It seems to be a general discussion of the difficulty and caveats involved in using a single magnitude value, or one biased towards a certain limited set of spectral bands, to describe all celestial objects; essentially it's just mistitled. The table is more in line with the title as is, but it's also pretty confusing (I recognise almost none of the units used, and I'm not sure why we can't just use watts or lux/lumen), and the only columns that seem to be directly relevant are the first (band designation) and one or other of the last two (luminous flux that's equal to zero magnitude in that particular band); the others could probably be dumped and just replaced with a link to an article about astronomical spectral bands, if one exists. 146.199.60.87 (talk) 19:27, 11 August 2019 (UTC)

Pre-photometric methods of determining magnitude...[edit]

The article mentions that magnitude determination was crude and subjective before the invention of photodetectors, but I do wonder if there would be a way of classifying things in a repeatable fashion to a certain arbitrary level of precision - say, 0.1 on a log2 scale? (Which would give us less than 100 steps from "too faint to see" up to "brightest known object other than the sun and moon", and it's entirely possible to rank printed or on-screen greyscales more finely than that, by eye, so long as you can compare between them, and the dynamic brightness of a VDU or piece of paper is far less than that of natural light)

There are various methods I could think of... for example, the earliest hour that a star becomes visible after sunset, especially if you make repeat measurements at the summer and/or winter solstice and equinoxes, using some way of excluding visual pollution from the horizon or nearby dwellings (e.g. the classic lensless paper tube "telescope", or the makeshift observatory of a building missing its roof - the latter of which, along with a parabolic support made of bricks, was something actually used by pre-optical-glass astronomers, especially in Arabia). Date and time was something much more easily measured even in antiquity, and the motion of the stars and planets themselves was used to measure such. Your determination could then be checked by seeing whether certain well known benchmark stars were or were not yet visible, and a ranked list drawn up and refined over time. Once you had sufficient entries, it would be enough to simply wait for the first moment the star / planet of interest became visible, and quickly check to see which other stars off the list in the general predicted neighbourhood were already visible, in order to add the as-yet unranked one into the catalogue in the right place...

Maybe it wouldn't be absolutely accurate, or mathematically precise other than in terms of direct comparison, but for the type of astronomy that was even possible (and thought relating to it) in the pre-telescopic age, it would likely have been more than sufficient, and still fairly scientifically valid. Astronomers of old weren't entirely stupid, after all, just limited in the equipment they had available. It's not beyond the realm of imagination to consider they might have come up with some clever scheme to repeatably determine the objective brightness of a star (after all, I just pulled one out of my ass, and I haven't had a lifetime of pondering on the meaning of the universe in an age long before multichannel TV and the internet); the brightening and darkening of the sky, on clear nights, in an age before any meaningful atmospheric or indeed much light pollution, would have been like the apocryphal clockwork, and something you could set your biological photometer by. 146.199.60.87 (talk) 19:41, 11 August 2019 (UTC)

And? None of this can go in the article without reliable references. However, when you've published your phD thesis on the subject ... :) Lithopsian (talk) 19:47, 11 August 2019 (UTC)