Talk:Umbra, penumbra and antumbra

message: This article has a whole heap of 'stuff' about the word umbra. Perhaps most of it could be put on an disambiguation page and the core of the article becomes umbra, with reference to shadows, as it once may have been intended? POds 03:58, 5 May 2006 (UTC)
thread_title: Clean up 2006/05

message: As mentioned, it has a whole heap of meanings lumped onto one page.  I tired seperating them out as best I could.  However I feel that the main focus of this page is the use of Umbra in an astronomy/physics sense, as in dealing with light sources.  Therefore, I propose a disambiguation page for Umbra, so that the other topics mention can be elaborated on as well.  Stovetopcookies 04:41, 5 May 2006 (UTC)
thread_title:  Disambig? 

message: It looks like both these words have lots of uses, but they do also have very specific definitions, as parts of shadows. How about:
#the definitions go to Wiki Dictionary
#we add a disambiguate page for penumbra (instead of the list of other meanings)
#the eclipse and sunspot specific uses of umbra, penumbra, and antumbra go to the articles on eclipses and sunspots
Lisamh 03:39, 20 September 2006 (UTC)
thread_title: merge umbra and penumbra

message: I've merged not only Penumbra, but also Antumbra, to Umbra. —Quarl (talk) 2007-02-28 10:41Z
* Why not move to, say, Umbra and penumbra? Seems to be more in line with what I've seen on other articles. Cctoide 18:02, 19 April 2007 (UTC)
thread_title:  Merged 

message: Could someone please address the legal use of the word penumbra. i.e. "If you are a history buff you will recall the confirmation hearings of Thomas, Scalia, and Robert Bork.  Specifically, the exchange of views concerning the US Constitution and its “penumbra of rights.”  The “penumbra” area is a dividing line for many constitutional scholars (and politicians)."  —Preceding unsigned comment added by 141.197.12.183 (talk) 13:26, 24 September 2007 (UTC)
thread_title:  question? 

message: I just changed the point source reference, as it said that a point source would cast an umbra and penumbra, but no antumbra.  I don't see how you can get a partial shadow from a point source - either you can draw a line to it or not, there's no partial shadow. --198.103.172.9 (talk) 17:19, 23 May 2008 (UTC)
thread_title: Point source

message: The article states that a penumbra is usually used in reference to the shadow cast by celestial bodies, and that it is a feature of visible light. In fact, it applies to any EM radiation. It's an important principle in radiation physics.  —Preceding unsigned comment added by Jonnylaney (talk • contribs) 12:20, 3 March 2009 (UTC)
thread_title:  Penumbra just for light source? 

message: There should be a simple line diagram, showing the situation from the side, with also end-on drawings of the shadows cast on a plane within and outside of the umbra.  The present artistic pictures should be scrapped. 94.30.84.71 (talk) 20:43, 16 September 2011 (UTC)
thread_title:  Diagram 

message: The diagram shows the antumbra to be lighter than the penumbra.
The text says the antumbra is darker than the penumbra.
A contradiction? Most likely.
It appears that the diagram is deceiving. To my understanding, the area labeled "antunumbra" is not; it is the area where an antunumbra may be observed. The actual antunumbra is the shadow on the shadow-casting object itself, when the light-source is larger than the object, as with an annular eclipse.
The "diagram within a diagram," displays the actual antunumbra on the shadow-casting object. 
Which raises a question... maybe two. Is the umbra the area of shadow, or is it considered to be what you see? Same Q for penumbra; because the "diagram within a diagram" labels the view of the semicircle of the light source as the penumbra, but the line/pointer indicates the penumbra is the area of shadow.
Maybe they are both (view, as well as shadow) the penumbra, or different definitions of penumbra. 74.100.137.109 (talk) 15:58, 23 May 2014 (UTC)
thread_title: Problem with diagram

message: : The "end" of the umbra is the point where the occluding body is equal in apparent size to the light source; for the Moon, this is roughly the semimajor axis of its orbit, since the angular size of the Sun and Moon are nearly identical.
This new sentence needs rewriting (and I'm just the Sloth to do it).  The apparent angular size of the Moon (as seen from where?) is not the cause of the length of its umbra! —Tamfang (talk) 21:48, 24 May 2014 (UTC)
thread_title:  the Moon's umbra 

message: The image subtitle was wrong, in a lunar sclipse Moon can cross the umbra and penumbra zones, but never the antumbra one.  — Preceding unsigned comment added by 135.245.248.72 (talk) 12:32, 18 May 2017 (UTC)
thread_title:  Moon is never in Earth's antumbra. 

message: Regarding this sentence "Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast." a point source is not a source of collimated light. If other agree I would suggest removing the part about point sources.  — Preceding unsigned comment added by Alexbhandari (talk • contribs) 18:06, 24 March 2020 (UTC)
replies: text: How about changing to something along the lines of "Only the umbra is cast when the light source is a point or collimated, assuming no diffraction" ? SlowJog (talk) 20:26, 21 December 2021 (UTC)
thread_title:  Incorrect statement: collimated beam (such as a point source) 

message: This phrase appears (undefined) on many solar-eclipse pages. It would helpful if it could link to a section of this article, but the phrase doesn't appear here. Thmazing (talk) 13:35, 19 April 2024 (UTC)
thread_title:  "Umbral eclipse"