# Talk:Upper and lower tangent arcs

(Redirected from Talk:Upper tangent arc)
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## Upper tangent arc to 46° halo as well

Some number of years ago I was in Fairbanks, Alaska (winter or early spring, if I remember right) and I saw a remarkable occurrence: a distinct 22° halo completely encircling the sun, a somewhat fainter 46° halo that spread all across the sky, and upper tangent arcs to both halos with bright spots at the points of tangency. I would imagine that an upper tangent arc to a 46° halo is a rather rare occurrence. Deepmath (talk) 09:14, 23 February 2009 (UTC)

## Error regarding dispersion

The final part of the introductory paragraph refers to dispersion in a halo. Whichever aspects of such effects are intended for particular attention, the explanation suffers a problem:

Like many other halos, upper tangent arcs grade from a red inner edge to a blue outer edge because red light is refracted more strongly than blue light.

Of course it may be a simple error of transposition—blue light is refracted more strongly than red. But the intent of the section is obscure. Given the sense of curvature of upper (or lower) tangent arcs, a reader might not be certain which edge is the "inner" one. I think the paragraph would benefit from being re-written. Aboctok (talk) 18:05, 27 September 2012 (UTC)

## Mathematical Definition

What curve (or rather, family of curves, as the article describes the shape of the arc changing over the course of a day) is being traced by the tangent arc? Arlo James Barnes 20:57, 6 March 2013 (UTC)

## crystal orientation

One of these was visible in Cambridge recently! "their long axis oriented horizontally, while otherwise rotated in any direction". This needs rewording, as it is not at all clear what is meant (e.g. is it the other axes that are oriented in any direction, or the long axes oriented anywhere in the horizontal plane?). --Brian Josephson (talk) 11:32, 18 July 2013 (UTC)

It's both: the only constraint is that the long axis is horizontal. The long axis can point in any horizontal direction, and there can also be an arbitrary rotation around the long axis. Can you suggest a better wording? --Amble (talk) 19:48, 31 July 2013 (UTC)

In that case can't 'while otherwise rotated in any direction' just be omitted? Just saying 'their long axis oriented horizontally' seems to cover it all? I must say by the way that it is nice to be on a talk page populated by intelligent people, which can hardly be said of other talk pages I've been involved with recently where the discussions have been extremely political, not to say nonsensical. It made my day! --Brian Josephson (talk) 20:00, 31 July 2013 (UTC)

Just omitting it still leaves it somewhat unclear whether the crystals all have their long axes oriented in the same horizontal direction, or each one in a different direction (as is actually the case). This is basically a condensed version of the discussion here of singly-oriented crystals. I split into a separate sentence and expanded slightly, but I think what the article really needs is to be expanded quite a lot. --Amble (talk) 20:07, 31 July 2013 (UTC)

Your addition certainly clarifies things. I've tweaked what follows; hope you like those changes.--Brian Josephson (talk) 20:18, 31 July 2013 (UTC)

## Merger proposal of Upper and Lower tangent arc articles

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.
The result of this discussion was to merge and rename. Pierre cb (talk) 19:43, 13 July 2015 (UTC)

Both articles "Upper and Lower tangent arc" are stubs talking about the same phenomenon but at opposite sides from the Sun position. Both should be merged into a new article, called "Tangent arcs" or "Upper and lower tangent arcs", as they are complementary.

Pierre cb (talk) 03:53, 9 July 2015 (UTC)

No objection from me. Really this is a whole class of stubs that might be better as a single better fleshed-out article. --Amble (talk) 07:00, 9 July 2015 (UTC)
Yes, I totally agree. I think it would greatly contribute to a better understanding of the phenomenon amongst the general public if we could make one general page for all halo types, as I have done a while ago for the Dutch version. Idea? Drabkikker (talk) 08:38, 9 July 2015 (UTC)
Hey, that looks great! If we had one good article like your Dutch one, we could redirect the others to it. -Amble (talk) 09:25, 9 July 2015 (UTC)
Thanks! I'm afraid I won't be able to work on it anytime soon due to lots of other commitments, but I think we already have a nice page if we just combined the information from the numerous daughter pages. Drabkikker (talk) 10:34, 9 July 2015 (UTC)

The above discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.