# Talk:Sagitta

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## Orion reference

I changed the reference to Orion as violating the Bayer rule of naming the stars in order of brightness into Sagittarius as Orion actually conforms rather well with Beta only being slightly brighter than Alpha and Alpha being variable and possibly brighter when Bayer named them. Sagittarius however has its two brightest stars named Epsilon and Sigma with Alpha way down in the list.--Kalsermar 17:52, 7 November 2005 (UTC)

## Depth of curve of a telescope mirror.

Defined by the formula

$S = \frac{r^2}{2 \times ROC}$

or

$S = \frac{r^2}{4 \times focal length}$

it refers to the glass removed to yield the optical curve. I am writing a book over at Wikibooks on Telescope making and would love to link to an article here at Wikipedia that referenced this bit of knowledge.

vorblesnak@peak.org —The preceding unsigned comment was added by 69.59.203.142 (talk) 20:40, 17 March 2007 (UTC).

Sagitta (optics)? ... said: Rursus (mbork³) 15:23, 3 November 2009 (UTC)

## Geometry

There needs to be a reference to the geometric term "sagitta" - which does not just refer to telescopic mirrors, but more broadly, to the depth of any arc. It is used extensively in architecture when calculating the arc necessary to span a certain height and distance.

Defined by the following, where s equals sagitta (the depth of the arc), r equals the radius of the circle, and l is one half the distance across the base of the arc:

$s = r - \sqrt{r^2 - l^2}$

or

$r = \frac{s^2 + l^2}{2s}$

Architects, engineers, and contractors use these equations to create "flattened" arcs that are used in curved walls, arched ceilings, bridges, and numerous other applications.

I'll try to find it. Versine is also called "sagitta", but that's a third thing. ... said: Rursus (mbork³) 15:13, 3 November 2009 (UTC)
Didn't find it. Made it! Sagitta (geometry)? ... said: Rursus (mbork³) 15:27, 3 November 2009 (UTC)

## This article name

If my creation of Sagitta (geometry) and Sagitta (optics) were correct, we should consider moving this article to Sagitta (constellation) and let this article name contain a disambiguation. ... said: Rursus (mbork³) 15:37, 3 November 2009 (UTC)

## Myths

Moving here some of the myth stuff, that couldn't find their citations (yet):

--§1--

Sagitta was further interpreted by some as Cupid's Arrow or as an arrow shot by Sagittarius at Scorpius.[citation needed]

Other interpretations consider the arrow to have been shot by Centaurus at Aquila, since Centaurus faces the correct direction and is at an appropriate angle to the arrow, whereas Sagittarius is immediately below it facing in the opposing direction (i.e. towards Centaurus).[citation needed]

As a result of the interpretations where Centaurus shot the arrow, may have come the myth in which Chiron (who was usually identified as Centaurus), having been painfully wounded by Herakles, gives up his immortality to rid himself of the pain, and takes the place of Prometheus, Herakles/Chiron then killing Aquila so that Chiron doesn't suffer as Prometheus did. As such, together with Lupus, this may have formed the basis of the tale of the Erymanthian Boar (which was one of Herakles' labours).[original research?]

... said: Rursus (mbork³) 16:18, 3 November 2009 (UTC)

Star tales (a reliable source) tell us a story where Sagitta is sent from Eros (Cupid) towards Ganymede (representend by Aquarius) on instigation on Zeus. Star tales refers to Germanicus Caesar. ... said: Rursus (mbork³) 16:47, 3 November 2009 (UTC)