Duskward: Astronomical Twilight
Cosmology & the Sky arc, page 156 of 193. Back to The Pixelated Physics Universe
Who they are
Duskward has one line, and says it often: “18 degrees below or it doesn't count.”
Duskward is a character of the Cosmology & the Sky arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
Astronomical twilight ends when the Sun's centre is 18° below the horizon.
$$ \begin{gathered} h_\odot = -18^\circ \quad \text{(end of astronomical twilight)} \\ -18^\circ \le h_\odot < -12^\circ \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $h_\odot$ | altitude of the Sun's centre | — |
Sources
Crossovers
Duskward meets Secantha (Airmass Sec Z). Duskward waits for the Sun to sink 18° below the horizon. Secantha races a target sinking toward it, where the airmass, roughly sec z, grows and extinction rises.
Duskward meets Siderelle (Sidereal Day). Duskward's twilight depends on the Sun's position. Siderelle's stars rise about 4 minutes earlier every day. Together they explain why the observable sky shifts through the year.
Wear the lore
Concept keywords: Astronomical Twilight, Duskward, Cosmology & the Sky, physics lore, Pixelated Physics