Backglowen: CCD Sky Background Noise
Cosmology & the Sky arc, page 158 of 193. Back to The Pixelated Physics Universe
Who they are
Backglowen has one line, and says it often: “Sky-limited. even my noise isn't mine.”
Backglowen 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
CCD equation: in the sky-limited regime, sky background noise dominates read noise and SNR ∝ √t.
$$ \begin{gathered} \text{SNR} \propto \sqrt{t} \quad \text{(sky-limited)} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $\text{SNR}$ | signal-to-noise ratio | — |
| $t$ | exposure time | s |
Sources
- S. B. Howell, Handbook of CCD Astronomy, 2nd ed. (Cambridge, 2006), §4.4
Crossovers
Backglowen meets Pelletine (Shot Noise). Backglowen's sky-limited images are limited by photon shot noise from the sky, which is Pelletine's physics applied to light. Signal-to-noise grows as √t.
Backglowen meets Nightglowe (OH Airglow). Backglowen's sky background noise is partly Nightglowe's OH airglow, which dominates the near-infrared night sky.
Backglowen meets Surgelle (Opposition Surge Full Moon). Surgelle's full Moon floods the sky with scattered light. Backglowen's sky-limited noise rises with it, so faint-object work waits for dark time.
Wear the lore
Concept keywords: CCD Sky Background Noise, Backglowen, Cosmology & the Sky, physics lore, Pixelated Physics