Emitters¶

The emitters are the physical light sources of the night sky. Each one is two objects:

a builder – Emitter and its subclasses – which holds astropy and numpy state and turns an Observation into arrays, in prepare(obs).
a runtime source – SpectralSource – which the builder hands to the scene in model(). It is a JAX pytree, it is traced and differentiated, and it owns every Parameter the optimizer can reach.

Emitter	Path	Scales?	Model
`Airglow`	diffuse	no	ESO SkyCalc, with an SFU curve
`ZodiacalLight`	diffuse	yes	Leinert et al. (1998)
`Moon`	point	yes	ROLO, after Jones et al. (2013)
`Stars`	both	yes	Gaia DR3 + Pickles (1998)
`BrightStars`	point	yes	XHIP or Gaia, points only
`PointSource`	point	yes	one source, one spectrum

“Scales” is whether the emitter takes a brightness: a fittable amplitude on everything it emits, on both the diffuse and the point path. Airglow is the exception: its spectral model already evaluates 0.2 + 0.00614 * sfu(t) with a trainable sfu.

Writing your own emitter¶

Subclass Emitter, call super().__init__(geo, spectral_model, ...) and implement _prepare(obs). The base records the geometry signature that lets build() catch a component built against a different Geometry, validates brightness, and checks the frame count before every prepare.

_prepare returns a SourceObsData. Two flags on it choose the render path:

direct: Whether diffuse radiance is extincted along the line of sight.
inscatter: Whether point sources are in-scattered individually, giving each its own scattered halo.

The builder layer¶

nyx.emitter.base Module¶

Classes¶

Emitter

Shared base for EmitterLike implementations.

nyx.emitter.catalog Module¶

Classes¶

CatalogEmitter

A star catalog.

The runtime layer¶

nyx.emitter.sources Module¶

Classes¶

SpectralSource

Routes the diffuse and point paths through one spectral_model call.

Zodiacal Light¶

nyx.emitter.zodiacal Module¶

Classes¶

ZodiacalLight

Zodiacal light with the Leinert spatial model.

Airglow¶

nyx.emitter.airglow Module¶

Classes¶

Airglow

Airglow source with van Rhijn weighting.

Moon¶

nyx.emitter.moon Module¶

Functions¶

lit_fraction(alt_rad[, disc_radius_rad, ...])

Fraction of the scattering column above the observer still lit.

Classes¶

Moon

Moon emission model.

Stars¶

nyx.emitter.stars Module¶

Functions¶

gaia_star_field(geo[, lim_mag])

Split Gaia DR3 into all-sky point sources and the background they leave.

Classes¶

`BrightStars`	Pure point-source star catalog, with no diffuse map.
`Stars`	Star catalog emitter with resolved bright stars and a diffuse map.

Point Sources¶

nyx.emitter.point_source Module¶

Classes¶

PointSource

One point source at a fixed ICRS position.

Catalogs¶

nyx.emitter.catalogs.gaia Module¶

Functions¶

`catalog_map`(g, bp, rp, ra, dec, npix)	Bin catalog stars into a HEALPix linear-flux map.
`color_grid`(bp, rp)	Reddened Pickles (1998) spectra indexed by the Gaia `RP - BP` colour.
`load_dr3`()	Download (once) and load the Gaia DR3 catalog and faint-star map.
`photometry`(catalog)	`(G, BP, RP)` magnitudes, with missing BP/RP filled by median colour.
`spectral_model`(grid, geo[, horizon_mask])	Wrap a `color_grid()` as a JAX model over Gaia conditions.

nyx.emitter.catalogs.xhip Module¶

Functions¶

`load_anderson2012`()	Positions and photometry from the XHIP compilation (Anderson & Francis 2012).
`spectral_model`(v_minus_b, geo)	Pickles (1998) spectra indexed by the Johnson V-B colour.

nyx.emitter.catalogs.astrometry Module¶

Functions¶

`altaz_array`(coord)	AltAz pairs as a plain array.
`altaz_track`(coord, times, frames)	Where coord is, in each observation's AltAz frame.
`angular_separation_deg`(ra, dec, ra_arr, dec_arr)	Great-circle separation in degrees.
`propagate_space_motion`(coord, time)	Move coord to time along its proper motion, position only.
`rotate_healpix`(map_in, frame_in, frame_out)	Rotate a HEALPix map between any two astropy coordinate frames.

nyx.emitter.catalogs.index Module¶

Classes¶

HEALPixIndex

Cone search over ra/dec, indexed by nested-ordering HEALPix pixel.