Coordinates

Antares

see http://antares.in2p3.fr/internal/dokuwiki/doku.php?id=astro_coordinatetransformation_howto

Conventions + Definitions

Neutrino direction vs Source Direction

We usually talk about the direction a neutrino is going to. When determining which source it came from, we obviously need to invert the direction.

Neutrino direction, polar coordinates: *theta* and *phi*

Neutrino source: *zenith* and *azimuth*

Azimuth Definition

Our definition of the azimuth angle differs from the more common definition that is used in SLALIB, SeaTray’s astro package, and astropy (used in km3astro).

true_azimuth = (90deg - azimuth) mod 360deg

Equatorial Coordinates

Equatorial coordinates are ICRS, i.e. J2000 Epoch, J2000 Equinox, Barycentric (barycenter of Solar system as coordinate origin).

If you’d rather have geocentric equatorial coordinates, use GCRS.

If you are looking for “J2000 Equatorial coordinates” you probably want ICRS and not FK5.

For more details on ICRS, see https://en.wikipedia.org/wiki/International_Celestial_Reference_System and maybe http://docs.astropy.org/en/stable/api/astropy.coordinates.ICRS.html#astropy.coordinates.ICRS .

UTM Grid

The UTM origin is noted at the head of the .detx v2 files: Dataformats#Detector_Description_.28.detx.29

A snapshot of these (July 2017) can be found at km3astro.constants.

Benchmarks

Antares astro benchmarks: http://antares.in2p3.fr/internal/dokuwiki/doku.php?id=benchmarks_astro

(Partial) replication with km3astro: Benchmark Calculations for Coordinates Transformations