Overview¶
Reduction¶
As of now, reduction can be performed on well-behaved spectrographs with an assumed a single trace per echelle order. Orders are traced with a density clustering algorithm (sklearn.cluster.DBSCAN). Flats are grouped together according to their “density” (metric ~ angular separation + time separation). Objects are mapped to a master flat according to the closest flat in space and time.
Calibration¶
Flat, bias, and dark calibration is performed when provided. Wavelength calibartion via ThAr lamps or LFC’s are not currently provided.
Extraction¶
The trace profile (seeing profile) is estimated by rectifying the order and taking a median crunch in the spectral direction on a high resolution grid. The background sky, sky(x) is computed by considering regions of low flux within the trace profile. The profile is then interpolated back into 2d space according to the order locations, y(x). An optimal extraction is iteratively performed on the non-rectified data. Depending on the nature of the user’s work, this may not be suitable and one should rely on using an instrument specific reduction package.
Tested Support Status:
- iSHELL (Kgas, K2, J2 modes, empirical and flat field order tracing)
- CHIRON (highres mode, R~136k, under development)
- NIRSPEC (K band, under development)
- Generic (single trace per order, minimal support)
Radial Velocities¶
Computes radial velocities from reduced echelle spectra by forward modeling the individual orders. Only certain instruments are supported, however adding support for a new instrument is relatively straightforward (see below).
Tested Support Status:
- iSHELL (Kgas mode, methane gas cell)
- CHIRON (highres mode, R~136k, iodine gas cell)
- Minerva-Australis (ThAr Lamp calibrated, soon iodine gas cell)
- NIRSPEC (K band, under development)
