You are here

Calibrations

, Updated

Calibrations sources include dark, flat, ThAr arc, and etalon comb frames. All sources are part of the instrument calibration system and GCAL sources are not available.

Calibrations for the object, sky, and simultaneous calibration fiber are recorded in separate frames. 

Baseline calibrations: include darks, flats, ThAr arc, etalon comb frames. The day before MAROON-X is scheduled for the night, a series of baseline calibration frames are taken. Those baseline calibrations are shared by all programs observed in that same night. Shortly after and before observations at night, etalon frames are taken to monitor the drift of the spectrograph. Applicants should not include time for baseline calibrations in their Phase I proposals. If additional calibrations are deemed necessary by applicants, for example bracketing etalon exposures to achieve the highest possible RV precision, then these must be included explicitly as part of the Phase I proposal and Phase II science program. No spectrophotometric, telluric, or RV standards are observed as part of the baseline calibration. Any time required for additional calibrations between the hours of nautical sunset and sunrise to obtain calibrations will be charged to that particular program.

Measurement Type Notes
Dark A series of darks with fiber shutter closed but detector shutter open are obtained for a range of exposure times that span the exposure time range of science frames for the night.
Flat field Flat field calibration frames are obtained as part of daytime baseline calibration using light from a Tungsten-Halogen lamp sent through fibers from the calibration unit either to the frontend (for object and sky fiber calibration) or  directly to the spectrograph (for the simultaneous calibration fiber). Typical exposure times are 5s on the blue and 2s on the red detector.
Wavelength calibration The main wavelength calibrator for MAROON-X is a stabilized Fabry-Perot etalon illuminated by a white light fiber laser providing a dense comb of emission lines with a spacing of 15 GHz and an unresolved line-width of 340 MHz. Typical exposure times are 40s on the blue and 2s on the red detector. 
ThAr exposures are used to supplement the etalon exposures and to provide both absolute wavelength zeropoints and a solution for the etalon dispersion. Typical exposure times are 20s on the blue and 5s on the red detector. 
Both etalon and ThAr exposures are obtained as part of daytime baseline calibration.
Flux standard stars Instrumental throughput is strongly seeing dependent. Observations to provide absolute spectrophotometric calibration are thus not included as part of the baseline calibration set.
Telluric standard star Removal of telluric lines should be facilitated by modeling the sky transmission.  Observations to provide telluric line removal are thus not included as part of the baseline calibration set. Telluric standard stars (early type, aka ‘featureless’ stars) can be observed as part of an observing program if requested by the applicant. Efforts will be made to observe these close in time and airmass to the science target but tight constraints can not be guaranteed.
Radial velocity standard star Radial velocity standards are not observed routinely as part of baseline calibrations. Any program that requires radial velocity standards should include these observations in the phase II for the program.
Bad pixel mask A bad pixel mask is produced by the MAROON-X extraction pipeline. 

Figure D1: Example frames are provided below. All frames are logarithmically scaled. The shortest wavelength is in the lower left and the longest wavelength in the upper right In all frames. ‘Black’ features are overscan regions (bias).

Flatfield (5s) Flatfield (2s)
ThAr (20s) Thar (5s)
Etalon (40s) Etalon (8s)