Calibration Details

Imaging Calibrations

		LUCI1	LUCI2
Non-Linearity		Linearization constant for LUCI1 was derived from calibration data from 2017 and 2018:k2 = 2.898e-6	Linearization should be the first step applied to raw LUCI data. The equation for the LUCI2 is:ADU_lin=ADU_raw+ k2(ADU_raw)*²k2 = 2.767e-6Since any reduction of the data will include subtraction of a dark or temporally adjacent image, the order zero constant term is not included from the linearization fit. The linearization coefficient for the MER readout mode has not explicitly been measured, but it should be the same as the equation above. Proceed with normal reduction algorithms using the linearized data. For particularly demanding observations, where data spans the full well of the detector and/or particularly tight requirements on the overall photometric accuracy are present, linearization using a full pixel map will be necessary as the above linearization equation uses an average linearization constant. This introduces errors, resulting in photometry being off as much as 1.2% at 80% full well. This is not a standard calibration.
Darks		Telescope/Instrument Configuration: Telescope stationary, dark chamber, rotator at the park position of 341deg. Blind blind filters in place, and Blind mask in the FPU.	Telescope/Instrument Configuration: Telescope stationary, dark chamber, rotator at the park position of 210deg. Blind blind filters in place, and Blind mask in the FPU.
Darks		Notes: Take in the afternoon as to minimize persistence effects. Take with the same detector mode, dits, ndits, as the science and calibration frames. If you pair subtract your data, with science data paired dithered positions and lights on/off calibration data, then there is no need to use dark frames. It is necessary to take darks if taking sky flats and only obtain exposures with one flux level. Darks are necessary used when making a bad pixel mask or dark-subtracting night-sky imaging data for a “super flat”. Darks taken with the blind mask have been demonstrated to be stable over partner runs, so only one set of darks needs to be taken per run if required.
Twilight Flats		Telescope/Instrument Configuration: All flats are taken in LIR detector mode, N3.75 camera. Check counts with short (1×2.51sec) LIR exp. It is recommended to predetermine a blank field to position the telescope for twilight flats for both morning and evening flats (some suggestions available at NOT site). Set up a script that will generate a preset in TRACK mode to your blank field. Otherwise, one can request the OSA to preset in TRACK mode to a predetermined blank field. OT Track mode preset examples, and random dither pattern script twilight flat examples for blank fields are available in the LUCI Library. Morning twilight fields should be selected in the west to avoid pointing the telescope towards sunrise. Notes: Twilight Flats must be taken in photometric conditions. Counts should be kept below 25K, with ideal min 5 exposures at each level to make a set. If in TRACK mode make small offsets between each skyflat to remove stars when flats combined. Twilight Flatfields are stable on timescales of months on the order of 2.5%, except for the J-.filter, where it is on the order of 4%. Two methods, method chosen is a matter of preference: 1) Take set of highly exposed twilight flats (15-20K), correct for dark current, normalize, & create master flat 2) Take set of highly exposed (15-20K ADU) and less exposed (5-10K ADU), combine separately (w/o correction for dark current), subtract from one another, then normalize for master flat. If taking twilight flats in K/Ks start with this after sunset or finish near sunrise, Switch to K/Ks when Br_gam counts drop below 2000 ADU after sunset, H, J, or z bands are usually started immediately after the K/Ks flats have completed (reverse order in morning).
Calibration Unit Flats		Telescope/Instrument Configuration: Telescope parked at zenith, with chamber lights off, rotator at the park position of 341deg, and calibration unit in.	Telescope/Instrument Configuration: Telescope parked at zenith, with chamber lights off, rotator at the park position of 210deg, and calibration unit in.
Calibration Unit Flats		Notes: Cal unit Flats should only be taken if twilight flats are not possible. Calibration unit does not illuminate the detector homogeneously. The Table Imaging Flats Exposure Times has dits, ndits, and number of exposures set such that the number of photons collected in the fainter portions are around 100,000, or 0.31% uncertainty from shot noise, without allowing the brighter portions of the flats exceed 5% non-linearity. Calibration Unit Flats should be taken Lamp-Off followed by Lamp-On. A set of OR Observations for all of the Calibration Unit Flats are available in the LUCI Libraries.
Photometric Standards		Notes: If only a photometric calibration accuracy up to 0.1mag or so is needed, you can use the 2MASS catalog to calibrate our field(s). The field of view of the LUCI instruments in seeing-limited mode is large enough to have always a few 2MASS stars in it.For decent photometric calibration to a few hundreds of a magnitude accuracy, a few photometric standards during the night may need to be taken. On the website for the Calar Alto observatory, a nice compilation of NIR photometric standard stars including finder chartscan be found: http://www.caha.es/pedraz/SSS/sss.html.
Bad Pixel Mask		Coming Soon	Coming Soon
Detector distortion		Coming Soon	Radial fit of distortion: D(r) = cr²,* where for the N1.80 camera c = 4.30e6 and for the N3.75 camera c = 2.97e6. Distortion is a residual of the optics of LUCI.

LongSlit and MOS Calibrations

		LUCI1	LUCI2
Non-Linearity		Linearization equation for LUCI1 still to be derived	Linearization should be the first step applied to raw LUCI data. The equation for the LUCI2 is:ADU_lin=ADU_raw+ 4.155×10^-6(ADU_raw)² Since any reduction of the data will include subtraction of a dark or temporally adjacent image, the order zero constant term is not included from the linearization fit. The linearization coefficient for the MER readout mode has not explicitly been measured, but it should be the same as the equation above. Proceed with normal reduction algorithms using the linearized data.For particularly demanding observations, where data spans the full well of the detector and/or particularly tight requirements on the overall photometric accuracy are present, linearization using a full pixel map will be necessary as the above linearization equation uses an average linearization constant. This introduces errors, resulting in photometry being off as much as 1.2% at 80% full well. This is not a standard calibration.
Darks		Telescope/Instrument Configuration: Telescope stationary, dark chamber, rotator at the park position of 341deg. Blind blind filters in place, and Blind mask in the FPU.	Telescope/Instrument Configuration: Telescope stationary, dark chamber, rotator at the park position of 210deg. Blind blind filters in place, and Blind mask in the FPU.
Darks		Notes: Take in the afternoon as to minimize persistence effects. Take with the same detector mode, dits, ndits, as the science and calibration frames. If you pair subtract your data, with science data paired dithered positions and lights on/off calibration data, then there is no need to use dark frames. It is necessary to take darks if exposures exposures with one flux level are obtained. Darks are necessary used when making a bad pixel mask or dark-subtracting night-sky imaging data for a “super flat”. They are also used when removing hot pixels from through-slit MOS or longslit acquisition data. Darks taken with the blind mask have been demonstrated to be stable over partner runs, so only one set of darks needs to be taken per run if required.
Spectral Flats		Telescope Configuration: Telescope parked at zenith, with chamber lights off, rotator at the park position of 341deg, and calibration unit in. Configure the instrument mechanisms (mask, grating, grating tilt, filters) to match that of the science observations.	Telescope Configuration: Telescope parked at zenith, with chamber lights off, rotator at the park position of 210deg, and calibration unit in. Configure the instrument mechanisms (mask, grating, grating tilt, filters) to match that of the science observations.
Spectral Flats		Notes: Spectral flats are taken with the calibration unit. The Table Spectral Flats Exposure Times has dits, ndits, and number of exposures set such that the number of photons collected in the fainter portions are around 100,000, or 0.31% uncertainty from shot noise, without allowing the brighter portions of the flats exceed 5% non-linearity. Calibration Unit Flats should be taken Lamp-Off followed by Lamp-On. Note that there is an illumination pattern visible on the N375 flats with LUCI1.
Twilight Flats		Telescope/Instrument Configuration: All flats are taken in LIR detector mode, N3.75 camera. Check counts with short (1×2.51sec), mask in place, LIR exp. It is recommended to predetermine a blank field to position the telescope for twilight flats for both morning and evening flats (some suggestions available at NOT site). Set up a script that will generate a preset in TRACK mode to your blank field. Otherwise, one can request the OSA to preset in TRACK mode to a predetermined blank field. OT Track mode preset examples, and random dither pattern script twilight flat examples for blank fields are available in the LUCI Library. Morning twilight fields should be selected in the west to avoid pointing the telescope towards sunrise. Notes: Twilight Flats must be taken in photometric conditions. Counts should be kept below 25K, with ideal min 5 exposures at each level to make a set. The purpose of these would be to take a through-slit image to correct the “slit function” (variations in slit width). Only needed for specific studies and not considered a standard calibration.
Arcs		Telescope Configuration: Telescope parked at zenith, with chamber lights off, rotator at the park position of 341deg, and calibration unit in. Configure the instrument mechanisms (mask, grating, grating tilt, filters) to match that of the science observations.	Telescope Configuration: Telescope parked at zenith, with chamber lights off, rotator at the park position of 210deg, and calibration unit in. Configure the instrument mechanisms (mask, grating, grating tilt, filters) to match that of the science observations.
Arcs		Notes: Internal calibration source include Ne, Xe, Ar lamp sources. Exposure times for arcs are in the table: Arc Exposure Times. Arc exposures obtained at the elevation of the science observations are not included as part of the baseline calibration as flexure compensation makes the need for them at the elevation of the science target unnecessary.
Tellurics		Telescope Configuration: Telluric should be at a comparable position and airmass to science target.Notes: A full list of A0 and G2V Telluric Targets is provided in the LUCI Library for the OT, along with telluric observation templates. The templates only require the user to change a few outlined parameters in the generation of the script. Be careful about the source magnitudes, LUCI2 will saturate on stars brighter than ~8th magnitude in the low-resolution (G200) modes, and brighter than ~7th magnitude in the higher resolution (G210) modes (estimated). Further details and notes available in Standards Section.
Bad Pixel Mask		Coming Soon	Coming Soon
Detector distortion		Coming Soon	Radial fit of distortion: D(r) = cr²,* where for the N1.80 camera c = 4.30e6 and for the N3.75 camera c = 2.97e6. Distortion is a residual of the optics of LUCI.