HET Calibrations

   
Good calibrations on the LRS2 and VIRUS instrument will always have observation numbers less than 1000.  
  
Calibrations or test frames with observation numbers larger than 1000 should (almost) NEVER be used for data reduction or analysis. 

From 2019 onward most of this calibration is treated automatically by our daily data reduction pipelines. 
 The contents of this document should not be necessary for most users to use their data.

1. Wavelength Comparison Arcs Standard complement per night, as of mid-2021:
   • LRS2:
     • 3xCd-A_B
     • 3xFeAr_R
     • 3xHg_R
     • 3xHg_B
   • VIRUS:
     • 3xCd-A
     • 3xHg
   • HPF evening cals:
     • 4x Alpha Bright
     • 2x LFC FCU
     • 2x LFC Cal
     • 1x Etalon Cal
     • 3x UNe Slave Cal
   • HPF morning cals:
     • 4x Alpha Bright
     • 6x LFC FCU
     • 2x LFC Cal
     • 4x Etalon Cal
     • 3x UNe Slave Cal
   Additional repeats with the same or modified integration (e.g. better to service a specialized goal) can be requested as outlined in Phase II.

2. Flatfields. Standard complement per night, as of mid-2021:
   • LRS2:
     • 5xQth_R
     • 3xLDLS_B
   • VIRUS:
     • 3xLDLS
   • HPF evening cals:
     • 7x Quartz FCU
   • HPF morning cals:
     • 7s Quartz FCU
   Additional repeats with the same or modified integration (e.g. better to service a specialized goal) can be requested as outlined in Phase II.

3. Biases Standard complement per night:
   • LRS2: 11x
   • VIRUS: 11x
   • HPF: n/a

4. Darks Standard complement per night:
   • LRS2:3x360s
   • VIRUS: 3x360s
   • HPF evening: 1x320s
   • HPF morning: 1x320s
   Additional darks can be requested as outlined in Phase II, but due to the very large required overhead, the request will have to be supported by a scientific justification.

5. Skyflats. These can provide, depending on instrument, tracing of the illumination, daysky wavelength information, or pixel-to-pixel response or slit illumination information. Standard nightly complement is:
   • LRS2: 6x
   • VIRUS: 5x
   • HPF: 1x (when conditions permit)
   Additional skyflats can be requested as outlined in Phase II. They are typically executed around sunset with an intended peak SNR > 200 and typical SNR > 100, unless otherwise specified.

6. FIFflats, FIFthars, PFIPflats. Standard complement is zero, but they can be requested as outlined in Phase II.

7. Flux Standards. A spectroscopic flux standard can be requested (see Phase II) for a PI-specified setup. If a PI wishes a specific standard to be observed, then that object should be entered into the queue as its own time-charged target. The PI can supply a list of selected preferred flux standard names, which it may be possible to conform to, possibly adjunct to the spectroscopic standards obtained for other programs. Exposure times will be chosen to aim for a suitable number of counts at the spectral peak, although exposure time constraints on very faint flux standards may need to compromise on this. The flux standard is normally carried out on the same night as the science target, unless delayed by rapidly deteriorating weather.

8. Radial Velocity Standards. A radial velocity standard of a desired or nearest available quality index can be requested (see Phase II) for a PI-specified setup. If a PI wishes a specific standard to be observed, then that object should be entered into the queue as its own time-charged target. Exposure times will chosen to aim for well-measured spectral peaks. The radial velocity standard is always a great priority to be carried out on the same night as the science target, and is always accompanied by a comparison arc.

9. Telluric Standards. A telluric standard can be requested (see Phase II) for a PI-specified setup. If a PI wishes a specific standard to be observed, then that object should be entered into the queue as its own time-charged target. Exposure times will chosen to aim for a good spectral peak.

Last updated: Fri, 29 Dec 2023 02:18:36 +0000 stevenj