HET Calibrations


  1. Wavelength Comparison Arcs. Standard complement per nightly setup/binning combination: HRS: 1, MRS: 2 (long and short), LRS: a number of lamps appropriate to the spectral coverage. By explicit request these can be obtained before science setup is altered (if there is any question of instrumental stability), but in general these are obtained upon reconfiguring to the science setup within the span of the same night, except that LRS-MOS mode cals are always taken before any changes. 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 nightly setup/binning combination: HRS: 11 (plus 3 with gascell in as appropriate, also additional long-exposure flats for cross-disperser work at 316g4931K and 600g4739K), MRS: 5, LRS: 5 generated off an interposable calscreen. By explicit request these can be obtained before science setup is altered (if there is any question of instrumental stability), but in general these are obtained upon reconfiguring to the science setup within the span of the same night, except that LRS-MOS mode cals are always taken before any changes. Additional repeats with the same or modified integration (e.g. better to service a specialized goal) can be requested as outlined in Phase II. HRS standard flats are internal to the instrument and come from a calibration fiber which illuminates the slit. As this illumination is not identical to that from that by the science fibers, fifflats for HRS can also be requested.

  3. Biases. Standard complement per nightly setup/binning combination: 5 or more.

  4. Darks. Standard complement is zero. They 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 complement is zero, but they 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. HRS fifflats being illuminated through the probe are more consistent with the illumination of the HRS science chip by the science target, but their brightness level is as yet not competitive with the internal flats. HRS fifthars are executed analogously to the fifflats. For MRS fifflats and fifthars are the regular MRS method. An HRS pfipflat resembles a conventional dome flat and is produced by illumination of the LRS calscreen reflecting up into the HRS science probe, but the fifflat as being illuminated by an interposable calibration arm is stronger.

  7. Flux Standards. A spectroscopic flux 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. 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 spectral peak of >10k counts, although exposure time constraints on very faint HRS 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 a spectral peak of >20/10/10k counts in the HRS/MRS/LRS spectrum. 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. Please note that we give different priorities to the standards. Priority 1 standards are the best characterized and priority 4 standards are from old literature samples and are probably only good for LRS standards. The special case of priority 5 standards is that they are all M giants.

  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 spectral peak of >20/10/10k counts in the HRS/MRS/LRS spectrum. The choice of standard generally has V < 5 for HRS and MRS, and V > 5 for LRS. The telluric standard is always a great priority be carried out on the same night as the target, and is always accompanied by a comparison arc.




Last updated: Fri, 07 Dec 2012 11:27:35 -0600 shetrone



Phase I

Phase I Information for New Users

Phase I Basics

Calibrations

Spectrophotometric Standard Stars

Radial Velocity Standard Stars

Telluric Standard Stars

Overscan Region

Ambient Light

CCD Parameters

Project Feasibility

Data Acquisition HETiosyncrasies