1. Introduction

LIRIS is our near-IR imaging spectrograph at the Cassegrain focal station of the 4.2m WHT. Its 1024×1024 detector yields a 4.2x4.2 arcminute field of view with a pixel scale of 0.25". Currently imaging, long-slit and multi-object spectroscopy, imaging polarimetry and coronography modes are available, however not all of them in service mode (see below). You can apply for up to 8h of LIRIS service mode observations. Proposals will be evaluated every month.

2. Available observing modes in service observing

Included in service mode are the following observing modes:

• Imaging and imaging polarimetry in all available filters
• Spectroscopy in all available long slits, the low resolution grisms (lr_zj, lr_hk) and the medium resolution J-band, H-band and K-band grisms (hr_j, hr_h, hr_k).
  

Excluded from service mode, due to their large overhead, are

• coronographic observations
• multi-object spectroscopy
• spectropolarimetry (not commissioned yet).

The readout speed is set to slow for all observations.
The pre-read will be subtracted automatically from the images.
A single read-out (correlated double sampling) is used for imaging,
and four non-destructive read-outs for spectroscopy.

3. Calibrations

• DARKs:
  Dark exposures are not taken by default, due to changes of the corresponding instrument characteristics during the night. If you require dark exposures, they must be taken immediately before or after your observations at night time, and thus have to be included in the total time you request.
• STANDARDs:
  Since the sky in the near-IR changes rapidly, observations of standard stars will not be taken unless explicitly asked for in the proposal and accounted for in the total time requested (photometry can often be done by means of 2MASS). If you request standard star observations of any type (photometric, spectrophotometric, telluric), then please explicitly state
  -- which (RA, DEC) specific standard star you wish for each object
  -- which instrumental configuration you wish (filters and grisms)
  The reason for this decision is that applicants are often very unspecific concerning their standard stars, or unaware of the need for particular standards (various spectral types, for example, depending on the main target), or unaware of the fact that certain standard types do not exist in the vicinity of their targets. Thus, any standards required must be defined in the proposal by the applicant.
• FLATs, spectroscopic FLATs and ARCs:
  These will be taken automatically at the beginning or the end of the night and do not have to be requested.