WFI Calibration Plan


The WFI Standard Calibration Plan for Period 76 encompasses the use of the following "standard" broadband filters.

  • BB#U/50_ESO877 (previously named U/360)
  • BB#B/123_ESO878 (previously named B/NEW)
  • BB#V/89_ESO843
  • BB#Rc/162_ESO844
  • BB#I/203_ESO879 (previously named EISI)

There are 2 components to the Standard Calibrations

Instrumental Calibration (ICa)

  • 10 biases
  • 5 dome flats in each of the standard filters
  • 5 twilight flats in each of the standard filters

If your program uses standard filters, the ICa will be performed automatically (i.e. there is no need to request it in the README file).

If your program contains filters other than these, you MUST create your own calibration OBs for skyflats and domeflats. You can only request a maximum of 3 flats/OB. Biases will automatically be taken for you. If these specific calibration OBs are not included, no calibration in these filters will be undertaken by SciOps. These calibrations are not a part of our Standard Calibration Plan but are executed where necessary. Repeat calibrations (on different days) must be specified individually, unless prior arrangements have been made with USG and La Silla SciOps.

Photometric Calibration (PCa)

  • 3-4 Landolt standard star fields taken at different airmasses every PHO night

PCawill be executed only under the following conditions:

  • The night is PHO
  • You have your transparency constraint as PHO

i.e. You cannot request PCa with CLR or THN conditions

If your program uses standard filters, the PCa will be performed automatically every PHO night.

If your program contains filters other than these, you MUST create your own calibration OBs for standard fields, and indicate clearly in your README file how you would like these OBs executed.

More Specifics

The following table shows the components of the Standard Calibration in more detail

Component Exposure Time/Level Scope Notes
Landolt Fields 60 s and 120 s per field for U
10 s and 30 s per field for BVRI
Two exposures per field;
3 - 4 fields per night
The Landolt Fields are chosen from the following list:
TPhe, RU149,SA92, SA95, SA98, SA101, SA104, SA107, SA110, SA113;
Neither dithering nor guide stars are used;
Minimum airmass is 1.05 for TPhe, 1.2 for the others, maximum is approximately 1.8;
Only a few stars occupy each CCD in the mosaic
Sky Flats approximately 20000 ADU At least five per filter used the previous night,
(provided the conditions permit)
In extreme cases it may not be possible to obtain this many sky flats for each filter in a single night.
The demands of non-standard calibrations will have a bearing on this and will similarly vary from night to night
Dome Flats approximately 20000 ADU Five for each filter used the previous night Taken with the flatfield lamp --
Bias Frames 0 s each frame Ten each day following a Service Mode night Taken irrespective of whether Standard Calibrations were done the night before

A tar file containing the Standard Calibration Plan OBs can be downloaded for perusal. Untar the file and use the Import function of P2PP to load the OBs for viewing.

Any further questions please email the ls-imaging. This account is checked daily.