|You are in: Instruments > AcqCam > Performance and Use > Baseline Calibrations|
Acquisition Camera Baseline Calibration
For all queue observations, a set of standard calibrations (the "baseline calibrations") will be taken by Gemini Staff to ensure the long-term utility of data in the archive. The baseline calibration set varies from instrument to instrument and from mode to mode.
Applicants should not include time for baseline calibrations in their proposals. If additional calibrations are deemed necessary by applicants, for example to achieve a precision beyond that achievable via the baseline set, then these must be included explicitly as part of the Phase I proposal and Phase II science program.
Baseline calibration data may be shared between programs and will be distributed
to the users as part of their dataset. Any time used between the hours of
nautical sunset and sunrise to obtain baseline calibrations will not
be explicitly charged to the program but will be charged to the
partner country whose NTAC recommended time (i.e. it is part of
the time accounting used to balance partner usage). The time will be charged
in proportion to the number of programs that receive the calibration data.
Any time required for additional calibrations requested by the PI will be
charged to that particular program.
|Bad pixel mask||For full frame observations, normal (unbinned) mode, last generated from data taken November 2001. For full frame, 2x2 binned mode, last generated from data taken December 2002. Bad pixel mask not yet available for other binned observations.|
|Flat field||For full frame observations (normal and
binned modes), twilight flats in BVRI filters. The S/N of the final (combined)
flat is ~ 300. Flats are taken at evening twilight.
For observations taken in windowed mode, window size is 200x200pix or smaller, GCAL flats in BVRI filters. Larger windows use twilight flats as the full frame above.
Blank sky flats at I band only for fringe correction.
|Dark||Generated from a master dark if exptime
< 60 sec; matching the exptime if longer than that.
Darks are taken for each observing night; different sets are taken for binned and normal modes.
|Bias||Bias images are taken for each observing night. Different sets are taken for binned and normal modes.|
|Wavelength calibration||Not applicable|
|Telluric standard star||Not applicable|
|Flux standard star||From a subset of Landolt 1992 standards
(see table). Each observed field includes more than one star. Exposure times
are adjusted as to have at least 1500 counts peak. For median conditions
and assuming a Gaussian profile, that corresponds to a S/N > 80.
Standards are taken either before or after each programme target, to no less than three and no more than six per night. However, there is no guarantee that the nightly set will span a range of zenith angles appropriate to derive an extinction correction. If the science objectives are dependent on those, the user should ask for specific calibrations.
|Atmospheric extinction||Not included as part of the baseline calibration set.|
|Point Spread Function star||Not included as part of the baseline calibration set.|
|World coordinate system||Defined during commissioning.|
|Focal plane mask image||Not applicable|
|Special standards||Not applicable|
Last update February 25, 2004; Rodrigo Carrasco