... There are two ways to produce flat fields for use with IR data. The standard method is to take 'LAMP ON' and 'LAMP OFF' exposures of the calibration spot on the telescope dome. The 'LAMP ON' exposure contains light from both the calibration lamp, which should provide the even illumination needed for the flat field, together with potentially uneven illumination from the telescope and instrument environments. ... In MIDAS, you may directly use COMPUTE/IMAGE to perform the subtraction. ...

... The absolute flux calibration of NICMOS will be calculated from observations of standard stars with known flux distributions F( ). ... In order to expand the set of IR standard stars in the appropriate flux range for NICMOS, M. Rieke, R. Thompson, and collaborators at the University of Arizona are making photometric observations of solar-analog stars, which will be used to normalize the solar spectrum to the observed IR magnitudes. ... Relative flux references accurate to 1.5% for standard...

... The first step to improve the FORS calibration is therefore to obtain data to allow a computation of the illumination correction across the field. ... Another limitation on the calibration accuracy has been the brightness of the Landolt standards which have forced the use of extremely short exposures introducing small but non-negligible shutter-time errors and also resulting in a very small number of useful standards per frame. ...

Next: THE SOURCE LIST Up: Spectral-Line Observing at AO Previous: THE RADAR BLANKER . ... You also need to decide how you want this correction to be applied - to the center of each correlator board or to the four boards as a whole (thereby preserving the topocentric frequency offset between the boards). Typically, this choice depends on whether each board is centered on a known spectral line, or if you are doing a search in velocity space for an object. ...

Last updated 5 November 2003 by JMD . Last link checked 9 October 2003 by JCB . Data from 191 observations of stars with the ARCES were analyzed to calculate exposure times to reach particular signal-to-noise values for bright standard stars. ... An exponential fit to the data shows pretty good agreement and allows for forecasting to fainter stars beyond the limit of the data set ( V ~ 12). The fit was used to calculate the exposure times in the table below: . ...