... Stellar Evolution is driven entirely by the never ending battle between Pressure and Gravity . As imbalances are reached, the star is driven to find a new Energy source. ... Pressure and gravitational forces are equal, the star is stable and its core is sufficiently hot to fuse Hydrogen into Helium More about main sequence stars . ... The luminosity generated by the core fusion of Helium into Carbon is far greater than the shell luminosity associated with the fusion of Hydrogen into Helium. ...

... 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...

Next: Reduction procedure Up: Extinction and transformation Previous: Strategy . Standard stars can be included in the extinction solution, if one is careful. The problem is that there are usually appreciable ``conformity errors'' due to mismatch between the instrumental and the standard passbands [ 16 ]. ... Thus, it is wrong to assume that the transformation between the instrumental system and the standard system is exact, even if there were no measurement error in either system [ 1 ]. ...

... Updates to HST Standard-Star Fluxes . ... These data are in an STScI data base named CRCALSPEC and have been divided into two categories to help the user understand the origin and accuracy of these flux distributions. ... 1990, ApJS, 73, 413) and Oke (1990, AJ, 99, 1621) spectra are available. Oke (1990) used the DoubleSpectrograph on the 5-m Hale Telescope to obtain these spectra for HST calibration; and these data are identified in the HST data bases by the keyword OBSMODE=OKE DBSP. ...

... Data Handling and Products > Data Reduction FAQ > The spectrum of my MOS flux standard star is shifted in wavelength by several pixels. Why is that and how can I correct for it? ... Observing with ESO Telescopes . ... The shift of the flux standard spectrum is caused by a combination of bad centering within the slit and possible wavelength calibration issues. To align the spectrum to the tabulated flux, use the parameter --resp_shift in vmmosscience when determining the response curve. ...

Next: Examples of Setup Files Up: Setup Files Previous: Setup Files Contents . Over 200 standard setup files have been created, covering many of the normal modes of observing. ... These especially include precisely defined, and somewhat complex cases like the Mark III standard modes (although MarkIII went the way of the dinosaur long ago. ... v '' files: . These are setup files for VLBI observations using VLBA recording formats. ... These are setup files for Mark III observations. ...