... Under certain conditions, like those in the nucleus of a QSO, all atoms can be made to emit light at particular wavelengths. ... If that source is approaching the observer, the wave is squashed up onto itself making the wavelength shorter. ... This is redshift. ... You can see how the section of the QSO spectrum which we observe changes with redshift. ... We then see how far we had to slide the observed spectrum along the scale to make it match and that is the objects redshift. ... The 2QZ team . ...

ST-ECF Instrument Science Report ACS-2008-01 Updated flux calibration and fringe modelling for the ACS/WFC G800L grism H. Kuntschner, M. KЭmmel, J. R. Walsh January 25, 2008 ABS TRACT A revised flux calibration is presented for the G800L grism with the ACS Wide Field Channel. ... We also include in this report an extensive investigation into the potential effects of fringing on the flux calibration based on the WFC CCDs fringing model as described in ST-ECF ISR ACS 2003-03 (Walsh et al. ...

Data Flow System Document Title: Document Number: Issue: Date: VISTA Data Reduction Library Design VIS-SPE-IOA-20000-0010 1.6 2006-12-20 Document Prepared by: Document Approved by: Document Reviewed by: Document Released by: Jim Lewis Peter Bunclark Simon Hodgkin (CASU) Mike Irwin (CASU Manager) Will Sutherland (Project Scientist) Malcolm Stewart (VDFS Manager) Signature and Date: Signature and Date: Signature and Date: Signature and Date: VISTA Data Flow System Data Reduction Doc: Library Design Issue: