Uncertainties in astronomical data

• All numerical quantities should have errors attatched - AstroGrid must supply defaults where necessary (e.g. Epoch default - between the data of construction of the telescope and the publication of the catalogue)
  • Systematic or absolute (e.g. whole catalogue may be offset due to error in position of telescope; such errors can sometimes be reduced by comparison with external data such as triangulation of a few objects with better positions in a different catalogue).
  • Random or relative (e.g. noise-based error in position, varies from object to object depending on brightness)
  • Apparent exceptions - things like Equinox - may normally have a zero error - but this should be left in as e.g. some old catalogues may be of uncertain Equinox.
• Each classification or Boolean quantity should have a probability, quality factor or other accuracy indicator.
• This should apply to output into MySpace also by default (although I suppose the user should be able to turn it off)

-- AnitaRichards - 24 Apr 2003