  The theory of General Relativity deals with very accurate measurements that
show significant divergences from Newtonian predictions only with speeds near
to the velocity of light. An introduction for educational purposes, based on
naked eye photometry, deals with the radiation near collapsing star's shells
like novae and supernovae. The theme of accuracy is drafted from entry level
observations to the precision of professional data, often of public domain on
the web. Thousand observations of variable stars, included the type 1a SN2014J,
the Nova Del 2013 and the Nova Cen 2013, sent to the AAVSO by the author, with
SGQ code, during the period 1998-2015 are analyzed to increase the photometric
accuracy, in the occasion of the International Year of Light 2015.
