Three photometric methods tested on ground-based data of Q 2237+0305
Burud, I × Stabell, R Magain, P Courbin, F Ostensen, Roy Refsdal, S Remy, M Teuber, J #
Astronomy and astrophysics vol:339 issue:3 pages:701-708
The Einstein Cross, Q 2237+0305, has been photometrically observed in four bands on two successive nights at NOT (La Palma, Spain) in October 1995. Three independent algorithms have been used to analyse the data: an automatic image decomposition technique, a CLEAN algorithm and the new MCS deconvolution code. The photometric and astrometric results obtained with the three methods are presented. No photometric variations were found in the four quasar images. Comparison of the photometry from the three techniques shows that both systematic and random errors affect each method. When the seeing is worse than 1." 0, the errors from the automatic image decomposition technique and the Clean algorithm tend to be large (0.04-0.1 magnitudes) while the deconvolution code still gives accurate results (la error below 0.04) even for frames with seeing as bad as 1." 7.