defocus for precision?

In a set of summer-student talks, Tanja Schroeder (MPIA) showed absolutely astounding photometry of transiting exoplanets taken with defocused data from Calar Alto and Bologna. Yes, defocused: By defocusing the telescope, she can avoid saturation in longer exposures and sample more of the (noisily known) flat-field, at the expense of more background. It sounds insane but when your noise has larger contributions from systematics (unknown and variable PSF, unknown and variable bias and flat), defocusing can increase precision. She also showed nice exoplanet-transit fits to those data. In the question period, Wolfgang Brandner (MPIA) brought up the idea of learning limb darkening from exoplanet transits, which is the subject of a (sleeping) project by Barclay (Ames), Foreman-Mackey, and me.

1 comment:

  1. Defocusing is a long-established technique for high-precision photometry - even the Kepler satellite is defocused! (And thus cannot be used for much else but planet hunting.)