HAT-P-20 b is a Jupiter sized planet orbiting a host star of Mag v 11.3.  This is a result I'm pleased with considering the night was not particularly clear with seeing of fwhm 3" at best. Also,  problems I had had with the mount and auto guider were resolved enabling  me  to keep the target star centred  on the same 2-3 pixels for nearly 4 hours. A requirement for some of the Pro/Am projects I have become involved with.

HAT-P-20 b host star has a   mag v 11.3 with mass and radius relative to the Sun of 0.756 and 0.694 respectively. Close to the host star there is a 12.5 mag star that makes photometry difficult.

AstroImagJ was used for the for the photometry and transit modelling for which the only variables fixed were a/R at 11.23. and the u1 and u2 limb darkening coefficients.

My Results       Rj 0.89,  Inc 86.9 Transit duration 112m 33sec       Depth of transit 0.01745

Accepted values  Rj 0.867 +/- 0.033, Inc 86.8 +/- 0.2 Duration 110m:52sec +/- 1m 9sec.  Depth of Transit 0.01649

(http://exoplanets.org/detail/HAT-P-20_b)

With regard to any Transit Time Variations (TTV) the transit minima was 2m:27s  early, which is in keeping with similar values on the EDT site and does not support any TTV changes. Note also that changing parameters only altered this value by ~1minute either way.

The drop in the total  C count resulting in exposure changes from 90-60-90 sec..