British Astronomical Association
Supporting amateur astronomers since 1890

BAA Images Eric Watkins

Observation by Eric Watkins: Exoplanet HAT-P-20 b Transit

Uploaded by

Eric Watkins


Eric Watkins


2018 Nov 08 - 03:00


2018 Nov 14 - 03:23



  • C14 Edge 0.356m @F7.7
  • ParamountME II
  • QSI 532 ccd camera binned 2x2 (1"/pix)
  • Lodestar OAG
  • Rc filter

90sec, small number at 60sec


North Essex

Target name



Exoplanet HAT-P-20 b Transit

About this image

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


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..

Files associated with this observation
Like this image
Copyright of all images and other observations submitted to the BAA remains with the owner of the work. Reproduction of work by third parties is expressly forbidden without the consent of the copyright holder. By submitting images to this online gallery, you grant the BAA permission to reproduce them in any of our publications.