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Exoplanet HAT-P-54b


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About this observation
Eric Watkins
Time of observation
19/01/2018 - 22:00
Observing location
North Essex
C14 Edge 0.356m @F7.7
Paramount MEII GEM
QSI 532 ccd camera binned 3x3 1.5"/pix
Seeing: Mediocre
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I have been wanting to successfully record an exoplanet transit for some time and have "spoilt" some attempts by simple errors; e.g. got the fov wrong, UT and civil time mixed up and transferring details to paper for use in the observatory wrongly.

Eventually, I managed to record the transit light curve of  HAT-P-54b, which orbits a 13.5 mv host star of 0.645 solar masses and a radius of 0.617 solar radius.  The planet has a documented period of 3.7998 days and is thought to be a Hot Jupiter of mass 0.944 Mj.  The magnitude drop at transit minima is  ~0.023 with a total  duration of ~ 1hr 47min.

AstroImageJ was used to process both the images and model the light curve. AstroImageJ is free and I can highly recommend a course, given by Denis Conti via the AAVSO, on its use.

Using and fixing both established values together with the predicted time of minima I obtained;

an O-C of the minima of -2.06 min and a transit duration of 1:57:38 (hh:mm:ss)

Allowing the same variables freedom I obtained;

an O-C of -2.04 min and a transit duration of 1:47:38 (hh:mm:ss)

Mass of the planet HAT-P-54b was determined to be ~1.07 Mj.

There would appear  to be a 2min difference between the observed and calculated minima.


Andy Wilson's picture

Hi Eric,

That is a great set of data, congratulations on capturing the exoplanet transit.

The BAA is shortly to publish a tutorial written by Richard Lee on using AIJ in combination with the VSS Photometry spreadsheet. It is a great tool for photometry.

Best wishes,


Derek Robson's picture

This is a great achievement.  At school, in the 70's, I knew of only 9 planets.  I didn't know then, any more planets would ever be discovered outside our solar system, even with the largest telescope in the world.  Marvelous work.  Would a Qhy5Lii cc and a GT81 be good enough to measure such transits, or would I need to use a bigger scope such as my 8.75" NR?

Americo Watkins's picture


firstly apologies for not replying earlier, but I've only just become aware of your comments which I thank you for.  Also the BAA has just set up a new sub-section of the Asteroids and Remote planets section led by Roger Dymock.

I have sent you a private reply on your BAA account.



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