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WASP-1b Transit Parameters

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clkotnik's picture
WASP-1b Transit Parameters

I recently had a chance to observe a transit of WASP-1b.  I compared my observations to the predicted times in ETD, and VSX.  I found much more variation in the prediction parameters (Epoch of mid trans, period and duration) than I have seen for most other exoplanets.  As I did the calculation for the night in question, I found ETD and differed by 3-6 minutes.  However, VSX differed by more than an hour.  I found the transit model I derived from my observations differed by less than a minute from the ETD prediction.

It seems to me that VSX needs to be corrected for this exoplanet.  Does anyone else see similar results?

Attached is the preditions I see.

best regards,


I often have difference in

I often have difference in minutes, but there might be two reasons. Sometimes there are exoplanets that need orbital period to be updated. The O-C graph would show a trend when the difference is getting larger on later years. And the other reason might be the prediction time shown in JD without HJD correction.

Sebastian Otero
Sebastian Otero's picture
VSX ephemeris updated

Hi Cliff,

In this case, it was the first option in Gabriel's post: the elements needed updating.
I have added the most recent information from a 2014 paper to VSX and now the predictions should be much better. Try them.


clkotnik's picture
Much Better

Thanks Sebastian, much better.


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