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Occultation of 3UCAC 064456146 (11m6) by (50000) Quaoar on 2012 April 17 for

Europe, Near East and Africa as well as the Atlantic Ocean

Based on astrometry from the RIO group for Europe and updated by other astrometry an occultation of a 11m6 star can be observed in the morning of the 17th of April 2012 at approx. 2h 19min UTC.

The occultation is very well in reach of many video and digital camera systems attached to telescopes as small as 8 inch. We urgently ask everybody, to take part in the international campaign for observation.

The goal is to determine the diameter of Quaoar and find out, if the TNO has an atmosphere. Therefore, not only the determination of the exact time point of dis- and reappearance is necessary, but also the exact determination of the lightcurve during dis- and reappearance of the star behind the disk of Quaoar.

On this site, more infos will be posted, to give you informations about how to observe. The RIO astrometry group, leaded by Marcelo Assafin, as well as many other observers have made astrometric observations with large telescopes, to define the position of the star as well as possible in the milliarcsecond range.

More informations about final updates of the astrometry can be found on Felipe Braga-Ribas (LESIA) Website about this and other actual events.

The astrometric situation is very poor despite the brightness of the star. The weather conditions in the last days for astrometry were very poor, therefore its not known at the moment, if better prediction can be get. In any case, you will either be informed on this page or on Felipe's page.

The occultation track …

Best and worst with repect to Europe....

The best occultation situation after calculations by Jean Lecacheux is the following, he used the UCAC2 positions of the stars and the Quaoar position corrected with an offset from the last observed occultations. It is as follows:















The worst calculation with respect to Europe is shown here:





For this calculation the star was observed for several night with TRAPPIST telescope. Julio Camargo measured the images with respect to UCAC2 catalog.
The star position is very good and consistent with WFI position.
Felipe
writes on the webpage about the Quaoar occultation (6th of April 2012)

We are expecting to have new astrometric measurements of Quaoar in the next days. Experience shows that the path can still change as Quaoar approachs the star, and the relative positions (i.e. ephemeris) gets better and better. So keep checking for new updates. And if its "costless" for you to observe, observe it whatever are the predictions.  

Keep an eye on the Website of Felipe!