International Occultation Timing Association

European Section 

Occultations by




Pluto, TNOs



Partners & Friends

Members login

Contact us :

Knaust-Str. 8
D-30459 Hannover

Occultation of 2UCAC 26029329 by
(50000) Quaoar on 2011 Feb 2 for Europe

Results of the Campaign

Many observatories have reported, that they were clouded out. In the graphics you see the area, where stations have observed no occultation (but not have been clouded out) marked in light blue. The most northern station as known for the moment, which was not totally clouded out, is the one marked with an asterik (Sudelfeld, by B. Gaehrken). He reported no occultation for longer than about 30 seconds. He observed with a 6 inch telescope and a video camera!

So we know, that either the true path was about south of the blue area, or north. Astronometry has to solve this in the future perhaps.

A big "Thank You" to all observers, who either traveled to an observing site, or observed from their own observatories! In any case it has been learned, that a star, such faint as 13m3, can observed easily in the beginning dusk! (sun higher than about 7.5 degrees below the horizon). This can largely extend the range of observability of such events for the future.

Following the old report about the announcement of the event can be found:

Based on astrometry from the RIO group for Europe an occultation of the 13m3 star 3UCAC 26029329 can be observed in the morning of the 2nd of February 2011.

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. For the moment, there are two predictions from the same astrometry available, one, from Bruno Sicardy from Paris/Meudon observatory and one generated using Occult V The RIO astrometry group, leaded by Marcelo Assafin, has made astrometric observations with large telescopes, to define the position of the star as well as possible in the mas range. The table of the astrometry you can find on Bruno Sicardy's Website.

The occultation track

The prediction based on the Rio group astrometry has been gernerated by Occult V as follows:

The track prediction by B. Sicardy puts the occultation line about one Quaoar radius farer south, the difference can not be explained at the moment. However, according to the relative large errors in the orbit and positions, this is not relevant for planning and observation.

More information about the event will come up soon, for the moment you will only get the local circumstances for European sites. More infos will come soon!