Below are the latest predictions for the occultation of P126A by Pluto and/or charon, after the mail by Ron Stone (July 5, FASTT/Flasgstaff) and Francois Colas, Jean Lecacheux, Agnes Fienga (July 9 and 11, Pic du Midi).
(1) The prediction after Ron Stone assumes a position for the centroid P126A+B:
17:00:17.9966 (+/- 0.070" ?)
-12:41:41.889 (+/- 0.070" ?)
and then a shift of:
+0.583"
-0.192"
to get finally the position of P126A alone:
17:00:18.0364
-12:41:42.081
I also used the O-C of Pluto derived by Ron:
+0.047"
+0.005"
to get the following prediction:
(2) The predictions after Pic du Midi observations use a centroid
P126A+B observed with the 0.55-m refractor:
17:00:17.9980 (+/- 0.090")
-12:41:41.9598 (+/- 0.034")
and then a modeling of the system P126A+B using images of the 1-m
refractor where the components are resolved. This yields for P126A alone:
17:00:18.0186
-12:41:42.060
The resulting prediction is shown in the image below. For consistent
comparison, I have used the same O-C as in (1) for Pluto, namely:
+0.047"
+0.005"
(3)
Attempts have been made by Jean Lecacheux to connect P126A (resolved from
P126B) to the star TYC 5651-01309-2 with the 1-m refractor at pic du Midi.
This yields the following position for P126A:
17:00:18.0102
-12:41:41.963
With the resulting prediction, and the same O-C again for Pluto:
+0.047"
+0.005"
My feeling is that the uncertainty on the O-C of Pluto could still be of the order of 0.05", i.e. that the tracks could be shifted laterally by one Pluto radius, due to the uncertainty on the Pluto O-C only.
Also, the derived positions for P126A are for the moment **model dependent**, i.e. they use the position of the observed centroid P126A+B, and then they use some models for the displacement of this centroid wrt P126A. Thus, great care must be taken in estimating the error bars on P126A position, since systematic arrors are entering in the derivations.
Thus, as of today, it looks like the Pluton occultation can be detected somewhere between southern Mexico and Chile (but not at all these places at the same time, of course).
Also, be aware that a Charon occultation is not ruled out in southern Chile, in case all the shadows go up to the north.
Bruno Sicardy