Stellar Occultations by Hydra(I) in 2011 and 2012 of UCAC Stars

The following occultation predictions are based on the nominal catalog positions of the star catalogs, they have not been refined by special astrometry. Therefore, the predictions should only be used as a first guess for planning or preparing astrometrical observations.

     Date      U.T.    Durn  Star   Mag-Drop Elon  Star      R.A. (J2000)  Dec.       
   y   m  d   h   m   sec/m   mag    V     R   o  No.         h  m   s      o  '   "  
.... ... ..  .. ....  ..... ....  .... ....  ...  ........   .. .. ...... ... .. .....
2011 Jan 18  9  8.5   3.0s 15.9   7.2  7.5   23  24675530   18 24 23.527 -18 49 34.87
2011 Feb  4 19  4.8   3.5s 15.1   8.0  7.9   39  24677822   18 26 43.711 -18 48 38.53
2011 Feb 16 22 55.9   4.1s 16.0   7.1  7.4   51  24679464   18 28  7.398 -18 47 37.00
2011 Feb 20  4 39.9   4.3s 13.3   9.8 10.5   55  24680013   18 28 27.375 -18 47 19.45
2011 Mar 21 10 16.3  10.6s 15.6   7.5  7.4   83  24683120   18 30 32.946 -18 44 54.73
2011 May 22  7 10.9   5.5s 15.5   7.5  7.7  144  24680978   18 29  3.068 -18 44 19.91
2011 Jun 27 14 57.1   4.2s 13.5   9.5  9.1  175  24676603   18 25 29.000 -18 48 47.57
2011 Jul 14  3 16.2   4.4s 14.7   8.3  8.0  164  24674954   18 23 44.226 -18 51 54.03
2011 Aug 12 11 43.3   6.3s 15.7   7.3  7.7  135  24673400   18 21 10.381 -18 58 27.17
2011 Oct 29 13 15.5   4.7s 16.0   7.1  7.4   59  24426525   18 21 56.436 -19 15 36.29
2011 Nov  5  3 57.4   4.2s 15.9   7.2  8.3   53  24427004   18 22 34.673 -19 16 35.40
2011 Nov 15  9 52.4   3.6s 12.9  10.2 10.0   43  24427862   18 23 42.743 -19 17 51.07
2011 Dec 19 23  9.2   2.8s 15.5   7.6  7.2   10  24433501   18 28 27.553 -19 20  1.73
2012 Jan  4 10 46.4   2.8s 15.7   7.4  7.5    7  24437002   18 30 48.000 -19 19 53.78
2012 Jan  7  0 23.6   2.8s 12.3  10.8 10.8   10  24437370   18 31 11.140 -19 19 49.85
2012 Jan 18 13  8.4   3.0s 15.5   7.6  7.4   20  24438802   18 32 52.678 -19 19 17.69
2012 Jan 26  9 31.3   3.1s 16.0   7.1  7.4   28  24439769   18 33 58.752 -19 18 42.86
2012 Jul  3  6 21.9   4.2s 14.6   8.4  8.2  175  24439597   18 33 47.497 -19 21  7.86
2012 Jul  8 12 10.5   4.2s 14.7   8.3  8.2  170  24439127   18 33 14.359 -19 22 12.21
2012 Jul 19  7 42.3   4.5s 14.2   8.8  8.5  160  24438158   18 32  7.969 -19 24 36.14
2012 Nov  2  2 19.2   4.5s 14.0   9.1  9.4   57  24194093   18 30 55.455 -19 46 13.76
2012 Nov  6  6 52.2   4.2s 13.9   9.2  9.1   53  24194403   18 31 20.195 -19 46 44.08
2012 Nov 14  4 27.0   3.7s 15.0   8.1  7.9   45  24195129   18 32 11.421 -19 47 30.80
2012 Nov 24 21 40.2   3.3s 14.8   8.4  8.4   35  24195986   18 33 29.608 -19 48 11.84
2012 Dec 27  3 18.7   2.8s 15.7   7.5  7.3    5  24200072   18 38  5.442 -19 48 24.94

Calculated using  WINOCCULT Version 4.0.8.16 with DE 423 and an position offset according to the following procedure:

An offset of Pluto's position versus DE413 is calculated by Bruno Sicardy from real occultations observed in the last 10 years. It may not be correct for the future, but may be the best approximation we can do at the moment.

This offset versus DE413 is converted in an offset versus DE423, which is the basis of the latest version of WINOCCULT 4.0.4.16.
Because of the approximate position of the stars, which may cause errors larger than Pluto's diameter, the offsets have been calculated only once for each year, at 2011.5 and 2012.5

2011:Offset in Declination: +75 mas, in Rectascension: +88 mas

2012:Offset in Declination: +86 mas, in Rectascension: +115 mas

UCAC stars have been used without any restriction. Events with a reasonable area of visibility have a link to a map with local circumstances. But keep in mind, relatively large errors are possible.

These data are only a first basis for your observation plans.

The table gives the following data:

Date and UT
The UT date and time of closest approach to the specified site [that is, the time listed here does depend on the site location, for both Local and Global summaries].

Duration 
This column gives the predicted maximum duration, in seconds or minutes.
 
Star mag
Star magnitude - visual

Mag drop V
Magnitude drop at occultation - based on visual magnitude

Mag drop R
Magnitude drop at occultation - based on the star's red magnitude, and an asteroid color (B-V) of 0.83. This may be a better guide for CCD observers

Elong
The solar elongation of the star, in degrees

Star number
The 2UCAC number of the star being occulted or the Tycho number

RA Dec
The J2000 coordinates of the star

Wolfgang Beisker

International Occultation Timing Association - European Section
Research and Development