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Occultations by Hydra in 2008, 2009 and 2010 of UCAC stars


     Date     U.T.   Durn  Star  Mag-Drop  Elon  Star#    Min          R.A. (J2000)  Dec.      
  y   m   d   h  m    sec/m  mag   V    R     o  2UCAC... D    Error   h  m   s      o  '   " 
.... ... ..  .. .... ..... .... .... ....  ...  ........  ....  ....  .. .. ...... ... .. .....
2008 Oct 24  17 16.1  4.5s 14.6  8.4  8.4   57  25145736  0.39  0.45  17 55 27.041 -17 33  4.45
2008 Nov 17   0 12.4  3.3s 10.5 12.5 12.5   35  25146786  1.22  0.64  17 58  7.279 -17 38 39.10
2008 Dec 10  13 37.2  2.8s 16.3  6.8  6.8   13  25149168  0.25  0.45  18  1 28.155 -17 42 34.01
2008 Dec 16  12 34.6  2.8s 15.0  8.1  8.1    8  25150136  0.16  0.46  18  2 22.396 -17 43 15.44

2009 Feb 11   6  5.2  4.0s 13.9  9.1  9.1   50  25152958  1.29  0.48  18 10 16.272 -17 43 54.49
2009 Oct  1  24  0.2  9.1s 13.8  9.2  9.2   82  24908777  1.10  0.43  18  2 37.599 -18  3  2.74
2009 Dec 26  12 13.8  2.8s 13.6  9.5  9.5    5  24912564  1.14  0.40  18 12 28.116 -18 17 54.00
2010 Apr 22  21 52.1 13.0s 16.2  6.8  6.8  117  24923797  0.75  0.44  18 21 49.674 -18 11 37.90
2010 May 17   9 43.1  5.7s 13.8  9.2  9.2  141  24922561  1.27  0.44  18 20 25.475 -18 11 46.47
2010 May 19  11  5.4  5.5s 14.2  8.8  8.8  143  24922334  1.10  0.44  18 20 15.644 -18 11 49.95

2010 May 19  19 47.9  5.5s 15.7  7.3  7.3  144  24922280  0.15  0.32  18 20 13.896 -18 11 51.00
2010 May 25   2 58.7  5.1s 14.5  8.5  8.5  149  24921605  0.12  0.41  18 19 46.899 -18 12  4.83
2010 May 29   0 29.6  4.9s 11.8 11.2 11.2  152  24921005  1.09  0.44  18 19 25.849 -18 12 18.71
2010 Jun 15  13 39.2  4.3s 15.5  7.5  7.5  169  24918075  0.84  0.33  18 17 40.946 -18 14  1.99
2010 Nov  8  18 28.7  3.8s 14.2  8.9  8.9   47  24665077  0.07  0.46  18 14 22.978 -18 45 25.70

2010 Nov 27  18  7.1  3.1s 14.4  8.7  8.7   29  24669361  0.61  0.42  18 16 45.857 -18 48  4.73
2010 Dec 28  14  2.7  2.8s 14.4  8.7  8.7    5  24673464  1.07  0.41  18 21 18.245 -18 49 58.38

Calculated using  WINOCCULT Version 4.05 with DE 421 and an position offset according to the following table.

This offset is calculated from the occultations observed in the last 3 years. It may not be correct at all, buit may be the best approximation we can do at the moment:

Declination offset relative to DE421 (O-C) in mas

1.Sep.2008 - 30.Nov.2008    90
1.Dec.2008 - 31.Jan.2009    95
1.Feb.2009 - 30.Apr 2009   102
1.May 2009 - 31.Jul 2009   111
1.Aug 2009 - 31.Oct 2009   120
1.Nov 2009 - 31.Jan 2010   129
1.Feb 2010 - 30.Apr 2010   141
1.May 2010 - 31.Jul 2010   150
1.Aug 2010 - 31.Oct 2010   159
1.Nov 2010 - 31.Dec.2010   164

The Error in Rectaszension is always set to -10 mas O-C because the alteration are to large and a linear increase or decrease could not be found. The data are calculated from linear interpolation fro a table collected by Dave Herald, Australia.


 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 klarge 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 her 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 of the Tycho number, depending on U or T

MinD
The minimum distance of the center of the occultation path from the center of the Earth

Error
The uncertainty in the location of the path, in Earth radii

RA Dec
The J2000 coordinates of the star

The main event will be the 10m4 occultation on the 14th of February 2010, a Pluto occultation passing over Europe could be possible, if the offset is changing a little.....


Wolfgang Beisker

International Occultation Timing Association - European Section
Research and Development