Years

Number of observers

Start date

End date

Number of observations

1993

5

May 5

November 30

338

1994

26

February 1

December 27

2616

1995

28

February 1

December 27

4089

1996

30

January 1

December 20

3596

1998

9

April 1

December 30

834

1999

19

April 1

November 30

1786

2000

20

January 10

December 30

2290

2002

29

March 1

November 30

3223

2003

29

March 1

November 28

2872

2004

9

April 1

December 28

776

2005

20

April 1

November 30

1704

2010

2

January 11

November 29

492

2011

3

January 11

December 30

596

2012

2

May 3

December 4

224