Year Observations     Objects
1858            3          3 
1889            1          1 
1901            1          1 
1920            6          2 
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          228         81 
1991          867        310 
1992          713        290 
1993         1264        471 
1994         1607        592 
1995         2807        983 
1996         2817        998 
1997         2801        957 
1998        24471      10296 
1999        13290       5072 
2000        37363      15393 
2001        42853      16848 
2002        40003      16769 
2003        59399      24287 
2004        46308      17663 
2005       309826     139323 
2006       336126     149903 
2007       195955      60644 
2008       113039      32348 
2009        94105      26414 
2010       144449      38501 
2011       151640      41426 
2012       179374      39448 
2013       236642      59930 
2014       532890     130696 
2015       762009     198726 
2016       625845     161699 
2017       528038     143554 
2018       319999      90041 
2019       827290     202173 
2020       549600     139191 
2021       750308     176189 
2022       578596     165753 
2023       527211     150961 
2024       572672     164549 
2025       557284     158240 
2026       244691      41930