Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          444        170 
1992          724        294 
1993         1283        478 
1994         1640        603 
1995         2909       1017 
1996         2898       1025 
1997         1793        621 
1998        21465       9134 
1999        12930       4981 
2000        38067      15725 
2001        39722      15383 
2002        31744      14072 
2003        56522      23556 
2004        45483      17473 
2005        80049      24667 
2006       103100      33152 
2007       188160      58313 
2008       107207      30797 
2009        89890      25378 
2010       141811      38138 
2011       151551      42084 
2012       142691      39583 
2013       215600      61478 
2014       549634     139951 
2015       794220     208942 
2016       647676     168186 
2017       545022     147517 
2018       339691      95491 
2019       851709     207853 
2020       595545     151169 
2021       806114     190843 
2022       609007     174353 
2023       549329     157214 
2024       605535     174091 
2025       500522     142860