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          468        178 
1992          743        301 
1993         1308        487 
1994         1675        615 
1995         3048       1064 
1996         2977       1052 
1997         1858        641 
1998        21674       9215 
1999        13395       5144 
2000        38597      15959 
2001        39423      15312 
2002        33282      14631 
2003        57736      24022 
2004        46283      17756 
2005        81360      25046 
2006       105008      33705 
2007       191741      59269 
2008       112200      32129 
2009        93056      26229 
2010       145469      39079 
2011       157838      43782 
2012       149062      41302 
2013       220967      62952 
2014       565154     144004 
2015       798400     210176 
2016       658828     171212 
2017       554513     150090 
2018       351456      98734 
2019       863249     210733 
2020       616656     156940 
2021       829511     196974 
2022       619649     177368 
2023       558597     159799 
2024       617569     177964 
2025       220714      63098