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        13412       5150 
2000        38601      15961 
2001        39431      15315 
2002        33269      14627 
2003        57748      24027 
2004        46298      17762 
2005        81379      25052 
2006       105033      33712 
2007       191767      59276 
2008       112239      32140 
2009        93089      26238 
2010       145504      39088 
2011       157902      43800 
2012       149190      41336 
2013       221013      62965 
2014       565112     143984 
2015       798667     210212 
2016       659085     171279 
2017       554615     150122 
2018       351523      98751 
2019       863490     210798 
2020       616817     156983 
2021       829748     197022 
2022       619836     177420 
2023       558785     159852 
2024       617794     178028 
2025       218836      62625