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          492        186 
1992          770        310 
1993         1356        504 
1994         2128        771 
1995         3351       1165 
1996         3567       1253 
1997         2326        793 
1998        23200       9783 
1999        14493       5557 
2000        40227      16684 
2001        41143      16031 
2002        32227      14411 
2003        60596      25143 
2004        47658      18279 
2005        84160      25889 
2006       109127      34912 
2007       200842      61713 
2008       122237      34824 
2009        99441      27973 
2010       115429      32107 
2011       171594      47490 
2012       160466      44412 
2013       243481      69159 
2014       585009     150272 
2015       708881     188076 
2016       680149     176599 
2017       579431     156721 
2018       381434     106975 
2019       909658     222892 
2020       674410     171914 
2021       874232     208551 
2022       657420     188031 
2023       602096     171944 
2024       303920      88015