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         2134        773 
1995         3354       1166 
1996         3567       1253 
1997         2326        793 
1998        23205       9785 
1999        14493       5557 
2000        40350      16740 
2001        42831      16606 
2002        32337      14459 
2003        60769      25209 
2004        47692      18293 
2005        84246      25914 
2006       109264      34951 
2007       201071      61774 
2008       122409      34870 
2009        99585      28012 
2010       115602      32152 
2011       171999      47598 
2012       160678      44468 
2013       244092      69321 
2014       585603     150423 
2015       709584     188268 
2016       684304     177549 
2017       579815     156860 
2018       381991     107129 
2019       909721     222990 
2020       659188     168458 
2021       874794     208700 
2022       658203     188246 
2023       604245     172227 
2024       289598      83994