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         3564       1252 
1997         2326        793 
1998        23183       9777 
1999        14486       5554 
2000        40197      16670 
2001        41118      16022 
2002        32195      14398 
2003        60512      25111 
2004        47619      18264 
2005        84061      25859 
2006       108900      34845 
2007       200287      61566 
2008       121753      34692 
2009        99202      27908 
2010       115052      32009 
2011       170737      47261 
2012       160020      44287 
2013       241653      68651 
2014       583812     149956 
2015       707168     187600 
2016       678801     176249 
2017       578280     156378 
2018       379637     106473 
2019       907104     222138 
2020       655899     167525 
2021       873243     208273 
2022       656341     187718 
2023       600953     171632 
2024       321596      93261