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          936        367 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2329        794 
1998        23258       9806 
1999        14522       5568 
2000        40463      16790 
2001        43022      16683 
2002        32476      14517 
2003        61197      25370 
2004        47953      18391 
2005        85313      26231 
2006       110780      35398 
2007       203919      62541 
2008       125079      35602 
2009       101716      28587 
2010       118247      32844 
2011       177282      49029 
2012       164544      45496 
2013       255476      72263 
2014       605447     155023 
2015       730907     193828 
2016       669245     173809 
2017       602342     162341 
2018       395848     110906 
2019       930930     228219 
2020       685608     175670 
2021       894205     214045 
2022       663813     189873 
2023       603235     173672 
2024       222188      64238