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          883        349 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14522       5568 
2000        40458      16786 
2001        43022      16681 
2002        32466      14512 
2003        61178      25363 
2004        47941      18387 
2005        85258      26214 
2006       110740      35385 
2007       203804      62510 
2008       125018      35584 
2009       101650      28569 
2010       118162      32822 
2011       177144      48989 
2012       164464      45475 
2013       255230      72191 
2014       605198     154951 
2015       730680     193768 
2016       699991     180936 
2017       601164     162149 
2018       395635     110845 
2019       930428     228137 
2020       685204     175558 
2021       893933     213966 
2022       663733     189840 
2023       602805     173559 
2024       244630      70829