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          767        309 
1993         1356        504 
1994         1746        640 
1995         3291       1145 
1996         3243       1142 
1997         2288        782 
1998        23088       9741 
1999        14416       5526 
2000        39972      16573 
2001        40800      15893 
2002        32313      14411 
2003        59802      24839 
2004        47315      18154 
2005        83053      25553 
2006       107094      34319 
2007       196421      60529 
2008       118031      33685 
2009        97312      27394 
2010       111874      31178 
2011       165617      45886 
2012       156607      43366 
2013       231266      65824 
2014       575105     146678 
2015       750679     196414 
2016       669731     173413 
2017       571172     154280 
2018       367835     103221 
2019       890522     217548 
2020       642977     163901 
2021       862935     205578 
2022       639894     183159 
2023       579314     165860 
2024       511671     147924