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          468        178 
1992          735        298 
1993         1283        478 
1994         1655        608 
1995         2945       1029 
1996         2941       1040 
1997         1810        627 
1998        21554       9171 
1999        13058       5026 
2000        38235      15800 
2001        39136      15198 
2002        30572      13698 
2003        57150      23797 
2004        45835      17598 
2005        80538      24811 
2006       103863      33376 
2007       189952      58792 
2008       109906      31519 
2009        91456      25798 
2010       143223      38506 
2011       154339      42843 
2012       145736      40412 
2013       217583      62030 
2014       558165     142225 
2015       797572     209781 
2016       654498     170035 
2017       549436     148724 
2018       345558      97116 
2019       857865     209330 
2020       607138     154387 
2021       816948     193806 
2022       613502     175627 
2023       553371     158352 
2024       607840     175013 
2025       362671     104345