Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           12          6 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          216         77 
1991          856        306 
1992          662        272 
1993         1192        448 
1994         1514        564 
1995         2471        871 
1996         2714        962 
1997         2599        887 
1998        24097       8601 
1999        12941       4933 
2000        36630      15048 
2001        41668      16372 
2002        35231      15078 
2003        57503      23536 
2004        45290      17243 
2005       304626     137165 
2006       331768     148068 
2007       192974      59732 
2008       109542      31220 
2009        90144      25196 
2010       138141      36777 
2011       145584      39595 
2012       173350      37745 
2013       228806      57664 
2014       476495     118303 
2015       717952     187868 
2016       605927     156682 
2017       513672     139717 
2018       305884      86483 
2019       810554     198652 
2020       533518     135364 
2021       722197     169378 
2022       561191     160904 
2023       514613     147412 
2024       555148     159552 
2025       529331     150172 
2026       321079      73186