Year Observations     Objects
1858            3          3 
1889            1          1 
1901            1          1 
1920            6          2 
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
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          228         81 
1991          867        310 
1992          716        291 
1993         1267        472 
1994         1616        595 
1995         2834        992 
1996         2847       1008 
1997         2861        977 
1998        24570      10331 
1999        13388       5109 
2000        37661      15534 
2001        43208      17005 
2002        40387      16941 
2003        59702      24426 
2004        46728      17837 
2005       311293     139867 
2006       337555     150421 
2007       197465      61036 
2008       115001      32875 
2009        96335      27015 
2010       146458      39031 
2011       154945      42324 
2012       183187      40482 
2013       241121      61178 
2014       539104     132317 
2015       769141     200627 
2016       622239     160614 
2017       536691     145839 
2018       326888      91981 
2019       835521     204089 
2020       564570     143009 
2021       770935     181511 
2022       587669     168327 
2023       535093     153181 
2024       583107     167586 
2025       568898     162423 
2026        54487      15202