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         1264        471 
1994         1610        593 
1995         2813        985 
1996         2823       1000 
1997         2813        961 
1998        24484      10300 
1999        13318       5083 
2000        37440      15429 
2001        42928      16883 
2002        40098      16812 
2003        59197      24228 
2004        46352      17684 
2005       310367     139541 
2006       336689     150124 
2007       196211      60705 
2008       113677      32521 
2009        94843      26617 
2010       144862      38616 
2011       152520      41673 
2012       180500      39754 
2013       238133      60350 
2014       532949     130746 
2015       764070     199267 
2016       618108     159556 
2017       530547     144215 
2018       322382      90730 
2019       829972     202889 
2020       553995     140381 
2021       756431     177865 
2022       581688     166637 
2023       530344     151848 
2024       575710     165422 
2025       570906     162241 
2026       118918      31482