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          713        290 
1993         1261        470 
1994         1602        590 
1995         2801        981 
1996         2814        997 
1997         2789        953 
1998        24442      10286 
1999        13268       5064 
2000        37293      15361 
2001        42774      16814 
2002        39902      16729 
2003        59182      24194 
2004        46166      17606 
2005       309337     139140 
2006       335742     149757 
2007       195593      60548 
2008       112481      32195 
2009        93387      26218 
2010       141657      37826 
2011       150839      41206 
2012       178469      39202 
2013       235321      59563 
2014       533777     131119 
2015       759963     198242 
2016       626881     162008 
2017       526891     143262 
2018       316466      89255 
2019       824789     201744 
2020       546242     138369 
2021       744985     174739 
2022       575121     164767 
2023       524733     150250 
2024       569602     163667 
2025       553780     156756 
2026       225063      45822