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         1604        591 
1995         2807        983 
1996         2817        998 
1997         2801        957 
1998        24467      10295 
1999        13290       5072 
2000        37334      15380 
2001        42834      16839 
2002        39976      16757 
2003        59284      24238 
2004        46250      17638 
2005       309662     139257 
2006       335982     149845 
2007       195825      60609 
2008       112897      32310 
2009        93957      26374 
2010       141999      37916 
2011       151341      41345 
2012       179087      39369 
2013       236225      59818 
2014       533924     131027 
2015       760966     198448 
2016       625919     161734 
2017       527278     143339 
2018       319490      89894 
2019       826486     201957 
2020       548235     138817 
2021       748195     175588 
2022       577615     165472 
2023       526671     150803 
2024       571561     164233 
2025       555047     157329 
2026       213785      41324