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        24445      10287 
1999        13271       5065 
2000        37295      15362 
2001        42776      16815 
2002        39908      16732 
2003        59184      24195 
2004        46175      17609 
2005       309367     139150 
2006       335751     149760 
2007       195609      60552 
2008       112503      32201 
2009        93433      26232 
2010       141665      37828 
2011       150868      41215 
2012       178508      39211 
2013       235356      59574 
2014       533750     131107 
2015       760093     198276 
2016       626871     162005 
2017       526992     143286 
2018       316525      89272 
2019       824767     201732 
2020       546299     138383 
2021       745129     174775 
2022       575263     164806 
2023       524865     150288 
2024       569658     163684 
2025       553932     156799 
2026       225657      45975