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        37344      15384 
2001        42846      16845 
2002        39986      16761 
2003        59292      24242 
2004        46265      17645 
2005       309744     139291 
2006       336071     149883 
2007       195898      60628 
2008       112923      32318 
2009        94008      26387 
2010       142030      37924 
2011       151454      41376 
2012       179175      39394 
2013       236369      59855 
2014       533723     130969 
2015       761358     198547 
2016       625895     161728 
2017       527577     143421 
2018       319650      89939 
2019       826810     202050 
2020       548655     138934 
2021       748779     175761 
2022       577984     165579 
2023       526937     150881 
2024       571913     164332 
2025       555720     157523 
2026       243955      41815