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         1267        472 
1994         1616        595 
1995         2834        992 
1996         2847       1008 
1997         2861        977 
1998        24573      10332 
1999        13406       5115 
2000        37671      15537 
2001        43214      17007 
2002        40387      16941 
2003        59718      24432 
2004        46728      17837 
2005       311506     139948 
2006       337813     150512 
2007       197669      61092 
2008       115220      32935 
2009        96564      27076 
2010       146763      39111 
2011       155520      42482 
2012       183782      40650 
2013       241746      61357 
2014       540916     132791 
2015       771152     201177 
2016       623595     160976 
2017       538819     146449 
2018       328204      92350 
2019       837861     204733 
2020       568627     144027 
2021       777362     183121 
2022       589360     168806 
2023       536494     153553 
2024       585580     168303 
2025       595557     170201 
2026        53623      14974