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        43216      17008 
2002        40387      16941 
2003        60029      24534 
2004        46811      17865 
2005       311607     139989 
2006       337907     150548 
2007       197861      61155 
2008       115304      32958 
2009        96608      27088 
2010       147091      39185 
2011       155839      42562 
2012       183914      40686 
2013       241886      61393 
2014       541291     132893 
2015       771527     201283 
2016       623873     161048 
2017       539518     146585 
2018       328605      92437 
2019       838073     204787 
2020       569324     144204 
2021       778925     183506 
2022       589700     168898 
2023       536810     153631 
2024       586896     168670 
2025       603131     172401 
2026        51962      14486