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        13394       5111 
2000        37671      15537 
2001        43214      17007 
2002        40387      16941 
2003        59710      24429 
2004        46728      17837 
2005       311403     139911 
2006       337684     150464 
2007       197558      61061 
2008       115054      32890 
2009        96430      27040 
2010       146610      39071 
2011       155183      42388 
2012       183429      40551 
2013       241314      61232 
2014       539812     132503 
2015       769860     200824 
2016       622734     160751 
2017       537410     146038 
2018       327439      92134 
2019       836569     204379 
2020       566247     143404 
2021       773426     182119 
2022       588307     168508 
2023       535601     153321 
2024       584045     167857 
2025       579978     165643 
2026        54378      15173