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         1264        471 
1994         1610        593 
1995         2819        987 
1996         2823       1000 
1997         2816        962 
1998        24484      10300 
1999        13332       5088 
2000        37448      15433 
2001        42947      16892 
2002        40109      16817 
2003        59225      24238 
2004        46382      17694 
2005       310458     139572 
2006       336736     150143 
2007       196317      60733 
2008       113858      32568 
2009        95006      26662 
2010       144937      38636 
2011       152642      41704 
2012       180762      39824 
2013       238427      60430 
2014       533146     130800 
2015       763750     199191 
2016       618098     159550 
2017       530466     144170 
2018       322604      90789 
2019       829104     202584 
2020       554474     140502 
2021       757269     178100 
2022       582364     166829 
2023       530715     151951 
2024       576472     165618 
2025       571792     162318 
2026        94220      25125