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         2819        963 
1998        24484      10300 
1999        13338       5090 
2000        37448      15433 
2001        42951      16894 
2002        40109      16817 
2003        59227      24239 
2004        46390      17697 
2005       310463     139574 
2006       336738     150144 
2007       196324      60735 
2008       113858      32568 
2009        95010      26663 
2010       144940      38637 
2011       152646      41705 
2012       180769      39826 
2013       238435      60432 
2014       533165     130804 
2015       763752     199193 
2016       617923     159505 
2017       530490     144177 
2018       322623      90794 
2019       828899     202527 
2020       554496     140507 
2021       757272     178101 
2022       582377     166833 
2023       530729     151954 
2024       576484     165622 
2025       571835     162321 
2026        93577      24961