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         2816        986 
1996         2823       1000 
1997         2813        961 
1998        24484      10300 
1999        13329       5087 
2000        37444      15431 
2001        42942      16890 
2002        40107      16816 
2003        59221      24236 
2004        46370      17690 
2005       310447     139569 
2006       336725     150140 
2007       196294      60727 
2008       113797      32552 
2009        94970      26652 
2010       144915      38630 
2011       152623      41699 
2012       180680      39802 
2013       238375      60416 
2014       533081     130781 
2015       763702     199175 
2016       618322     159608 
2017       530629     144224 
2018       322527      90769 
2019       829426     202677 
2020       554374     140478 
2021       757089     178052 
2022       582227     166791 
2023       530622     151925 
2024       576319     165575 
2025       571721     162304 
2026        94575      25204