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         1270        473 
1994         1616        595 
1995         2845        996 
1996         2850       1009 
1997         2870        980 
1998        24586      10336 
1999        13438       5126 
2000        37707      15551 
2001        43237      17015 
2002        40423      16952 
2003        60094      24559 
2004        46847      17877 
2005       311929     140138 
2006       338040     150600 
2007       197956      61180 
2008       115446      32995 
2009        96768      27132 
2010       147229      39216 
2011       156064      42622 
2012       184159      40748 
2013       242198      61482 
2014       543045     133298 
2015       778889     202927 
2016       624788     161234 
2017       540296     146765 
2018       329217      92601 
2019       838357     204850 
2020       570859     144565 
2021       780451     183891 
2022       591073     169281 
2023       537525     153830 
2024       587864     168944 
2025       604707     172812 
2026        50848      14091