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          225         80 
1991          867        310 
1992          705        287 
1993         1261        470 
1994         1596        588 
1995         2794        979 
1996         2811        996 
1997         2780        950 
1998        24429      10281 
1999        13230       5051 
2000        37253      15342 
2001        42721      16789 
2002        39849      16706 
2003        59067      24144 
2004        46081      17573 
2005       309057     139045 
2006       335530     149680 
2007       195307      60470 
2008       112161      32107 
2009        93031      26119 
2010       141254      37720 
2011       150188      41032 
2012       177888      39044 
2013       234662      59382 
2014       532443     130768 
2015       757867     197666 
2016       625690     161688 
2017       525879     142997 
2018       314664      88827 
2019       823001     201360 
2020       545065     138113 
2021       740772     173652 
2022       573351     164266 
2023       523528     149913 
2024       567394     163046 
2025       548852     155572 
2026       225767      46050