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         1267        472 
1994         1616        595 
1995         2840        994 
1996         2847       1008 
1997         2867        979 
1998        24580      10334 
1999        13426       5122 
2000        37683      15541 
2001        43234      17014 
2002        40419      16950 
2003        60056      24544 
2004        46833      17872 
2005       311890     140125 
2006       337992     150585 
2007       197901      61165 
2008       115380      32977 
2009        96646      27099 
2010       147165      39199 
2011       155940      42588 
2012       184019      40710 
2013       242008      61428 
2014       542778     133228 
2015       778408     202828 
2016       624862     161258 
2017       539694     146633 
2018       328914      92518 
2019       838256     204827 
2020       570454     144453 
2021       779877     183741 
2022       590635     169157 
2023       537335     153776 
2024       587402     168810 
2025       604046     172624 
2026        52493      14630