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         1616        595 
1995         2828        990 
1996         2832       1003 
1997         2840        970 
1998        24525      10315 
1999        13355       5097 
2000        37551      15479 
2001        43082      16947 
2002        40232      16869 
2003        59414      24305 
2004        46526      17750 
2005       310784     139682 
2006       337068     150254 
2007       196694      60833 
2008       114372      32705 
2009        95630      26826 
2010       145583      38805 
2011       153476      41927 
2012       181807      40107 
2013       239577      60745 
2014       534578     131147 
2015       765164     199580 
2016       619300     159851 
2017       532929     144803 
2018       324018      91183 
2019       830915     203012 
2020       557500     141221 
2021       762129     179301 
2022       584793     167520 
2023       532443     152437 
2024       579052     166395 
2025       570620     162945 
2026        59728      16747