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         2825        989 
1996         2832       1003 
1997         2840        970 
1998        24522      10314 
1999        13355       5097 
2000        37543      15475 
2001        43071      16942 
2002        40230      16868 
2003        59406      24302 
2004        46511      17744 
2005       310762     139674 
2006       337051     150248 
2007       196657      60823 
2008       114325      32692 
2009        95592      26816 
2010       145543      38794 
2011       153416      41911 
2012       181717      40083 
2013       239439      60707 
2014       534481     131121 
2015       765553     199686 
2016       619123     159806 
2017       532654     144734 
2018       323951      91164 
2019       830721     202968 
2020       557226     141165 
2021       761643     179189 
2022       584459     167425 
2023       532273     152392 
2024       578747     166309 
2025       570194     162832 
2026        63182      17760