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        37545      15476 
2001        43076      16944 
2002        40230      16868 
2003        59409      24303 
2004        46514      17745 
2005       310765     139675 
2006       337061     150251 
2007       196664      60825 
2008       114358      32701 
2009        95619      26823 
2010       145563      38800 
2011       153449      41920 
2012       181771      40098 
2013       239522      60730 
2014       534526     131133 
2015       765620     199701 
2016       619227     159833 
2017       532761     144763 
2018       324004      91179 
2019       830914     203014 
2020       557397     141192 
2021       761960     179251 
2022       584672     167486 
2023       532361     152415 
2024       578883     166350 
2025       570539     162922 
2026        62390      17531