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        37549      15478 
2001        43078      16945 
2002        40230      16868 
2003        59412      24304 
2004        46514      17745 
2005       310765     139675 
2006       337061     150251 
2007       196664      60825 
2008       114358      32701 
2009        95619      26823 
2010       145567      38801 
2011       153456      41922 
2012       181771      40098 
2013       239526      60731 
2014       534525     131133 
2015       765431     199648 
2016       619227     159833 
2017       532776     144767 
2018       324008      91180 
2019       830884     203005 
2020       557400     141193 
2021       761974     179255 
2022       584697     167493 
2023       532368     152416 
2024       578897     166354 
2025       570578     162933 
2026        60791      17061