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         2834        992 
1996         2847       1008 
1997         2861        977 
1998        24573      10332 
1999        13406       5115 
2000        37671      15537 
2001        43214      17007 
2002        40387      16941 
2003        59718      24432 
2004        46728      17837 
2005       311489     139942 
2006       337792     150504 
2007       197644      61085 
2008       115162      32920 
2009        96535      27068 
2010       146715      39099 
2011       155438      42458 
2012       183677      40620 
2013       241619      61321 
2014       540604     132712 
2015       770973     201122 
2016       623449     160937 
2017       538404     146328 
2018       327978      92285 
2019       837441     204620 
2020       567977     143873 
2021       776202     182805 
2022       589064     168722 
2023       536233     153483 
2024       585226     168197 
2025       588046     168013 
2026        53622      14975