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         1273        474 
1994         1616        595 
1995         2848        997 
1996         2856       1011 
1997         2870        980 
1998        24589      10337 
1999        13441       5127 
2000        37715      15554 
2001        43248      17020 
2002        40436      16958 
2003        60118      24569 
2004        46864      17884 
2005       311984     140157 
2006       338126     150636 
2007       198044      61205 
2008       115565      33027 
2009        96932      27180 
2010       147334      39244 
2011       156323      42693 
2012       184421      40819 
2013       242656      61604 
2014       544101     133550 
2015       780889     203413 
2016       624991     161261 
2017       541467     147055 
2018       329701      92733 
2019       839982     205271 
2020       573688     145333 
2021       784107     184910 
2022       594925     170346 
2023       539233     154294 
2024       590091     169575 
2025       608059     173746 
2026        38113      10499