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         2845        996 
1996         2850       1009 
1997         2870        980 
1998        24589      10337 
1999        13438       5126 
2000        37715      15554 
2001        43242      17017 
2002        40430      16955 
2003        60114      24567 
2004        46853      17880 
2005       311958     140149 
2006       338100     150627 
2007       197992      61190 
2008       115476      33002 
2009        96837      27153 
2010       147273      39228 
2011       156237      42669 
2012       184286      40783 
2013       242512      61566 
2014       543705     133458 
2015       780429     203288 
2016       625050     161295 
2017       541198     146994 
2018       329509      92679 
2019       839600     205172 
2020       573264     145225 
2021       783520     184744 
2022       594353     170182 
2023       539040     154240 
2024       589506     169403 
2025       606607     173327 
2026        50386      13910