Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          471        179 
1992          743        301 
1993         1308        487 
1994         1681        617 
1995         3081       1075 
1996         2980       1053 
1997         1866        644 
1998        21858       9277 
1999        13572       5203 
2000        38672      15987 
2001        39480      15337 
2002        35024      15215 
2003        57819      24058 
2004        46400      17802 
2005        81560      25106 
2006       105233      33772 
2007       192099      59367 
2008       112779      32284 
2009        93513      26352 
2010       135161      36712 
2011       158676      44006 
2012       149899      41532 
2013       222031      63253 
2014       565629     144098 
2015       798638     210131 
2016       659776     171433 
2017       555189     150323 
2018       353006      99166 
2019       866221     211463 
2020       619295     157646 
2021       834366     198151 
2022       622852     178279 
2023       560368     160279 
2024       621327     178987 
2025       206115      58900