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          492        186 
1992          770        310 
1993         1356        504 
1994         1752        642 
1995         3318       1154 
1996         3437       1208 
1997         2294        784 
1998        23135       9759 
1999        14451       5540 
2000        40073      16618 
2001        41570      16161 
2002        32709      14550 
2003        60117      24960 
2004        47455      18204 
2005        83465      25676 
2006       107809      34528 
2007       198051      60969 
2008       119496      34086 
2009        98207      27640 
2010       113250      31532 
2011       167834      46476 
2012       158036      43755 
2013       235465      66978 
2014       578977     148699 
2015       699942     185604 
2016       675059     175247 
2017       575870     155527 
2018       372900     104627 
2019       898315     219622 
2020       649672     165656 
2021       868243     206989 
2022       643488     184236 
2023       587133     168067 
2024       450384     131282