... A Comet Tail Horizon . ... To the surprise of many Northern Hemisphere observers, the tail of Comet McNaught remained visible even after the comet's head set ahead of the Sun. ... Comet McNaught, the Great Comet of 2007, has grown a long and filamentary tail. ... The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument onboard the Solar TErrestrial RElations Observatory (STEREO) satellite had just opened up on January 11 when it snapped the above image of Comet McNaught. ...