SIGNS: The constellations were all in alignment as the stars came out for a screening of David Fincher's new thriller "Zodiac" (Paramount) at the Tribeca Grand Hotel presented by the Cinema Society and GQ on Wednesday. After the screening, celebs including David Schwimmer, author Robert Graysmith, Willem Dafoe, Tim Robbins and Patricia Clarkson, headed to the Soho Grand Hotel Grand Lounge and Gallery for dinner. Star Jake Gyllenhaal noted that this film was so heavily researched that making it "became a kind of obsession itself." And in other obsessional appearances, Gotham Magazine held its own special screening of the film on Monday night in honor of its cover boy and "Zodiac" star Mark Ruffalo at the Bryant Park Hotel. And on Thursday in Los Angeles, Paramount host a premiere at the studio lot in Hollywood that brought out Viacom's Sumner Redstone, Paramount'a Brad Grey, the film's Chloe Sevigny, Mark Ruffalo and Robert Downey Jr., writer/director/producer James Vanderbilt and producer Bradley J. Fischer and James Ellroy.