I completed the three Astrariums (solving the star chart puzzles) and the beams pointed to a cave in the south western part of the map. Looks like I need to get through there to collect shards. Anyway, when I go to the cave, there is a column of light that fades when I stand in it, but there is no way to enter the cave - door isn't open. Is this a glitch? Am I at the wrong cave? Very strange. Other maps with Astrariums worked just fine. Any help would be appreciated. Thanks!