For sewing darts in sheer fabric you can use the bobbin stitch method for a clean finished dart point.
With this method you stitch the dart with only 1 thread from the bobbin so you can avoid the backstitching or knotting the threads together at the point like you would normally finnish the dart..
-Fold and pin the dart in place.
-Remove the thread from the needle eye,thread the bobbin thread through the needle from the back to the front.
-Tie the bobbin and needle thread in an overhand knot above the needle eye,then careful draw the bobbin thread up through all thread guides until the knot reaches the spool.
-For extra long darts draw up even more thread
-Beginnning at the dart point,stitch to the dart cut end;backstitch and clip the threads.
-Repeat to rethread the machine for each next dart.
It may seems a lot of work but it surely is worth the effort.
REMEMBER TO START STITCHING FROM THE TOP.