I've never seen a chatter pattern that uniform along the length of a workpiece, but I'm almost sure that's what it is. To get rid of it on this piece try just putting the tube between centers and at max speed put your skew onto the blank so that NO cutting is taking place, only the blank hitting the bevel of the blade with the cutting edge of the tool at about a 20 or 30 degree angle from vertical on the blank, then very slowly raise the butt of your skew till you start getting the first fine wisps of material removed. move back and forth till the blank is smooth, and then reassemble and turn as usual.
Remember a skew used as a scraper is only half as efficient as a real scraper because of the way the edge is ground. If the bevel is evenly ground, the edge is effectively only supported by half the thickness of the tool. If you want to scrape with the flat of the tool laying flat on the toolrest, consider regrinding a skew from a > shape to a 7 shape. That way the full thickness of the tool supports the cutting edge. To be really efficient with this tool you will need to learn how to burnish a curl onto the cutting edge, but that's a different woodworking show altogether.
Good luck,
James