I just looked at the BPASS code: when autocorrelation only is selected (BPASSP(1) > 0), the divide byy channel 0 option is turned off. This makes BPASSP(10) = 1 (VLB) or 2 or 3 (VLA) essential. I have added comments to the help file and a warning to the code to point this out. Thanks for your help. Eric Greisen