NavList:

I have an old octant with a strange error which I doubt is octant-specific.   If I set the instrument to zero and adjust the index arm so the reflected and direct images form straight and continuous horizon (as if to measure the index error), everything appears normal.   If I then tilt up or down even slightly, as if noding "yes",  the horizon separates again into a stepped pattern.  The horizon returns to a continuous line only when the instrument is restored to its original line of sight.  As far as I can tell, there is no perpendicular error and only slight side error.  With a normal instrument, once the the index error is dialed out, the horizon remains continuous no matter how it is tilted or rocked.   Has anyone else ever experienced this type of error?