is they are all ephemeral ! They are all about _observable_ positions of moving bodies from a moving point of observation. Maybe they also have a table of astronomic positions or a "fixed stars" kind of observation point. OK, solar accel would be a nice short-cut if it was relative to a fixed inertial frame. Otherwise, instantaneous position of a planet and sun, in any frame, enables calculation of distance hence gravity. magnitude of net gravitational force and probably its z-axis component is probably what should be plotted. The 4 black tick marks above the time axis indicate points where the z-axis motion has a 'hiccup' near the solar surface (orange band on the plot is +/- 0.1 solar radii relative to the x,y,z radial distance of the barycentre from the solar centre (which is at around -700,000 km = -70,000km on the left y axis of the plot). Landscheidt noticed that solar activity crashes whenever the radial distance hangs around near the solar surface for more than 3 years or so. (Mechanism unknown). This is not correct Rog. Landscheidt saw the radial distance that hangs near the solar surface as a boundary condition that enables phase reversal and also influences the human mind, stocks, etc etc. He does not mention a reduction in sunspots. Hi Geoff and welcome back to the talkshop. In the interests of harmony within the solar system I'm going to leave the Landscheidt issue uncontested and move on to your interesting observation about the degree