OK tom  Thanks for responding  Im sure it was considerable work but since it is your code I assume you ptobably use the Synodic moon period  Can you simply change it to the Siderial to see what the number scomes out to  My only possible but unbeliveable doubt if any is basing the time on the Siderial moonperiod but at least one site i found so far validates that  Until someone can clearly explain why the calculation must use the synodic I still feel my algorithm is impecble as validated by the clock hands algorithm  I am not sure convinced that the presence of an analemma is alone a sufficient proof that everything about your algorithm must be correct  If you could report the effect of only going to the Siderial moon period Id really appreciate hearing if it goes haywire or still looks reasonable keeping the analemma and all other salient behaviors  When I put the  synodic in my calculator Excel I get  so you are indeed using the algorithm that at least mathwise implicitly assumes the moon stops at  hrs waiting for Earth to catch up  That is what my math does to get that number  I just can not see how synodic is the correct basis for the position of the moon relative to the earth Good ole Sol has no standing as I can see  If it wasnt so cold Id really be tempted to take out the scope and reticle eyepiece and let it sit overnight pointed at a moon crossing spot I think a meridian crossing should do it for one cycle If you celebrate it have a nice holiday Regards