I am intrigued by the cycle of the black moon ( moon apogee) and the node ( mean position), which runs on an almost exact 6 year cycle. That is to say every six years when the conjunction happens it does so when the sun is at the same place (well to be precise 1 degree and 5 mins less)
Of course the dates below don't look quite right for that - but once you build in leap years it is perfect.

20-Sep-55 14:13 21?Sg31' R
18-Sep-61 22:32 25?Le32' R
18-Sep-67 06:52 29?Ar32' R
16-Sep-73 15:12 03?Cp34' R
15-Sep-79 23:33 07?Vi34' R
14-Sep-85 07:55 11?Ta35' R
13-Sep-91 16:17 15?Cp36' R
12-Sep-97 00:41 19?Vi36' R
11-Sep-03 09:05 23?Ta37' R
09-Sep-09 17:30 27?Cp38' R
09-Sep-15 01:55 01?Li39' R
07-Sep-21 10:22 05?Ge39' R
06-Sep-27 18:49 09?Aq40' R
05-Sep-33 03:17 13?Li41' R
04-Sep-39 11:46 17?Ge41' R
02-Sep-45 20:16 21?Aq43' R

You'll note that it is currently occurring at about 18 Virgo and that the 1997 conjunction actually occurred at that degree.

Thing is I can't find anything about this cycle and wondered if any of you knew of any articles etc about any of the maths of it ( reason why it moves as it does- does it tie with saros cycles or something?) or the effects. Thanks

A node cycle is 18.613 years
A anomalistic cycle is 8.85 years

thus

1/18.613 + 1/8.850 = 1/5.998

reciprocal is 5.998 years or almost exaclty 6 years with a mean error of about 0.7 days.

There may indeed be a resonance between the two as there are resonances between many of the planet and asteroid orbits.

Martin