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5b Cillchroisd (ML7) (MN 3773 5348)


A single stone on open ground which slopes down gently to the NE  A rectangular slab:  2.6m x 1.4m x 0.6m.  The longer nearly flat NW face is aligned to about 35º.

1a. View to NE - Cropped


2a. Indicated direction - Cropped

3a. Indicated direction - Cropped










Alignment(s) shown.   Discussion follows.

4a. Alignment - Cropped

The alignment  for the major standstill in the extreme north ( +29º 27′.5, September )  at about 31º.7  azimuth is clear.  The moon could never have reached further north.  As required the moon would have been clearly visible before reaching the alignment,the moon being  just hidden by the hill.  At the immediately previous lunations the maximum north of the moon would be slowly approaching the extreme declination. This could have been observed by moving as far up the slope behind the stone as necessary to bring the moon up to the foresight.  The monthly maximum positions would be marked by a stake.  The stakes would be successively nearer to the stone, but would move back up the slope following the extreme position.    [ Extrapolation:-  Except by chance the  moon, at any given lunation, would not be at the maximum position for that lunation.  Extrapolation using three or more observations near the maximum would be necessary.   See Discussion, Extrapolation].  The objective would be to determine the day of the extreme north position.  i.e. +29º 27′.5

Note:  There might appear to be a possible alignment in the dip for the upper limb with 'wobble' to the south (29º 09′.5,  March).  In principle advance warning of the approaching moon could be given by having observers stationed further up the slope and to the right. However the moon would be at first quarter and hence in daylight.  This might not absolutely rule it out ( see Discussion,  Addendum ) but since only the tip of the crescent would be observed it seems unlikely.  One positive point is that the expected time (day**) would be known from the observation of the alignment previously discussed.

( ** The alignments would be 173 days apart).