NavList:

This useful thread, together with Frank’s recent “Latitude and longitude around noon” problem, have stimulated me to increase my understanding of this effect. I set out in the attached PDF various snippets that I have gleaned. They will bore the cognoscenti but may be of interest to those who share my curiosity. Please note that the tabular information therein is solely to illustrate the magnitude of the effects under study and should not be used as a source of data.

Thanks. I have just had a Euereka! moment.

I could not  understand why there was an offset for a STATIONARY observer. Your Table 1 makes it obvious - it is due to the hourly change in the dec of the sun. So simple......... no need for complicated spherical mathematics to undersatand the concept!