NavList:

Greetings,

I recently got the book by L. Gray "100 Problems in Celestial Navigation".   The very first problem, which had quite a lot of explanations  "how to" for some reasons (?) didn't mention and didn't counted for interpolation for longitude in calculating nautical and civil twilight time.  The interpolation for the latitude was done but not for the longitude.  If I'm not mistaken (correct me please if I'm wrong) but the time of the phenomenon (twilight, f.e) is tabulated to the zone meridian. In the problem 1-1 DR longitude is 50 deg.W.  The way I understand it the interpolation should be done for the closest zone meridian which in this case will be 45 deg.W.  I looked in the Appendix but still didn't figure out why interpolaion for Longitude wasn't included.  I made the interpolation and of course the results were different from what were in the book.

Quite possible the explanation for this can be very trivial:

1.  I overlooked something in the text

2.  I didn't understand something which quite obvious for everyone else

3.  ??? "Oh, sorry, we forgot to include it"  (which I doubt because the book is very well-known and definitely well-proved).

So, this is my question: am I mistaken regarding this ?

Thanks