NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Douglas Stephen
Date: 2023 Dec 20, 15:59 -0800
Thanks to all those that replied to my questions about longitude by moon culminations. I know more now than I did before and when the weather, the moon and my other obligations all align I will give it a try and post the results. In answer to Frank's question about what I would want in an almanac to determine longitude by this method: With what I know now I don't think I need any new info, I am not looking for a historical re-creation, I just wanted to see how difficult it would be and the advantages and disadvantages of the method. The big disadvantages seem to be, only a few chances per month to make the measurements and the need for a theodolite. From a map making and sureveying point of view where they really like to make many measurements to have high confidence in the results, you would have to stay in one place a long time. I do not know how much this was really used, I have not seen a lot of actual longitudes by this method and certainly once a telegraph and or good time was available it would be obsolete. In A Manual of Surveying for India (an interesting book on many levels, available for free from google books) they give the method a so so recommendation.
9. (B) Transits of the moon ;- a very simple and tolerably accurate method ; but as only about eight observations can (usually) be taken in a month, and as the moon can be observed at no time but on the meridian, it will not be safe to rely upon it, except in a residence of many months continuation.
Again, my thanks to all who helped me learn more about this technique. I live in Colorado, far from ready made horizons, so the mapping side of celestial and it's use on land is of special interest to me. I'll post my results but it may be a while.
Doug
