A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2023 May 17, 13:34 -0700
"I don't have a calculator and so I'm trying to use the Borda method and Bowditch's Table 44 (now 3) to clear the Lunar Distance. I am getting some negative numbers and don't know what to do. Can you help me?"
Yes. I can help you. I will buy you a calculator and send it to you.
Ha ha ha. :)
Myself I don't think I've worked a lunar from start to finish using Borda's method even once. I looked at it long enough to understand it years ago, but it had no appeal for me. Why not use Thomson's method like we did in the workshop? After the "pre-clearing" it's just two quick logarithmic calculations and then one lookup. You could turn to the original Bowditch-Thomson instructions and tables in one of the editions of Bowditch from 1837 through the late 19th century. There's a list with links here: https://navlist.net/historical-navigation-texts.
If you still prefer to work using Borda's method, I'm sure there are folks here (including me if I have time) who would be very happy to help. But can you give us some details? How far have you gotten?
PS: For other NavList members who may not know Max Mulhern, author of this inquiry about Borda and lunars, I'm attaching a photo of the "Maxotron", so-called. It's an astronomy education instrument --an armillary sphere-- built by Max Mulhern based on an idea by Phil Sadler (that's my understanding of the background of this at least). It's here seen on the roof of the CfA, Center for Astrophysics at Harvard in Cambridge, Massachusetts. Phil Sadler posted the photo on social media last year. You can tell its Cambridge because, as I pointed out previously, the "astronomer" in the driver's seat is wearing Birkenstocks with socks. Still fashionable in the hallowed halls of the CfA. :)