# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Calculating the time when GHA is equals zero?
From: Steve E. Bryant
Date: 2020 Mar 12, 20:20 -0700

Tony, I attempted to reply to you earlier, but was not successful.

The next paragraph is what I intended you to see after your posting on March 11, 2020, at 5:04PM.

"Dear Tony,

Thank you for following up.  At the time of my posting, I was more concerned about the arrangement of the proportions in the interpolation of the GHA than I was about the accuracy of the times and resulting GHA.  “Actually, the greater truth was that I made a sloppy error.”  As it turns out, that lack of attention to details has resulted in more confusion for which I do apologize.

As I am now trying to apply your method and as I am doing that, I am also putting together a step-by-step outline of your method for purposes of teaching it to others in our navigation study group.  Your original explanation was adequate for me to struggle through figuring out the answer, but for me to understand it well enough that I can teach me mates is what I want to do.  I’m working on that right now.

I have another question which I anticipate our group (of four other guys) will ask me.  But first please allow me to reevaluate my understanding and teaching technique and then pose to you my “new” question.

I’d like to give you here a little preview of where I am going.  I am going to apply your method to resolving the timeUT that the GHAmoon is zero between 1900UT and 2000UT on 4 March 2020.

Then, I would like you to explain to me the usefulness of the sun-moon mer. pass. data located at the righthand bottom of the odd numbered pages in the Nautical Almanac and how it compares to the hand calculation using your method.

Thank you again, Tony, for pointing out the inconsistency.  I would very much like to continue this discussion.

Steve"

I'm still working on my "Zero GHA presentation"  which may also reference the "sun-moon mer. pass. data located at the righthand bottom of the odd numbered pages in the Nautical Almanac..."  if you can help me understand that too.

Thank you,

Steve

PS: Jeremy C has suggested another "related" means for approximating the time at GHAMoon = 0.

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