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Re: Calculating the time when GHA is equals zero?
From: Paul Hirose
Date: 2020 Mar 14, 13:21 -0700

```On 2020-03-13 9:46, Steve E. Bryant wrote:
> 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.

My solution, beginning with 2020 March 4 Almanac data:

19:00 UT 349°15.4′ GHA
20:00 UT 003°41.4′ GHA

v = 6.9

The required GHA increment is 360°00.0′ - 349°15.4′ = 10°44.6′. The
Almanac increments and corrections table will give the corresponding
time increment. Opposite the best match (10°44.5′) find 45m01s.

But we're neglected the v correction (5.2′), which will cause GHA to
overshoot by the same amount. Therefore, subtract v correction from the
required increment: 10°44.6′ - 5.2′ = 10°39.4′.

Find that in the table. The change is only a few minutes, so the desired
entry is not far away. The best match is 10°39.5′, which corresponds to
time increment 44m40s. As a check, note that 10°39.5′ plus v correction
5.1′ = 10°44.6′, the original GHA increment we needed.

This successive approximation method is necessary because the increments
and corrections table is designed to convert a time increment and v
correction to an angle increment. We're using it in the reverse sense.

So, Moon GHA should be zero at 2020 March 4 19:44:40s UT. An electronic
check says I missed by 0.1′.
```
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