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Dear Antoine,

With Paul Hirose’s Lunar 4.4 I get following results:

1) Date: 15.12.2025.

Time UT1: 06:31:47

Position Fix: 46° 37,6’N; 2° 30,7’W (position lines are shown in attached pdf file)

2) Date: 16.12.2025.

Time UT1: 06: 35:06

Position Fix: 46° 40,7’N ; 2° 32,4’W (position lines are shown in attached pdf file)

I cleared these distances also with Paul Hirose’s  Chauvenet’s method calculator (to see how it would perform at these low altitudes):

1) Date: 15.12.2025.

Cleared distance: 32° 21,8’

Time UT1: 06:31:48

Graphycally constructed position fix: 46° 37,3’N; 2° 31,4’W

2) Date: 16.12.2025.

Cleared distance: 23° 9,04’

Time UT1: 06:35:03

Graphycally constructed position fix: 46° 40,3’N; 2° 31,9’W

Can you provide some more details about your Mercury lunar observations:

1) what sextant model did you use? What is manufacures declared accuracy of it? Have you somehow tested it? Do you apply any arc correction (or instrument is declared to be free of errors for practical use)?  

2) How many observations did you made? Did you avarage several individual lunars? If yes, how many observation were in one set?

3) how did you get the altitudes? Were they observed or calculated?

 Modris