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In further reference to :

R Gleason's initial query 

including ref RG1 :  156889.open.cpn.altitude.calculation.error.pdf.pdf 

and :

Andrés Ruiz' subsequent reply,

including ref AR1 : https://navlist.net/img/156889.sun.recalt.out , and

including ref AR2 : https://navlist.net/img/156889.venus.recalt.out, and

including ref AR3 : https://navlist.net/img/156889.regulus.recalt.out

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Dear Gentlemen,

I have performed a careful review of both your contributions.

I have worked all these examples through the Nautical Almanac and through own software, where both methods used here yield similar results to within +/- 0.1'

I would then offer the following results for your review and investigation :

(1) - Sun LL sight  (References RG1 and AR1 listed hereabove)

Computation with the Nautical Almanac

Nov 13th, 2024 , UT=20h17m45s, 15°C, 1013mb, HoE=2.4 m N45°00.0'/W076°00.0'

Once corrected for Index Error, SUNL Hs = 11°21.8' 

Dip Correction = -2.8'      

For 11°19.0' , Refraction + Parallax + SD correction (OCT. - MAR.)  = +11.6'

Xtra T and P correction (H column) = +0.1'

Total corrections : -2.8' + 11.6'  + 0.1' = +8.9'  .   Hence  Ho = 11°30.7'

Nautical Almanac data for observation UT give : GHA = 128°20.5' and Dec = S 18°15.2' .

Altogether with LHA = 052°20.5' and Lat N45°00.0' , solving the triangle yields :

Hc = 10°52.9'  Zc = 229.96°

Hence Intercept "Ho - Hc" = +37.8' , i.e. 37.8 NM towards the Sun in Azimuth 230.0°

Significant difference with Andrés' results (Intercept at +44.2', Az 230° ), and

Most significant difference with Open CPN (Intercept at -7.4 NM / 228.94°)

(2) - Venus sight (References RG1 and AR2 listed hereabove)

Computation with the Nautical Almanac

Dec 28th, 2024 , UT=22h45m10s, 13°C, 1013mb, HoE=4.9 m N17°56.6'/W076°45.5'

Once corrected for Index Error, VENUS Hs = 42°18.9' 

Dip Correction : -3.9'     

For 42°15.0', Refraction = -1.1'

Xtra Parallax Correction = + 0.2'

Xtra T and P correction (G column) : +0.0'

Total corrections : -3.9' - 1.1' + 0.2' = -4.8' .   Hence  Ho = 42°14.1'

Nautical Almanac data for observation UT give : GHA = 111°55.0' and Dec = S 14°53.9' .

Altogether with LHA = 35°09.5' and LAT = N17°56.6' , solving the triangle yields :

Hc = 42°15.4'  Zc = 228.751°

Hence Intercept "Ho - Hc" = -1.3' , i.e. 1.3 NM away from Venus in Azimuth 228.8°

Small difference with Andrés' results (Intercept at -0.4'  / Az 228.8°) . I perform the phase correction for Venus, which is significant here. The NAL performs it too. Maybe an explanation for this small difference, Andrés ?

I cannot conclude from comparison with Open CPN since the RG1 published results for Venus seem inconsistent (typos ?)

(3) - Regulus sight (References RG1 and AR3 listed hereabove)

Computation with the Nautical Almanac

Jul 04th, 2025 , UT=20h39m23s, 9°C, 1013mb, HoE=4.9 m N31°54.372'/W014°55.35'

Once corrected for Index Error, REGULUS Hs = 26°58.3'

(hint ! RG1 first height at 28° seems a typo)

Dip Correction : -3.9'     

For 26°54.4', Refraction = -1.9'

Xtra T and P correction (G column) : +0.0'

Total corrections : -3.9' - 1.9' = -5.8' .   Hence  Ho = 26°52.5'

Nautical Almanac data for observation UT give : GHA = 080°31.4' and Dec = N 11°50.6' .

Altogether with LHA = 65°36.1' and LAT = N31°54.372' , solving the triangle yields :

Hc = 26°51.1'  Zc = 267.466°

Hence Intercept "Ho - Hc" = +1.4' , i.e. 1.4 NM towards Regulus in Azimuth 267.5°

Small difference with Andrés' results (Intercept at +2.4' / Az 267.5°)

Significant difference with Open CPN (Intercept at +7.7 NM / Az 267.6°)

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Hope it helps, and hopefully with no typos on my behalf,

Antoine M. "Kermit" Couette

For any subsequent contact : antoine.m.couette[at]club-internet.fr