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Re: Moon Venus Lunar - Interpretation of results
From: Antoine Couëtte
Date: 2020 Feb 7, 05:09 -0800
Ref : Moon-Venus-Lunar-Interpretation-results-Hirose-feb-2020-g46975

Hello to all.

I have decided to check on my own the validity the statement given in the post referenced here-above.

I first ran this exercise through my own Lunar Software.

I then very easily fine-tuned my own results to again compute them onto FER’s Lunar Calculator (http://reednavigation.com/lunars/lunars_v4.html).

Hence any interested reader will very readily reproduce all the results here-under since they all come from this Calculator.

Environmental Data : 29 Jan 2020, UT1 = 22h10m, N42°58.80’ / W070°57.40’ , Height of Eye = 0 ft, 35°F, 29.95”

Aim of this Lunar : Observe the Lunar Distance to Venus and compare the UT1 value derived from this Sextant LD to the actual UT1 given here-above.

First Series of results :

From the here-above feeding data, the Lunar Calculator indicates that the “no error / perfect” Sextant Observed Lunar Distance for UT1 = 22h10m00.0s is 15°35.012’ .

If you feed 22h10m00.0s / 15°35.012’ into the Calculator you get :
Cleared Distance equal to 16°11.3’, with the following message :

“ Error in Lunar 0’ Approximate error in Longitude 0.0’ ”.
Second series of results : Our aim is to determine the UT1 value from a Sextant Observed distance exactly equal to 15°.34’012 i.e. representing a -1.000 arc minute observation error.

The Calculator results indicate that the new UT1 is 22h06m16.0 s.

If you feed 22h06m16.0s / 15°34.012’ into the Calculator (no change in the other environmental data) you get :
A (second) cleared distance equal to 16°09.7’ with the very same following message:

“ Error in Lunar 0’ Approximate error in Longitude 0.0’ ”.
Third series of results : Our aim now becomes determining the UT1 value from a Sextant Observed distance exactly equal to 15°.36’012 i.e. representing a +1.000 arc minute observation error.

The Calculator results indicate that the new UT1 is 22h13m43.2 s.

If you feed 22h13m43.2s / 15°36.012’ into the Calculator (no change in the other environmental data) you now get :
A (third) cleared distance equal to 16°12.9’ with still the very same following message:

“ Error in Lunar 0’ Approximate error in Longitude 0.0’ ”.
DISCUSSION OF RESULTS

In the second series of results the UT1 value corresponding to a -1.000 arc minute error happened 3m44.0s earlier than the “perfect” observation.
Hece a -1.000’ arc minute error here translates into a UT1 determination error equal to -3m44.0s (-3.73 m).
While the Observed Sextant Distance increased by 1.0 arc minute from 22h06m16.9s until 22h10m00.0s , the Cleared Lunar Distance increased by 1.6 arc minute.

In the third series of results the UT1 value corresponding to a +1.000 arc minute error happened 3m43.2s later than the “perfect” observation.
Hence a +1.000’ arc minute error here translates into a UT1 determination error equal to +3m43.2s (+3.73 m).
While the Observed Sextant Distance also increased by 1.0 arc minute from 22h10m00.0S until 22h13m43.2s , the Cleared Lunar Distance kept increasing by the same 1.6 arc minute.

A a conclusion :

the statement given in the in the referenced post - i.e. “ Thus, the multiplier to convert minutes of arc to minutes of time is about 1/.271 = 3.7 for that observation. “ - is entirely true.

Best Regards to all, and thanks for your attention

Antoine M. “Kermit” Couette
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