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

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Re: The "Death to the Intercept Method" revisited?
From: Tony Oz
Date: 2017 Sep 7, 01:52 -0700

Hello!

I'm trying to find a way to fix myself in case of a serious trouble - like all records are wet and (hopefully - temporarily) unaccessible, so no DR or very inaccurate DR because of a long storm with no proper logging being done during those days. No aliens involved, of-course! :)

The interpolated input data gives much more reasonable output than the obviously wrong input. The body1-body2-body1 sight with the interpolation of body1's HO to the moment of body2 HO put me quite close to the actual position - though I took the three "sights" one hour apart each.

2017-09-07T00:00

• GHAAries = 346°15.7', SHAVega = 80°36.9', DecVega = 38°48.4', GHAVega _T00:00 = 66°52.6', HOVega _T00:00 = 29°44.5', Zn = 297°;

2017-09-07T01:00

• GHAAries = 1°18.2', SHACapella =  280°30.3', DecCapella = 46°0.7', GHACapella _T01:00 = 281°48.5', HOCapella _T01:00 = 58°42.6', Zn = 94°;
• GHAVega _T01:00 = 81°55.1', Zn = 308°;

2017-09-07T02:00

• GHAAries = 16°20.6', SHAVega = 80°36.9', DecVega = 38°48.4', GHAVega _T02:00 = 96°57.5', HOVega _T02:00 = 17°58', Zn = 319°;

I "interpolated" Vega's HO at T01:00 as: ( 29°44.5' + 17°58') / 2 = 23°51.2', that I used for the round of 7.5x formulas.

D12 = 93°19.6'

A = 13°41.5'

B = 15°53,3'

LatA+B = 60°48.8'E

LatA-B = 74°55.6'E

Using the actual Vega's azimuth - I select the  LatA+B = 60°48.8' for the further calculations.

LHAA+B = 112°3.7'

Lon = LHAA+B -  GHAVega _T01:00 = 112°3.7' - 81°55.1' = 30°8.5'N

I think - considering the huge time interval between the "sights" (which I choose to evaluate a "worst-case") - the fix is rather close to the position for which those HO's were pre-calculated: the 60°N30°E.

I will try some more realistic sets of data - with reasonable inter-sight intervals of 10 minutes to see if the fix would be closer to the actual position.

Regards,

Tony

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