A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tony Oz
Date: 2017 Sep 7, 01:52 -0700
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.
- 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°;
- 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°;
- 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.