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Hello Tony,

Taking in account your revised value of 28°42.3 ' (vs. 28°38.6') for ⑦ Sun observation #4 at 12:54:05, i get the following results :

⑦ Sun averaged values become : UT = 12:52:18.75 (unchanged value) and Ha = 28°52.58' (vs. 28°51.65'),

Mean Values Intercept becomes -1.0' (vs. -1.9') with Azimuth unchanged at 230.0°

Updated Final Fix ② becomes N60°10.6' - E029°47.7' (vs. N60°10.6' - E029°48.8', i.e. 0.5 nm West of previous Final Fix ② )

Compared to GPS Position N60°10.3' - E029°48.5' Updated Final Fix ②  is now 0.5 NM away (vs. 0.35 NM away), which still remains excellent.

Antoine

Remarks :

1 - Since observation # 4 changed by 3.7', if it processed just in its own, its new intercept should change by 3.7' also. The differential refraction is totally insignificant here.

2 - Observation # 4 having changed by 3.7' implies that the averaged values (4 samples) should change by 0.9' and that the updated intercept should also change by 0.9', which is verified in both cases.

3 - I cannot reconcile your 2.7' intercept difference [(+0.8' - (-1.9') ] with either value listed above, although you indicate averaging samples.