NavList:

Hi Andres

Thank you very much for sticking with me on this!  I discovered that I had inverted one of the terms in Young’s equation. 

For the calculated distance

Morris              40d 21m 20.92s. 

Ruiz                 40d 21m 17.96s, a trivial difference between us of 3 seconds.

For the observed distance, I now get

            Corner Cosines            40d 22m 4.67s

            Young’s Equation        40d 22m 4.70s

Now there is no difference between my two results and therefore can readily retract my question about which is better. 

Corner Cosines and Young’s Equations yield the same result.

Your result for the observed distance is

            Ruiz                             40d 21m 55.26s

There is a small discrepancy between our results of about 8 seconds. 

In tracing this down, I believe it to be the altitude correction and most likely the atmospheric conditions

            USNO                          1m 36s  Sirius altitude correction

                                                1m 36s Alphard altitude correction

            Morris                          1m 35.47s Sirius

                                                1m 35.79s Alphard

            Ruiz                             1m 33.43 Sirius

                                                1m 33.74 Alphard

Not only have I corrected this deficiency in the spreadsheet, I have re-cast the interface to accept GHA Aries, SHA Object 1, SHA Object 2, Declination Object 1 & Declination Object 2.  Of course, these items will now come from the Nautical Almanac, not my Skyscout. 

Now on to the calibration of the arc of my sextant! 

Best Regards

Brad

Brad, now i see your two results, and your calculation must have something wrong!

This is using the exact method by Young’s formula:

DSSc = 40.354990        040º     21.3'

DSSo = 40.365349        040º     21.9'

Regards,

Andrés

My solution to Brad problema:

Sextant Error by a Star-Star Distance

Input data:

Star 1: Dec = -8.706685 GHA = 39.824131

Star 2: Dec = -16.733655 GHA = 80.449904

star-star distance - sextant: DSSs = 40.353447

Position of the observer:

B = 40.883333

L = -72.800000

heye = 0.000000

Atmospheric parameters:

P = 1010.000000

T = 10.000000

Calculated altitudes:

Hc1 = 31.860800

Z1 = 140.694573

Hc2 = 31.946864

Z2 = 188.640699

Refraction:

R1 = 0.026040

R2 = 0.025953

apparent altitudes:

Ha1 = 31.886763

Ha2 = 31.972740

star-star distance: Calculated and Observed

DSSc = 40.354990

DSSo = 40.365349

Sextant error = Index Error + Instrumental Error:

IE = -0.010359º = -0.621526'