Celestial Navigation · Sight Reduction — Interpolation
After extracting a tabulated Hc from Pub. 229 for whole-degree declination, why is the 'd' correction (with declination increment) applied?
- ATo account for the equation of time
- BTo convert Z to Zn
- CTo correct for dip and refraction
- DTo interpolate Hc for the actual minutes of declination between the whole-degree table entries✓ Correct
Explanation
Pub. 229 tabulates Hc for whole-degree declination. The tabulated 'd' value, combined with the declination's minutes (the increment), gives the correction to Hc so the computed altitude matches the body's actual declination — often via the table's interpolation columns.
Authority: Pub. No. 229, interpolation; Bowditch (Pub. No. 9)
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