Spherical offset positions

[attipaci]

Added functions / methods to calculate offset spherical positions from the reference position along a great circle, which crosses the reference at a specified direction. It is based on the astropy offset_by() implementation. (thanks to @aleberti).

C99 API

Added

• novas_offset_by() and novas_equ_offset_by() to calculate offset spherical / equatorial positions at some distance along a great circle that intersects the original position at the specified angle.

C++11 API

Added

• Equatorial::offset(), Ecliptic::offset(), Galactic::offset(), and Horizontal::offset().

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[coveralls]

Coverage Report for CI Build 25454050092

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Coverage: 99.119%

Details

• Patch coverage: 81 of 81 lines across 5 files are fully covered (100%).

Uncovered Changes

No uncovered changes found.

Coverage Regressions

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Coverage Stats

Relevant Lines:	9080
Covered Lines:	9000
Line Coverage:	99.12%
Coverage Strength:	41233.42 hits per line

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💛 - Coveralls

[attipaci]

@aleberti,

I think this PR is ready. It passes all the sanity checks I came up with. Please take a look too, in case there is more to be done. Otherwise I plan to merge it in a couple of days...