v1.3.0

[attipaci]

Feature release with many new convenience functions, such as for handling times and angles as strings; calculating rise, set, transit times; and other common astrometric calculations. In addition, the release brings various changes to improve performance.

Fixed

• transform_cat() corrections to parallax when changing epochs. #116: transform_cat() to update parallax to the recalculated value when precessing or changing epochs. (This was a NOVAS C 3.1 bug.)

• transform_cat() insufficient checking for out_id length #128: transform_cat() had insufficient string length checking of out_id parameter. Prior to the fix it checked for the longer object name size instead of the catalog name size. However, even if longer than expected input names were left uncaught, only the appropriatre number of characters were used -- hence it broke nothing, only failed to remind the caller (with an error) when the supplied name was too long.

• Reorganize source code into smaller modules #139: Legacy linking of external solarsystem() / solarsystem_hp() provider modules was blocked by solsys-ephem.c inadvertently definining these functions when BUILTIN_SOLSYS_EPHEM was set to 1 (default) during the build, even though it was not supposed to.

• Use of TT vs TDB dependent on accuracy #156: obs_posvel() called geo_posvel() with TDB instead of TT. It less than a 2 ms difference, so not typically signifficant, unless <10-m level poitioning is required for Earth-orbiting satellites.

Added

• New functions for v1.3 #113: New novas_frame_lst() convenience function to readily return the Local (apparent) Sidereal Time for a given Earth-based observing frame.

• New functions for v1.3 #113: New novas_hms_hours() and novas_dms_degrees() convenience functions to make it easier to parse HMS or DMS based time or angle values, returning the result in units of hours or degrees, appropriately for use in SuperNOVAS.

• New functions for v1.3 #113: New novas_rises_above() and novas_sets_below() functions to return the date/time a source rises above or sets below a specific elevation on a given date, and novas_transit_time() to calculate the time a source transits over the local meridian. (For Earth-based observers only). rise/transit/set times calculation #140, rise/set times discrepancy 2 #146: Further fixes to these calculations after the v1.3.0-rc5 release candidate [thanks to @valeriy-sokoloff].

• New functions for v1.3 #113: New novas_helio_dist() function to calculate the heliocentric distance of a Solar-system body on a given date. The novas_solar_power() function can be used to estimate the incident Solar power on a Solar-system body, while novas_solar_illum() can be used to calculate the fraction of a spherical body that is illuminated by the Sun seen from the observer location.

• New functions for v1.3 #113: New novas_hpa() and novas_epa() functions to calculate the parallactic angle (a.k.a. vertical position angle) for a given location on sky, using the local horizontal coordinates, or else the equatorial position, respectively. The parallactic angle (PA) can be useful to convert local Cartesian offsets (e.g. from a flat image or detector array) between the local horizontal and equatorial orientations, e.g. via the newly added novas_h2e_offset() or novas_e2h_offset() functions. The conversion between offsets and absolute coordinates usually requires a WCS projections, such as described in Calabretta & Greisen 2002.

• New functions for v1.3 #113: New novas_sep(), novas_equ_sep(), and novas_object_sep() functions can be used to calculate the precise apparent distance between to spherical or equatorial locations, or between two sources, respectively. novas_sun_angle() and novas_moon_angle() can be used to calculate the apparent angular distance of sources from the Sun and Moon, respectively.

• New functions for v1.3 #113: New novas_observable and novas_track data structures to provide second order Taylor series expansion of the apparent horizontal or equatorial positions, distances, and redshifts for sources. They can be calculated with the newly added novas_hor_track() or novas_equ_track() functions. Such tracking values, including rates and accelerations, can be directly useful for controlling telescope drives in horizontal or equatorial mounts to track sources (hence the name). You can also obtain instantaneous projected (extrapolated) positions from the tracking parameters via novas_track_pos() at low computational cost.

• New functions for v1.3 #113: New novas_los_to_xyz() and novas_xyz_to_los() functions to convert between line-of-sight (δφ, δθ, δr) vectors and rectangular equatorial (δx, δy, δz) vectors.

• New functions for v1.3 #113: New novas_xyz_to_uvw() and novas_uvw_to_xzy() functions to convert between ITRS Earth locations (absolute or differential) to equatorial projections along a line of sight in the direction of a source. Such projections are oft used in interferometry.

• LSR vs SSB-based radial velocities for cat_entry #114: New novas_lsr_to_ssb_vel() can be used to convert velocity vectors referenced to the LSR to Solar-System Barycentric velocities. And, novas_ssb_to_lsr_vel() to provide the inverse conversion.

• Add benchmarks #117: Added benchmarks under the benchmark/ folder, for SuperNOVAS as well as equivalent benchmarks for astropy. To run the SuperNOVAS benchmarks, simply make benchmark in the distribution directory.

• Additional date/time functions #118: New novas_parse_date() / novas_parse_date_format() to parse date/time specifications, novas_parse_dms() and novas_parse_hms() to return hours and degrees for HMS and DMS specifications, as well as the updated parse position.

• Additional date/time functions #118: New novas_timescale_for_string() to match timescale constants to string representations, such as "UTC", or "TAI", and novas_print_timescale() to convert to string representation.

• Additional date/time functions #118: New novas_iso_timestamp() to print UTC timestamps in ISO date format with millisecond precision, and novas_timestamp() to print timestamps in specific timescales. Incorrect ISO timestamp formatting in some cases #151: Various fixes to new timestamping after rc7. [thanks to @valeriy-sokoloff]

• Disambiguate Gregorian and Roman/Julian calendars. #122: New novas_jd_to_date(), and novas_jd_from_date() which convert between JD day and calendar dates using the specific type of calendar: Gregorian, Roman/Julian, or the conventional calendar of date.

• Further date parsing functions #131: New novas_date() and novas_date_scale() for the simplest conversion of string times to Julian days, and in case of the latter also to a corresponding timescale (without returning a parse position).

• Add novas_parse_timescale() #133: New novas_parse_timescale() to parse a timescale from a string specification, and return the updated parse position after also.

• Add novas_parse_hours() / novas_parse_degrees() #134: New novas_parse_hours() and novas_parse_degrees() to convert strings in decimal or HMS/DMS formats to floating point values for SuperNOVAS, and return the parse position after the time/angle specification.

• Add novas_str_degrees() and novas_str_hours() #135: New novas_str_hours() and novas_str_degrees() for the simplest conversion of strings in decimal or HMS/DMS formats to floating point values for SuperNOVAS (without retruning a parse position).

• Improved support for coordinate epochs #137: New novas_epoch() to convert string coordinate system specifications to the Julian date of the corresponding epoch, and new make_cat_object_sys() and make_redshifted_object_sys() to make it simpler to define ICRS catalog sources in the coordinate system of choice.

• Add FORTIFY config setting #143: Added FORTIFY build configuration setting to enable gcc source code fortification checking by setting the _FORTIFY_SOURCE macro to the specified value. It is now used with a value of 3 in the build and test CIs.

• Use standard C initializers instead of non-standard {} #150: Further initializers for SuperNOVAS structures that can be used to empty initialize data.

• Add novas_print_hms() / novas_print_dms() functions #154: Added novas_print_hms() and novas_print_dms() functions to convert time / angles to their HMS/DMS string representations, with the chosen separators, and the desired decimal places on the seconds.

• Add novas_parse_iso_date() #155: Added novas_parse_iso_date() for pasing ISO 8601 timestamps, including those expressed in the proleptic Gregorian calendar prior to the Gregorian calendar reform of 1582, for which the ISO 8601 timestamp differs from the astronomical calendar date assumed by novas_parse_timestamp().

• Added example-time.c and example-rise-set.c under examples/, for demonstrating date/time handling functions and rise, set, and transit time calculations.

Changed

• Use restrict keyword to enforce unaliased pointer args #130 Use C99 restrict keyword to prevent pointer argument aliasing. Modern compilers will warn if restricted pointer arguments are aliased. At the least, it is a hint to users that pointer arguments marked as such should be distinct from (not overlapping with) the other pointer arguments.

• Reorganize source code into smaller modules #139 Reorganized code into more manageably sized modules. It also makes the API documentation by source file more logically organized.

• Reorganize source code into smaller modules #139: Legacy source code moved to legacy/ folder.

• Use standard C initializers instead of non-standard {} #150: Use standard C initializers instead of the non-standard empty backets {}. While the empty brackets have been OK with gcc for quite a while, they only became standard in C23. Other compilers might barf at their use.

• cpp compatible naming #152: For C++ compatibility do not use class as a parameter name. [thanks to @valeriy-sokoloff]

• Use of TT vs TDB dependent on accuracy #156: Omit TDB-TT time difference, a maximum of 2 ms, in Earth tilt calculations, where it really does not make any difference. As a result some calculations are now faster than before.

• Use of TT vs TDB dependent on accuracy #156: Higher precision time match requirement for re-using cached ephemeris calculations.

• Use of TT vs TDB dependent on accuracy #156: tt2tdb() now caches last calculation also.

• Use of TT vs TDB dependent on accuracy #156: Eliminate redundant caching of calculations. (Also in Tweak which calculations are cached #158).

• Use of TT vs TDB dependent on accuracy #156: Tighten precession() time checking.

• Use the IAU 2000B nutation series for reduced (mas-level) accuracy #157: Switch to iau2000b() as the low-precision nutation series. It is good to about 1 arcsec, which is the promised precision in reduced accuracy, but a lot faster than the nu2000k() series, which in turn is barely faster than the full iau2000a() nutation series.

• Use the IAU 2000B nutation series for reduced (mas-level) accuracy #157: fund_args() to always calculate full polynomial expansion. There is little performance to gain from the truncation we used in the vicinity of J2000. No real change in the results.

• Add caching to ee_ct() #159: Add caching to ee_ct(). Just in case someone wants to call it repeatedly with the same parameters, it will be much much faster now.

• In reduced accuracy mode apply gravitational deflection for the Sun only. In prior versions, deflection corrections were applied for Earth too. However, these are below the mas-level accuracy promised in reduced accuracy mode, and without it, the calculations for place() and novas_sky_pos() are significantly faster.

• Modified julian_date() to add range checking for month and day arguments, and return NAN (with errno set to EINVAL) if the input values are invalid.

• julian_date() and cal_date() now use astronomical calendar dates instead of the fixed Gregorian dates of before. Astronomical dates are Julian/Roman calendar dates prior to the Gregorian calendar reform of 1582.

• precession() to cache matrices to/from J2000 separately.

• Use SIZE_OF_OBJ_NAME and SIZE_OF_CAT_NAME instead of sizeof(obj->starname) and sizeof(obj->catalog) internally for improved portability.

• Various arithmetic simplifications to give a minor performance boost.

• Updated README.md for v1.3 and benchmarks, including comparisons to astropy.

• Default THREAD_LOCAL definition extended to C23 thread_local keyword also.

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This discussion was created from the release v1.3.0.