Version 4.2 - 21st August 2020
The following information is intended for existing users who are already familiar with AstroGrav and want to quickly find out about the main changes.
Version 4.2 of AstroGrav is an upgrade containing a large number of improvements and bug fixes. It is a free upgrade for customers who have already purchased a license for AstroGrav 4, so that all you need to do is to download Version 4.2 and use it in place of your old version. If you have any problems with this new version, please don't hesitate to contact us so that we can help you out.
Version 4.2 of AstroGrav has the following new and improved features.
Editing Objects
Version 4.2 of AstroGrav includes the following improvements to editing objects with the Edit / Edit Object..., Edit / Add Object..., and Edit / Remove Objects commands.
- The object editor has been completely redesigned, and includes the following improvements over its predecessor.
- It's smaller, easier to understand, and easier to use.
- The units of fields have been changed from labels to popup menus, so that the units can now be adjusted while editing the fields.
- Pasting text with leading or trailing spaces into number fields now works as expected, instead of being classified as an error.
- The absolute magnitude of an asteroid or comet can be specified in a solar system simulation.
- The pericenter distance can be specified as an alternative to the semi-major axis.
- The descending node can be specified as an alternative to the ascending node.
- The time at pericenter can be specified as an alternative to the true longitude, mean longitude, true anomaly, or mean anomaly.
- When editing an object that is orbiting the Earth in a solar system simulation, the orbital elements and rectangular elements can be specified relative to J2000 or JNow.
- When adding an object to a solar system simulation with the Edit / Add Object... command, the opportunity is provided to add the object at a specified epoch.
- In the Edit / Add Object... command, the orbital elements of the default new object have been simplified when the Sun is the parent.
- The keyboard shortcut of the Edit / Remove Objects command has been changed from Alt+Control+O (Alt+Command+O on a Mac) to Alt+Delete to reflect the fact that removing objects is an alternative to deleting them.
Importing Objects
Version 4.2 of AstroGrav includes the following improvements to importing objects with the Edit / Import Objects... command.
- The Lowell Asteroids option has been added, which gives access to about 1,000,000 asteroids in the Lowell Asteroid Orbital Elements Database.
- The JPL Unnumbered Asteroids option is now working again after a recent change to the format of the downloaded data had made this option unusable.
- There are now asteroid categories for the Trojans of all eight planets, although three of these (Mercury, Venus, and Saturn) currently contain no members.
- Neptune Trojans are no longer excluded from the Kuiper Belt Objects in the asteroid categories.
Simulation Evolution
Version 4.2 of AstroGrav includes the following improvements to simulation evolution.
- The accuracy of simulation evolution has been improved, particularly when using the Evolve / Evolve To... command.
- The oblateness of the planets is now taken into account when evolving solar system simulations, which dramatically improves the accuracy of the simulation of the major planets' inner moons.
- A bug has been fixed that could cause running to an event with the Evolve / Evolve To... command to take an extremely long time.
- A bug has been fixed that could cause minor inaccuracies and inconsistencies in the evolution of simulations.
- The accuracy of evolution with general relativity has been much improved.
- The accuracy of evolution has been greatly improved when repulsive radiation pressure exceeds attractive gravity.
- Several minor performance improvements have been made to the evolution algorithm.
Ephemeris Generation
Version 4.2 of AstroGrav includes the following updates to generating ephemerides with the Tools / Generate Ephemeris... command.
- A Use JNow checkbox has been added that allows you to choose between an ephemeris in which the J2000 reference frame is used for the equatorial coordinates, or an ephemeris in which the JNow reference frame is used for the equatorial coordinates.
- The viewpoint of the frontmost window is now used as the default view location for an ephemeris if possible.
- The default columns of an ephemeris table have been improved.
Other Improvements
Version 4.2 of AstroGrav also has many other minor improvements and bug fixes, including the following.
- A new Barycentric Dynamical Time (TDB) unit has been added to the date units of solar system simulations, and the date unit of the solar system sample simulations has been changed from Coordinated Universal Time (UTC) to Barycentric Dynamical Time (TDB).
- Date units now correctly handle leapseconds.
- The Light-Time Correction labels have been changed to Planetary Aberration labels to reflect the fact that stellar aberration and diurnal aberration are taken into account in addition to light-time correction.
- The background stars of solar system simulations are now adjusted for stellar aberration and diurnal aberration. This was missing in earlier versions of AstroGrav, resulting in errors in the positions of background stars of up to 21 arcseconds.
- Repulsive orbits (which occur when repulsive radiation pressure exceeds attractive gravity) are now indicated with a negative eccentricity instead of with a negative semi-major axis.
- A bug has been fixed that could cause messages to be displayed behind the window they referred to, where they couldn't easily be read.
- A bug has been fixed that could cause a tool palette to get obscured by the window that it's referring to.
- A bug has been fixed that made it impossible to hide AstroGrav on a Mac when the frontmost window was a view window showing its tool palette.