Heliacal Phenomenon
The Heliacal Phenomenon study finds heliacal risings and settings, when a body first reappears from, or is last seen before, the Sun's glare.
Creating a Heliacal Phenomenon Study
To create a Heliacal Phenomenon study:
- Click Mundane Studies → Declination Studies → Heliacal Phenomenon on the menu bar.
The new study opens with the workspace's default settings, ready to configure. You can also create it from the study-group dropdown button on the main toolbar.
Events Captured
A heliacal rising occurs when a star or planet becomes visible again in the eastern sky just before sunrise, after a period of being hidden by the Sun's glare. A heliacal setting occurs when a star or planet is seen for the last time in the western sky just after sunset, before disappearing into the Sun's glare for a period of invisibility. This study finds these first-and-last visibility events for the selected bodies within the study's date range.
An Event Type dropdown limits results to a single heliacal phenomenon type: All Heliacal Phenomenon (both risings and settings), Heliacal Risings, or Heliacal Settings.
Because heliacal visibility depends on the observer and the atmosphere, three dropdowns model the observing conditions used to determine when a body is visible:
- Visibility Model: the visibility criterion applied. Options are Arcus Visionis, Schaefer Visibility Limit, Schoch Minimum 7°, Schoch Minimum 9°, and Pannekoek-Törnquist.
- Sky Conditions: the assumed atmospheric clarity. Options are Poor, Good, and Excellent.
- Visual Acuity: the assumed sharpness of the observer's eyesight. Options are Normal, Good, and Superior.
Events Table Columns
The events table shows the following columns for a Heliacal Phenomenon study. Many are hidden by default; you can show or hide any column by right-clicking a column header (see Event Column Visibility).
| Column | Description |
|---|---|
| Date Time | Date and time of the heliacal event. |
| Event Type | Heliacal phenomenon type (e.g. heliacal rising or setting). |
| Body | Name of the body. |
| Phase | Visibility phase of the phenomenon. |
| Body Longitude | Ecliptic longitude of the body (relabeled "Body Right Asc" in equatorial mode). |
| Body Sign | Zodiac sign of the body. |
| Body Latitude | Ecliptic latitude of the body (relabeled "Body Declination" in equatorial mode). |
| Body Distance | Distance of the body. |
| Body Speed | Longitudinal speed of the body. |
| Solar Elongation | Angular distance of the body from the Sun. |
| Sun Longitude | Ecliptic longitude of the Sun (relabeled "Sun Right Asc" in equatorial mode). |
| Sun Sign | Zodiac sign of the Sun. |
| Ascendant Longitude | Ecliptic longitude of the Ascendant (relabeled "Ascendant Right Asc" in equatorial mode). |
| Ascendant Sign | Zodiac sign of the Ascendant. |
| Descendant Longitude | Ecliptic longitude of the Descendant (relabeled "Descendant Right Asc" in equatorial mode). |
| Descendant Sign | Zodiac sign of the Descendant. |
| Event Interval | Time interval since the previous event. |