Occult (software)
| Original author(s) | David Herald |
|---|---|
| Stable release | v4.5.5.4
|
| Written in | C# using the dotNetV4.5 framework |
| Engine | |
| Operating system | Windows, |
| Platform | x86-64 |
| Size | 6.2 MB: Windows includes Manual |
| Available in | English |
| License | freeware |
| Website | http://www.lunar-occultations.com/iota/occult4.htm |
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Occult is a freeware program used for the prediction and analysis of; occultations, eclipses, and transits of astronomical objects. It can generate ephemerides for Solar System objects, including all planets and their moons (to magnitude 20) for any site coordinates.
It is used to archive historic occultation observations.
Occult is also known as WinOccult, Occultv4, Occult4.[1]
Asteroid occultation[edit]
Occult is fundamental in the world wide effort to observe asteroid occultation events with the goal to measure the size and shape of asteroids, and to produce precise astrometry on asteroids, tied to the occulted star at the equinox of date. The effort is coordinated by the International Occultation Timing Association (IOTA).
Predictions[edit]
Occult can generate predictions of asteroid occultations using a wide selection of star catalogues and asteroid orbit source data.
An Asteroid Occultation Prediction Map shows the path of the asteroid's shadow as it passes over the earth. In the header are; the event circumstances; star catalogue identifier, UTC duration of the asteroids shadow is on the ground, details of the star, details of the asteroid, details of the event. The shadow path has time check marks and indications of path certainty (combination of star positional uncertainty and asteroid orbit uncertainty), as well as indication of day-time, night-time and twilight. Also shown is the Occult version number and the source of the asteroid orbit data.
Occult is the engine for Steve's Asteroid Occultation Updates.
Occult is used to create Occult Watcher feed data, to propagate occultation predictions to the world wide community and to aid the coordination of observer efforts.
Analysis[edit]
Occultation observations reports are collected, collated and analysed (reduced) by a system maintained by IOTA, and Occult is the primary analysis tool. The basis of the reductions are the coordinates of the star, the asteroid and the observer, or multiple observers, computed with reference to the fundamental plane on the equinox of date.
The reduction plot shows;-
- star paths computed for 2 minutes before each disappearance timing, and 2 minutes after each reappearance timing.
- disappearance timings are shown in red, while reappearance timings are shown in green.
- Visual observations are shown with '+', video or photoelectric observations are shown with circles. Miss events are marked with an 'x'
- The prediction chord is shown as a dotted pink line and with an asterisk.
- The header lists; asteroid number and name, date of event, size of best fit ellipse, and Geocentric coordinates of the asteroid at equinox of date.
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The shape of the asteroid becomes apparent with multi-chord observations, as shown in this (uncredited) reduction plot shown in a popular magazine depicting the discovery of an asteroid moon.[2]
An ellipse can be fitted to determine the size of the asteroid. The ellipse is represented by the equation: x2/a2 +y2/b2=1 Scale on the plane is expressed in kilometres.
For many asteroids, the DAMIT or ISAM services offer 3D models which are unscaled. If a multi-chord occultation is observed, Occult has the ability to import the models, correctly oriented for the observation time and allow for small adjustment of the rotational orientation, caused by uncertainty in the period of rotation, to get the best fit of the asteroid model to the observed chords, thereby setting a scale to the 3D models. With DAMIT models, the scale is expressed in two values: Volume Mean diameter and Surface Mean diameter.
Reporting and Archiving[edit]
On an annual basis, IOTA deposits all asteroid profiles that were reduced by Occult, into the NASA Planetay Data System - Asteroid and Dust Archive - Asteroid Occultations, as described in this paper.[3]
They are made available for research by free download.[4]
High Precision astrometric observations are processed by Occult, and are reported to the Minor Planet Center and are published under Observatory Code 244 - Geocentric Occultation Observation, in the Minor Planet Circulars.
Lunar occultation[edit]
Occult has numerous tools to aid in the observation, reporting and archiving of lunar occultation observations.
Predictions and Reporting[edit]
Occult can generate lunar occultation predictions for; selected sites, selected objects, or for multiple sites and multiple objects. It includes tools to aid the planning of grazing lunar occultation expeditions. It is the basis of a system of reporting and archiving of lunar occultation observations, including grazing occultations via a group of IOTA regional and global collectors.
Archiving[edit]
Occult maintains files of historical lunar occultation observations, 1623 to recent times.
In 2009-2010 a review of all known lunar occultation observations was made by Dave Herald and Dave Gault using Occult as analysis engine. Prior to this review, many observation records were spread over many sources, including private computers. Also many circumstances for lunar graze observations, like observer and site names were lost. The old records contained many errors, like typographical, site coordinate, date, or star identifier errors, typical of data entry from hand written reports. The review collected all known lunar occultation observations into one file, errors were identified and corrected where possible, and lost data was restored from source records if available.[5]
The complete Archive of Lunar Occultation Observations 1623 to recent times, is available for free download at VizieR - lunar occultation archives.[6]
The Lunar Occultation Archives were used in the recent study - Measurement of the Earth's rotation: 720 BC to AD 2015[7][8]
Eclipses and transits[edit]
Occult can provide Solar and Lunar eclipse and Solar transit predictions are the range of years, -13000 to +17000 years, corresponding to the coverage of the DE431 ephemeris.
Baily's Bead phenomena observed during Solar Eclipse can be analysed by the generation of animations, that can be compared to timings on a video recording observation. From these observations and analysis using Occult, determination of Solar diameter can be made.[9][10][11]
Ephemerides[edit]
Occult can generate ephemerides of solar system objects brighter than mag 20 for any site coordinates, including:-
- Positions of Planets, Asteroids, comets, satellites of planets and asteroids.
- Appearance or planets and moons.
- Diary of astronomical events phenomena.
- Mutual conjunctions of the planets.
- Rise and set times for the major planets.
- Moonrise and Moonset times.
- Altitude of an object.
- Satellite eclipses, occultations and transits of Planets.[12]
- Mutual eclipses and occultations of the satellites of Jupiter, Saturn and Uranus.
Source of Reference Data[edit]
- ↑ Roth, Günter D. (2009-06-18). Handbook of Practical Astronomy. Springer Science & Business Media. ISBN 9783540763796. Search this book on
- ↑ "Amateur Observers Find an Asteroid's Moon - Sky & Telescope". Sky & Telescope. 2017-07-14. Retrieved 2018-06-16.
- ↑ David, Waring Dunham,; Russell, Herald, David; Steve, Preston,; Bradley, Timerson,; Paul, Maley,; Eric, Frappa,; Tsutomu, Hayamizu,; John, Talbot,; Atila, Poro, (2015-08-01). "Sizes, Shapes, and Satellites of Asteroids from Occultations". IAU General Assembly. 22. Bibcode:2015IAUGA..2258262W.
- ↑ Dunham, D.W. "NASA PDS Small Bodies Node - Asteroid Data Sets - Asteroid Occultations". sbn.psi.edu. Retrieved 2018-05-04.
- ↑ Herald, David; Gault, David (2010-10-01). "VizieR Online Data Catalog: Lunar Occultation Archive (Herald+ 2010)". VizieR Online Data Catalog. 6132. Bibcode:2010yCat.6132....0H.
- ↑ Herald, David. "VizieR - Lunar Occultation Archive (Herald+ 2012)". vizier.u-strasbg.fr. Retrieved 2018-05-11.
- ↑ Stephenson, F. R.; Morrison, L. V.; Hohenkerk, C. Y. (2016-12-01). "Measurement of the Earth's rotation: 720 BC to AD 2015". Proc. R. Soc. A. 472 (2196): 20160404. doi:10.1098/rspa.2016.0404. ISSN 1364-5021. PMID 28119545.
- ↑ Morrison, L. V.; Stephenson, F. R.; Hohenkerk, C. (2017), "The Science of Time 2016", Astrophysics and Space Science Proceedings, Astrophysics and Space Science Proceedings, Springer International Publishing, 50, pp. 165–165, doi:10.1007/978-3-319-59909-0_22, ISBN 9783319599083, retrieved 2018-07-15
|chapter=ignored (help) - ↑ Sigismondi, Costantino (2009-10-27). "Guidelines for measuring solar radius with Baily beads analysis". Science in China Series G: Physics, Mechanics and Astronomy. 52 (11): 1773–1777. doi:10.1007/s11433-009-0233-8. ISSN 1672-1799.
- ↑ Sigismondi, C.; Dunham, D. W.; Guhl, K.; Andersson, S.; Bode, H.; Canales, O.; Colona, P.; Farago, O.; Fernández-Ocaña, M. (2009-07-24). "Baily's Beads Atlas in 2005 – 2008 Eclipses". Solar Physics. 258 (2): 191–202. doi:10.1007/s11207-009-9400-3. ISSN 0038-0938.
- ↑ Andrea, Raponi,; Costantino, Sigismondi, (2011-12-02). "Solar Limb Darkening Function from Baily's Beads Observations". arXiv:1112.0403 [astro-ph.SR].
- ↑ Tsumura, Kohji (2013-11-10). "Follow-up Observations of Galilean Satellite Eclipses Aimed to Detection of the Cosmic Infrared Background" (PDF).
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