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Bright

Bright Lunar Occultations

Explanations

Total or grazing lunar occultations are among the events with the longest tradition in occultation astronomy.

The table of Bright Lunar Total Occultations has a lot of abbreviations, which are explained in the following. Many of the information is given by WINOCCULT, the program, which also has been used to generate the predictions.

First informations about the time of the event:

Item

Meaning

Day

The day of the event. Occult searches for events on the basis of geocentric conjunctions that occur within a 24hr - with that period starting at the UT indicated in the date selection box. Users should ensure that the period starts near the middle of their day.

Time

The predicted UTC, in hours, mins and secs.

This is followed by the kind of event, marked with a P

P ... the Phase (or kind) of the event.

  • D - disappearance

  • d - disappearance, but star is less than 1 mag brighter than the predicted visibility limit.

  • R - reappearance

  • r - reappearance, but star is less than 1 mag brighter than the predicted visibility limit.

  • Gr - grazing occultation at site. At mid-occultation, or closest approach, the star is less than 4" from the limb of the moon (either above or below).

  • gr - grazing occultation at site, but star is less than 1 mag brighter than the predicted visibility limit.

  • M - miss. At closest approach, the star is more than 4" above the limb of the moon

  • m - miss, but star is less than 1 mag brighter than the predicted visibility limit.



STAR is the the star identifier. Three formats are used:

  • nnnn - A ZC star. When reporting occultations, the catalogue is identified with 'R'.

  • nnnnn, or nnnnnn - An SAO star. When reporting occultations, the catalogue is identified with 'R'.

X nnnnnn - an XZ star. When reporting occultations, the catalogue is identified with 'X'.

D is the double star code, SP the Star's spectral type (only basic infos are supplied.

Mag v ist the star's visual magnitude

%ill is the percent illumination of the moon. If followed by a +, values are for a waxing moon; - for a waning moon; and E for illumination during a lunar eclipse.

Many angles and values, which give a lot of informations are given in the following columns as follows:

Item

Meaning

Elon

the elongation of the moon from the sun, in degrees. [Strictly, the quantity is calculated as the elongation of the star from the sun]

Sun Alt

the altitude of the sun. The field is blank if the sun is lower than -12 deg. (Nautical twilight)

Moon Alt

the altitude of the moon

Moon Az

the azimuth of the moon

CA

Cusp Angle - the angle of the event around the limb of the moon, measured from the nearest cusp. -'ve values indicate a bright limb event. The cusps are usually N (north) or S (south), but near full moon can be E (East) or W (west).
If a lunar eclipse is in progress, CA gives is the % distance from the centre of the umbra, and is followed by a 'U'. Values up to 103% are possible. Where an event occurs more than 103% of the umbral radius, the usual Cusp Angle value is displayed.

PA

Position Angle - the angle of the event around the limb of the moon, measured from true north.

VA

Vertex Angle - the angle of the event around the limb of the moon measured anticlockwise from the vertex of the lunar limb - i.e. the point on the limb highest from the horizon

Libration L

the libration of the moon in longitude, as seen from the site at the time of the event

Libration B

the libration of the moon in latitude, as seen from the site at the time of the event

A

coefficient for correcting the prediction for changes in site location. The units are minutes of time per degree (or seconds of time per minute of arc). The correction to the prediction for a change in site, in seconds of time, is found by multiplying A by the change in site longitude (+'ve for changes towards the East) from the prediction site.

B

same as for A, but for changes in latitude (+'ve to the north).

RA

The J2000 RA of the star. For planets and asteroids, the position is for an integral hour closest to the time of geocentric conjunction - although the prediction includes full allowance for the object's motion...

Dec

The J2000 Declination of the star.- as for Right Ascension.