There will be an interesting astronomical event that is worth observing this September 30.  It is the occultation of bright star cluster Pleiades by the 19th day old Waning Gibbous Moon.  An occultation event happens when the Moon pass in front of a certain celestial object such as a star , deep sky object, asteroid or a planet thus covering the object for a certain period of time.  

An occultation event has two stages, namely Ingress (Enters) and Egress (Exits). In Metro Manila area, The Moon will start with the star cluster already undergoing Ingress so we will be observing the event on its Egress (Exits) stage. During that time, The Moon will just be rising from the ENE horizon.  

THE MOON HAD ALREADY OCCULTED SOME STARS OF THE PLEIADES STAR CLUSTER AT MOONRISE.

THE PLEIADES STAR CLUSTER EXITS THE MOON'S DISK AROUND 9:15 PM.

This event will be visible  from the Philippines.  Below are the estimated timings of the occultation from selected main cities.  All predicted times are in Philippine Standard Time (PST). To get a feeling on what you will expect to see from this event from locations below, please click the CITIES to download an animated AVI movie of this event.   Please note that the animated movie clip is a bit large (average 1.5 MB files), so please be patient specially if you are using a dial-up internet access.

MANILA

BAGUIO

CEBU CITY

DAVAO CITY

To observe this event clearly, the use of a pair of binoculars or a telescope is highly recommended to get view the disappearance (Ingress) and the reappearance (Egress) events.

If you use a telescope to view this event, it is highly recommendable that you time the disappearance and reappearance event.  To get an accurate timing, you need to get the correct time by either synchronizing your watch with an Atomic Clock like  the one found in PAGASA Observatory in UP-Diliman, a GPS, or getting the time signals from a short wave radio channel.  If you have a Global Position System (GPS), you also need to get your exact coordinate of your observing location.

Concerning the value of total occultation observations and timings , it is still useful in refining the limb corrections. Also, occultation can be used to analyze the errors of the Hipparcos proper motion system. In the near future, visual timings of total occultation may become less useful than photoelectric and video timings. Video timings are more accurate than visual timings and it is for that reason that they are highly recommended as it is now easy to acquire sensitive video cameras now.  The standards now for getting accurate lunar occultation timings can more or less be achieve to reach to an accuracy of 0.03s.

ALP members will  observe this event at the roof deck of PAGASA Observatory at UP-Diliman . They will be setting up telescopes and video cameras at around 7:00pm that night to document this event. In case you plan to join us there at the site, please inform us in advance so we can expect you there as well. You can contact me at jkty@astroleaguephils.org or +639178559863 .

You can help us by submitting your timings of the event to jkty@astroleaguephils.org .