Friday, November 14, 2014

6th Southeast Asian Astronomy Network Conference Invitation

The  SEAAN 2014 will be held at Rizal Technological University, Mandaluyong City, Philippines on 16-17 December 2014. The event will be sponsored by the Department of Science and Technology (DOST)-Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) and the Rizal Technological University (RTU).

In addition to the National Focal Points and 20 participants from the SEAAN member countries. Interested local astronomy organizations should register online and are advised to observe the important dates
(November 19, 2014 deadline of subsmission of registration form).

The  Conference aims to promote cooperation in the field of education, research and popularization of astronomy among Southeast Asian member countries. It will be divided into business and scientific sessions. The  business session will be the 6th SEAAN Meeting and will be held on 16 December 2014. The scientific session will be held on 17 December and will include plenary and invited talks and oral and poster presentations.

Please download and complete the registration form below and submit to
Ms. Ruby-Ann dela Cruz, Head, Department of Earth and Space Sciences, RTU  through her email address: OR


-There is no registration fee.
-Travel expenses and accommodations will not be shouldered by the organizers.
-You will receive an email of confirmation if you have successfully registered as participants.

For more information please visit:

Download form here. 

Friday, September 12, 2014

Why do the Sun and Moon appear to be the Same Size in the Sky?

Why do the Sun and Moon appear to be the Same Size in the Sky?

The Sun and Moon’s physical diameters are obviously different from each other, so what causes them to appear in the same size? It’s their ANGULAR DIAMETER that’s coincidentally almost the same. The angular diameter or apparent size of an object is its apparent diameter as seen by an observer in a specific point. Intuitively, the angular diameter of an object changes as the observer’s distance changes.

How do we derive the equation for the angular diameter?

Figure 1: Angular Diameter

With θd as the angular diameter, it’s easy to see that the tangent of the angular radius (half of the angular diameter) is equal to the actual radius (D/2) over the distance.

Solving for θd:
Therefore the equation for the angular diameter is:
Now we can use this to calculate for the angular diameters of the Sun and Moon.
Note that the distances used were the average distance, since orbits are elliptical. The Sun’s corona is excluded in the diameter.

For the Sun:                                                  For the Moon:

D = 1 392 684 km                                        D = 3474 km
l = 1.496 x 108 km                                        l = 384 405 km
θd = 0° 32’ 0.18’’                                          θd = 0° 31’ 4.07”

As we can see, their angular diameters are nearly the same with the moon being a little bit smaller, that’s why when perfectly in line during a solar eclipse in a given position, an annular or total eclipse could be seen; annular when the moon is a little bit farther and a total eclipse when the moon’s distance is enough to make its angular diameter equal or a little greater than the Sun’s.

By: Lanz Anthonee Lagman
       BS-Astronomy Student

International Observe the Moon Night

September 6, 2014
In celebrating the event “International Observe the Moon Night”, the Department of Earth and Space Sciences and BS-Astronomy Technology students conducted a lunar observation at RTU - Boni Campus quadrangle. The observation team was headed by Ms. Pauline Pearl Divinagracia and Mr.
Miguel Artificio, who were assisted by the 5th year OJT students, Jhoana Marie Tabios and Andrew Bayot. Other astronomy students were also there to help in conducting the public observation.

We started the observation by 6:00 PM PST. The sky condition was perfect by the time we started, with 0% cloud cover. We used 3 telescopes for this observation. The 10-inch newtonian reflector telescope, a 6-inch newtonian reflector telescope on a german equatorial mount and a 3-inch refracting telescope.
The lunar observation was attended by BS Astronomy students, and College of Arts and Science students and other students from various courses. A Natural Science instructor Ms. Rubelyn Narra invited her class to also participate the observation. While observing the moon, the observation team also showed the planets Mars and Saturn to the students which amazed them on how beautiful these planets are.

The nightsky has been perfect for moon observation until the clouds started forming at around 8:00 PM. We took advantage of the remaining hour for further discussions regarding the moon and nightsky observations. The troupe started packing up at 9 PM.

For more information about "Inomn (International Observe the Moon Night)" go to their website

Here are some of the pictures taken by the observation team during the observation.

Prepared by: Jhoana Marie Tabios, Andrew Bayot and Miguel Artificio