Basic Photometry

Since a lot of my students are getting into 'research mode' and require a knowledge of the means to analyze data, I thought it would be good to make a post on some basic info here. Among the easiest and most accessible is doing photometric analysis. [Forgive me if I once again go about some technical info in this blog, I will try to make it as basic as possible]

Photometry or the 'measurement of light' allows you to do a variety of things, such as identify magnitudes, sky brightness, limiting magnitudes, render light curves, etc. A variety of research subjects can be tackled by photometry.

Your digital camera can act as a detector which can be used to gather photometric data for analysis. You also need a list of standard stars (stars with fixed magnitudes) if you wish to make a comparison of magnitudes. Here is a sample list of standard stars (A. U. Landolt, 1992). And lastly you need a program that can do photometric analysis like IRIS or IRAF [I personally recommend Iris since it's more user friendly].

We can compare magnitudes by using the equation

m1 - m2 = -2.5 log (b1 / b2)

where m1 and m2 are the magnitudes of two stars and b1 and b2 are their corresponding brightness.

First you have to acquire an image with a standard star in your field of view. I then can set point 1 as my standard star and set point 2 for any object I wish to compare. Using IRIS or IRAF, I can measure the pixel count/intensity for both points and use them as b1 and b2 in the equation. By doing so I can identify the magnitude of any other point in the image in contrast to the standard star. 

----Side note----

This type of measurements become more accurate when standard data reduction is done (lights, darks, flats, bias) and also when the appropriate filters are used (standard Johnson filters). However, I'll leave those out for another post or for you to find out on your own.

Solar Observation: 9 January 2014

Here are some images taken for the Solar Observation Program (SOP) in RTU. With me were Raven Pelobello and Babie Rose Quiniquis, two of the freshmen members of the SOP.

Of particular highlight right now is the huge sunspot group AR 1944 (above image) which over the past few days has released several flares including an X-class flare. The size and structure of the sunspot group puts it at an Fkc classification which corresponds to a high solar flare probability. NOAA forecasters estimate an 80% chance of M-class flares and a 50% chance of X-ray flares over a period of 24 hours.

Andromeda Mobile Planetarium

A new planetarium service has opened in the Philippines, and it opened up in my home town - Baguio City.

Welcome the Andromeda Mobile Planetarium, a private business in partnership with Rizal Technological University's Department of Earth and Space Sciences that caters to students all over the Cordillera region. The planetarium features a 6 meter dome, and various exhibits such as a meteorite collection and images taken from John Nassr's Stardust Observatory in Baguio City.

The Andromeda Planetarium is temporarily set-up at the Porta Vaga mall to allow the public to come and visit. The dome will be circulating in the different schools in the region to promote awareness and interest in the science of astronomy.

Space Science and Technology Applications Scoping-Consultation Workshop

The Manila Observatory and DOST-PCIEERD held a Space Science and Technology Applications (SSTA) scoping-consultation workshop at the SEAMEO Innotech from November 4-6. This two day workshop is participated by various sectors of the government, academe, as well as private and international  groups.

The workshop is designed to get information with regards to space science in the country and how it could progress. The Manila observatory hopes to design a 10-year plan on the progress and development of SSTA in which all the sectors are involved.

This particular project is interesting for astronomy and space science enthusiasts since it is another step to the realization of a Philippine Space Agency.

The Sextant (Escape Plan)

The movie Escape Plan (starring Stallone and Schwarzenegger) is about a man who's been testing federal prisons for their capacity to prevent an escape from their maximum security. He is then recruited by the CIA to test a certain underground prison facility.

In the movie, Breslin (Stallone) ends up creating a sextant to figure out where the prison was located. A sextant is an old astronomical tool used commonly in nautical navigation (celestial navigation). It is a tool used to measure the angular height/ altitude of a star with respect to the horizon. Seafarers had to be familiar with the night sky in order to put the sextant to use. First of all one must locate Polaris, the north star. A common misconception is that Polaris is a really bright star; this however is not true. Being familiar with the patterns of the constellations and knowing which is next to which can help. Of course it helps also if one has a compass to point you in the general direction.

The measured angular height of Polaris will give you the angle of your latitude. As an example, if we were to say that we measure Polaris to be ~13 degrees from the horizon in Manila then we can say that Manila is located at a latitude of 13 degrees.

35th International School for Young Astronomers

From August 25 - September 14, 2013, I was given a chance to become a delegate at the 35th International School for Young Astronomers (ISYA 2013) held in Bandung, West Java, Indonesia. The activity is organized by the International Astronomical Union (IAU) in cooperation with the National Institute of Aeronautics and Space (LAPAN) as well as the Bandung Institute of Technology (ITB). The activity is in line with commemorating the 50th anniversary of LAPAN.

 

The ISYA 2013 is a program of the IAU Commission 46 on Astronomy Education and Development. The program seeks to broaden the participants' perspective on astronomy through international lectures, seminars, practical exercises and observations, and exchange of experiences. The topics discussed in the ISYA include space weather, space science, astrophysics, cosmology, galaxies, observation and instrumentation. The participants belong to a dynamic range from undergraduate to PhD students, including students from different disciplines and cultures.

The ISYA 2013 was a worthwhile learning experience. New things were learned, new friends were made, and new visions for the future of astronomy were instilled in our minds. We all go back to our respective countries carrying with us new insight that will help us educate and develop our local astronomy communities.

The Magnetic Flip

Recent news have been mentioning the upcoming flip of the Sun's magnetic poles.
What is a magnetic flip and how exactly does it happen?

Our sun transfers energy from the core to the radiative zone, and then to the convective zone, and out to the photosphere (the visible disc of the sun). The vertical motion of the plasma in the convective layer causes the magnetic field lines to twist into flux tubes. When the flux tube increases its energy it then rises as an active region. The magnetic field lines arch from these areas from one polarity (+) to the other (-). The magnetic polarities of each active region is similar but reversed in each hemisphere.

Now, the Sun has a solar cycle described as a period of very few magnetic activity followed by increasing activity over a time of 11 years. The year 2013 is the solar maxima which signifies the end of the current solar cycle. After the 11-year cycle, the magnetic polarities of the active regions suddenly reverse and will remain as such for another 11-year cycle. So a period of 22-years make up one magnetic cycle of the Sun.

The Sun's northern hemisphere has already reversed its polarity as you can notice in a period of almost 0 activity for the month of July (see absence of AR regions in the Northern part for the month of July in these solar images). The southern hemisphere is following suit.

So what does a magnetic flip do?

Well, the Sun has a region of influence called the heliosphere which reaches out to the ends of the solar system. We monitor this sphere as what we call space weather. Charged particles (cosmic rays, plasma, etc.) in space travel with respect to the magnetic field lines of the Sun and of the planets. When the magnetic orientation of the Sun flips then so does the orientation of these charged particles. The sudden switch causes a storm in the space weather.


Solar Observation Program
Department of Earth and Space Sciences
Rizal Technological University