30 January 2018

Watch Lunar Eclipse at Planetarium, Bangalore

Jawaharlal Nehru Planetarium is organizing Lunar Eclipse viewing at planetarium campus, Bangalore. Interested public can visit planetarium and enjoy the eclipse and get questions answered about eclipse and astronomy.

The event is from 6:15pm to 8:45pm on January 31st. 2018. Association of Bangalore Amateur Astronomers (A.B.A.A) members will also be there to help public understand and enjoy the eclipse.

03 January 2018

Earth and Sun Closest

Sun so close yet so cold...Yes Today Sun and earth will be closest to each other at a distance of 14,70,99,586 km. This point of any object closest to Sun is called Perihelion. The reason for the cold in northern hemisphere is due to the orientation of earth's axis and as you can see in the illustration, the Sun is moved to southern hemisphere where they are experiencing Summer now. 

Since earth's orbit is almost circular, at farthest point from Sun which occurs on July 6th the distance will be 15,20,96,155 km. This farthest point from Sun is called Aphelion. The angular size of the Sun which we measure in degrees at perihelion is 0.542018074degrees. And as we know the orbit is almost circular the difference in angular diameter of Sun from Perihelion to Aphelion is very small. At Aphelion the angular diameter is 0.5243709741degrees. 

 If we compare this to Mercury, the perihelion distance is 46,000,000 and this gives the angular diameter of Sun Seen from Mercury at 1.73434325degrees. The Aphelion distance of Mercury is 69,820,000 and this gives the angular diameter of Sun as seen from Mercury at 1.14247784degrees, almost half a degree difference. You can compare this to earth and Sun.

26 September 2017

Remembering names of Moon Phases

We are seeing moon getting brighter in the evening sky every day from the last new moon on 20th. With each passing day more area of the moon is illuminating and we can see lot of features on the moon. Many people have confusion when it comes to naming the phases of the moon, so here is a something useful to remember the names.

First, we start with couple of days after the new moon, the phase we are seeing is crescent phase a thin sunlit part of the moon and since the sunlit part is getting bigger with passing days we call it waxing crescent. This is from old English meaning something that grows, here the brighter side is growing.

Waxing crescent moon. Sunlit part towards west.

Next is First quarter, this phase happens when the Sun, earth and the moon align in such a way that Sun and moon are at right angles as seen from earth. We can seen this in the evening sky, on the evening of the first quarter at sunset, we can measure the angle between Sun at the horizon and the moon and the angle will be 90 degrees or close to 90 degrees depending on actual time of alignment.

First Quarter moon. Sunlit part towards west.

Between First quarter and Full Moon, when more then half of the moon is lit up by sunlight we call it gibbous phase and since the brightness is increasing its waxing gibbous phase.

Waxing gibbous moon. Sunlit part towards west. 

After the first quarter comes the Full moon phase, which we are all familiar with, in astronomy we call moon is in opposition. The moon and the sun are on the opposite sides of the earth, if they are exactly aligned then we have a lunar eclipse.

Full moon

From new moon phase the moon was in the sky before the sunset and would set late as the days passed until Full moon when it rises at sunset. After this the moon rises late after sunset and the brightness starts decreasing.

Waning gibbous moon. Sunlit part towards east.

Since its decreasing and more then half is lit, but not fully lit, we call it waning gibbous phase. After that moon reaches last quarter again attaining right angle with the sun. This means the moon will by high in the sky at sunrise. The next phase in waning crescent where we see thin lit surface of the moon and finally reaching new moon phase.

From new moon to full moon, we see the lit part is towards west and from full moon to new moon, we see the lit part towards east, the lit part will be towards the sun.

Now I think there is no problem in telling the phases below,

Last Quarter moon. Sunlit part towards east.
Waning crescent moon.Sunlit part towards east.


01 March 2017

Venus Watch at ABAA

After I announced about Venus being in its brightest phase many people showed interest in looking at Venus through telescope following Sunday. On Sunday we were happy to see public and members coming in large numbers to watch Venus in crescent phase. After sunset we put the telescope out and focused on to Venus, members of ABAA were present there in showing and explaining all about Venus. Using the 6 inch telescope of ABAA people saw amazing sight of the crescent phase, and immediate reaction of most people was “is it Moon?”, that lead to discussions and members helped them in getting idea of orbits and phases of inner planets.

ABAA is open on all Sundays from 5:30pm and always ready to show the celestial wonders to people and members showing interest. People can come and see moon and planets, learn about them and also learn about telescopes and how to use them. Observing through a telescope has steep learning curve, its best to learn about them before buying or going out for observing and ABAA can really help in that section. ABAA can help in choosing the best telescope for you or help you in building your own telescope, you can come to ABAA on any Sunday evening and discuss your needs.

Here are photos of Sunday sessions of Venus watch



15 February 2017

Watch Brightest Venus on Friday

After Sunset in the western twilight sky we see a bright star outshining all the starts in the evening sky, this is the planet Venus. The visual apparent magnitude of the planet Venus is now -4.6 and the apparent magnitude of brightest star in the night sky, Sirius, in the constellation of Cains Major is -1.46 this makes Venus 18 times brighter than Sirius. 
Brocken Inaglory, Venus-pacific-levelled, CC BY-SA 3.0
On February 17th Venus will reach its brightest crescent phase and this is called Greatest Illuminated Extent, the amount of illuminated crescent and the angular diameter of the planet Venus. Venus will have an angular diameter of 39 arc seconds and fraction of illumination is .273 of the angular diameter. After this day the illuminated side will start decreasing and we will see the crescent getting thinner. By second week of March the illuminated fraction will be only .085 of the diameter of the planet and magnitude would have come down to -4.4 still brightest in the evening sky. 

View Through the Telescope on 17th of Feb

View Through the Telescope on 10th March

The planet Venus will slowly fade into glare of the Sun and will reach inferior conjunction on March 25th. In April we will see Venus in early morning sky before sunrise and again the Greatest Illuminated Extent will happen on April 30th. Time to take out the telescopes and observe Venus in coming days, if you don't have one you are always welcome at ABAA on Sundays evening and see the Venus through our telescope. Venus sets at 9pm now and in middle of March the planet will set at 7:30pm.

03 February 2017

Sunday Talk "Lesson Learned:The 2003 Space Shuttle Colombia Accident"

Hi All

ABAA in collaboration with JNP presents this Sunday talk titled "Lesson Learned:The 2003 Space Shuttle Colombia Accident" and will be delivered by Christopher Kirchhoff who investigated the Columbia Space Shuttle disaster which happened in February 1, 2003. He will speak about the circumstances that led to the Space Shuttle disaster in which Indo-American astronaut Kalpana Chawla was killed along with crew of the Shuttle. All are Welcome.

Date: 5/2/2017
Time:4:30 Pm
Venue: Jawaharlal Nehru Planetarium, Bangalore.

All are welcome.

15 November 2016

Aldebaran occultation by Moon tonight

Most of you would have enjoyed the supermoon yesterday evening and most of you have taken wonderful photos. Today evening we have one more exciting astronomical event and that is occultation of star Aldebaran by Moon. Tonight moon will occult giant Aldebaran. since both objects are bright enough it will be easy to observe even with naked eye, a pair of binoculars and of course with telescopes. I would suggest you get all the setup ready before the given time and wait for the event rather than waiting until last minute. The chart below will be helpful to show the entry point and exit point of the star during occultation. 

Astronomers have used occultation to know about the size, shape and distance of the objects. Aldebaran is the brightest star in the constellation of Taurus, it is at a distance of 65 light years from Sun. By measuring the time taken for that star from disappearing and reappearing and getting reports from different parts of the world we get a pretty good idea of the shape of the object. Today evening moon will occult Aldebaran from the south near the crater Tycho. Use the chart below to follow the star from disappearance to its re emergence. Try and measure the time taken between the star disappearance and re emergence using stop watch. All the best and hoping for clear skies. 

Time of disappearance 15:26:46 UT
Time of re emergence 15:57:45 UT

 Moon in the constellation of Taurus and close to star Aldebaran.

Moon about to Occult the star.

Aldebaran re emerging after Occultation.