Thursday, November 26, 2009

Timings for Pleaides occultation for Delhi, Hyderabad and Kolkata


Occultation prediction for DELHI India

       day  Time   P   Star No Mag Moon CA   PA
 y   m  d  h  m  s      No Alt Az  
09 Dec  1 13 25 38 m     556   5.4 29  78  28S 160
09 Dec  1 13 26 56 Gr    556   5.4 30 ** GRAZE
09 Dec  1 13 42 37 D     564   6.2 33  79  87N  96
09 Dec  1 13 50 51 d     567   6.8 35  79  62N  72
09 Dec  1 13 57 31 d     560   3.6 36  80  -5N   4
09 Dec  1 14 13 58 Gr    560   3.6 40 ** GRAZE
09 Dec  1 14 18 43 d     570   7.0 41  82  55N  65
09 Dec  1 14 24 50 r     560   3.6 42  82 -55N 315

Occultation prediction for hyderabad india

       day  Time   P   StarNo Mag Moon   CA   PA
 y   m  d  h  m  s         Alt Alt Az  
09 Dec  1 13 13 38 d     559   6.5 25  71  75N  85
09 Dec  1 13 17 13 Gr    552   2.9 26 ** GRAZE
09 Dec  1 13 17 51 M     552   2.9 26  71 -30N 339
09 Dec  1 13 27 24 D     560   3.6 28  71  39N  49
09 Dec  1 13 43 13 d     567   6.8 31  72  84S 106
09 Dec  1 13 56 44 m     564   6.2 34  73  32S 159
09 Dec  1 13 56 53 Gr    564   6.2 34 ** GRAZE
09 Dec  1 14  8 57 d     570   7.0 37  73  88N  99
09 Dec  1 14 29  3 r     560   3.6 42  73 -77S 268

Occultation prediction for KOLKATA india

       day  Time   P   Star No  Mag Moon   CA   PA
 y   m  d  h  m  s       Alt Alt Az  
09 Dec  1 13 20 42 d     559  6.5 31  75  68N  77
09 Dec  1 13 21 59 Gr    552  2.9 31 ** GRAZE
09 Dec  1 13 26  2 M     552  2.9 33  75 -30N 339
09 Dec  1 13 37 44 D     560  3.6 35  76  31N  41
09 Dec  1 13 49 39 d     567  6.8 38  76  88N  97
09 Dec  1 13 50 12 D     564  6.2 38  77  60S 130
09 Dec  1 14 16 48 d     570  7.0 44  78  80N  90
09 Dec  1 14 37 59 r     560  3.6 49  79 -85S 277






Timings are in UT. To convert these into IST add 5 hours and 30 mins.

P: Phenomenon, R – Reappearance, D – Disappearance

Mag (v): Visual Magnitude of the star occulted.

CA: Cusp angle of the event. This is the number of degrees from the northern (N) or southern (S) cusp to the event. The positive (+) events occur on dark limb and are easiest to see; negative (-) events occur on bright limb. See the figure below.

PA: is the position angle measured in degrees. Similar to the position angle for double stars, it is the angle from due north (0°) to the point on the Moon's limb where the Event occurs. 90° is celestial east (to the left), 180° is celestial south, 270° is celestial west (to the right). See left figure below.







Pleiades occultation by Moon oN Dec 1st, 2009

Eclipse of stars in night

Imagine moon covering the sun to bring darkness in broad daylight, what would that event be? Eclipse, you would say but is it really eclipse? Well give it a thought. We know eclipse as “An astronomical object coming under shadow of another astronomical body and seen from other astronomical body” but the solar eclipse is not coming under this category because we are on the object where shadow is falling. So then what is this event? In astronomy we call it an “occultation” which means that a celestial body is directly coming in front and blocking the light from another body. Solar eclipse is a perfect example of occultation.
Now the greatest eclipse of the century is history and why we are discussing this again? Moon, our nearest neighbor, keeps on coming in front of so many stars in night that each night one can see numerous occultations. So one does not have to wait for a solar eclipse to happen to see an occultation. Now the whole talk about occultation goes to an interesting juncture where moon comes in front of a group of stars and in span of few hours you see 10-15 stars being occulted.  As the occultation can and only happen with stars and planets and lying on the path of ecliptic, some interesting events occur. Pleiades star cluster happens to be in Taurus and it provides us humans a rare treat in visual astronomy when moon comes in front of it.
December 1st 2009 night is one of those nights when moon is coming in front of the Pleiades as seen from earth and we get a chance to see this event though the moon is almost full and most of the Pleiades stars get washed out in the brilliance of it.



Occultation of Pleiades photographed by SPACE team on March 30, 2009

Occultations have been used to know more about the celestial mechanics as well as these have helped us finding new things in the skies. The discovery of the Uranian Rings was made by astronomers James L. Elliot, Edward W. Dunham, and Douglas J. Mink on March 10, 1977, using the Kuiper Airborne Observatory, and it was an unexpected event. They planned to use the occultation of the star SAO 158687 by Uranus to study the planet's atmosphere. However, when their observations were analyzed, they found that the star disappeared briefly from view five times both before and after it was eclipsed by the planet. They deduced that a system of narrow rings was present. Observations of occultation by Neptune were observed by UP state Observtaory, nainitaal and they confirmed presence of rings around Neptune. Stellar occultations by Moon gives us more and more accurate data about the Lunar orbit.
On December 1st 2009, around 7:00 pm IST get hold of any optical astronomical instrument you have. Binocular, spotting scope, small refracting scope or a telescope. These all will show you the moon sitting pretty in front of Pleiades.



Moon with Pleiades at 7 pm from Delhi

Tuesday, November 17, 2009

Next bright star occultation coming up for india (path going through Maharahstra, andhra pradesh)

On 2009 Dec 24 UT, the 58 km diameter asteroid (224) Oceana will occult a 6.6 mag star in the constellation Auriga for observers along a path across India, Arabia, Africa.

In the case of an occultation, the combined light of the asteroid and the star will drop by 5.9 mag to 12.5 mag (the magnitude of the asteroid) for at most 4.7 seconds.




For interactive google map click here courtesy BREIT IDEAS Observatory

This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, TMO astrometry for the asteroid kindly provided by Bill Owen, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: .

The event at a glimpse
----------------------
    * Rank: 98
    * date and approx. time of event: 2009 Dec 24, 21:23  - 2009 Dec 24, 21:40  UT
    * magnitude of target star: 6.6
    * magnitude drop [mag]: 5.9
    * estimated maximum duration [s]: 4.7
    * Moon: 52 % sunlit, 78° distance
    * Sun: 167° distance
    * rough path description: India, Arabia, Africa

The occultation path
--------------------
    * approximate projected width [km]: 59
    * 1 sigma uncertainty interval [path widths]: +/- 0.37
    * 1 sigma uncertainty interval [seconds]: +/- 2.4
    * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .027 +/- .017)
    * 1 sigma uncertainty ellipse (major, minor, PA): ( .027", .017", 88° )
    * approx speed of asteroid's shadow [km/s]: 12.4406


Prediction courtesy -
Calculator (s): Steve Preston
Date of update: 2009 Nov 14, 21:37 UT

www.asteroidoccultation.com

Steve Preston
7640 NE 32nd St
Medina, WA 98039
425-688-9965

mailto: stevepr@acm.org

What is an Asteroid Occultation ?

 What is an Asteroid Occultation ?

Occultation is a generic astronomical term for a situation where one body "covers" or "passes in front of" another body.  Eclipses and transits are common examples of occultations.  In a solar eclipse, the moon occults (covers) the sun for observers on the earth.  In a lunar eclipse, the earth occults the sun for observers on the moon.  We use the term asteroid occultation for the situation where an asteroid occults a star for observers on the earth. During an asteroid occultation "event" the asteroid momentarily hides the star.  We use the term "asteroid's shadow" to refer to the "shadow" thrown by the asteroid with respect to the light from the occulted star. And the term "shadow path" refers to the path of the asteroid's shadow as it passes across the earth. Depending on the size of the asteroid, its distance from the earth, and its speed in its orbit, the asteroid may cover the star for a fraction of a second or close to a minute.  If the star is relatively bright compared to the asteroid, an observer will see a noticeable drop in magnitude as when the asteroid covers the star.  As asteroids move through the sky they often pass in front of stars from the perspective of an observer on the earth.  However, the vast majority of these occultations involve small asteroids and relatively dim stars, and these events would be very hard to detect with amateur equipment.