Edited by: Vidur Parkash, Contributions by Dr. N Rathnasree

In this Edition

Beyond the Hubble

The Monsoon Eclipses

Deep Sky Guide to Scorpius

Ephemeris for July-August 08

For now over two decades the Hubble Space Telescope has allowed astronomers all over the world

look deeper and farther out into space and time than any other observatory present on the ground.

Since its launch in 1990 on board the Space shuttle Discovery, the Hubble has revolutionized our

understanding of the universe.

The James Webb Space Telescope (JWST) will be a large infrared telescope with a 6.5-meter

primary mirror. Launch is planned for 2013 aboard an Ariane-5 rocket. JWST will be the premier

observatory of the next decade, serving thousands of astronomers worldwide. It will study every

phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to

the formation of solar systems capable of supporting life on planets like Earth, to the evolution of

our own Solar System. (continued on next page)

K

RIT

TIK

A

WEB

ED

ITIO

N,

JULY

– A

UG

UST

20

08

Beyond the Hubble: The James Webb Space Telescope

A technician works on the mirror assembly of a 1/16th

scale model of the JWST. Image Courtesy NASA

YOUR AD HERE. For advertising Opportunities in Krittika, please contact Vidur, vidur_itm@yahoo.com

(continued from previous page) Several innovative technologies have been developed for JWST. These include a folding,

segmented primary mirror, adjusted to shape after launch; ultra-lightweight beryllium optics; detectors able to record

extremely weak signals, microshutters that enable programmable object selection for the spectrograph and a cryocooler for

cooling the mid-IR detectors to 7K.

(Left) The famous Hubble Deep Field. This revolutionary image changed our

perception of the universe. Each spec of light in this image is a galaxy.The Hubble

took this image in n area of the sky which has relatively very few foreground stars

in Ursa Major). After over ten consecutive days of exposure between December

18 and December 28, 1995 scientists were astonished to see thousands of galaxies

in the picture. These galaxies are the oldest known Baryonic matter (the stuff you

and me are made out of) in the universe. The image was assembled from 342

separate exposures taken with the Space Telescope's Wide Field and Planetary

Camera 2. Imagine staring at something continuously for 10 days!

The Webb’s Lagrangian Orbit ( This material was adapted from a NASA press release)

The L2 orbit is an elliptical orbit about the semi-stable second Lagrange point . It is one of the five solutions by the

mathematician Joseph-Louis Lagrange in the 18th century to the three-body problem. Lagrange was searching for a stable

configuration in which three bodies could orbit each other yet stay in the same position relative to each other. He found five

The JWST will observe primarily the infrared light from

faint and very distant objects. But all objects, including

telescopes, also emit infrared light. To avoid swamping

the very faint astronomical signals with radiation from

the telescope, the telescope and its instruments must

be very cold. Therefore, JWST has a large shield that

blocks the light from the Sun, Earth, and Moon, which

otherwise would heat up the telescope, and interfere

with the observations. To have this work, JWST must be

in an orbit where all three of these objects are in about

the same direction. The answer is to put JWST in an

orbit around the L2 point. The L2 orbit is an elliptical

orbit about the semi-stable second Lagrange point .

DID YOU KNOW?

Saturn has moons like Prometheus and Pandora orbiting it within its system

of rings. These moons are called “Shepherd moons” . They are called that

because their gravity helps to stabilize the shape of the rings.

such solutions, and they are called the five Lagrange points in honor of their discoverer. In three of the solutions found by the

mathematician Lagrange, the bodies are in line (L1, L2, and L3); in the other two, the bodies are at the points of equilateral

triangles (L4 and L5). The five Lagrangian points for the Sun-Earth system are shown in the diagram below. An object placed at

any one of these 5 points will stay in place relative to the other two.

In the case of JWST, the 3 bodies involved are the Sun, the Earth and the JWST. Normally, an object circling the Sun further out

than the Earth would take more than one year to complete its orbit. However, the balance of gravitational pull at the L2 point

means that JWST will keep up with the Earth as it goes around the Sun. The gravitational forces of the Sun and the Earth can

nearly hold a spacecraft at this point, so that it takes relatively little rocket thrust to keep the spacecraft in orbit around L2.

Monsoon Eclipse – Aug 1 2008

In recent times most of the eclipses have been visible with a very small fraction of the Sun being seen as eclipsed, from India.

The last total solar eclipse from India had not been too happy an experience, with most of the totality belt having been

clouded out during the eclipse. We now have the eclipses of 2008 and 2009, also falling in the monsoon season, and will

therefore need to gear up and scan Indian Geography and its monsoon vagaries very carefully, to decide where we are going

to be, to observe the 2009 Total Solar Eclipse. The August 1st 2008 Total Solar Eclipse will be seen as a partial eclipse from

India, so perhaps people might not travel to different locations in India, for this eclipse, and will more likely want to know

what are the chances from their home location, of viewing this eclipse. Before we discuss anything else, it is very important to

emphasise that viewing the eclipse with naked eyes would be very dangerous for the eyes. Viewing the Sun through a

telescope or a binoculars without a proper filter is many times more dangerous - do not ever do that, it could destroy your

eyesight. The safest way of viewing a partial solar eclipse is through the method of projection. Let us now, look at the

circumstances of the August 1st 2008 eclipse, for different locations in India. We may be missing the totality of this eclipse,

but, the northern parts of India do get to see a large fraction of the disc of the Sun eclipsed.

Circumstances for the Aug 1 2008 Eclipse

TRIVIA: Which Lagrange Point is NASA’s Solar and Heliospheric Observatory

(SOHO) orbiting in? ( Go to the end of the newsletter for the correct answer )

In this figure, adapted from http://eclipse.gsfc.nasa.gov/SEpath/SEpath2001/SE2008Aug01Tpath.html

The path of totality is marked in dark blue, and passes well to the North of India. The dark green lines indicate regions where

the eclipse will start at the times indicated. These timings are in Universal Time (UT) to which we need to add 5.5 hours to

obtain the Indian Standard Time. The light blue lines are contours of constant Eclipse Magnitude.

The Eclipse Fraction is defined as the fractional diameter of the Sun eclipsed, at the maximum of eclipse at any given point.

The southern parts of the country will see between 20 -40 % eclipse fraction, the central regions between 40-60 % while the

Northern parts of the country see between 60-70 eclipse fraction, at maximum, during the 2008 eclipse. There is another way

of looking at a partial eclipse - through a quantity known as the Obscuration Fraction. The obscuration fraction is the fractional

area of the disk of the Sun covered by the disk of the Moon. For Delhi, for instance, the eclipse magnitude is 62.26 % while the

maximum obscuration fraction is 53.7 %. Using the box projection apparatus mentioned above, and by projecting an image of

the Sun on to a graph sheet and photographing that image, one can make some estimates of the obscuration fraction as the

eclipse progresses from beginning to end and check them against known theoretical values. Try it, it is great fun!

Here is a graph of the measured obscuration fraction of the eclipse of March 2006, compared with theoretical values. The

measurement and comparisons were done by members of the Amateur Astronomers Association, Delhi, at an eclipse

skywatch organized at the Nehru Planetarium, New Delhi.

Eclipse obscuration fractions obtained from images taken by AAAD member Guntupalli Karunakar and processed for

obtaining the measurements by Vidur Prakash and Vidushi Bhatia

The binocular box projection apparatus can also be used to measure the relative angular diameter of the Sun and the

Moon, using simple school geometry. This is an exciting activity to do, if we are located in the partial zones of a total or an

annular eclipse. With such a measurement we can discern whether the eclipse is total or annular, in the central belt, even if

we are situated far from the central belt. A kind of a celestial ventriloquism that we can practice :-)

We might also be able to measure the position angle of the first contact point, with such an apparatus, if there is a sunspot

visible on the day of the eclipse. The First contact is the very beginning of the eclipse as the first dent or a miniscule bite

appears to have been taken out of the Sun – the first external tangency between the Moon and the Sun, as seen from a

given location. The position angle of this contact point is defined as the contact angle measured counter-clockwise from the

north point of the Sun's disk.

What we need is an X-Y axis drawn on the image of the Sun, along the North-South and East-West directions. How do we

do this, with our projected image of the Sun?

Well, first, have a circle drawn on a sheet of paper that would exactly be of the same diameter as that of the projected

image of the Sun that you get with a telescope or the binocular box projection apparatus. Let the projected image of the

Sun, fit exactly in this disk and image it at this point. Now, let the image drift out of the circle with the diurnal rotation of

the Earth and keep marking the new location of the sunspot (the smaller the sunspot, the better will be our accuracy). This

straight line path within the circle is the direction East West. Well, if there are any sunspots on the disk of the Sun, mark

their position on the page as the image drifts. This will give the direction East West. Giving a little nudge to the apparatus in

a rough North direction and noting the direction in which the image shifts, will allow one to locate the relative North-South

perpendicular to this East-West axis.

There, we are all set, if we manage to do this carefully and obtain our East-West and North-South axis on our projected

image that we capture just at first contact, we should be able to pull out the position angle of the first contact reasonably

accurately.

So, go ahead and make your binocular box projection apparatus, or a simple projection apparatus for a telescope with a

stand, and enjoy watching the eclipse safely. Be sure to do a little something quantitative, with measurement of some

eclipse related parameters, to enhance your enjoyment of the eclipse! And look ahead, to the July 22nd 2009 Total Solar

eclipse in India.

Here is a screen captured image of the location of the totality belt passing through India, for this eclipse.

The website of the Nehru Planetarium, New Delhi, has detailed discussions compiled from http://fallingrain.com/ about the

weather conditions expected for each and every city, town and village falling within the totality belt. You might find this

useful to decide where you wish to be located, to observe the July 2009 Total Solar Eclipse. . Preview it at

http://www.aaadelhi.org/?q=node/6

Safely View the Sun

A tree with dense foliage would work very well, to give projected images of the Sun, and for discerning that there is an

eclipse. However, we need to look out for suitable trees that would show pinhole images at the time of the eclipse.

Moreover, the eclipse of August 1st 2008 is an evening one and that of July 2009 is a morning one, so that we may need to

look for suitable walls on which pinhole images from tree foliage might show us the eclipse in a beautiful and interesting

way. One method that allows us to view a reasonably large sized disk of a projected image of the Sun, would be through a

handmade box projection apparatus that can be used in conjunction with a pair of binoculars or a small telescope. It would

be easily possible for every school to have such a box projection apparatus made and they will then be well equipped with a

safe apparatus for viewing the Sun, sunspots and all solar eclipses.

We need a long rectangular box – about 4-6 feet in length and about 1 ft by 1 ft in cross section. Make a plywood

rectangular box (firm thick cardboard will also serve the purpose for short term usage) – blacken the inside of the box for

better contrast and visibility. Cover one end of the box with some firm material that allows you to cut small holes in it and

insert the eyepiece end of binoculars or a small telescope. Make two small holes, just a little smaller than the diameter of

the eyepiece holder of your binoculars – If you are using a small telescope then make one single hole to fit its eyepiece

holder. Insert the Binocular or telescope eyepiece in these holes and try pointing the box towards the Sun and obtain a

projected image on the screen side of the box. The other end should have a white blank sheet of paper placed on the inside

to serve as the screen. (Graph paper for some of the observations)

This will need a bit of a practice with pointing the box towards the Sun and the dealing with the required focusing – but, it

can be done, and soon one will get a good feel for doing the adjustments and obtaining a projected image of the Sun.

The author demonstrating binocular projection of the sun

Armed with such an apparatus, you can do many quantitative observations, related to a partial solar eclipse. Do check out

the website of the Nehru Planetarium http://nehruplanetarium.org/

For a detailed discussion of possible measurements during a partial solar eclipse, that you can do with such a box

projection apparatus. The website will also give timings of the eclipse for various locations in India and other interesting

information related to the eclipse.

Authored by N. Rathnasree, Director, Nehru Planetarium, New Delhi

Deep Sky Guide to Scorpius

One of the most recognizable constellations in the night sky. It is one of those constellations that actually looks like its object it

represents, namely a scorpion. Sometimes I really would like to go back in time and scold the guy who named constellations

Aries and Libra. Scorpius boasts of a red supergiant star that incidentally is the brightest star in the constellation named

Anatares (α-Scorpii)

So what all is there to hunt for in Scorpius? Well the good news is that the tail region of the constellation actually passes

through the galactic core region of the Milky way, so anytime you point your scope at it, chances are you will be able to see

millions of stars in the region like small bright diamonds sprinkled on a black paper. That’s quite a sight in itself! Besides that

the amateur can hunt for a variety of DSOs in Scorio. Messier M6 (also known as the Butterfly Cluster) is a open cluster near

the tail of the scorpion with an apparent magnitude of about 5.0 (varies a bit from time to time). M6 is mostly comprised of hot

blue stars with the exception of a single bright orange-giant star that kind of stands out of the rest. M7 (also known as

Ptolemy’s Cluster) is another open cluster in a dense milky way background, so sometimes it is very easy to miss it in the

background of stars.

Moving towards Antares, the Red supergiant that forms the head of the scorpion, move 1.3 degrees west of it and you run into

M4, a Globular cluster which appears like a dim fuzzball of light in small telescopes. At the distance of about 7,200 light-years

that has been determined for M4, it is perhaps the closest globular cluster to our Solar system. There are two more

Messiers; M19 and M62 in Scorpio at a magnitude of 7.0 and 8.31 are challenge objects for amateurs with 6” and smaller

aperture class scopes.

Talking about Scorpius I couldn’t but help peek into nearby Sagittarius, and talk about the magnificent Lagoon Nebula M8

and the Trifid Nebula M20. The Lagoon has a bigger angular spread than the Full Moon but a very poor apparent magnitude,

and you may need a nebulosity filter to appreciate it. It can be easily located by an open cluster of stars in the foreground.

However the Trifid is a spectacular emission nebula which can be readily compared with those pretty pictures you may have

seen in an astronomy book.

This Month’s Ephermeris July 15th 2008 – Aug 15th 2008

(July 14, 2008) — Moon at apogee

The point in the Moon's orbit when it is farthest from Earth.

(July 18, 2008) — Full Moon

3:59 A.M.

(July 25, 2008) — Last Quarter Moon

2:42 P.M.

(July 29, 2008) — Mercury in superior conjunction

A conjunction occurs when two or more bodies appear close together in the sky.

(July 29, 2008) — Moon at perigee

The point in the Moon's orbit when it is closest to Earth.

(August 1, 2008) — New Moon

3:58 P.M.

(August 8, 2008) — First Quarter Moon

4:20 P.M.

(August 9, 2008) — Juno stationary

The body appears motionless in the sky due to the turning point between its direct and retrograde motion.

(August 10, 2008) — Moon at apogee

The point in the Moon's orbit when it is farthest from Earth.

(August 16, 2008) — Full Moon

5:16 P.M.; partial lunar eclipse

ANSWER to Today’s Trivia: The L1 Lagrange Point

You have been reading Krittika- Web Edition

Krittika is a presentation of the Amateur Astronomers Association Delhi. To contact us email Vidur

(vidur_itm@yahoo.com) or Anurag Garg at the Nehru Planetarium (anu_astro@yahoo.com)

Visit Us at www.aaadelhi.org

The material present in this document is Copyright © 2005-08 Amateur Astronomers Association of Delhi, unless stated

otherwise.