Credits : B. S. Shylaja [email@example.com]
Chintamani Ragoonathachari1 (1840–80)served the Madras Observatory under various cadres. His meticulous contributions fetched him the honour of membership of the Royal Astronomical Society. He conducted two solar eclipse expeditions in 1868 and 1871, and was the first Indian to be credited with the discovery of two variable stars, R Ret and V Cep. The transit of Venus which occurred in 1874, was a great astronomical event observed by many Indian and European teams on the Indian soil. Ragoonathachari prepared a treatise on this subject sometime in the early part of 1874. The English and Kannada versions are available at the archives of the Indian Institute of Astrophysics, Bangalore. Here a comparative study of the two texts is done to demonstrate the new light it throw son the status of contemporary Indian astronomy.
The two texts It is widely publicized that Ragoonathachari1authored a book on the Transit of Venus in English and Indian languages. The archival collection has the coverage of the Persian version. The entire texts of the English and Kannada versions are available2,3. A couple of pages are missing in the Kannada version. They correspond to the diagrams at the end of the text. Since these diagrams are identical with the English version according to the figure captions, the text may be considered as complete. At the outset the two versions appear to be one and the same; however, a careful study shows that there is a variation. It is interesting to note that the same content has been presented differently to suit different readers. The English version has the text in the form of a dialogue, where a Siddhanti (scientist, astronomer aware of modern/European astronomy)answers and convinces the Indian pundit on the importance of the event. The Kannada version The mode of presentation in the Kannada version is different. It is not in the form of a dialogue, but a smooth reading text.
Some astrological aspects are also discussed, citing from older scriptures. The language is simple and reads through without much complication. However, it is interesting to note that mathematical symbols and formulae have been avoided and the same is expressed as long sentences. This tries the patience of a reader, since every word has to be written downs a unit and the mathematical symbols introduced. At the same time, it provides an opportunity to use technical words and some have been coined for this purpose.
For example, the word ‘riputpashika’ (caused because of the enemy)
was used by astrologers to mean the conjunction of two planets. It would have been the same with transits, since the sun is also considered a ‘planet’ in the sense of a moving object. A new word ‘shukra grastha surya grahana’ has been coined to indicate the eclipse of the sun by Venus. Two new words for the maximum and minimum distances of a planet from the earth are coined as ‘paramakarshana’ and ‘sannikarshana’. The book addresses local astronomers who were perhaps well versed in Sanskrit as well as mathematics. The explanations offered for the transit are simple and can be easily understood. The first few sections are devoted to the explanation of the phenomenon like inferior and superior conjunctions. The event of transit is explained in terms of the conical shadows caused by Venus. A person close to the planet will see total, annular or partial eclipse depending on his distance within the cone or outside. As he moves farther and farther from the
planet, the same event will be termed a transit. This is explained with the help of a diagram and extended as a general expression for a shadow either from the moon or Venus. To clarify the point that a total eclipse of the sun will not be visible from the earth (in the context of the shadow of Venus) the expression used is: ‘All these varieties of eclipses will be visible only to those celestial beings like Yakshas, Gandharvas and Kinnaras, since we cannot reach those heights . . . .’ Subsequent sections explain the importance
of the event in the determination of the precise value of the astronomical unit
(AU). The derivation of parallax from transit observations is relatively simple compared to the description of Halley4. (See appendix for the complete derivation which is not available in the English version too. Moreover, there is a typographical error in the equation.)
The pros and cons of an approximate value for this unit for AU are explained in detail. The derivation is explained using circular orbits; but it is mentioned that the corrections according to the elliptic orbits are necessary. Kepler’s law is explained as a mere statement. It reads: ‘The square of the orbital period should be multiplied by a number called Beeja to get the cube of the
semi-diameter of the orbit by the square of orbital period of any planet.’
Beeja is a constant defined as the ratio (T2/a3) of the earth. Using the accurate value of AU, the deduction of the distances to the planets, their diameters and volumes is also explained. There is an unusual way of defining the volume of a sphere – as the product of the circumference and square of diameter divided by 6. Parallax is introduced to the reader in a simple way. The corresponding drawings also are clear and precise. Later sections are devoted to the details of the event of 1874. The timings for various locations are listed. The need for observations from different latitudes is highlighted and examples of planned locations are given. The method of determination
of parallax also is described in simple terms. The notation of Jya which is equivalent of product of R, a constant, with sine of an angle is used
and the formula is modified to suit this notation (see appendix). But the most interesting are the last three sections which are completely missing in the English version. Appeal to Indian astronomers to take up observations
The last three sections deal with an emphasis on the need for observations.
The HISTORICAL NOTES 1272 CURRENT SCIENCE, VOL. 96, NO. 9, 10 MAY 2009 astrological predictions also are mentioned, but the emphasis is on revival of observational techniques. It states: ‘Many astronomers in this country have been doing calculation of celestial events like eclipses, conjunction of planets following texts which were written several centuries ago. Thus there is always a difference of five galige in eclipses, for others it is about 12 galiges and for planetary positions it is almost two months. The main reason for this is not updating the calculations from time to time’.
Galige and Vigalige are measures of time. In order to initiate the local astronomers into actual observations, he gives details of an occultation and eclipses of the same year. He calls them interesting and enjoyable experiences. One of them is the daytime occultation of Venus by the
moon. It is said that this should be observable in the northeast at noon. Perhaps this has been suggested as an attraction to observe the event during
broad daylight. It also raises doubts on the visibility, whether the skies were
good enough for the daytime visibility or whether the use of a telescope or binoculars was implied. The text also gives a clue on the contemporary
method of computations. All calculations that are provided in the table
have Chennapuri (Madras/Chennai) as the reference and for the different places the correction for longitude is offered in minutes. Further, the actual timings of the event are given in terms of Shankuchchaya, which is the length of the shadow of a gnomon of 12 in. There is a subunit indicated with the abbreviation as vyam, which may mean a fraction of an inch, now forgotten. One may infer that a person interested in observing the event had to set up a gnomon and monitor the shadow length. Simultaneously, he had to watch the sun for catching a glimpse of the dark spot of Venus on the disc. How the two things had to be achieved practically remains a mystery.
The daily observation of the meridian transit of the sun as a ritual is hinted at as an essential technique for fixing the thithis. The last section also deals with citations from various texts, old and new, which emphasize the need for observations. Some of the texts like Brihat Samhita and Griha Laghava are well known.
However, there is a mention of some
authors whose works were perhaps used
as reference books. They are Mallari
Bhatta, Papu Devashstri of Kashi Vedhashala,
Srinivasa Dikshit, Vaidyanatha
Dikshita and Raja Tolappa, whose works
have not been documnented anywhere.
He further refers to correspondence with
Papu Devashastri. It may be worth searching
the books of these scholars.
The Indian context
Although Ragoonathachari served the
colonial government, he was aware of
the local expertise and drawbacks in this
field. He has put forward a suggestion
for setting up not one but several observatories
in India, arguing that a small
continent like Europe has several observatories.
Ragoonathachari expresses concern
about the valuable Sanskrit texts and offers
to render them into English. This request
appears in the English version of
the text available in the archives3. (It appears
that he was not well versed in Sanskrit,
according to the statement. This is
also reflected in the fact that there were
several typos and grammatical
errors in the Sanskrit verses written in
Kannada script; these were corrected
with the help of the original texts)5. He
has put forward a request for a sum of Rs
6000 for printing the copies to be distributed
to a selected list of people. He
also mentions that the proposed title is
Jyotishya Chintamani. There is a mention
of the financial help from the Nizam
of Hyderabad of Rs 1600; this may be
the reason for offering to bring out the
book in Telugu also. (He does not specify
the third language planned for translation.)
This text may be used to infer some
personal details about the author; for example,
his mother tongue. According to
language specialists6, the Kannada text is
authored by him and is not a translation.
This is inferred from the clarity in the
language and the flow. Mastery over the
content also is immediately apparent.
The figures are identical in the English
and Kannada versions, with numbers and
legends. However, in the Kannada text,
reference to figure 3 appears before figures
1 and 2, indicating that it was written
after the English version was prepared
and planned independently. There is a
reference to Madhwacharya, which may
hint at the author’s affiliation to the
Vaishnava community, established in
Udupi, Karnataka. The manuscript
appears to be handwritten and printed
perhaps using a technique like lithography.
This may be partly responsible for
the many spelling mistakes which could
not be corrected.
It appears that there was a strong opposition
from traditional astronomers for
the adoption of correction based on the
European system of calculation. Each
school continued making calendars according
to the texts prescribed by their
religious leaders. As a consequence the
errors added up to large values, although
by different amounts. Ragoonathachari
specifically refers to Thithi Nirnaya by
Madhwacharya. After several citations in
his defence, he argues that correction by
actual observations is the only solution.
It is interesting to note that he cites some
verses whose sources are unknown5. It is
worth searching those references, which
are likely to throw light on the development
of Indian astronomy during the colonial
period. He concludes with the
following statement which is valid even
‘There is an objection raised by many
people that these observed timings are
unsuitable for religious ceremonies because
several timings which need to be
observed with great difficulty show lot
of discrepancy although the timings are
exactly agreeable in case of eclipses.
This book gives the opportunity to absolve
these objections and I appeal to
all the experts and religious authorities
to view this book without bias and
publish their opinions supported by sacred
The method of estimation of the parallax
The text describes a simple explanation
of this procedure. The diagram (Figure 1)
is redrawn here with more legends for
the sake of clarity.
Consider the view from above the orbital
plane, i.e. the ecliptic. S is the sun,
circle A B C D denotes the equator of the
earth. Let us assume that four observers
are located at these points. The orbit of
Venus is marked and the position of Venus
is given by V and V ′ at two different
instants, which will be defined now. The
observer at A sees the western edge of
CURRENT SCIENCE, VOL. 96, NO. 9, 10 MAY 2009 1273
Venus touching the eastern edge of the
sun at an instant T, such that the sun (and
Venus) is on his meridian. As seen by the
observer at D, the sun is rising at his
eastern horizon and Venus is far away
from the sun. He cannot see Venus owing
to the brightness of the sky. The parallax
of Venus is defined as the angle
subtended by Venus at the earth’s radius.
This angle CVD is difficult to measure.
Now we may extend the lines CV and DV
to the celestial sphere to M and O. Thus
MVO will be same as CVD.
Horizontal parallax of Venus = angle
CVD = OM.
The parallax of the sun also is defined
with the radius of earth as the base. Angle
CSD is the parallax of the sun. Extending
CS and DS to the celestial sphere
we notice that CSD is the same as MSN.
Horizontal parallax of sun = angle
CSD = NM.
It can be shown that
since the angles involved are small.
The advantage of this explanation over
the method given by Halley is clear from
the following equation.
OM = ON + MN, (2)
where OM is the parallax of Venus,
MN = parallax of sun and ON = Relative
parallax of Venus with reference to the
sun = parallax of Venus – parallax of
Let V ′ be position of Venus seen by
the observer at D at the instant T′.
VV ′ = Relative parallax of Venus with
reference to the sun = ON.
At the instant T ′,
Parallax of Venus 1000 .
Parallas of sun 277
Here we assume that if 1000 units correspond
to the distance of the sun, 723 is
the distance to Venus. This ratio was accurately
Equations (2) and (3) are written in the
Kannada version as long, complicated
sentences. Equation (2) may be rewritten
Parallax of Venus Parallax of sun
Parallax of sun
1000 277 2.61.
= − = (4)
The numerator in eq. (4) is the relative
parallax corresponding to VV ′ or ON.
The transit of Venus gives an opportunity
to measure this precisely. As mentioned
earlier, the observer at D can, in
principle, measure this angle. However,
in reality this is not possible. Therefore,
he waits for Venus to reach V ′, which
corresponds to the first point of contact
as seen by him. This implies that the
time difference between sunrise and the
first contact is a measure of VV ′. Thus, it
is important that the observations be
made at places separated by 90 degrees
Equation (4) is written in the English
version (p. 14) as
Relative horizontal parallax 723 . Sun,s horizontal parallax 277
Here the equality symbol ‘=’ appears as
‘–’, causing confusion.
Thus the parallax of the sun is obtained
precisely. The ratio 2.61 can also
be calculated precisely knowing the relative
positions of Venus and the earth in
their respective orbits. The text further
describes the estimate of the distance to
Sine of the horizontal parallax of the sun
Earth,s radius in miles , . Sun s distance from the earth
This is a simplified version of the
method described by Halley, who generalizes
it to any two longitudes.
The convention of the Indian method
namely writing the sine as Jya, is followed
in the Kannada version. The tables
of Jya were available with mathematicians
in this format. Therefore, the result
has to be divided by R, which is called
1. Archives of IIA; http://hdl.handle.net/
2. Archives of IIA; http://hdl.handle.net/
3. Archives of IIA; http://hdl.handle.net/
4. Woolf, H., The Transit of Venus, A Study
of Eighteenth Century Science, Princeton
University Press, 1959.
5. Sripada Bhat, K., 2008, pers. commun.
6. Venkatasubbaiah, G., 2008, pers. commun.
ACKNOWLEDGEMENTS. The author acknowledges
the Director and Librarians of IIA
for providing access to the original manuscripts
in their archives. Funding was partly
provided by INSA. Author is grateful to Dr A.
Sripada Bhat of Sanskrit University, Tirupathi,
for the invaluable help in correcting the
typographical mistakes in Sanskrit verses and
in identifying the sources of these verses.
Helpful suggestions by Prof. G. Venkatasubbaiah
and comments from Prof. S. Balachancra
Rao have greatly enriched the final
B. S. Shylaja is with the Jawaharlal
Nehru Planetarium, High Grounds, Bangalore
560 001, India.