Aktivitäten mit dem Mond
Merkurtransit Mai 2003
Venustransit 8.6.2004
Astrofotografie 04/05
Historischer Rückblick
Verlauf des Tages

Venus Transit -
The Portuguese contribution and German participation on the international campaign of 1874 and 1882
Common Project of Escola Secundaria de Albufeira (P) and Schloßgymnasium Düsseldorf (D)

A transit is when a star or an astronomical body   passes in front of another greater without occulting. In the eclipses, one of the objects hides the other significantly.  A transit of Venus or Mercury in front to the sun is therefore the visual travel of one of these planets for our star.  What it is seen is only one small point to pass slowly in front to the sun, so small that we have to be prepared to see. Mercury and Venus are inner planets, which pass in front to the sun.  During centuries, nobody saw Mercury or Venus to be crossed in front to the sun.  Some medieval astronomers had arrived to think that this happened for these two planets because they were transparent.

In beginning of XVII century, the german astronomer Johannes Kepler supposed that the orbits of the planets were ellipses and this allowed to foresee the movement it of the astros with much severity and to verify that exacts alignments of planets were rare. Build tables that had been famous, the Rudolfinas tables.  When making the calculations to complete them, perceived that Mercury if went to interpose between the Earth and the sun in 1631. Died one year before this date and cannot verify if his prediction was right.  Kepler was the first one to understand the reason because the mercury transits and Venus are rare. Pierre Gassendi had in account the invites made by Kepler and started to observe Mercury two days before the date that this had foreseen. Pierre Gassendi was the first astronomer to observe a planetary transit, Kepler had made a mistake in only five hours!  The first transit of Venus was seen in 4 of December of 1639 by Horrocks.  This remade the calculations of Kepler and verified that this had left to pass the 1639 transit.    Throughout centuries the Astronomers had obtained reasonable estimates of the relative distances of the solar system.

After Copernicus and Kepler, disposal of the planets and its orbits was known it.  For extraordinary creative geometric processes, it was obtained a reasonable idea of the relative distances in the solar system, but it lacks to know in the distance absolute (real) of the Earth to the Sun.  Halley understood that a transit of a planet would allow to discover this distance.  This English astronomer suggested that the transit was observed from different places, it was possible determine the solar parallax and the astronomical unit (dist. Earth-Sun) different one.   

Halley had correspondence with other astronomers, as Deslile that also was corresponded with many astronomers (mainly European).  This astronomer proposed alterations to the method considered for Halley to calculate the solar parallax, according to it, it was not necessary to observe all the transit but at least one or two moments (entered and exit).

Deslile sent letters with instructions for many countries and among these countries was Portugal, where its main interlocutor was João Chevalier. João Chevalier had a relation of great friendship with another portuguese astronomer, Teodoro de Almeida.  João Chevalier could not observe the transit of Venus of 6 of June of 1761 because political reasons, he was forced to running away for France in 1760.  Teodóro de Almeida was exiled in the city of Porto to the date of the transit of 6 of June of 1761.  It observed the transit of the planet and elaborated a register that the João Chevalier sent to Paris, and arrived at the hands of Deslile.  For beyond Teodoro de Almeida, the transit of Vénus of 1761 still was observed by others two Portuguese observers, Miguel Ciera in Lisbon (in the “Colégio dos Nobres”) and Soares Barros in Paris (in the monastery of Genoveve Saint).

Teodoro de Almeida is placed with frequency in a list of 20 detached observers of the transit of 1761 of about 120 that observed the transit it, fact that demonstrates the attributed importance to this comment.





Teodoro de Almeida (1722-1804)

Observation of Teodoro de Almeida, publish in “Mémories de Mathématique et Physique, Presentés à l’académie Royale des Sciences, par divers savants & lûs dans ses assenblées, 1774 (Bibliothèque Nationale de France)



The German expeditions of 1874 and 1882


During the “ Deutsches Kaiserreich (1871-1918) “ five expeditions to the Venustransit 1874 and four expeditions to the Venustransit 1882 were prepared. They were coordinated by the astronomers Auwers and Foerster. The best conditions for observing Venustransit 1874 were given in the Indean Ocean. To reach a noticeable effect by the parallax-effect the observation-stations were built in the northern hemisphere in Tschifu (China) and Isfahan (Persia), and in the southern Hemispere in Mauritius, in Kegulen (French South Territories) and in Auckland (South of Newseeland).


Expedition 1

The first expedition (Tschifu) was performed by Wilhelm Valentiner, astronomer from Leiden (Netherlands), Carl Adolph from  Elberfeld (today Wuppertal), Eugen Reimann from Ratibor (Oberschlesien) and the photographer Carl Kardaetz from  Franzoesisch Buchholz near  Berlin. Two assistants were added: the mechanic  Friedrich Deichmüller from Leipzig and the painter Oskar Eschke from Berlin.

The two month trip from Southampton to Shanghai was overcome with English steamers; with a small ship they arrived at Tschifu on October 27th - in addition to the expedition members,  107 bags of 14 tons of weight in total. The station was surrounded by a wall and secured, where the team of the ship  Arcona that was stationed in East Asian waters, gave help. We take the following from a letter of Kardaetz from Tschifu:


»Day before we were afraid because of the bad weather, full with thousands of fears. Sleeping was not possible. We had luck, the wind turned and chased the clouds.  At night around 3 o'clock we had the most marvellous sunrise. Everything was at early 7 o'clock in its place.  Mr. Baron of Reibnitz, Commandant Sr. Majesty’s ship Arcona said: » The location looks like  the deck of a tank frigate, which is clarified for the fight.«. All ships in the port had flown flags, all ambassies showed flags and many private houses presented their festive flags; the Chinese in the city burned down fireworks at sunrise and  asked for a clear sun through it. The requests are fullfilled, because we had quite clear weather about two hours long. To end of the phenomenon namely with the last plate, it was also past as cut off, the sky wrapped itself completely in clouds. Day after we had in the morning snow and hail«


The members of expedition 2 (Bettsy Cove, Kerguelen lsland) were Carl Börgen, director the Navy-Observatorium in Wilhelmshaven, Arthur Wittsteinkind from Munich, Theophil Studer of the Zoological Museum of the University of Bern, Ladislaus Weinek from Budapest, the photographer H. Bobzin and of the mechanics Carl Krille, both from Schwerin.
The Kerguelen expedition was part of an almost two-year investigation trip by the steam corvette “M.S. Gazelle” which was also used for oceanographic, geographic and  zoological investigations. The gazelle left Kiel  on June 21st , sailed to Capetown, and arrived in Betsy Cove on October 26th, and on the next day began the look-up to a place for the station.
Börgen noted : »An of the southern side of the Cove arises the terrain  to a hill which ascends in the last 40 feet at steep rock measures. On half height tipped over us we saw  a number white crosses which signed the graves of the whale hunters.  The only to some extent dry spot that was also flat found itself above the graves. We decided to choose this place for our camp.«
 Ladislaus Weinek wrote his impressions the Venus transition :>> It rained in the evening of December 8th: at the 9th, the day of the phenomenon, the sun rised clear and friendly. The entry of Venus into the solar disc was immediately after 6 ½ o’clock in the morning, the withdrawal at 11 o'clock. Several minutes before the calculated time everybody hurried on his posts, the astronomers to their telescopes, the photographer into the darkroom, Börgen stood at the heliometer, Weinek at the refractor and the Wittstein at the telescope.- Meanwhile the sky was covered by a rather dense cloud veil; in the west over the snow covered mountains were stored dark clouds. The Venus, a small black spot of 1/30 of the solar diameter, began to shift itself into the sun. We expected the so-called second or inner touch of the two edges with tension; because if we could observe the phenomena in a successful manner, we could say, we were  not in vain in this unhospitable region The crucial momentum already approaches, everybody  looks again to the ticking chronometer in order to control the seconds counted in thoughts. The Venus already seems to want to free itself from the solar edge,  a bridge is build, which becomes thinner and is  divided. This was the momentum to be observed. We had fixed him with joy. - while the Venus is now freely in the sun, the work of an astronomer changes; now begin the distance measurements of Venus from solar center Börgen remained at the eyepieces of the heliometer, Wittstein determined continuously the scale of the objective ; on the other hand, Weinek accompanied by Crille hurried to the photographic heliograph. The first one did the exposition, the second changed the photographic plates, which were processed by Bobzin and Studer in the darkroom.

[...] We were satisfied with the images of the transit especially since the observation of the inner and external contact of Venus also succeeded completely. After December 9th bleak and stormy weather followed [...]again so that we had to wait until December 19th, to do futher sun photographs again.«

End of January the station was broken off and we started the trip home. We arrived in Mauritius on February 26th, where the astronomers travelled back with a mail steamer, while the ship Gazelle continued its trip with Dr. Studer around the world. He returned in April 1876 to Kiel.
Expedition 3

The third expedition  (Port Ross, Auckland Island) consisted of two astronomers, Hugo Seeliger (Bonn) and Wilhelm Schnur (Strßburg), two photographers Herrmann Krone and G. Wofram (both Dresden), and two assistants, the mechanic Leyser jun. (Leipzig) and Johannes Krone (Dresden).

Most participants traveled to Melbourne by means of steamers in 53 days of London where they were already expected by Seeliger and two naval officers. The chartered bark» Alexandrine « transported the  researcher, cases and a wooden residential building to the Auckland Island, where the station was built up at the shore of the Terror Cove close to the settlement Port Ross.

From October 1874 18th until  March 1875 6th, the Auckland station remained acting. The best insight offer the images, reports and poems by Herman Krone , one of the pioneers of photography. He published  in journals, he made three video series the Auckland islands, and he wrote several volumes around 1900 in which the events of 1874 are reported in form of a modern Odyssee.

Expedition 4


The fourth expedition (Solitude, Mauritius) consisted of the two astronomers Moritz Loew (Berlin) and Carl Frederik Pechüle (Hamburg) and two assistants, the mechanic Herman Doelter from Strassburg and the janitor of the Goettinger observatory, Dietrich Heidorn.

They had chosen Mauritius, because in the case of possible failures of the expeditions to  Kerguelen and Auckland a further, meteorologically more reliable southern site is available. A free face, close to an uninhabited country house - Solitude -, place in the southeast of the island at a railroad track appeared as a suitable site because in the northeast, an English expedition has found a location for their observations. The weather was extremely bad, some heliometer measurements nevertheless reach through clouds.

Expediton 5

The four members of expedition 5 (Isfahan) were the photographer Gustav Fritsch, assistant on the anatomical institute of the Berlin university, the astronomer Ernst Becker, Observator at the Berlin observatory and two further photographers, Franz Stolze from Berlin and Hugo Buchwald from Breslau.

Some of the thrilling personalities of the project belonged to this expedition. Franz Stolze was the son of the inventor of stenography »System Stolze«. At the end of his astronomical studies, he participated in an archaeological expedition, his series of photographic images appeared as a collection» Persepolis «. He developed a new gas turbine in Berlin later. Gustav Fritsch led an immotional and versatile life. A three year trip through Africa was reported in an adventure book in the way the german author Karl May wrotes his famous stories. Astronomical expeditions followed to Aden and Isfahan. He wrote scientific treatises on electrical pisces, the eye and the growth of hair of the human being. A combination of the combination of anatomy, art and photography he published in his book »Nackte Schoenheit«, where for photographs of »Akteurs« of every sex and of every age are shown with critical comments of Fritsch. Such a colored bird had little chances in the academic hierarchy: His career ended as a extraordinary professor.


The trip of the Persian expedition started with the railroad trip to Wolgograd, then with a steamer on the Wolga to Astrachan, over the Kaspian Sea to the port of Rescht, then with a caravan of 58 pack-animals to Teheran. After an audience of the Schah, the caravan continued its way to Isfahan where a »Gartenpalais( gardenhouse)« was constructed in the direct proximity of the astronomical  instruments .

The photographic observations to those one had linked great expectations proved as a disappointment. The heliographs had no parallactic mounting with an exception because exposure times were chosen so short, that the sun was represented sharply. In this case, one had ignored that turbulence of the air unrest can cause a strong distortion of the pictures. Wilhelm forester writes in his life memories and life hopes (1911):

» during our preparatory works we tied to limit the effects of sunlight on the photographic plate to the shortest possible time, and we succeeded, in limiting the time of exposure of the plate to  ten thousand of a second. We could attain sharp pictures of the solar disc and of the details [...] only this way. When however we now went to the finest measuring of the photographic solar images of our Venus expeditions of 1874, the  solar pictures were completely unsuitable  for the finest measurement results, namely because of the until then not sufficiently recognized enormous variations, which the direction of propagation of the rays of light suffer  by the steady modifications of the states of the different regions of the atmosphere. «
The solar edge was defined badly, the Venus picture appeared distorted. Auwers, as a classical astronomer with critism towards  the modern photography, decided without far too big resistance of team to refuse completely to photographic images for the Transit of 1882,  not only  from financial reasons.

The costs might at this point be mentioned: the effort of the photograph, the higher personnel costs and costs of materials combined with expenditures for building  observation stations at faraway places resulted in the fact that the expeditions in 1874 being more expensive than the later ones: 620000 marks compared to 80.000 Euro. About 2/3 pure expedition costs and 1/3 was employed for instruments, domes and other costs. The total costs correspond to a contemporary value of about twelve millions Euro - for instance, '/3 of the German year contribution to the European southern observatory ESO.


The Expeditions of 1882

The Venus transition was favorably to observe in the western hemisphere. Four expeditions were furnished in 1882: two to the United States (Hartford, Connecticut and Aiken, South Carolina), one to Argentina (Bahia Bianca) and one to Chile (Punta Arenas). In addition, the German polar expedition had been equipped on the island of Sued-Georgien with a dome sited south of the Falklands and a fifth heliometer.

The first expedition  (Hartford) consisted of four participants, Gustav Müller, assistant on the astrophysical observatory in Potsdam, Friedrich Deichmüller, observator of the Bonn Observatory, the student of astronomy Julius Bauschinger from Munich and the technical assistant Herman Doelter of Diedenhofen (Thionville, Lorraine). The later had already assisted in Mauritius before

The delegation accepted an invitation of professors of the Trinity college sited outside of the city to build up the station there. Their activity is documented in a long official report of Müller and a contribution in Frank Leslie's Illustrated Newspaper.  One the day before the transition the snow melted, it rained at the night, and it was in the morning cloudy. The sky cleared up an hour to entry. The team began with measurements on the heiometer. However the third contact was disturbed by clouds a little.

The four members of second expedition (Aiken) were Julius Franz, Observator at the Königsberger Observatory, Herman Kobold, Observator at the Konkoly-Observatory in Hungaria, the Adolf Marcuse, astronomy-student of Berlin and the mechanic F. Carl of Würzburg.

Franz gave a full report in the “ Schriften der Königsberger Gesellschaft”. The trip started by steam-ship to New York and from there with the railroad to Aiken in South Carolina.  This small city with only 2000 inhabitants is steadily growing and from many foreigners because of the mild climate is considered as a climatic health resort. The station was constructed at the northern edge of the city.

In the morning of the decisive day the sky was covered, however, cleared itself gradual. The first test of 16 observations occurred through dense clouds, two further through lighter veils. On December 22nd, the team returned from New York to Hamburg  on the steamer Cimbria, that - for luck for the astronomer – sank during its next crossing of the  Atlantic to the bottom of the ocean.


The four members of the third expedition (Bahia Bianca) were Ernst Hartwig, assistant on the Strassburg-Observatory, Bruno Peter, Observator on the Leipzig-Observatory, the astronomy student Walter Wislicenus from Strassburg and the mechanic H. Mayer from Munich.

Peter wrote a report for the bulletin of the Academy in Cordoba whom we take the following: The trip was made on steamers of Hamburg to Buenos Aires and from there with a small warship of the Argentine Government to Bahia Bianca. As a location a small farm was chose about one mile west of the small town. Peter writes: » The used terrain was fenced in with strings in order to protect it against the animals which free in the pampas lived. «
On the day of the transition the sun rose in a cloud shift and was visible only few moments. The clouds removed themselves ten minutes before the first contact, the contact was observed. But clouds then shifted themselves before the sun again. It cleared, two series of measurements are done, strong wind drove new clouds here, it began to may rain. Then the sun was visible again, the measurements became consecutive, and also the third and fourth contact could be observed.


The fourth expedition (Punta arena) consisted of the astronomers Friedrich Kuestner and Paul Kempf from Berlin, the geologists Gustav Steinmann of Straßburg and the mechanic Friedrich Schwab from Marburg. Auwers decided to follow the expedition. They traveled with the steamer to Montevideo and long from there one after Punta arena. The official report only quotes short diary memos.

We let follow some arcades of public speech published from Auwers' elsewhere: » The place [Punta Arenas] now only counts for instance one and a half thousand inhabitants and is only a group wooden houses scattered on a green lawn.
Their appearance in primitive forms and in the natural colour of weathered wood fits just into the landscape.« At the lighthouse, the station was built up. They began to prepare for the transition by means of observations at an artificial model. Auwers writes: » In the afternoon of the 5th  [December] the rain at so normal thickness let our hopes sank deep. [...] The rising sun rising made a transparently blue sky; only flocks of small cumuli rose behind the Cordillere .« The first contact occurred and twenty minutes later the important second: » Just the Venus is entering the edge of the sun, a dense cloud slips before the sun. As she has gone one and a half minutes later, Venus stands completely inside the sun.>> Nevertheless the team succeeded in many heliometer observations as well as in the determinations of the times of the third and fourth contact.


The fifth Expedition (Sued-Georgien) was a »non regular « undertaking. The expedition of Germans Polar-Commission of the year 1882/83 led to the island Sued-Georgien. The station in the Moltke-Bay was inhabited from August 20th, 1882 by September 6th of the following year by eleven persons. The observations were managed by Carl Schrader, an Observator of the of Hamburg Observatory. He was assisted by the physicists O. Clauss and P.Vogel and the engineer E. Mosthaff.


The Venus transition occurred in the case of clear sky, however presumably considerable air unrest. Mosthaff reports: »Most favorable ran the observation of the Venus transition on December 6th, in spite of vehement tempest that in such a way brought the revolving dome into danger that the same has to be hold by three and four man on cables. nevertheless a very favorable result was supplied, because the weather all day long was bright and the sun remains clear.«  From Auwers' comments follows, that because of reading errors and of  bad calibration of the employed heliometer the observations of the Station Sued-Georgien was only of small benefit.


The actual observations were finished. But further investigations of the qualities of the heliometers were necessary. Little by little the results of the expeditions, the instructions and reports, measurements and reductions, and finally also the final results were published by Auwers: six large-formats volumes, which contained more than 3600 pages were written. Auwers was not only meticulous in the list of the reports and of the data, he also held correct arrangement in his correspondence and in such a way, the administrative unit of writings and answers exists in 110 files today, manuscripts, bills, receipts, telegrams, sea boards, plans, photographs, provided often with receipt stamp and inventory number.


The Report of Auwers is only a aspect of the project. Expedition participants wrote popular reports about their experiences - some samples were given here. In letters of Fritsch to Förster, Fritsch claims on the often “bookkeeping and arrogant attitude” of Auwers. Although only a correct pedant could lead the project to a successful end, shared by different temperaments of researchers and assistants. And how the result lookes like?

Auwers compiles all contact observations meticulously, without determining the solar parallax after Halley’s method – no doubt with good reason – (Vol. 6, P. 49). The results of the photographic observations of the four stops of 1874 (Vol. 6, P. 186) follow.  A solar parallax derives Auwers from this from 8.810 ± 0.120 arcseconds.

The detailed analysis of the Heliometer observations then follows (Vol. 6, P. 714).
 Auwers calculates a value of 8.8796 ± 0.0320 arcseconds. Interesting is, that the photographic result includes the modern value of the solar parallax (8.794142 arc seconds) within a disappointingly great mistake. The result of the heliometer is almost 1 % too large. Apparently in case of the Heliometer measurements there occurred systematical mistakes, whose existence Auwers did not note and whose reason in our days cannot be revailed.

At the time, when Auwers closed the manuscript of the last volume, detected Gustav Witt and Felix Linke at the Berlin Urania Observatory detected onto single photography a minor planet that received the name Eros and that can come very close to the path of earth. The Eros opposition of 1900 provided a value of the solar parallax whose accuracy overcome all former values. In this way, interest went out rapidly and thoroughly at the Venus transitions. It awoke again, since such events again be present in our days.

Science will only give little attention to the phenomenon today. However in amateur associations and schools the Venustransit is one of the thrilling events in the life of the students and teachers.




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