1°) The first journey to Cajaneborg (1761)

When Planman left for his first journey to Cajaneborg to observe the transit of Venus under the authority of the Royal Swedish Academy of Sciences, he held a tutor ship in astronomy at the University of Uppsala. He wasn’t only charged with the observation of the transit of Venus, but the Commission for the Survey of Finland also commissioned Planman to determine the geographical latitude and longitude of as much important places as possible. On the expedition he also carried out measurements with a pendulum in order to establish the flattening of the earth. He didn’t travel all by his own, but was accompanied by a number of assistants, including his younger brother Arvid Planman.

Set off from Uppsala, Planman had to cross the Åland Sea in order to reach the mainland of Finland. Although such boat trips were everyday business, this particular crossing turned out to be difficult, dangerous and therefore very unpleasant as well, as Planman became unwell and had to stay in Turku and Hämeenlinna (Tavastehus) for some time to recover. In order to make up for the lost time, he went on travelling the heavy going roads night and day. The need to hurry up and an ever cloudy sky but once prevented Planman to measure the latitude of the villages he passed by on his outward journey. Having announced his advent, Planman arrived at the vicarage of Jämsä in early April. Here, he was able to determine the latitude by measuring the sun’s altitude at noon with a newly designed geographical instrument.





At the end of April Planman’s expedition arrived at Cajaneborg, just in time to observe a total lunar eclipse on May 18 and a partial solar eclipse on June 3. These observations could help to establish the geographical longitude of Cajaneborg and were consequently eagerly performed in an accurate fashion with a respectable telescope of six feet focal length. Equipped!with a 21-feet telescope, a 5-feet telescope by Dollond and the above mentioned 6-feet telescope fitted with a micrometer, Planman set up for Venus’ showcase on the morning of June 6.

The transit of Venus would commence shortly after sunrise en end before noon. Next to his fellow workers, Planman was assisted by local parson Frosterus. No clouds intervened, but a thick smoke, produced by farmers burning brushwood, became a nuisance to Planman in the early ours after dawn – the air was darkened until 5 p.m., when at last a strong east wind blew away the smoke. At 3h 59m 56s he first noticed a dent in the south eastern edge of the solar disk, as though it had been cut with a knife. Within seconds the presence of Venus on the sun was apparent. At 4h 18m 5s Planman discerned Venus completely on the sun’s disk, but due to the smoky air he was uncertain of this timing. Though, this time differed from Frosterus determination only by two seconds. As seen through the small telescope, Venus seemed pitch-black, but with the 21-feet telescope he observed a reddish shimmer which faded towards the centre of Venus’ disk. From this peculiar phenomenon, Planman concluded that Venus should have a dense atmosphere. The edges of Venus and the sun touched at 10h 7m 59s and by the time of 10h 26m 22s Venus wasn’t on the sun’s disk anymore. At last interior contact, Planman’s assistant who counted the seconds at the clock, mistakenly attributed 10h 8m 59s to the time of contact, but happily this fault was discovered afterwards and accordingly corrected.

After his successful observation of the transit of Venus, Planman travelled to Oulu (Oleåborg) to see the medicinal springs, because for the next five to six weeks there was no astronomy to do in Cajaneborg. During his stay at Oulu, he paid a visit to father Pazelius at the vicarage of nearbyLiminka, an ardent amateur astronomer who had also observed the solar eclipse with but poor means. To Planman’s judgment, his dioptric telescope of 3 1/2 feet was only fit to observe the moon and therefore he offered Pazelius a lunar map by Riccioli and gave an explication of the use of it. Also, a proper way of determining the true time was lacking. Though Pazelius owned a quite accurate timepiece, it could only be corrected with reference to a nail’s shadow. To improve conditions, Planman constructed an accurate meridian line in one of the parsonage’s rooms. In early August Planman returned to Cajaneborg through Paltamo. Here he observed a couple of occultations of Jupiter’s satellites to secure the longitude of Cajaneborg even more accurately.

Next, in September he set off for his return trip; the survey of Finland could start now! Travelling through successively Sotkamo, Maanselkä and Nurmes, the party ended up at Lieksa in early October. Here, they had to pause for a little while, because their fellow traveller Arvid Planman fell seriously ill. This interlude was made used of to measure the geographical location of Lieksa by means of the occultations of Jupiter’s satellites. When Arvid had recovered, Planman carried on. Traveling through swamps and lakes by boat, sledge, horse and on foot, he reached the village of Liperi at the end of October. Anders Planman, in a worrying state of health and suffering a raging headache, was confined to bed for a period of three weeks. He therefore instructed his assistants to observe the occultations of Jupiter’s satellites so as to find the longitude of Liperi.

Being fully recovered, he reached Mikkeli halfway December, where he observed the occultation of the star Kappa Tauri by the moon. Meanwhile, temperatures had dropped below freezing point and a bitter cold caused Planman’s telescope to be covered with rime, making the timing of the occultation more difficult. The journey then continued through Sysmä to Asikkala. Eager to establish the geographical coordinates of this village, Planman felt compelled to travel on emptyhanded after days waiting in vain for the weather to improve. With Christmas time approaching, he went to his native village Hattula, a rural parish at that time, where he joined his family to celebrate Christmas and to regain his strength after his months long journey through the rivers, lakes and bogs of Finland.