Transit of Venus 2012
by Lorenzo Comolli

The Transit of Venus of 6 June 2012 was the last one I'll observe in my life, being the next one in 2117. I moved South toward the Apennines because of the changeable weather of my home region. Moreover the altitude helped to reduce the lower clouds. The selected location was Pian dell'Armà, at the "prato dei milanesi" (44°42'57"N, 9°12'33"E, 1365 m elev.).

This phenomena has many interesting aspects, both historical and scientific. Now astronomers observe the Venus atmosphere, that produces a faint and thin aureole between the ingress and egress phases. An example of a professional paper is Tanga et al., Icarus 2012, where I was honored to contribute with my 2004 data.

The local conditions in Italy where quite bad, with the Sun rising at local 5.36, only an hour before the transit egress. But this was an opportunity for nice portraits of the Sun rising with Venus. The egress phase was observed at about 10° elevation, and so the seeing was really very bad.

I observed with a TEC 140 apo refractor (140 mm f/7), and I imaged using a Canon 5D for rising and a Philips Vesta Pro (BW mod) for the egress phase. I planned to image the Venus aureole with a 3x barlow, but the seeing was so bad that I removed and imaged at direct focus. The resulting images are absolutely not good, but nevertheless I've tried to process them to evidence a little part of the North Pole of Venus.
I shared the observing trip wit Emmanuele Sordini, which observed with a similar setup. See below for the images of the observing field.

While I moved on the Apennines, my father remained at home and he was indeed able to image the transit, except the rising that was obscured by low clouds. He observed with a Pentax 75 apo refractor (75 mm f/6.7) and a Canon 350D, with a glass solar filter.

See also my pre-transit images of 2 and 4 June 2012, showing the large cusp extension while Venus is at 2° from the Sun.


Venus aureole at egress. Because of bad seeing from my observing location I was not able to capture the ring of fire like in 2004. Nevertheless a very faint aureole on the North Pole of Venus was visible. This image is a composition of a short exposure for the Sun (time 4.46.55 UT) and long exposure for the aureole (time 4.46.28 UT). For more data, please refer to the image below.

The egress phase was imaged alternatively with long and short exposures, from 1/100 s to 1/2500 s. Each panel is a composition of frames extracted from the captured video. I was able to observe the atmosphere of Venus for about 7 minutes, from 4.41 to 4.48 UT.

The seeing was really very bad, so that I needed to reduce the focal length from 3 m to only 1 m, by removing the 3x barlow lens. This video was obtained with the barlow on, at 4.16 UT, with the Sun at about 5° elevation. TEC 140, webcam Philips Vesta Pro (BW mod), barlow 3x.

Sunrise with Venus and the green rim. Note also the differential refraction in the Venus disk (red rim above, blue-green rim below). TEC140, 5D, ND3.8 astrosolar, 1/30 s, 100 ISO, 4.49 UT.

Same as above, full field of view.

Rising above the low clouds. TEC140, 5D, ND3.8 astrosolar, 1/160 s, 100 ISO, 4.53 UT.

Nearly free of clouds. TEC140, 5D, ND3.8 astrosolar, 1/320 s, 100 ISO, 4.58 UT.

First glimpses of Venus between clouds. Imaged by my father from Tradate (VA). Pentax 75, 350D, glass solar filter, 1/15 s, 400 ISO, 5.07 UT.

A banded Sun with Venus in transit. Imaged by my father from Tradate (VA). Pentax 75, 350D, glass solar filter, 1/50 s, 400 ISO, 5.16 UT.

My main setup in the Apennines: TEC 140 + 5D.

Emmanuele (left) and me (right) at the end of the transit.

Emmanuele (left) and me (right) at the end of the transit.

TEC 140 with Baader ND 3.8 astrosolar filter.

The setup of Emmanuele, a Vixen 102 ED refractor with a Chamaleon camera.

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