Gallery of Masterpieces

The transits of Venus of 8 June 2004 and 6 June 2012

For the first time since 1882, on 8 june 2004 amateurs had the opportunity to observe and picture the transit of Venus in front of the Sun. Imagine that nobody on Earth had the chance to observe this event for 122 years !

This time Europe was at the first place to observe this event with a sky clear to parly cloudy in most area with temperatures over 20°C. Venus was at 43.1 millions km from the Earth at 0.288 AU only, showing a disk 5 times larger that the one of Mercury and twice as larger as the one of Mars at perihelic opposition, with an angular diameter of 57.7".

In the United States conversely, amateurs could only see the end of the transit because the event had already began several hours before the sunrise. As far as the weather conditions are concerned, in the early morning hours most photographs were recorded under a misty sky or partially cloudy, invaded with cumulus and stratus. 

Although the seeing conditions in the United States where not at all favorable for this kind of spectacle, some amateurs didn't hesitate to go out with their apochromatic refractor or their telelens to get some pictures of a great aesthetic value as show the three documents displayed below.

Venus Transit 2004 Animation

A 7.4 MB Mpeg simulation prepared by GSFC

Postcards from the States... At left, a general view of the Sun during the transit of Venus at 10h30 UT (5h30 EDT). Even naked eye, we could see the small black disk of Venus in front of the Sun. This very fine picture was taken by Abe Megahed from Olin Park in Madison, WI, with a reflex body Nikon D70 equipped with a 70 mm telelens. Inserts have been recorded with a 8" SCT and a Nikon Coolpix 450 digicam by 11h UT. At center a picture taken at third contact at 11h10 UT (6h10 CDT) by Steve Sprengel from Lincoln in Nebraska, with a reflex body Canon 300D equipped with a Tamron 28-300 XR-LD telelens. Exposure 1/800th sec. No solar filter was necessary in this morning hour. At right, even under bad conditions and with low cloud, this dramatic view of the Sun taken at 10h35 UT confirms that it is always possible to get pictures of great aesthetic value. It was taken by David Cortner at prime focus of an Astro-Physics 130 mm f/6 refractor equipped with a Nikon D100. Exposure 1/3200th at 200 ISO, without solar filter. The location was along the Catawba river near Connelly's Springs, NC. Keep up the excellent job, guys !

The equipement

Let's see now what kind of material used amateurs to record this event. Clubs and groups of amateurs often used optics from 50 to 300 mm wide with an ocular projection on a screen and thus without solar filter. When they worked alone, most amateurs used a solar filter offering a transmission lower than 1/1000th (optical density from 3 to 5), adjusted to the diameter of their objective or off-centered, sometimes simply attached with a rubber band when it was a simple flexible sheet.

Many amateurs used small achromatic refractors (doublets) like Orion ST-80 ED, Tele Vue Pronto 76 or 85, Celestron NexStar 102SLT or an apochromatic refractor equipped with an objective solar filter. Some amateurs fixed it on a simple tripod or on an equatorial mount, others fixed it in piggyback on a larger telescope that, for once, was used as guider.

Some lucky amateurs didn't hesitate to use their large Astro-Physics, Pentax, Takahashi or Zeiss apochromatic refractor from 100 to 200 mm of diameter, their Newton-Cassegrain or their Schmidt-Cassegrain scope from 125 to 300 mm (5-12") of diameter or a solar telescope equipped with an interferential filter.

Among the accessories used in this special occasion, let's quote the sun glasses protected with a polymer film, the Mylar sheet or the Baader AstroSolar film made of alumined polyester, the full-aperture metal-coated glass filter up to 250 mm in diameter (e.g. Orion Telescopes or Thousand Oaks Optical 2+), the Coronado (SolarMax) or Daystar Hα interferential filter, the Herschel wedge, the 1.8 and 2x Barlow lens and long focal eyepieces (32 to 12 mm).

At left, Math Heijen and his friends preparing the observation of the transit from Holland. The TAL 200K Klevtzov-Cassegrain, the Celestron "Comet cachter" 114 mm f/3.2, the binoculars and the camcorder are all protected with a Baader AstroSolar filter. At center, a terrestrial refractor 60 mm wide equipped with a 8 mm eyepiece (60x) projecting the Sun image on a screen durant Venus transit 2004 at 9h15 UT. This technique used by Tim Smith from Crawley, West Sussex, U.K., allows to several observers to follow the event with modest means. A right, the size of Venus during a transit on a 24x36-mm film or CCD according to the focal lenght of the scope. Using a 4000 mm, the respective size of the Sun and Venus is 36.7 mm and 1.1 mm across at the focal plane. Document S&T/Gregg Dindermann.

Among the cameras used, for close-ups all amateurs choosed a digital model, from the smallest webcam to the more recent DSLR or simply using HD camcorders.

About the coupling between the ocular system and the digicam, if most amateurs used a special T-ring suited to their body and worked at prime focus of their scope or by ocular projection with an extension ring, in several cases the objective of the digicam, the webcam or the camcorder could not be removed. In this case they worked afocal, placing the eyepiece or the ocular system close to the lens of their digicam, focusing to the infinite when possible and setting the optical zoom mode to the maximum.

They were some accidents without gravity like this amateur, although it was well informed, who saw his solar filter screwed on his eyepiece be broken under the Sun heat (this solution is disadvised for this reason), this other who noted that his Mylar filter was full of pinholes and who had in a hurry to block out all the prick holes with a fine point felt marker and black paint (hence the interest to buy a quality solar filter) to avoid parasitic glare or this other amateur who crashed his CCD camera and had to fall back on his digicam.&

Our preparations being finished and the transit being about to start, let's see some among the most beautiful images recorded during this event which, should it be pointed out, will not reproduce again before 2117.

To see : NASA Eclipse Web site

At the first look through the eyepiece, all amateurs where surprised by the size of Venus (we all have in mind the minuscule disk of Mercury) but still more by the sharpness of the disk, like cut with a knife. Indeed, we are used to see its crescent which is a bit fuzzy.

Thanks to eclipse glasses, even naked eye we could see the small black disk of Venus in front of the Sun. Definitely this event had to be spectacular, and it confimed our foreboding all along its evolution.

Animations of the transit of Venus of 8 June 2004 around the second (5h40 UT) and third (11h04 UT) contacts. Both sequences were recorded from CAST Observatory located at Talmassons in north Italy by Roland Ligustri and Lucio Furlanetto using a SCT Celestron C11 equipped with a Nikon Coolpix 4300 digicam in zoom mode 3x. Exposure 1/250th sec. under an AstroSolar filter. The left sequence extents from 05h20 to 05h42 UT, the right one from 11h00 to 11h20 UT. Clic on images to run the animated GIF (494 KB and 732 KB).

Venus Transit of 6 June 2012

On 6 June 2012, only observers living in the time zones +7 to +12h GMT (Russia-China-Philippines-Australia-New Zealand) had the opportunity to follow the entire transit of Venus. This time Venus passed in front of the higher part of the Sun as indicated above (the time indicates the greatest transit).

In Europe, the Sun rising only around 4h UT, in Berlin or London the observers only saw the end of the transit (3^rd and 4^th contact) which began in the U.S.A. by 22h UT. In Europe the Sun was only at 6° or 14° above l'horizon at the time of the 3^rd contact. Conversely in New York or Los Angeles amateurs assisted to the first phase of the transit (1^st and 2^nd contacts) a few times before the sunset.

Two stunning pictures of Venus Transit on 5-6 June 2012. A left, an image recorded by the Hinode spacecraft on June 5 at 22h26m53s UT just before the 2d contact. In front of the turbulent solar surface and its prominences note the thin ring of light surrounding the planet's dark silhouette; it is the sunlight refracted by Venus' thick atmosphere. At right, an image in yellow light recorded by the Solar Dynamics Observatory on 6 June 2012 just before the 3d contact. Documents JAXA, NASA, Lockheed Martin and NASA/SDO.

The black drop effect and the halo

Among the "side effects" that we were all waiting for since 1882, note the "black drop" effect at the instant of the 2^d and 3^d contact more or less visible on three of the next images (Ayiomamitis, Bishop and Chrisman) and the arc of light or halo in the atmosphere of Venus in three images recorded before the 2^d contact and after the 3^d contact (Comolli, Smaal and Seip). This effect lasted 20 minutes according to the observation made by Lorenzo Comolli using a 200 mm (8") SCT.

Both phenomena were already noticed by James Cook and Charles Green during an expedition in Tahiti in 1769 as displayed on the sketch at left, by the australian astronomer Henry Chamberlain Russell in 1874 and by the French astronomer Camille Flammarion in 1882.

Usually one told that the "black drop" effect becomes hard to see in scopes over 150 mm (6") of aperture but this time at least two american observers members of the Warren Astronomical Society, and using scopes of 250 mm f/10 (10") and 317 mm f/17 (12.5") observed it as shows very well the last picture at the end of this page. It was taken by Vince when the Sun was only 20° over the horizon, the scope tracking on Venus to get a stable image. But what is the origin of this strange effect ?

According to Thomas Van Flandern (1940-2009) from Meta Research Institute, "the black drop effect is caused by variable refraction from moving air cells in the Earth's atmosphere". 

Bradley Schaefer^[1] states that "the ideal image...will suffer smearing...that will produce a somewhat fuzzy image with contour lines (i.e., what is perceived as the edge) that are shaped like the Black Drop. The primary causes of smearing are the usual astronomical seeing (associated with small angle scattering in our Earth's atmosphere) and the usual diffraction in the telescope (the Airy pattern). Other contributing smearing mechanisms that generally do not dominate are imperfections in the telescope's optics, imperfections in the observer's eyes, the finite angular resolution of the detector, and even the physical size of the telescope's aperture". 

So for short, the "black drop" effect is first of all depending of the height of the Sun above the horizon (seeing), then of the diffraction effect, while the instrumental resolution, and thus the aperture of the scope comes far behind. Its 's good to know.

Here are the pictures. All images displayed below have been inverted, displaying the north at top and the west to the right, like observing the Sun naked eye. The chronology of events was also respected.

For more information

Planetary transits across the Sun, NASA-GSFC

2004 and 2012 Transits of Venus, by Fred Espenak/NASA-GSFC

Transit of Venus of 9 december 1874, by H.C.Russell

Where was the black drop ?, Sky & Telescope

The black drop effect, by Chuck Bueter

The Black drop effect, by Tom Van Flandern

Picture galleries

Transit of Venus observed by TRACE

Spaceweather

ESO Gallery of Venus Transit 2004

CAST Ossevatorio

Filters

Orion Telescopes & Binoculars (Metal-coated glass solar filter)

Baader-Planetarium (AstroSolar film made of alumined polyester)

Thousand Oaks Optical (Metal-coated glass filter, black polymer and Hα Lumicon filter)

Coronado (Hα filter)

Daystar (Hα filter)

See also my 1001 Links, Manufacturers.

Back to Gallery of Masterpieces

[1] Bradley Schaefer, "The Black Drop Effect", Journal for the History of Astronomy 32:4 (Nov. 2001), p334.