Venus Transits the Sun, 2012 June 6

The transit of Venus in June 2012 will be an opportunity to see one of the rarest astronomical events - weather permitting. No one alive today has seen a transit of Venus from New Zealand. The transit in June 2004 was visible from the other side of the Earth. Before that the previous transit was in December 1882, there were none in the 20th century.

Viewing the transit.

To view the transit it will be necessary to use suitable eye protection see note above. Any attempt to view the Sun without suitable protection will result in permanent eye damage or blindness. Apart from that you wouldn't see the planet on the Sun's disk - the glare would be too great.

With suitable eye protection to cut down the Sun's brightness, by 99.9%+, or by projecting an image of the Sun onto a white surface, Venus will be visible during the transit as a small black dot on the Sun's disk. Venus will be only 3% of the diameter of the Sun, so very small. It will be an intensely black spot in contrast to the bright solar disk which will make it stand out.

If you are able to link up with your local astronomical society, it is likely they will have specially prepared equipment which will allow a larger image of the Sun to be viewed. Many have web sites, they are likely to publish their observing programmes on them.

What you can expect to see.

During the over 6 hours of the transit Venus will be visible (using suitable eye protection to cut down the Sun's glare) as an intensely black dot making its way across the face of the Sun. The 2012 transit will last for nearly six and a half hours as seen in New Zealand, so its motion across the Sun will be very slow. All stages of the transit will be visible from New Zealand, although the final part, just before Venus moves off the Sun, will occur with the Sun very low. This part is only likely to be visible from places with a very low horizon to the west. The time of mid transit is just before 1.30 pm, so near the time the Sun is highest, but even so, being close to mid-winter, the Sun will be rather low, especially from the south of the country.

Where the transit can be seen

The world maps show the hemisphere from which the start and end of the transit is visible. The start is shown in the left diagram and the end on the right. The Sun is so low in NZ at the end of the transit that NZ is lost at the edge of the second map. As can be seen, Eastern Australia will have good views with the Sun at a reasonable altitude throughout, but the northern hemisphere is better placed with the Sun higher. Japan looks to be one of the best places to see the entire transit. For an observer at Hawaii, close to the centre of the first map, the Sun will be directly overhead at the start. Similarly it will be almost overhead at the Philippines at the end.

The best views in New Zealand will be obtained from the extreme north where the Sun is highest, especially towards the end of the transit in late afternoon. From North Cape the Sun will be 7° up as Venus moves off the Sun, higher than anywhere else in NZ. The sun is lowest at the end of the transit along the east coast of the North Island, with an altitude only 1° from East Cape through to Gisborne, Napier, Hastings and in the Wairarapa.

The path of Venus across the face of the Sun
	In this diagram the south of the Sun has been kept at the top, with east to the right. Venus crosses the northern hemisphere of the Sun, the lower part as seen from New Zealand. The planet will be visible as a black dot only while crossing the face of the Sun. It will not be visible at all when off the Sun even though its position is shown on the diagram. Stages and their times as seen from New Zealand are:    1. Exterior ingress, first contact with Sun, 10.15.37 am.    2. Interior ingress, second contact with Sun, 10.33.45 am.    Mid transit, Venus closest to center of the Sun, 1.29.19 pm.    3. Interior egress, third contact with Sun, 4.25.23 pm.    4. Exterior egress, fourth contact with Sun, 4.43.38 pm. The times shown are for Wellington. Times at other places vary by a few seconds. See transit times for places in New Zealand and Australia
The path of Venus across the Sun - New Zealand view
	As the Sun moves from east to west across the sky it appears to rotate in an anticlockwise direction, just as the constellations do through the night. This makes the south point of the Sun swing from right to left as the Sun crosses the sky. In this diagram the top of the Sun as seen from New Zealand is kept at the top of the diagram. The resulting apparent positions of Venus on the Sun's disk are marked every half hour, with times, using NZST, shown at hourly intervals from close to the start to close to the end of the transit. This shows the apparent path of Venus across the Sun, an observer, using suitable eye filters, would see from direct viewing of it. A similar view would result If the image of the Sun is projected onto a screen using binoculars. If a telescope is used the image is likely to be inverted. An equatorial mounted telescope will show a direct path across the sun similar to that in the previous diagram. Don't forget the Sun must not be viewed directly through binoculars or a telescope unless the instrument is fitted with a specially designed solar filter. The filter MUST be at the front of the telescope, NOT the viewing end.

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Times of stages of the transit for places in New Zealand (NZST) and Australia (UT)

               Exterior INGRESS Interior       Maximum       Interior EGRESS Exterior
Site              am.     Alt     am.         pm.     Alt       pm.       pm.     Alt
                h  m  s  deg    h  m  s     h  m  s   deg     h  m  s   h  m  s   deg
Auckland       10 15 31   24   10 33 37     1 29 10    28     4 25 15   4 43 28    4
Christchurch   10 15 43   17   10 33 52     1 29 29    23     4 25 32   4 43 46    2
Dunedin        10 15 48   15   10 33 58     1 29 39    21     4 25 41   4 43 56    2
Gisborne       10 15 26   24   10 33 33     1 29  4    26     4 25 13   4 43 28    1
Greymouth      10 15 45   18   10 33 53     1 29 31    24     4 25 32   4 43 46    3
Hamilton       10 15 31   23   10 33 38     1 29 10    27     4 25 16   4 43 29    3
Invercargill   10 15 51   13   10 34  2     1 29 46    20     4 25 47   4 44  1    3
Napier         10 15 30   22   10 33 37     1 29  9    25     4 25 16   4 43 31    1
Nelson         10 15 40   20   10 33 48     1 29 23    25     4 25 26   4 43 40    3
New Plymouth   10 15 36   21   10 33 43     1 29 16    27     4 25 20   4 43 34    3
Palmerston N   10 15 34   21   10 33 41     1 29 14    25     4 25 20   4 43 34    2
Queenstown     10 15 50   15   10 34  1     1 29 43    22     4 25 43   4 43 56    3
Stewart Is     10 15 53   12   10 34  4     1 29 50    20     4 25 51   4 44  5    2
Taupo          10 15 31   23   10 33 38     1 29  9    26     4 25 16   4 43 30    2
Tauranga       10 15 29   24   10 33 36     1 29  7    27     4 25 14   4 43 28    3
Timaru         10 15 46   16   10 33 55     1 29 35    22     4 25 37   4 43 51    2
Wellington     10 15 37   20   10 33 45     1 29 19    24     4 25 23   4 43 38    2
Whakatane      10 15 28   24   10 33 34     1 29  5    27     4 25 13   4 43 28    2
Whangarei      10 15 30   25   10 33 36     1 29  9    30     4 25 14   4 43 27    5

    Times (U.T.) of the stages of the Transit of Venus for places in Australia 2012 June 6

                Exterior INGRESS Interior      Maximum       Interior EGRESS Exterior
Site              U.T.    Alt     U.T.        U.T.    Alt       U.T.      U.T.    Alt
                h  m  s   deg   h  m  s     h  m  s   deg     h  m  s   h  m  s   deg
Adelaide       22 16  7-   4   22 34 18-    1 31  8    30     4 27  8   4 45  9   26
Alice Springs  22 15 45-   6   22 33 53-    1 31 18    39     4 27 36   4 45 32   38
Brisbane       22 15 49-  19   22 33 55-    1 30 11    40     4 26  8   4 44 10   24
Cairns         22 15 26-  19   22 33 30-    1 30 27    49     4 26 45   4 44 41   36
Canberra       22 16  5-  11   22 34 15-    1 30 32    32     4 26 24   4 44 29   21
Darwin         22 15  8-   9   22 33 13-    1 31 21    47     4 28 10   4 45 59   49
Hobart         22 16 12-   6   22 34 24-    1 30 44    24     4 26 38   4 44 45   16
Melbourne      22 16 10-   7   22 34 21-    1 30 48    29     4 26 42   4 44 46   21
Perth               Before sunrise          1 32 19    23     4 29  3   4 46 58   35
Sydney         22 16  2-  13   22 34 11-    1 30 24    33     4 26 17   4 44 21   21

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The impossible view: the transit as "seen" from the Sun

The diagrams below give an impression of the view from the Sun where Venus would be seen to occult the Earth. The observer is imagined situated in the middle of the black dot, diagram above, representing the silhouette of Venus on the Sun close to the time of mid transit in New Zealand. From such a position on the Sun, Venus would be seen to move in front of the Earth, that is occult it. From anywhere on the Sun outside the black spot, Venus would be seen to miss the Earth, passing either above or below it. Venus is actually slightly smaller than the Earth, but looks larger in these diagrams because it is closer to the Sun.

The times on the diagram are UT, but can be taken as New Zealand time, pm. It only takes 26 minutes for Venus to move completely across the Earth, this would correspond to the silhouette of Venus to moving more than its own diameter across the Sun.

The Earth has been kept fixed at the middle of each diagram. In reality it would move a distance equal to its own diameter to the east, left, in 7 minutes . This motion would have to be added to Venus as well. At the time of the transit the moon would appear to be just on 11 Earth diameter to the east, left of the Earth.

	Venus makes its first contact the Earth.
	Venus is about half way across the Earth.
	Venus centrally covers the Earth. The position of the centre of the Earth is shown by the red cross.
	Venus is about half way off the Earth.
	Venus moves off the Earth making its last contact.