The transition of Venus in 6/6/2012

[willis]

I used the Stellarium to simulate the transition of Venus in 6/6/2012. I found that the path of Venus on the sun disc during the transition would be funny. In contrast to that of 2004, which is basically a straight line, http://www.hko.gov.hk/gts/event/event-v ... nsit_e.htm, the path is a non-trial curve with non-uniform speed. The first contact will be at about 06:08. It will move on a curve of small curvature. As it approaching the edge of the sun at about 12:00, it will not leave the sun but will move close to the edge and accelerate within the sun accordingly. It will move about 180o, half of the circumference of the sun, and finally will leave the sun at 12:42. This means that it moves slowly on sun surface relative to an observation on Earth for about 6 hours and moves fasters for the last 40 mins. I don’t know whether there is error in the simulation. I counter checked the 2004 transition with Stellarium. The result was the same as Hong Kong Observatory. Anyone can try this in Stellarium and see if there is the same result.

[willis]

Oh! Maybe the "funny" is not funny at all, but the rotation of the sun's coordinate of Stellarium.

[社長]

我沒用Stellarium模擬金星凌日，但至少是以前的情況，這免費軟件是有不少bug的，例如模擬木衛掩食便不準確。

我買了有The Sky X Pro, The Sky 6 Pro, Starry Night Pro 5，有機會可以試試

可以告訴你，金星在地球與太陽之間的相對比例不可分略，所以不可單純以無限遠來計算的，你看金星凌日跟水星凌日比，金星的背影看來遠遠比水星大得多。

[willis]

我買了有The Sky X Pro, The Sky 6 Pro, Starry Night Pro 5，有機會可以試試

No need to try. As I pointed out that it is produced by the rotation of coordinate of Stellarium. The path of the transition is normal. (Title changed accordingly )

[mwtse]

Oh! Maybe the "funny" is not funny at all, but the rotation of the sun's coordinate of Stellarium.

I've simulated it with SkySafari, the rotation of 180 degree is due to the fact that, the sun past its highest point at that moment, as a result, the software just rotate the view so that you do not have to raise your head more than 90 degree.

Choosing another location for observation e.g. Tokyo, the rotation will be less dramatic.

[社長]

今次的條件比8年前差：

http://www.astro.hk/85.html

若要在香港觀測，要有心理準備，因為大氣條件，第一及第二接觸是看不到的：

http://astro.ukho.gov.uk/nao/transit/V_2012/

若要觀測好金星離開日面時，被日珥的熊熊大火燒烤的奇景，似乎我跑到西藏的勝算更高。一來整個藏區有不少地方可以走動，避開雲層，若我的天文台位置當日天氣理想則更好，因為Paramount可以啟動Protrack，直接按金星軌道追蹤，推上高倍拍攝。我有內地用LS152T及Paramount MX的用戶，已有心理準備要最少早一天到埗，做上百多個T Point model去優化Protrack。

但若要在4000海拔以上用日珥鏡，又要請Lunt幫我調一下Etalon才成，有點大費週章的。