The Transit of Venus and the Parallax of the Sun

 

The Transit of Venus provided the first accurate value for the Sun's parallax which enables one to determine its distance. Edmond Halley proposed the method in a 1716 paper published in Philosophical Transactions, Vol. XXIX, No. 348, p. 454 and is written in Latin. There is an abridged English translation available at Google Books and a .pdf version online which includes a better view of the figure.

 

 

The paper suggests viewing the May 25, 1761 (O.S.) transit from different location on the Earth, viewing the entire transit from the north coast of Norway and using different locations to improve the opportunities for observation under poor weather conditions.

 

Supplemental (Jun 19): For an account of the observations see Newcomb, Popular Astronomy, p. 177.

 

BAA Meeting May 30

 

A video from the British Astronomical Association meeting on May 30, 2012.

 

 

src: britishastronomical

 

The Upcoming Merger of the Milky Way and Andromeda Galaxies

 

src: ScienceCasts

 

 

After seeing this video and later browsing some other YouTube videos I came across a Triplanetary ebook by E. E. "Doc" Smith. Triplanetary is the first book of the Lensman series and begins with the collision and merger of two galaxies. Smith's first science fiction book, The Skylark of Space, is much better than the contemporary works by Edgar Rice Burroughs such as A Princess of Mars which is the basis for the recent movie, John Carter. These books and others such as Buck Rogers mark an advance in science fiction which took place in the Twenties.

 

Image Resolution With Eyepiece Projection

 

I used a small telescope with a 50mm diameter, f = 625mm objective lens to do the eyepiece projection and photographed the image with a Kodak Z981 digital camera. The eyepiece was a 12.5mm Huygens*. The resolution of the projected image was better than the posted images indicate since the Z981 has a 33mm diameter aperture for its zoom lens. The image motion due to the windy conditions and the difficulty capturing the images by hand probably also affected the resolution somewhat. This zoomed in image of the sunspots shows the greater detail available.

 

 

One can compare the enhanced detail with an image captured by Big Bear about the same time.

 

 

*see R. A. Houstoun, A Treatise on Light for a description of the Huygens eyepiece.

 

NASA Video of Venus Transit via CNN

 

cnn.com

 

MICA's Predictions Were Accurate

 

MICA's predictions for the start of the Venus Transit were quite accurate. The time stated for the start of the transit here was 3:06:23.8 pm PDT. The following two images were captured at 3:07:50 pm and 3:09:16 pm. One can just make out the silhouette of Venus crossing the limb of the Sun at about 45° counterclockwise from the top in the second image.

 

 

 

The time predicted for midtransit or the "least angular separation" was 6:25:34.1 pm. The relative positions of the two objects are given by MICA in polar coordinates with the "Position Angle" and "Angular Separation" being the angle counterclockwise from North and the radial distance respectively.

 

Midtransit

 

 

Captured at 6:27:06 pm PDT.

 

Checking Current Weather Conditions

 

The weather could be better here in Fresno for tomorrow's Venus Transit. It's a little overcast and breezy today. A small storm front is moving through and there is a chance of rain tonight. The cloud cover should improve tomorrow but it may still be a little breezy with 18-22 mph winds. Here are some links for the weather at Mauna Kea, Hawaii which is best situated in the US for observing the transit.

 

Current Hawaii Wondermap   GEOS-W Central Pacific Satellite   GEOS Hawaii Satellite

 

NOAA satellite index   European satellite animation   MTSAT SW Pacific

 

Note that Mauna Kea is the northern peak on the island where the observatories are. One can see from the satellite maps that the clouds flow around the volcano.

 

What's Up For June? - JPLnews

 

JPLnews

 

Venus Transit from Norway

 

The northern part of Norway is above the arctic circle where the "midnight sun" exists. This would enable someone to observe the Venus Transit in its entirety if weather conditions were favorable. Current conditions at Tromso appear to be such that some observations may be possible. Its time zone is CEST or UTC + 2 hrs.

 

UiT weather cam (South)

 

MICA gives the following details for the transit there on Wednesday, Jun 6th for the first part of the day.

 

 

Supplemental (Jun 4): The transit will start just after midnight CEST and the Sun will be towards the north at that time.

 

LIVE COVERAGE for the Transit of Venus

 

Check the NASA GSFC site for Live Stream Coverage of the Venus Transit from various locations around the world. You can select a location by clicking the markers on the map. There is also a link to NASA's Observing Challenge on this page.

 

ISS Transit of Venus

 

ScienceCasts: ISS Transit of Venus    NASA Science