The Venus Transit 2004

Walkiry writes "In just 47 days our friendly neighbour planet Venus will be passing right in between Earth and good ol' Sun, giving us the chance to see a small black spot going accross the disk (last one was in 1882). This is called the Venus Transit. The interesting thing is that there is a project asking for volunteers to perform their own measurements of the phenomena and submit their own results, in what will be the first accurate and public measurement of an extraterrestrial distance. Do you have a spare telescope and some free time on June 8th?"

Comments

low frequency of occurance!

[ALLXSTHINGS]

Apaprently, the next Venus transit after this one will be in 2012, but the next two after that won't be until 2117 and 2125. Looks like a once in a lifetime deal. (source: http://sunearth.gsfc.nasa.gov/eclipse/transit/venu s0412.html)

Re:low frequency of occurance!

[Deadstick]

They come in pairs eight years apart, once in a bit over a century. The one in 1769 provided the principal funding for Captain Cook's voyage to Tahiti, where it was visible...timing the transit gave a measure of the size of the Earth's orbit.

rj

Venus Atmosphere

[Via_Patrino]

It was in a situation like that that Venus athmosphere (its clounds) was discovered, when Venus was against the sun an astromer saw a fog over the planet. A lot of light passed trough where previously was thoug to be solid.

Wikipedia Info

[Bobdabishop307]

This is what i found in Wikipedia on Venus Transits:

"Transits of Venus, when the planet crosses directly between the Earth and the Sun' visible disc, are important astronomical events. The first such transit was observed on December 4, 1639 by Jeremiah Horrocks and William Crabtree. A transit in 1761 observed by Mikhail Lomonosov provided the first evidence that Venus had an atmosphere, and the 19th century observations of parallax during its transits allowed the distance between the Earth and Sun to be accurately calculated for the first time. The previous set of transits of Venus occurred within the interval of 1874 - 1882, and the next set of transits will occur in the period of 2004 - 2012."

equipment

[dspeyer]

A telescope alone isn't enough. Looking at the sun through a telescope is almost as safe as gouging out your eyes with a knife. It is possible to get a filter adaquate for sun-viewing, but make sure it's explicitely designed for your size telescope.

What's proabaly better is a projection scope. A prpoer one is very expensive, but you can just hold any convex lense or piece of shirt cardboard with a really tiny hole in it above a piece of white paper. You'll need very good resolution to see this though, so you should probably calculate that ahead of time.

Re:A small black spot on the Sun

[NortWind]

Okay, everybody stare directly at the Sun.

You can glance at the Sun, or else all baseball fielders would be blind. However, if you're using a nice 8" reflector, even closing your eyelid is not going to help. They make metalized "solar filters" for many telescopes, which keep most of the energy out of the scope body while preserving the aperature so you can still have good resolution at high magnification.

If you have a smaller telescope, or a a pair of binolculars, you can project an image of the sun onto a sheet of paper through the eyepiece. Use a cardboard box to make a darker area for the paper to be in. If there is some distance to the paper, the image of the Sun will be big enough that it will not burn the paper. Experiment with distance and focus to see what works.

Or you can just buy a Solar Viewer. American Science & Surplus has 'em for under $100.

Re:Of course we do

[WalksOnDirt]

I have a spare telescope and the free time, but I live in California.

The west coast of North America and most of South America won't be able to see the transit.

find out if you'll be able to see it

[whatamidoing]

you should go here

Just don't look directly at the sun.

[Anonymous Coward]

Despite warnings every year people get blinded because they wanted to see a partial eclipse or some other solar event directly.
Use a telescope or binoculars and project the image onto a piece of white cardboard or paper.
Even just a few seconds can ruin your eyesight so be careful. It's no joke.

Re:Photos?

[deglr6328]

From 1882? I don't think so.


Think again. We do have photos of it. A movie has even been made.

Eye gouging vs wallet gouging

[Latent Heat]

There are two kinds of telescope sun filters. An objective filter fits over the front end of the telescope. It filters light out before the light enters the telescopy. It is more expensive but the only safe kind.

The other kind of sun filter fits over your eyepiece or inside your eyepiece. I once had a 2.4 inch refracting telescope that came with this piece of welder's glass that fit over the eyepiece. I never used it because I was warned not to.

The advantage of the objective sun filter (the ones I have seen advertised are aluminized mylar) is that 1) it blocks out intense sunlight before it even gets to your telescope, and 2) it is exposed to no more than normal sun intensity because it hasn't been concentrated by the telescope.

The wee bit of welder's glass at the telescope eyepiece is unsafe because it is getting the full focus of sunlight from the telescope and the thing and crack from the heat and then your eyeball is in peril.

The other safe method is projection through the telescope on to a piece of paper. Safe for one's eyes -- I ruined my beginner's refractor doing that because the heat cooked a cheap plastic element in the one eyepiece it came with.