June 5, 2012 Transit Of Venus Across Face Of Sun

[Fat Man]

On June 5 to June 6 of this year, 2012, there will be a transit of Venus slowly moving across the face of the sun.

A transit is sort of like an eclipse, like, when the moon passes in front of the sun, but the moon is much closer so it appears large enough to completely cover the sun, as in a total eclipse.

But, since Venus is much further away, it looks much smaller, so when it passes in front of the sun, it will appear as a small round black dot slowly moving across the face of the sun.



I did a Google search for when I can see it here in El Paso Texas, my local time.

Here is a screen shot of my Google search result, which I then up-loaded to my Photobucket account so I can post it here.



Notice, that I have blacked out my residential address and zip code to protect my privacy.

Anyway . . . . .

There was a transit of Venus across the sun back in June of 2004, but I missed seeing it.

But I won't miss seeing this one!

OK, I have a refractor telescope, the Galileo brand name, with a 60 mm objective lens having a 900 mm focal length. It's a used telescope that my therapist gave me back in January 2009.

So, I need to order eyepieces for it.

But today, I ordered a 2x Barlow lens which doubles the magnifying power of the telescope.

I placed an order with High Point Scientific using my debit card, and it cost me about $30 dollars including shipping and handling.

Of course, when I observe the transit of Venus across the face of the sun, I will NOT be looking through the telescope, since I don't have a sun filter.

So, instead, I will just point the telescope toward the sun, insert the Barlow lens where an eyepiece normally goes, and project the sun's image onto a white sheet of poster-board.

Of course, I'll use another square sheet of card-board about 18x18 inches with a small hole in the middle, slightly smaller than the tube diameter (for a snug fit) where the eyepiece normally goes, then I shall insert the 2x Barlow lens.

The sheet of card-board will cast a shadow onto the white poster-board where the sun's image will be projected. Then by turning the focus knob, I will get a nice sharp image. The further away the sheet of white poster-board is from the Barlow lens, the larger the projected image will appear.

I've done this before, so I know from experience that I can get a nice sharp image of the sun about 8 to 12 inches across projected onto the white poster-board, and you can see the sun spots. When Venus slowly moves across the face of the sun, it will appear as a round black dot, which is larger than the size of a typical sun spot image.

Yeah! This is the safest way to observe the sun, by NOT looking through the telescope, but by projecting the sun's image onto the white poster-board and looking at the projected image.

When I was 16 years old, I had a telescope about the same size as the one I have now, which my brother ripped off from me years later back in 1985.

Back then I had a small sun filter that screwed onto an eye piece. But one day, it cracked, because the filter was at the focal point of the objective lens, and you know how a magnifying lens can burn a piece of paper. Well, the heat was enough to crack the sun filter.

Of course, one can get a sun filter that covers the big objective lens in front, but a 60 mm sun filter costs about $150 to $200 dollars.

So, I just use the projection method instead, which is much safer, and also much cheaper.

OK, I have created this diagram for this purpose, using my Microsoft Paint.



Yeah! I know! The drawing is not to scale, so sue me!

And of course, in reality, the projected image of the sun is not actually yellow, but is white instead.

ALSO, I MUST ADD . . . . .

It would be a good idea to cut out a cardboard circle the size of the objective lens, put a hole in it that is less than the diameter of the lens, for example, my telescope had a 60 mm objective lens, so I will make a hole about 20 mm to effectively reduce the objective diameter. That way, less sunlight enters the telescope, and the projected image on the white poster-board will not appear as bright. The image will be dimmed down some more so it will be more comfortable to look at. Also, the hole should be off-center so that only the off-axes light enters the telescope.

Anyway . . . . .

Transits of Venus, and Mercury, across the face of the sun have been observed since Galileo first observed the planets and stars with his telescope.

He also looked at the sun, covering the objective lens with a piece of smoked glass!

But, smoked glass does not block out ultra-violet light as modern sun filters do.

They didn't know about invisible ultra-violet light back then, and even though you can't see it, ultra-violet light can still damage your eyes, eventually leading to blindness, which is why poor Galileo started going blind in his old age.

Anyway, here is a list of transits of Venus across the sun as they had occurred in the past, and when they will occur far into the future.

AD 1631 Dec 07
AD 1639 Dec 04
AD 1761 Jun 06
AD 1769 Jun 03
AD 1874 Dec 09
AD 1882 Dec 06
AD 2004 Jun 08
AD 2012 Jun 06
AD 2117 Dec 11
AD 2125 Dec 08
AD 2247 Jun 11
AD 2255 Jun 09
AD 2360 Dec 13
AD 2368 Dec 10
AD 2490 Jun 12
AD 2498 Jun 10
AD 2603 Dec 16
AD 2611 Dec 13
AD 2733 Jun 15
AD 2741 Jun 13
AD 2846 Dec 17
AD 2854 Dec 14
AD 2976 Jun 16
AD 2984 Jun 14
AD 3089 Dec 18
AD 3219 Jun 20
AD 3227 Jun 17
AD 3332 Dec 20
AD 3462 Jun 22
AD 3470 Jun 19
AD 3575 Dec 23
AD 3705 Jun 24
AD 3713 Jun 21
AD 3818 Dec 25
AD 3956 Jun 24

Anyway . . . . .

This is what my Galileo brand of telescope actually looks like.



This is the one with the 60 mm objective lens and the 900 mm focal length.

On the tripod, it has the German style equatorial mount that has to be adjusted at the correct angle (here in El Paso is about 32 degrees for my north latitude) so that the polar axes points to the celestial north pole, or Polaris, the north star.

But, of course, on my telescope, the little guide scope, the counter-weight, the 45 degree diagonal prism, and the triangular accessory tray are missing, so, eventually I'll have to order them, and then I'll have to order a set of eyepieces.

I can't complain since it was given to me, used, as is.

But, in the meantime, I have ordered the 2x Barlow lens which set me back about $30 dollars.

Yeah! I really can't afford it, so my money will be rather tight this month.

But, it will be worth it.

I knew years ago, from reading Astronomy books from the public library that their will be two transits of Venus across the sun within my lifetime. I missed the one back in 2004, but I'll be prepared to see this one when it comes on June 5,2012.

The next one after this won't be until December 11,2117.

So, I feel damn lucky that I'll be able to see the one that is coming up next month.

[Earl]

Again, excellent writing! You lost me, though, when you referred to "the off-axes light"; but that's okay because I know absolutely nothing about astronomy. I appreciate the use of diagrams when material of this sort is presented in an informative way. As a layman I appreciate your descriptions as to why certain celestial phenomena appear the way they do to us humans here on Earth. Observation is not enough if you don't understand what is happening before your eyes.

Good luck! I hope the weather permits you to see the transit of Venus across the face of the sun.

[Fat Man]

Again, excellent writing! You lost me, though, when you referred to "the off-axes light"; but that's okay because I know absolutely nothing about astronomy. I appreciate the use of diagrams when material of this sort is presented in an informative way. As a layman I appreciate your descriptions as to why certain celestial phenomena appear the way they do to us humans here on Earth. Observation is not enough if you don't understand what is happening before your eyes.

Good luck! I hope the weather permits you to see the transit of Venus across the face of the sun.

OK, the axis is straight down though the center of the telescope.

By covering the objective lens with a poster-board circle and having a hole in it that is smaller than the diameter of the objective lens, it reduces the amount of sunlight that enters the telescope, sort of like the iris diaphragm of a camera.

And by having the hole off-center, then that is what is meant by only allowing only the off-axis light to enter the telescope, thus, reducing the brightness even further.

Anyway, thank you for your response.