APOD: A Picturesque Venus Transit (2012 Jun 03)

[biddie67]

I've been wondering how these various transit predictions are made. What kind of math is used ~~ could someone discribe it without getting too technical? Thanks.

[bystander]

http://asterisk.apod.com/viewtopic.php?f=44&t=28734
http://asterisk.apod.com/viewtopic.php?f=31&t=26916

[neufer]

Or you could just walk down to Air & Space after work: http://airandspace.si.edu/events/eventD ... entID=4027

The Mall doesn't have a good view of the western horizon, though; too many trees. Capitol Hill would be better, and indeed, that's one of three or four places I'm considering. Others are Goddard (though I'm concerned about the view from there, too; I should have moseyed over today to check it out) and UMd, and then there's a hill near me that has as good a view of the horizon as one is going to find out out here, so that might be a possibility, too. I have spare eclipse glasses if you want some, free to good home!

I doubt that any group advertising Transit Viewings will not have a good view of at least the start of the transit. Goddard Visitors Center is certainly on a hill with an excellent view of the WNW and if it is cloudy they will probably have high quality live satellite views available. (Besides which it is close to where my grandson Kai lives.) Eclipse glasses with binoculars might work but Venus is still going to be pretty small. My old Astroscan telescope projects a nice softball sized sun off to the side which I'll probably try out for the fun of it.

[owlice]

Eclipse glasses with binoculars are a no-no, from what I've read. Yes, Goddard will have live feeds, according to their web site; also bathrooms. Are you taking your Astroscan there?

[saturno2]

Next transit of Venus will be in 2117
After of 105 years
Many time for the humans
Few time for the Universe...

[neufer]

Eclipse glasses with binoculars are a no-no, from what I've read.

I don't know why.

The sun should be low and the glass lens themselves will protect from UV if the eclipse glasses should slip.

Yes, Goddard will have live feeds, according to their web site; also bathrooms. Are you taking your Astroscan there?

50-50 (...depending upon the weather).

[alter-ego]

Eclipse glasses with binoculars are a no-no, from what I've read.

I don't know why.

The sun should be low and the glass lens themselves will protect from UV if the eclipse glasses should slip.

Generally speaking, it's not a good idea to rely ONLY on protective eyeglasses when using binoculars or a telescope. At the binocular exit pupils, the power density can be 100x higher than what the glasses were designed / intended for, and could lead to the eyeglasses failing. Sure there's a grey area with several variables, like atmospheric attenuation and what the observing time is, but It's not worth the risk.

[owlice]

What I've read is that there should be something on the lens(es) facing the sun specifically designed for that use.

Can one fry ants with binoculars?

Neufer! I watched tonight's weather forecast; Tuesday's has improved to only a 30% chance of rain/showers. Woo-hoo!!

[Chris Peterson]

Eclipse glasses with binoculars are a no-no, from what I've read.

I don't know why.

The sun should be low and the glass lens themselves will protect from UV if the eclipse glasses should slip

Viewing the Sun through binoculars, even when low, can cause permanent blindness faster than your blink reflex can occur. Just holding binoculars on the Sun can melt or burn internal elements of the binoculars, and can melt the eclipse glasses. You never want to use any solar viewing scheme where the filter or attenuator is at the eyepiece. The correct way to view the Sun with binoculars (or any telescope) is with a full aperture filter. The same material that the eclipse glasses are made of (metalized plastic) is placed over the objective(s). This can be used safely.

[neufer]

Eclipse glasses with binoculars are a no-no, from what I've read.

I don't know why.

The sun should be low and the glass lens themselves will protect from UV if the eclipse glasses should slip

Viewing the Sun through binoculars, even when low, can cause permanent blindness faster than your blink reflex can occur. Just holding binoculars on the Sun can melt or burn internal elements of the binoculars, and can melt the eclipse glasses. You never want to use any solar viewing scheme where the filter or attenuator is at the eyepiece. The correct way to view the Sun with binoculars (or any telescope) is with a full aperture filter. The same material that the eclipse glasses are made of (metalized plastic) is placed over the objective(s). This can be used safely.

I strongly recommend the projection method myself for all sorts of reasons
(few of us own full aperture filters or eclipse glasses... besides
... would "astrobob" King put our binoculars in jeopardy ):

[b][color=#0000FF]If you're able to put your binoculars on a steady mount, the projection method is a good one for viewing the transit. Photo: [url=http://astrobob.areavoices.com/2012/05/31/dont-miss-next-weeks-rare-and-wonderful-transit-of-venus/]Bob King[/url][/color][/b]

---

Los Alamos From Below: Reminiscences 1943-1945, by Richard Feynman

<<I flew back, and I just arrived when the buses were leaving, so I went straight out to the site and we waited out there, 20 miles away. We had a radio, and they were supposed to tell us when the thing was going to go off and so forth, but the radio wouldn't work, so we never knew what was happening. But just a few minutes before it was supposed to go off the radio started to work, and they told us there was 20 seconds or something to go, for people who were far away like we were. Others were closer, 6 miles away.

They gave out dark glasses that you could watch it with. Dark glasses! Twenty miles away, you couldn't see a damn thing through dark glasses. So I figured the only thing that could really hurt your eyes - bright light can never hurt your eyes - is ultraviolet light. I got behind a truck windshield, because the ultraviolet can't go through glass, so that would be safe, and so I could see the damn thing. OK.

Time comes, and this tremendous flash out there is so bright that I duck, and I see this purple splotch on the floor of the truck. I said, “That ain't it. That's an after-image.” So I look back up, and I see this white light changing into yellow and then into orange. The clouds form and then they disappear again; the compression and the expansion forms and makes clouds disappear. Then finally a big ball of orange, the center that was so bright, becomes a ball of orange that starts to rise and billow a little bit and get a little black around the edges, and then you see it's a big ball of smoke with flashes on the inside of the fire going out, the heat.

All this took about one minute. It was a series from bright to dark, and I had seen it. I am about the only guy who actually looked at the damn thing the first Trinity test. Everybody else had dark glasses, and the people at six miles couldn't see it because they were all told to lie on the floor. I'm probably the only guy who saw it with the human eye.

Finally, after about a minute and a half, there's suddenly a tremendous noise - BANG, and then a rumble, like thunder -- and that's what convinced me. Nobody had said a word during this whole thing. We were all just watching quietly. But this sound released everybody- - released me particularly because the solidity of the sound at that distance meant that it had really worked.

The man standing next to me said, “What's that?"

I said, “That was the bomb.">>

[moconnor]

I have a question concerning Venus transits.

If they occur in pairs every 100 years, or so, how many of the previous ones were forecast? I assume scientists forecast the ones in the 1900's. How about the 1800's? the 1700's? Earlier ones?

[neufer]

I have a question concerning Venus transits.

If they occur in pairs every 100 years, or so, how many of the previous ones were forecast?
I assume scientists forecast the ones in the 1900's. How about the 1800's? the 1700's? Earlier ones?

http://asterisk.apod.com/viewtopic.php? ... 12#p176512

[owlice]

The transit was predicted and observed in 1639; see here for more history: http://sunearth.gsfc.nasa.gov/sunearthd ... ck_his.htm

Also here: http://asterisk.apod.com/ampersand/?p=493

[owlice]

Oh, sure, beat me to it, Art!!

[Chris Peterson]

I strongly recommend the projection method myself for all sorts of reasons
(few of us own full aperture filters or eclipse glasses... besides
... would "astrobob" King put our binoculars in jeopardy?

What this guy is doing is very dangerous. I would never do it unless I was alone. What is coming out the end of those binoculars could instantly blind someone, and it is difficult to be so in control of the equipment and the people around you that you can guarantee nobody will end up looking for a moment when your back is turned. Modern projection systems have structures built around them is such a way that it's impossible to get your head in the beam. And yes, projecting an image the way this picture shows could quite easily damage the optics.

Los Alamos From Below: Reminiscences 1943-1945, by Richard Feynman

They gave out dark glasses that you could watch it with. Dark glasses! Twenty miles away, you couldn't see a damn thing through dark glasses. So I figured the only thing that could really hurt your eyes - bright light can never hurt your eyes - is ultraviolet light. I got behind a truck windshield, because the ultraviolet can't go through glass, so that would be safe, and so I could see the damn thing. OK.

Of course, Feynman was completely wrong. Bright light can hurt your eyes. When you look at the Sun, it isn't the UV that's the problem, it's the visible light. The retina is thermally damaged. Without magnification, the image is so small that the blood flow in the retina can carry away the heat, so you need several seconds of deliberate (and highly uncomfortable) staring before damage occurs. With magnification, the light of the Sun- still the same brightness as with the naked eye- is spread out over a large area, and the heat cannot be carried away. The retina can be permanently damaged in only a fraction of a second. Feynman might well have damaged his eyes in viewing the initial flash of the bomb. That flash was spatially small, so a retinal scar could go unnoticed. Had he attempted viewing it through binoculars, the situation might have been much worse.

The deal with the UV and IR components of the Sun is that these are invisible, and don't trigger any aversion reflex. So if you have a poor solar filter, these may make it through and you'll not know it. In staring at the Sun, they will eventually damage your retina... silently. But they are not themselves the primarily dangerous part of sunlight.

[Sam]

Thank you, Art, for the afternoon's worth of reading about Feynman and Trinity and atomic bombs and materials opaque to UV and Klaus Fuchs..........ah wikipedia [/size]

Regarding filters and binocular projection techniques, I feel obliged to share my two pertinent experiences with the sun and binoculars:

1) In 2003, I acquired my first solar glasses from Rainbow Symphony. After a little bit of naked-eye viewing and attempts at picture-taking from my room, I held the glasses to the eyepiece of some binoculars; I had about two seconds of looking at the orange disc before I saw a big white explosion and I jerked the binocs away: the heat from the focused image had burnt through the filter! I haven't noticed any vision damage yet, but who knows what could be in store as I get older-maybe I can expect to contribute to Chris's fortune.

2) A few winters ago, with my current Celestron Skymastyer 15x70's I was trying to find Venus in the daytime near inferior conjunction; I was very careful not to get the field too close to the sun, using the house to block it off, but even still, when I reached a bright enough area of sky, I started to see smoke inside my binoculars. Something melted or burnt, I'm not sure what, but I am not anxious to ever again point my beloved binoculars directly at the sun without filters snugly taped to the objective lenses.


So, my question is, how are other people getting around the tendency for binoculars to burn things up at the eyepiece?

--
Sam

[owlice]

Sam, I combined directions from here and here. I have binoculars I can mount on a tripod (or a bottlepod with a 2-liter bottle) courtesy of a homemade platform and bungee cords. I have a long funnel I attach to the one open eyepiece (the other is covered) with a hose clamp. I can then project the image, or, if I want a small, fine, bright image, I can put something at the end of the funnel (rear projection screen material is what the instructions say to use; wish I had some!). I'll let you know tomorrow night what I accidentally set fire to.

[neufer]

Thank you, Art, for the afternoon's worth of reading about Feynman and Trinity and atomic bombs and materials opaque to UV and Klaus Fuchs..........ah wikipedia [/size]

Any time, Sam

[b][color=#0000FF]Art instructing Sam about observing transits[/color][/b]

---

Regarding filters and binocular projection techniques, I feel obliged to share my two pertinent experiences with the sun and binoculars:

1) In 2003, I acquired my first solar glasses from Rainbow Symphony. After a little bit of naked-eye viewing and attempts at picture-taking from my room, I held the glasses to the eyepiece of some binoculars; I had about two seconds of looking at the orange disc before I saw a big white explosion and I jerked the binocs away: the heat from the focused image had burnt through the filter! I haven't noticed any vision damage yet, but who knows what could be in store as I get older-maybe I can expect to contribute to Chris's fortune.

I had no idea how flimsy such solar glasses were. Oh, Fuchs!

Fortunately you still were safe from UV.
(Note that Feynman, himself, never went blind thanks to quick reflexes.)

2) A few winters ago, with my current Celestron Skymaster 15x70's I was trying to find Venus in the daytime near inferior conjunction; I was very careful not to get the field too close to the sun, using the house to block it off, but even still, when I reached a bright enough area of sky, I started to see smoke inside my binoculars. Something melted or burnt, I'm not sure what, but I am not anxious to ever again point my beloved binoculars directly at the sun without filters snugly taped to the objective lenses.


So, my question is, how are other people getting around the tendency for binoculars to burn things up at the eyepiece?

I was thinking that Astrobob's recent suggestion of looking at Venus with binoculars ~6º off axis from the Sun was probably more problematic for the binoculars, themselves, than directly pointing binoculars at the sun (particularly with a Celestron Skymaster) since the sunlight would be concentrated on the dark interior of the binoculars rather than on the transparent optics (sans cheap solar glasses). However.... you claim that you were using a house to block off direct sunlight (If so, I find your story rather incredible. Did the house catch fire?)

[Chris Peterson]

Sam, I combined directions from here and here. I have binoculars I can mount on a tripod (or a bottlepod with a 2-liter bottle) courtesy of a homemade platform and bungee cords. I have a long funnel I attach to the one open eyepiece (the other is covered) with a hose clamp. I can then project the image, or, if I want a small, fine, bright image, I can put something at the end of the funnel (rear projection screen material is what the instructions say to use; wish I had some!). I'll let you know tomorrow night what I accidentally set fire to.

Just use cheap binoculars. The key to using unfiltered optics to project an image of the Sun is to keep them aimed. By design, optics are transparent and will absorb very little energy... otherwise they wouldn't work! But if you are just near, not exactly on, the Sun, a lot of energy is focused inside the binocular housing- typically on elements that are painted black and can easily melt or burn.

Of course, if you have anybody else around, you need to be very careful that they don't walk up and look into the eyepiece. This has happened at star parties, with tragic results.

[Chris Peterson]

Fortunately you still were safe from UV.

Not really (although as I pointed out earlier, solar UV is only dangerous when you use a filter). Glass only blocks shorter wavelength UV- UVB and shorter. Near UV and UVA are transmitted, and have similar ability to damage cells as the shorter wavelengths. If you were viewing the Sun with a visible light filter that passed UVA, you'd be in trouble. This guy drove a truck for 28 years, and was exposed only on his left side to sunlight passing through glass.

[owlice]

Just use cheap binoculars. The key to using unfiltered optics to project an image of the Sun is to keep them aimed. By design, optics are transparent and will absorb very little energy... otherwise they wouldn't work! But if you are just near, not exactly on, the Sun, a lot of energy is focused inside the binocular housing- typically on elements that are painted black and can easily melt or burn.

Of course, if you have anybody else around, you need to be very careful that they don't walk up and look into the eyepiece. This has happened at star parties, with tragic results.

Thanks. Yes, I plan to keep them aimed, and I hope both my presence and the long funnel on the eyepiece will discourage people from trying to look through the eyepiece. If it doesn't, I've sharpened my talons and have a bullwhip handy by in my transit bag.

[neufer]

Of course, if you have anybody else around, you need to be very careful that they don't walk up and look into the eyepiece. This has happened at star parties, with tragic results.

Thanks. Yes, I plan to keep them aimed, and I hope both my presence and the long funnel on the eyepiece will discourage people from trying to look through the eyepiece. If it doesn't, I've sharpened my talons and have a bullwhip handy by in my transit bag.

[neufer]

---

Fortunately you still were safe from UV.

Not really (although as I pointed out earlier, solar UV is only dangerous when you use a filter). Glass only blocks shorter wavelength UV- UVB and shorter. Near UV and UVA are transmitted, and have similar ability to damage cells as the shorter wavelengths. If you were viewing the Sun with a visible light filter that passed UVA, you'd be in trouble. This guy drove a truck for 28 years, and was exposed only on his left side to sunlight passing through glass.

Au contraire mon ami This is clear evidence of:

• 1) the safety of windshield glass in preventing solar UV skin damage
  
  2) the fact that our truck driver ain't British:

<<A "trucker's tan" one arm from the sleeve downward is tanned significantly more than the other arm due to driving with the windows down. In the United Kingdom "trucker's tan" is known as "taxi driver's arm" and is exclusively, since driving on the left, the right arm which rests on the open window.

A biker's tan is tan line that goes up 3/4 of leg, where lycra bike shorts would normally begin to cover. Depending on the activity, the inner side of the arms may be paler than the outer side. Unless you use cycling gloves made to allow tanning, the area on the back of each hand will usually not be tanned.

A "Franciscan tan" is a tan that is associated to the Franciscan order. The reason behind this is that Franciscans usually wear sandals during the summer. This creates an odd tan line when the sandals are off because, depending on the sandal, will have a tan line.>>

[neufer]

Click to play embedded YouTube video.

<<Venus is moving in!

The LASCO C3 coronograph on board the SOHO spacecraft has been watching the approach of Venus for its last solar transit until 2117.

With coronagraphs, the Sun is blocked by an occulting disk, seen here in blue, so that SOHO can observe the much fainter features in the Sun’s corona.

The actual size of the Sun is represented by the white disk.>>

http://asterisk.apod.com/viewtopic.php?t=28777

[Chris Peterson]

Au contraire mon ami :!: This is clear evidence of:

• 1) the safety of windshield glass in preventing solar UV skin damage
  
  2) the fact that our truck driver ain't British:

That he isn't British is clear. However, an interesting thing about this case is that the driver's exposure to sunlight was not through an open window, but through the side glass- which does pass UVA.