U.S. Solar Eclipse of Aug. 21, 2017

[Stavros Kiri]

What will the weather be like?
I remember going to Paris for the 1999 solar eclipse (on the edge of the millennium), only to find that the complete solar eclipse was obscured by a cloud!
In the end I only experienced a partial solar eclipse.

Wasn't Paris in the totality zone in the Aug 11, 1999 Eclipse? I saw it from London. It was my 3rd and Cool! (1st in 1984 - annular, 2nd in 1994, 4th in 2005, - this is my 5th [a man is never happy! ...])
What exactly do you mean by

In the end I only experienced a partial solar eclipse.

?
Because of the clouds? What difference does it make? Totality is totality ...

but frankly I don't get why people make such a big deal out of a shadow.

I did happen to be in a great location for the eclipse of 1984 (New Orleans). Yep, it's darker. Kinda eerie. Not a big deal.

In a sense, you're right. I agree. But seeing the sun's corona during totality is not just a shadow! It's a unique opportunity.

 

[mfb]

Yes, you can use your phone camera. But don't do long-term exposures (pointless anyway as the sun is so bright), and don't use additional lenses without a proper filter.
Phone cameras don't have a shutter and can have the sun in view during normal use - they are typically built to survive a short (seconds) exposure, otherwise the cameras would break down frequently.
According to this article, Apple confirms that iPhones can survive it, and NASA says that a few seconds with any type of phone should be fine. I didn't find the original statements, but it agrees with what I saw elsewhere as well.

What difference does it make? Totality is totality ...

You don't see the corona and the diamond ring effect before/after it with clouds.
You have the darkness, but apart from that it is just like a partial eclipse. Interesting, but not the reason why you go into the region of totality.

 

[Stavros Kiri]

You don't see the corona and the diamond ring effect before/after it with clouds.
You have the darkness, but apart from that it is just like a partial eclipse. Interesting, but not the reason why you go into the region of totality.

I agree on one part:

In a sense, you're right. I agree. But seeing the sun's corona during totality is not just a shadow! It's a unique opportunity.

And you need no clouds to see it properly!

But a clouded total eclipse is totally dark, while a partial one is not!* That's the difference and that's what I meant.

* Unless on extreemly heavy cloudiness

 

[jim hardy]

The article said that many people feel like their eyes hurt with a #12, but #14 seems too dark,

If you tried the #14 shortly after the #12 i think your eye might still be recovering , like at night when you're driving into bright Xenon headlights.
What i noticed with two #10's is it's so dark that light from alongside and behind floods in and reflections make the image really hard to see.

So i bought an inexpensive welding helmet with a #10 in it and taped the second one over the first. It works fine, blocks side light and will keep me from sunburning my face . I have an assortment of lenses so can find a comfortable combination that day. I will err toward conservative - might have to drive home after dark.


.

Got one for Fair Anne, too.

Home Depot, farm supply stores, and autoparts stores are likely places to find them not yet sold out.

 

[Blank_Stare]

Just my luck...

I bought a 10-pack of solar eclipse glasses on Amazon... Apparently Amazon is recalling them, as fakes, or knock-offs. The price should have been my first clue, I suppose...

So, now I am looking for a solution in the 11th hour. Of course, all the welding supply houses are out of the lenses required.

I do have some filter paper and binoculars, as well as an old K-Mart telescope with a solar filter, but sharing them between at least 4 people will be less than ideal, so I was hoping for a solution that scales to the individual.

The guy at the welding supply store claims I can stack lenses, as long as they "add up to 12 or higher".

I didn't find anything about that at the NASA website, so I thought I'd ask here.

Can anyone speak knowledgeably on this subject, please?

Do the shade numbers simply add together to get the right number? Can I really stack a shade #8 and a shade # 5 to get the same as a shade #13 lens?

Thanks.

EDIT: NM, according to http://perkins.owu.edu/solar_viewing_safety.htm , you can not simply stack and add for a total. Thanks

 

[anorlunda]

Edit: As @mfb pointed out, total solar eclipses are common. What is special about this one? i heard on the radio that 90 million people live within 200 miles of the totality.

 

[russ_watters]

Just my luck...

I bought a 10-pack of solar eclipse glasses on Amazon... Apparently Amazon is recalling them, as fakes, or knock-offs.

I wouldn't take that as a guarantee. I got the same email regarding glass filters for my telescope, which I bought from a reputable telescope supply company and tested (and am not going to use visually anyway). It's a paperwork problem. Do some homework on what you got -- they might be ok.

[edit]
Hmm -- reading the rest of the email and checking more, I see Amazon credited my account, de-listed the products and recommended I throw them away. That's insane. It hurts quality vendors and also as a stockholder is bad for business.

 

[Blank_Stare]

I wouldn't take that as a guarantee. I got the same email regarding glass filters for my telescope, which I bought from a reputable telescope supply company and tested (and am not going to use visually anyway). It's a paperwork problem. Do some homework on what you got -- they might be ok.

[edit]
Hmm -- reading the rest of the email and checking more, I see Amazon credited my account, de-listed the products and recommended I throw them away. That's insane. It hurts quality vendors and also as a stockholder is bad for business.

The glasses I received lack the proper stamps/stickers designations for ISO standards. They do warn not to gaze at the sun more than three minutes, but when I looked at my ceiling lamp through them, the elements were clearly visible, and the bulbs were dimly visible. I don't think I got what I ordered...

 

[mfb]

Edit: As @mfb pointed out, total solar eclipses are common. What is special about this one? i heard on the radio that 90 million people live within 200 miles of the totality.

It is over a somewhat densely populated region where most people speak English and internet access is widespread. It is natural that the topic is discussed a lot on English websites.

The July 2009 eclipse went over the densely populated regions of India, Bangladesh and China, and a huge number of people saw it. But most of them are not on English websites, or don't have internet access at all.

 

[George Jones]

My wife, daughter, and I are traveling, as the crow flies, about 1000 kilometres (620 miles) to see the eclipse.

We will leave from north central British Columbia, Canada on Saturday morning, drive about ten hours to Seattle, and then stay Saturday night at our friends' house. On Sunday, we drive to a campsite (already booked by our friends) about 100 km (62 miles) from the centre of the eclipse zone

The highway that we hopefully will take just reopened after being closed quite some time because of the forest fires. If it closes again (a definite possibility; current Weather Network headline "Wildfires will likely be enhanced by strong winds in BC interior"), the trip to Seattle will be more like eleven or twelve hours.

 

[jim hardy]

Can anyone speak knowledgeably on this subject, please?

@Blank_Stare

It's difficult finding what the "SHADE" numbers mean.

I found this on a photography referenced at a photography site.
http://www.x-celoptical.com/occupational_eyewear.php
It references an ANSI standard which ought to be credible

but i was unable to find the standard itself.

Anyhow to your question , check my arithmetic and logic here ?
If a #5 has nominal transmittance of 1.93 %
two of them would transmit 0.0193² = 0.000372 = 0.0372% just about a number nine . That's almost an add but not quite...

Taking square root of a #14 's nominal transmittance, 0.00027% = 0.0000027 , gives transmittance of 0.00164 = 0.164% which falls between nominal #7 and #8 (actually right on a #7's minimum).
That's another 'almost add' .
So i think they don't quite exactly add, but close enough for estimating.

For two #10's i calculate 0.0139%² = 0.000139² =1.93 X10^-8 = 1.93X10^-6% and that's what i plan to use. I know it's plenty dark because i tried it.
I also tried a #5 and #12 together for which i calculate 1.93% X 0.0019% = 0.0193 X 1.9X10^-5 = 3.67X10-7 = 3.67X10^-5% . I found that quite comfortable yesterday afternoon .
I found a single #12 , 1.9 X10-3% painful.
So I'm thinking i want transmittance less than 10^-4%. That keeps me a decade away from pain.
A single #14 is 2.7 X 10^-4 % , myself i'd want darker. EDIT this line has been edited see belowNote in the table how widely the maximum and minimum values bracket nominal .
Since in multiplication we add exponents i think you can add welding shade numbers for purposes of estimating. They seem almost logarithmic per that table.


Lastly , It's stressful converting units.
Attenuation is inverse of transmittance , so i'd want attenuation greater than 1/10^-4% , > 1/10^-6 , > 10⁶
Maybe you'll find a diverse source to cross check me ?

Believe me at my age i value what's left of my eyes.

old jim

LATE EDIT notice i fixed a mistake in this line it reads different from earlier.

So I'm thinking i want transmittance less than 10-4%. That keeps me a decade away from pain.
A single #14 is 2.7 X 10-4 % , myself i'd want darker.

original was darker by a decade.

 

[Blank_Stare]

@Blank_Stare

It's difficult finding what the "SHADE" numbers mean.

I found this on a photography site. It references an ANSI standard which ought to be credible
View attachment 209180

but i was unable to find the standard itself.

Anyhow to your question , check my arithmetic and logic here ?
If a #5 has nominal transmittance of 1.93 %
two of them would have transmittance of transmit 0.0193² = 0.000372 = 0.0372% just about a number nine . That's almost an add but not quite...
Taking square root of a #14 's nominal transmittance, 0.00027% = 0.0000027 , gives transmittance of 0.00164 = 0.164% which falls between nominal #7 and #8 (actually right on a #7's minimum).
So i think they don't quite exactly add, but close enough for estimating.

For two #10's i calculate 0.0139%² = 0.000139² =1.93 X10^-8 = 1.93X10^-6% and that's what i plan to use. I know it's dark because i tried it.
I also tried a #5 and #12 together for which i calculate 1.93% X 0.0019% = 0.0193 X 1.9X10^-5 = 3.67X10-7 = 3.67X10^-5% . I found that quite comfortable yesterday afternoon .
I found a single #12 , 1.9 X10-3% painful.
So I'm thinking i want transmittance less than 10^-4%.
A single #14 is 2.7 X 10^-4 % , myself i'd want darker.Note how widely the maximum and minimum values bracket nominal .
Since in multiplication we add exponents i think you can add welding shade numbers for purposes of estimating. They seem almost logarithmic per that table.


Lastly , It's stressful converting units.
Attenuation is inverse of transmittance , so i'd want attenuation greater than 1/10^-5% , > 1/10^-7 , > 10⁷
Maybe you'll find a diverse source to cross check me ?

Believe me at my age i value what's left of my eyes.

old jim

Unfortunately, that math is way over my paygrade, so I will take your word for it.

I get the gist, however.

It leaves me with a question: "When stacking, does the effect translate to all wave lengths?"

For example, are x-rays also cut the same as visible wavelengths, and therefore the stacking becomes safe in the x-ray spectrum, as well? The Website I quoted above suggests that they do not, but it may be more a question of whether stacking keeps them in the ranges of tolerance that are acceptable.

Thanks for your input.

 

[Greg Bernhardt]

My wife is leaving me to go to the southwest corner of Iowa for the eclipse. I have to stay home and watch the dog

 

[Blank_Stare]

My wife is leaving me to go to the southwest corner of Iowa for the eclipse. I have to stay home and watch the dog

I guess the important question is, "Is she coming back afterwards?"

 

[russ_watters]

Yes, you can use your phone camera. But don't do long-term exposures (pointless anyway as the sun is so bright), and don't use additional lenses without a proper filter.
Phone cameras don't have a shutter and can have the sun in view during normal use - they are typically built to survive a short (seconds) exposure, otherwise the cameras would break down frequently.
According to this article, Apple confirms that iPhones can survive it, and NASA says that a few seconds with any type of phone should be fine. I didn't find the original statements, but it agrees with what I saw elsewhere as well.

Wow, I'm totally shocked/stand corrected. This one mentions the GoPro too:
https://www.usatoday.com/story/tech...dont-need-solar-filter-your-iphone/545768001/

Basically it says the lens is too small to bring in enough light to do damage.

 

[arabianights]

i just realized that i need a pair of solar eclipse glasses to view the sun, and it's nowhere to be found, all sold out...online and stores

 

[mfb]

@Blank_Stare

It's difficult finding what the "SHADE" numbers mean.

I found this on a photography referenced at a photography site.
http://www.x-celoptical.com/occupational_eyewear.php
It references an ANSI standard which ought to be credible

To a good approximation, the visible light follows e^(-n+1) where n is the shade number. As an example, shade n=4 would suggest e^(-3)=0.0498=4.98% transmission - the table says 5.18%. What adds up is "shadenumber-1", so 4+4 is as good as 7 because (4-1)+(4-1)=(7-1).

Converting the Sun to a full Moon like brightness needs a factor 400,000, about shade number 14.

This does not apply to infrared, where stacking more than one shade blocks much more than using a higher shade number.

 

[Blank_Stare]

i just realized that i need a pair of solar eclipse glasses to view the sun, and it's nowhere to be found, all sold out...online and stores

At this point in time your options will be pretty limited.

The easy answer is a pin-hole projector in a cardboard box, but I suspect that the resolution may leave something to be desired.

My local farm supply still has auto-darkening welding helmets that work as dark as shade 13, which is considered by many to be the best choice in shades. However, I do not know how well an electronically controlled auto-darkening lens will do, with regards to sun-gazing. Not to mention the fact that the cheapest ones I found went for over 30 bucks, and they go as high as 150 bucks, for the more "stylish" ones.

Does anyone know if an auto-darkening helmet would be acceptable for sun-gazing?

 

[jim hardy]

"When stacking, does the effect translate to all wave lengths?"

Excellent question. The table above that's attributed to ANSI has a column for UV transmittance, look how small are all the numbers.
I know that welding shades protect against UV because I've got many a sunburn from arc welding with no shirt on.
I have to assume they also protect against IR because welding makes plenty of that , anything designed to protect eyes would have to. The IR column in the table is a little frightening though . Shades transmit IR a lot better than visible and UV.

Workers in hot environments, exposed to IR, developed lenticular opacities due to IR irradiance in the order of 80–400 mW/cm2 on a daily basis for 10–15 years.[9] Pitts and Cullen[10] showed that the threshold exposures for acute lenticular changes caused by IR-A were of the order of 5 kJ/cm2 for exposure durations of the order of an hour or longer and the threshold irradiances for damage were at least 4 W/cm2. The ICNIRP commission therefore recommended that to avoid the thermal injury of the cornea and the possible cataractogenesis, IR exposure (770 nm–3 µm) should be limited to 10 mW/cm2 for lengthy exposures (> 1000 seconds), and to 1.8 t–3/4 W/cm2 for shorter exposure durations.

source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3116568/

So NIH suggests 0.01 watts per cm2.

Per Wikipedia , sunlight is about 1361 W/m²
https://en.wikipedia.org/wiki/Solar_constant
which is 0.136 watts /cm² some 13X the 'safe' limit for lengthy exposure to IR .
Now the sun isn't all IR
but attenuation greater than 13.6X will attenuate the whole sun spectrum below that IR limit from NIH.

1/13.6 = 7.3% , so transmittance less than that should make the IR level safe .
Shades 4 or greater should give protection against IR.
Your eye will hurt from the visible with just a #10 . If your retina is comfortable with the visible i think your lens is safe from IR.

X-rays ? I don't know, will carry a shade in my pocket to next chest x-ray .

The more i look at that table the more i realize what should have been intuitive - welding shades protect against short wavelengths. See the two notes at bottom.

I'm no optics expert by any stretch - just i do always apply my basics to figure things out. I welcome corrections by anyone.

@mfb made a great post while i was typing.

old jim

 

[OmCheeto]

i just realized that i need a pair of solar eclipse glasses to view the sun, and it's nowhere to be found, all sold out...online and stores

Now I feel bad. I have enough extra ISO approved material to make 30 pairs of glasses.

ps. I ordered mine in May, and got the material 8 days later.
pps. I would really like to see a video of the "Rainbow Symphony" factory(?).
A feed came through yesterday from one of our counties saying they'd just bought 75,000 pairs of solar glasses from them, and the county's population is only 26,000.
My interpolation of the numbers involved with such an altruistic act, boggled my mind. And hence, I googled:

http://www.buzzfile.com/business/Rainbow-Symphony,-Inc-818-708-8400

Business Description

Rainbow Symphony is located in Reseda, California. This organization primarily operates in the Paper Die-cutting business / industry within the Paper and Allied Products sector. This organization has been operating for approximately 43 years. Rainbow Symphony is estimated to generate $880,000 in annual revenues, and employs approximately 12 people at this single location.​

I'm guessing they've been running 24/7 for a few weeks(months?) now, and may have hired some extra staff.

I personally hope everyone there is a bazillionaire at the end of all this.

 

[OmCheeto]

My wife, daughter, and I are traveling, as the crow flies, about 1000 kilometres (620 miles) to see the eclipse.

We will leave from north central British Columbia, Canada on Saturday morning, drive about ten hours to Seattle, and then stay Saturday night at our friends' house. On Sunday, we drive to a campsite (already booked by our friends) about 100 km (62 miles) from the centre of the eclipse zone

The highway that we hopefully will take just reopened after being closed quite some time because of the forest fires. If it closes again (a definite possibility; current Weather Network headline "Wildfires will likely be enhanced by strong winds in BC interior"), the trip to Seattle will be more like eleven or twelve hours.

Hopefully, it's not anywhere near where I'm going.

OMG...

14 hour traffic jam, already, starting before noon yesterday, and not clearing up until ≈3 am this morning. (Trust me)

ps. Ok. It's a bunch(30,000!) of stupid hippies that caused this, and is only slightly connected to the eclipse.
pps. I have a "steam of consciousness/googlieness" from this morning, if you're interested. Ehr, mehr, gerd...

 

[Stavros Kiri]

Necessity in plans and arrangements requires that I will not be in the States for the Eclipse on Mon. Unfortunately I had to make that final decision today (Thu). So I'll be watching it via the internet, either from here (PF), or on-line, live streaming, etc. . So I will have to rely on you guys for cool videos and pictures, comments, etc.

Other than that, I will just suffice on monitoring how close the moon gets to the sun, from wherever I will be ...

 

[BillTre]

There is a forest fire east of Roseburg in the Umpqua forest, causing people to evacuate.
Not in path of totality though.

Forest fires in the Pacific NW.

 

[anorlunda]

i just realized that i need a pair of solar eclipse glasses to view the sun, and it's nowhere to be found, all sold out...online and stores

Wendy's restaurants inside the totality zone in Kentucky are selling them for $1

 

[scottdave]

Wendy's restaurants inside the totality zone in Kentucky are selling them for $1

So Amazon had a 5 pack for $40, but said it was out of stock till today. Now it is $60 for a 5-pack and it is out of stock till Monday. We are only getting a partial here in Texas. I think I will buy some on Tuesday for maybe $1 each (perhaps less). Next one within driving distance is Oct 14, 2023 (only 6 years away). And it is a Saturday to boot Actually it is an Annular Eclipse - so the moon is a little farther away and the sun makes a ring around the moon. Still should be cool. I remember being in middle school in '79 and seeing the partial eclipse (where we lived). They let us go outside and made some pinhole viewers.

 

[jim hardy]

Check Tractor Supply stores. My local one had a huge display of welding helmets with #10 shades on sale . And a good assortment of lenses to get upward of #15.

 

[hsdrop]

Hi guys what kind of equipment and quality of said equipment would one have to have to do a "do it yourself relativity test"??
I'm going to be viewing the event with my 16 son. We were wondering how difficult it would be to run the test like they did in Einstein's day??

 

[scottdave]

Hi guys what kind of equipment and quality of said equipment would one have to have to do a "do it yourself relativity test"??
I'm going to be viewing the event with my 16 son. We were wondering how difficult it would be to run the test like they did in Einstein's day??

I almost forgot about that experiment. Have you researched it? I am on my phone right now. But here is what came up on a search.
https://www.sciencenews.org/article/2017-solar-eclipse-einstein-general-relativity

 

[hsdrop]

From what I have read about the experiment it's just taking sets of photos at 2 different times of the year. Then comparing the stars places with and without the sun in the sky to see if the stars moved. I'm just wondering if I can get away with using the telescope and the camera I have "which are the only tools I have to work with" and still make it work??

 

[nsaspook]

ps. Ok. It's a bunch(30,000!) of stupid hippies that caused this, and is only slightly connected to the eclipse.

It's going to get very strange over the weekend there.

 

[russ_watters]

I'll be watching it via the internet, either from here (PF), or on-line, live streaming, etc. . So I will have to rely on you guys for cool videos and pictures, comments, etc.

Last rehearsal before packing the equipment up:



I will of course be busy during, so I'm not sure how much live streaming or posting I will be able to do, but I'll try.

 

[mfb]

Hi guys what kind of equipment and quality of said equipment would one have to have to do a "do it yourself relativity test"??
I'm going to be viewing the event with my 16 son. We were wondering how difficult it would be to run the test like they did in Einstein's day??

The deflection is about 2 seconds of arc for stars directly at the edge of the Sun. I would be surprised if you can get such a good angular resolution without a very good telescope.

 

[Stavros Kiri]

Last rehearsal before packing the equipment up:



I will of course be busy during, so I'm not sure how much live streaming or posting I will be able to do, but I'll try.

Wow! Eclipse videos are starting! ...
Not necessary to be live. I like them anyway, even later, pictures too. I would say go ahead and focus on your important work during ...

I already found a live streaming link (at least one). I will post it later (before the eclipse).

 

[dlgoff]

Have glasses, will travel.

 

[Stavros Kiri]

Have glasses, will travel.

View attachment 209255

If you're traveling wearing them ... you won't get very far! ...