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

[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! ...

 

[OmCheeto]

Weird. I wonder if this is what they call the "quiet before the storm".
The roads are basically clear to all "eclipse destination" points in Oregon.

Live road conditions in Oregon

Spent the day disassembling my telescope, trying to determine if I could fix it.
After determining that the 9 volt supply was making it to the "guts", I saw the printed circuit board was all surface mount, and said; [Expletives deleted]
I do plan on taking it though, in the hopes that those stupid stinkin' hippies, with all their "LASER" lights, don't cause too much light pollution the night before.
And their "LASER" lights might make for an interesting composition against the backdrop of the milky way.
They are only 13 miles away, and due south of my intended position.

 

[Blank_Stare]

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

Depends on who's steering, methinks...

 

[Stavros Kiri]

Depends on who's steering, methinks...

... and whether he/she is wearing it too or not

 

[Blank_Stare]

... and whether he/she is wearing it too or not

..Hands @Stavros Kiri a tissue for that Anal-Retentiveness...

 

[Stavros Kiri]

..Hands @Stavros Kiri a tissue for that Anal-Retentiveness...

I hope you're still joking

 

[Blank_Stare]

I hope you're still joking

Well, aren't we both?

(I thought it was obvious that it "depending on who was steering" implied that wearing/not wearing the glasses was part of the concept... Trust me, I am as AR as the next guy - more so than many - I'd like to think I included you in good company. Anyway, just having fun, no harm intended.)

 

[Stavros Kiri]

Well, aren't we both?

Of course. Your replies were smart and funny. (I just had to make sure about the previous one.)
We're all getting cheered up, fired up and excited about the eclipse ...

 

[MidgetDwarf]

I do not watch any tv, so I do not keep up with current events. I only found about the solar eclipse from my boss that is taking a trip to Idaho to go see it.

My question is the following:

I will start school on Monday. I live in Southern California. I will be at school from 8am to 5pm. Should I go buy some protection? I do not plan to look at the eclipse (not that interested). I will be walking on campus, and my campus is located on a hill.

 

[Janus]

I do not watch any tv, so I do not keep up with current events. I only found about the solar eclipse from my boss that is taking a trip to Idaho to go see it.

My question is the following:

I will start school on Monday. I live in Southern California. I will be at school from 8am to 5pm. Should I go buy some protection? I do not plan to look at the eclipse (not that interested). I will be walking on campus, and my campus is located on a hill.

Unless you are planning at looking at the Sun, no. The protective glasses are just so that you can directly watch the eclipse during its partial phase without damaging your eyes. There is no more danger from an eclipse that there is at any other time. (other than the fact that it impels the curious to stare at the Sun.)

 

[Tom.G]

In case it hasn't been mentioned before (I didn't read ALL those previous posts!)

https://eclipse2017.nasa.gov/safety

About half way down the page under "Additional Safety information":

"Viewing with Protection -- Experts suggests that one widely available filter for safe solar viewing is welders glass of sufficiently high number. The only ones that are safe for direct viewing of the Sun with your eyes are those of Shade 12 or higher[/color]"

 

[anorlunda]

I will start school on Monday. I live in Southern California. I will be at school from 8am to 5pm. Should I go buy some protection? I do not plan to look at the eclipse (not that interested). I will be walking on campus, and my campus is located on a hill.

See post #201 in this thread for a safe alternative to glasses for you and your classmates.

 

[jim hardy]

See post #201 in this thread for a safe alternative to glasses for you and your classmates.

Worth repeating here for newcomers
from post 201 , https://www.physicsforums.com/threads/u-s-solar-eclipse-of-aug-21-2017.866521/page-11#post-5821619

 

[jtbell]

Eclipse mania has even affected the cheesy TV commercials of car dealers in the area.

 

[OmCheeto]

Still eerily quiet here, traffic-wise:

(about an hour ago)

Guessing either the carpocalypse scared everyone away, or there aren't as many "campers" in Oregon as I thought.

On a sad note, 400 homes were ordered to evacuate yesterday from a small town on the edge of totality, due to a fire:

http://www.opb.org/news/article/sisters-milli-fire-evacuation-level-3-leave-now/

Residents of more than 400 homes in a prime eclipse-viewing location in Oregon were ordered to evacuate Friday because of a rapidly growing wildfire that had already closed access to a portion of a wilderness area and a regional highway.​

Stupid fires...

Not sure if the smoke is going to be a problem:

Images courtesy of earth.nullschool.net

 

[dlgoff]

I'm going to be wearing one of my PF tee-shirts.

 

[Borg]

I'm going to be wearing one of my PF tee-shirts.
View attachment 209322

I was planning on doing the same.

 

[jtbell]

More eclipse mania. I went to a stamp show in Columbia today:

After holding my thumb on the stamp to warm it up a bit:

 

[jtbell]

See post #201 in this thread for a safe alternative to glasses for you and your classmates.

Another alternative is to use a pair of binoculars as a projector, as I did with the transit of Venus five years ago:

https://www.physicsforums.com/threads/see-the-transit-of-venus-live-here.611663/#post-3944420

 

[Stavros Kiri]

I was planning on doing the same.

Just planning? ...

 

[Stavros Kiri]

Time again to see the current sun's activity (while everyone is getting ready and preparing for the eclipse tomorrow). Currently there is still a spot group, region 2671 (significant) and (coincidence or no) there was a new big solar flare last night [today is Sun Aug 20, 2017], from a new spot group, rotating now into view, which will get the name 2672 by tomorrow (eclipse day! - now that's coincidence!). More details for all coming up on my next post.

Here is why looking at the activity (together with the eclipse) is important:
1. Watch this short and concise NASA's eclipse history review video:

2. See
https://www.physicsforums.com/threads/u-s-solar-eclipse-of-aug-21-2017.866521/page-10#post-5817925
(and useful links there)
3. As @russ_watters pointed out

Oh, awesome - this will help with focus and give something else to look at during partial.

https://www.physicsforums.com/threa...17-nice-spot-group.919696/page-2#post-5823041

So in focussing your instruments for the eclipse (cameras, telescopes, binoculars ... with sun filters of course), first take your chance with focussing on the current sun spot group (region 2671). It will be sectacular and useful.

Imagine if there was another big solar flare tomorrow during the eclipse [totality ]?
There is actually a new promising spot group (getting the name 2672) rotating into view to the Earth by tomorrow! (See next post) Wow! May be we are lucky after all! ...