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

  1. Aug 17, 2017 #251

    anorlunda

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    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.
     
    Last edited: Aug 17, 2017
  2. Aug 17, 2017 #252

    russ_watters

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    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.
     
    Last edited: Aug 17, 2017
  3. Aug 17, 2017 #253
    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....
     
  4. Aug 17, 2017 #254

    mfb

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    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.
     
  5. Aug 17, 2017 #255

    George Jones

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    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.
     
    Last edited: Aug 17, 2017
  6. Aug 17, 2017 #256

    jim hardy

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    @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
    upload_2017-8-17_10-9-4.png

    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 below


    Note 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.
    original was darker by a decade.
     
    Last edited: Aug 17, 2017
  7. Aug 17, 2017 #257
    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.
     
  8. Aug 17, 2017 #258
    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 :cry:
     
  9. Aug 17, 2017 #259
    I guess the important question is, "Is she coming back afterwards?" :oldlaugh:
     
  10. Aug 17, 2017 #260

    russ_watters

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    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.
     
  11. Aug 17, 2017 #261
    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
     
  12. Aug 17, 2017 #262

    mfb

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    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.
     
  13. Aug 17, 2017 #263
    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?
     
  14. Aug 17, 2017 #264

    jim hardy

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    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.



    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
     
    Last edited: Aug 17, 2017
  15. Aug 17, 2017 #265

    OmCheeto

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

    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.
     
  16. Aug 17, 2017 #266

    OmCheeto

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    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.........
     
  17. Aug 17, 2017 #267
    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 ...
     
  18. Aug 17, 2017 #268

    BillTre

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  19. Aug 17, 2017 #269

    anorlunda

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    Wendy's restaurants inside the totality zone in Kentucky are selling them for $1
     
  20. Aug 17, 2017 #270

    scottdave

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    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). :woot: Next one within driving distance is Oct 14, 2023 (only 6 years away). And it is a Saturday to boot :smile: :cool: 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.
     
    Last edited: Aug 17, 2017
  21. Aug 17, 2017 #271

    jim hardy

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    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.
     
  22. Aug 17, 2017 #272
    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??
     
  23. Aug 17, 2017 #273

    scottdave

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    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
     
  24. Aug 17, 2017 #274
    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??
     
  25. Aug 17, 2017 #275

    nsaspook

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    It's going to get very strange over the weekend there.
    2F%2Fscontent-sea1-1.xx.fbcdn.net%2Fv%2Ft1.0-9%2F20841027_1447725195281780_4890113905233237115_n.jpg


    20727883_1472163326184275_4065713658998860243_n.jpg

     
    Last edited: Aug 18, 2017
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