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

  1. Aug 16, 2017 #226

    mfb

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    In the 21st century, we have 67 total eclipses (list), or 5.6 per calendar month on average.

    Jan: 5 <- perihelion Jan 3
    Feb: 0
    Mar: 6
    Apr: 7
    May: 7
    Jun: 3
    Jul: 6 <- aphelion Jul 4
    Aug: 12
    Sep: 8
    Oct: 1
    Nov: 3
    Dec: 9

    The Moon has to cross the ecliptic at the same time as new moon for an eclipse, this leads to about two "eclipse seasons" per year. They shift around over time, however, with a period of 18.6 years, or -20 days shift per year. This year it is in late February/August, next year in early February and July/August, in 2019 in early January/July and then late December, 2020 in June/December and so on. Typically we get one solar eclipse and one or two lunar eclipses per season, in rare cases we get two solar eclipses, but then they are both partial, and only visible from far north/south, respectively.

    Overall this leads to a roughly uniform distribution of eclipses, with a small bias towards the summer for total eclipses where the Sun appears smaller today, and a small bias towards the winter for partial eclipses. The position of the perihelion relative to the seasons has a period of ~23,000 years, or just 1.5 days per century, too small to be notable over a human lifetime.

    By the way: If you want to be as close to the Sun as possible, 2020 is your opportunity. Kilimanjaro or maybe some place in the Indian ocean, 5th of January around 8 am GMT. The closest perihelion this century.
    If you want to be as far away as possible: 4th of July 2019, around 8 am GMT, probably somewhere south-east of Hawaii.
     
  2. Aug 16, 2017 #227
    my local weather forecast (Washington DC) says partly sunny on 8/21 eclipses day, will keep finger crossed
     
  3. Aug 16, 2017 #228

    OmCheeto

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    Duh....

    https://www.greatamericaneclipse.com/

    Upper right hand image link.
    TODAY'S CLOUD COVER PREDICTION FOR AUGUST 21ST COURTESY OF WDTINC.COM, ESRI.COM, AND GREATAMERICANECLIPSE.COM. GET HI-RES FORECAST MAPS AT THIS LOCATION.

    hmmmm......


    ...for the rest of the nation. Lot's more black! Less traffic for me!


    Today is the first time in 5 days we have not been overcast in the hours before 1 pm.
    (The only time I can do solar PV experiments.)
    [expletives deleted] trees........
     
  4. Aug 16, 2017 #229
    Relax guys! It will be seen getting dark anyway! ... during the day, which is the amazing part. No clouds can do that.
     
  5. Aug 16, 2017 #230

    Janus

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    I've already experienced that once, in '79. This time I hope to actually see more.
     
  6. Aug 16, 2017 #231
    I sure hope so too! Seeing the Sun's corona during totality is of course amazing and unique! It's also a big opportunity to study better and more effectively the sun's activity during that time (e.g. flares etc.) ...

    But if clouds get on the way ... at least we ought to see the "bright side" of daytime darkness! ... Or a video from high altitude totality, or different location. [Personly, I consider nice videos equally as spectacular! ...]

    I guess we'll find out in a few days.
     
    Last edited: Aug 16, 2017
  7. Aug 16, 2017 #232
    Will direct sun damage camera lenses?
     
  8. Aug 16, 2017 #233
    I think, during totality, no.
     
  9. Aug 16, 2017 #234
    What about before? Especially concerning a GoPro.
     
  10. Aug 16, 2017 #235
    I don't think that should be a problem either, as long as you limit appropriately the exposure time (don't keep it too long).
    However, let's wait for more responses to your question (from more people), because I am not a cameras expert.
    [I recall taking short exposure pictures of direct sun at different times and with different types of cameras (even a video) with no problem at all ... just there's not much to see on a bright sun. But on the eclipse it would still be interesting.]
     
    Last edited: Aug 16, 2017
  11. Aug 16, 2017 #236

    russ_watters

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    Yes, it will almost certainly damage the camera without the appropriate filter
     
  12. Aug 16, 2017 #237

    russ_watters

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    A Go-pro, like many modern digital cameras, especially video cameras, doesn't have an active shutter. Exposure is controlled electronically. So this logic will not save the camera.

    Also, a go-pro without a giant lens attached is too low of a magnification to see the eclipse anyway.

    I expect an awful lot of people are going to destroy their cameras on Monday.

    When I was in high school for the 1994 eclipse, I successfully took a photo with a film camera and no filter. The focal length was 900mm and if I remember correctly I traced and cut out a dime on my lens cap, for a focal ratio around 50.
     
  13. Aug 16, 2017 #238
    Even with short exposure time?
     
  14. Aug 16, 2017 #239

    russ_watters

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    Not sure if you saw my last post after posting this, but; No shutter = infinite exposure time

    [Edit] And even on my SLR, with shutter, I'd be worried about melting the shutter.
     
  15. Aug 16, 2017 #240
    We posted ~simultaneously. Ok I get it now. I think you're right.
     
  16. Aug 16, 2017 #241

    scottdave

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  17. Aug 16, 2017 #242

    jim hardy

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    I was in the autoparts store today and noticed welding goggle lenses.

    Took a #12 out to parking lot to look at sun and decided a single #12 isn't enough . It was mildly painful, as was a single #10 i tried last week. ...
    Got a #5 , it and the #12 together gave a quite comfortable image with no afterglow when i blink.

    So i bought two of each. about ten bucks total.

    Here's a picture through two #10's that i made last week, just held them over the lens on Fair Anne's Ipad:
    sunthrutwo#10lenses.JPG
    two #10's is so dark it took the Ipad quite a while to figure out there was an image present.
    I don't know if the numbers add like decibels, but two tens was a bit too dark and a single 12 was too bright.

    The guys behind the counter got enthused and tried to order a case of #12 lenses for themselves. Their suppliers are all sold out.

    old jim
     
  18. Aug 16, 2017 #243

    I like Serena

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    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.
     
  19. Aug 16, 2017 #244

    scottdave

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    I found something, then accidentally closed the window. It said that NASA recommends using #12 or higher welding goggles. The article said that many people feel like their eyes hurt with a #12, but #14 seems too dark, so I guess you have something, combining a #5 and #12. It must be some sort of logarithmic adding, like you suggested.
     
  20. Aug 16, 2017 #245
    A school I'm working with is taking a field trip to Greenville, SC to see it:

    http://www.bju.edu/eclipse/

    They invited me, but I'm too busy to make a whole day of it. I'll probably step outside and have a peak from wherever I am in the SE on Monday, 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.
     
  21. Aug 16, 2017 #246
    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
    ?
    Because of the clouds? What difference does it make? Totality is totality ...

    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.
     
    Last edited: Aug 16, 2017
  22. Aug 17, 2017 #247

    mfb

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    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.

    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.
     
  23. Aug 17, 2017 #248
    I agree on one part:
    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
     
  24. Aug 17, 2017 #249

    jim hardy

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    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.


    . upload_2017-8-17_7-50-47.png
    Got one for Fair Anne, too.

    Home Depot, farm supply stores, and autoparts stores are likely places to find them not yet sold out.
     
  25. Aug 17, 2017 #250
    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
     
    Last edited: Aug 17, 2017
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