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Thread: Total Solar Eclipse - August 21, 2017

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    Total Solar Eclipse - August 21, 2017

    Within a day or two of April 19, the Sun will rise at the same azimuth as it will on August 21. This will give a good preview of the Sun's location and motion through the sky on eclipse day.

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    Cool. I am not doing a lot of precise observing that day (just photography and videography), but if I were, April 19th would be a big day for my prepping.
    Forming opinions as we speak

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    I plan to practice pointing a telephoto lens out the sunroof of my wife's car that day, to verify that pointing at that elevation will work and preferably is not too uncomfortable. (Better than trying to use a tripod that high; I surely can't get the right part of my varifocal glasses behind the viewfinder without putting a tripod on table...)

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    Quote Originally Posted by ngc3314 View Post
    I plan to practice pointing a telephoto lens out the sunroof of my wife's car that day, to verify that pointing at that elevation will work and preferably is not too uncomfortable. (Better than trying to use a tripod that high; I surely can't get the right part of my varifocal glasses behind the viewfinder without putting a tripod on table...)
    I keep looking for the like button... good plan.
    Forming opinions as we speak

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    For the Nashville crowd, though set for the middle ball field at Triple Creek Park in Gallatin, TN...

    Gallatin, TN [36 24' 43" N, 86 25' 39" W]
    First contact 12:00:00
    Alt. 63d 7m
    Az. 152.7d

    Meridian crossing 12:48:54 [~ 1/2 R]
    Alt. 65d 27.4m
    Az. 180d

    Beginning of totality 13:28:05
    Alt. 63d 54.5m
    Az. 202d 17m

    End of totality 13:30:39
    Alt. 63d 42.5m
    Az. 203d 36.7m

    End of eclipse 14:54:39
    Alt. 52.5d
    Az. 237d


    [Per Stellarium. Placing it here allows meto have an easy way to find this. ]

    [Note: I have added the eclipse end info, which was mistakenly used for totality end.]
    Last edited by George; 2017-Apr-13 at 02:14 PM.
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    Quote Originally Posted by George View Post
    For the Nashville crowd, though set for the middle ball field at Triple Creek Park in Gallatin, TN...
    That's about 5 miles from our hotel (which I have called just to make sure they're not doing what some places in Oregon did with vanishing reservations). Looking at the map, I just realized that from growing up in Nashville, I do know exactly where that is.

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    Hey! I'll be in Nashville for the eclipse, too. I'll be doing a little outreach at the new Kimpton Hotel in town.

    Anyone else who's planning to be there, let me know via PM. Maybe we can meet up!

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    Quote Originally Posted by ngc3314 View Post
    That's about 5 miles from our hotel (which I have called just to make sure they're not doing what some places in Oregon did with vanishing reservations). Looking at the map, I just realized that from growing up in Nashville, I do know exactly where that is.
    It is a large park with 12 ball fields, but given its proximity to Nashville and that it is a bullseye for the central totality track, I wonder if they can accommodate what could be a huge turn-out? Locally, we have one State park (Enchanted Rock) that simply closes its gates when the parking is full.

    Triple Creek is advertising the eclipse event and I've registered with them, but there is no hint of any reservation space.

    [I fixed a mistake above, btw.]
    Last edited by George; 2017-Apr-13 at 02:15 PM.
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    NASA will have a presence at Southern Illinois University, Carbondale, ILL., This is the Maximum Duration window, IIRC. Two hours from St. Louis.

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    Quote Originally Posted by Noisy Rhysling View Post
    NASA will have a presence at Southern Illinois University, Carbondale, ILL., This is the Maximum Duration window, IIRC. Two hours from St. Louis.
    I think max. duration is between Carbondale and Gallatin, though the difference in time is negligible, no doubt.

    Here are some useful links.

    Path by states............... http://www.eclipse2017.org/2017/path_through_the_US.htm
    Google zooming map..... http://xjubier.free.fr/en/site_pages...leMapFull.html
    Cloud cover map........... http://www.eclipse2017.org/2017/weather/2017_clouds.htm
    Gallatin Registration...... http://www.visitsumnertn.com/see-do/...ipse-encounter
    We know time flies, we just can't see its wings.

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    Here is a simulation I made of the eclipse from different cities.
    http://orbitsimulator.com/gravitySim...17Eclipse.html

    The lighting conditions are simply my guess from seeing many partial and annular eclipses. I've been to 2 total solar eclipses, and it rained during totality both times, so I've never seen the corona. But I have watched the sky turn dark.
    I've also noticed that until the Sun is 90% covered, an unsuspecting person won't notice anything. Beyond that, the sky slowly grows darker (its been darkening the whole time, but your eyes have been compensating), and the planets become visible.
    As totality arrives, the remaining light is squelched in just a few seconds, like a person operating a dimmer switch.

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    Quote Originally Posted by tony873004 View Post
    Here is a simulation I made of the eclipse from different cities.
    http://orbitsimulator.com/gravitySim...17Eclipse.html

    The lighting conditions are simply my guess from seeing many partial and annular eclipses. I've been to 2 total solar eclipses, and it rained during totality both times, so I've never seen the corona. But I have watched the sky turn dark.
    I've also noticed that until the Sun is 90% covered, an unsuspecting person won't notice anything. Beyond that, the sky slowly grows darker (its been darkening the whole time, but your eyes have been compensating), and the planets become visible.
    As totality arrives, the remaining light is squelched in just a few seconds, like a person operating a dimmer switch.
    That's excellent, thanks! It gives a good idea of what to expect, and the local timing. I'm heading to Wyoming, and looking forward to my first total eclipse :-)

    Re the darkness of eclipses, we had a very nice partial up here in Dundee a couple of years ago, which was over 90%. As it was very gradual, I, and most people, didn't really feel it was getting very dark, although it did get noticeably colder. However, someone had set up a camera taking a timelapse of the crowds of people at the observatory, and it was quite remarkable watching it afterwards, and seeing just how dark it actually got.
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    What a birthday it will be for me, and I'm not far from the band of totality!
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    Quote Originally Posted by molesworth View Post
    That's excellent, thanks! It gives a good idea of what to expect, and the local timing...
    Thanks. As for the timing, note that my page says that the timings in my simulations are roughly 1 min 45 seconds early compared to other published predictions. Which one of us is correct? Probably them. So don't expect it to be down-to-the-second accurate!

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    Quote Originally Posted by tony873004 View Post
    Thanks. As for the timing, note that my page says that the timings in my simulations are roughly 1 min 45 seconds early compared to other published predictions. Which one of us is correct? Probably them. So don't expect it to be down-to-the-second accurate!
    "Close enough for government work" as the saying goes :-)

    Certainly good enough to make sure we're set up at a good observing site with cameras at the ready in plenty of time. Now, if we can just make sure the clouds stay away...
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    I am curious if we will see any background stars or planets worth noting.

    Regulus is reasonably close at a distance of 1.3 deg (1.6 deg from Idaho), but Mars is 8.4 deg away. Mercury is a little farther, apparently.
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    Going from East to west we should be able to see Jupiter, Mercury, Mars and Venus. Mars and Mercury may be tough as they will be close to the sun


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    Quote Originally Posted by schlaugh View Post
    Going from East to west we should be able to see Jupiter, Mercury, Mars and Venus. Mars and Mercury may be tough as they will be close to the sun.
    During totality, we should have no problem seeing Mars and Mercury, right? It looks like totality is equivalent to about an apparent mag. = 1, though it is also an extended object so "surface" brightness will be much less.
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    The innermost corona has surface brightness more comparable to a near-full Moon, fading rapidly away from the Sun. OTOH, Regulus especially will show up in the field of binoculars, telephoto lenses, or wide-field telescopes. (Oddly I can't find much on the way of numbers via Google, probably because of confusion with "eclipse magnitude").

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    Quote Originally Posted by ngc3314 View Post
    The innermost corona has surface brightness more comparable to a near-full Moon, fading rapidly away from the Sun. OTOH, Regulus especially will show up in the field of binoculars, telephoto lenses, or wide-field telescopes. (Oddly I can't find much on the way of numbers via Google, probably because of confusion with "eclipse magnitude").
    That's cool to know. I was thinking of trying to do some photography (setting it up to run more or less automatically, so I can let the camera do its thing while I just watch the eclipse). For the partial phase stuff, I can just test on the non-eclipsed Sun prior to the event. But if the corona is on the same order of magnitude of brightness as the Moon, I can just do some test photography of the Moon to see what I get at different exposure lengths and other settings.

    Does anyone have any experience with eclipse photography, and want to tell me the things I'm overlooking?
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    According to this site Mercury will likely not be visible to unaided viewing. But the other objects mentioned above should be visible.

    Mercury. This elusive but sometimes bright planet is often too near the Sun to be easily observed except during optimal times when in twilight skies. Solar eclipses, however, sometimes provide thrilling opportunities to spot Mercury. On eclipse day Mercury will, in fact, be about three quarters of the way from the horizon to the eclipse Sun. Unfortunately for this eclipse Mercury will likely be too faint for most eyes to see.
    Better star chart here.
    Last edited by schlaugh; 2017-Apr-20 at 10:39 PM.

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    Quote Originally Posted by Grey View Post
    Does anyone have any experience with eclipse photography, and want to tell me the things I'm overlooking?
    I may have posted this earlier - but here's a montage made from transparencies of the 1979 eclipse in Oregon, so you can scale to any ISO speed and f/ratio. The wide surface brightness range of prominences and corona means that a huge range of exposures will show something interesting.

    For partial phases, I've had unexpectedly good results by cutting a hole in the bottom of a black 32-ounce fast-food plastic cup and duct-taping a solar filter there. The cup provides a way to make sure the filter stays over the lens even for large-long telephoto lenses (additional dust tape recommended at that point).
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