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Old 2019-10-17, 15:36   #1
tServo
 
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Default Mercury's transit

Will the transit of Mercury next month be visible to the unaided eye ?
I would be using the glasses I used for the last solar eclipse a short time ago
and, of course, assuming no clouds. I have seen video on youtube, and it looks like one would
need at least good binoculars. TIA
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Old 2019-10-17, 16:11   #2
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Quote:
Originally Posted by tServo View Post
Will the transit of Mercury next month be visible to the unaided eye ?
I would be using the glasses I used for the last solar eclipse a short time ago
and, of course, assuming no clouds. I have seen video on youtube, and it looks like one would need at least good binoculars. TIA
It's undoubtedly not visible to my unaided eye. I'm severely myopic.

Assuming you have typical vision, you can probably resolve something about an arc minute across. The diameter of the sun and that of Mercury, in kilometers, are easily available from Wikipedia. I'll throw in the angular diameter of the sun as seen from the earth for free --- it's 30 arc minutes to an adequate degree of accuracy. To adequate accuracy, the relative distances between the sun, Mercury and the Earth can also be obtained from Wikipedia.

All the rest is left as a simple exercise in geometry for the reader. You didn't expect me to do all your work for you, did you?

Just to be clear, I do know the answer.

Last fiddled with by xilman on 2019-10-17 at 16:15 Reason: Add final sentence
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Old 2019-10-17, 16:12   #3
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Quote:
Originally Posted by tServo View Post
Will the transit of Mercury next month be visible to the unaided eye ?
I would be using the glasses I used for the last solar eclipse a short time ago
and, of course, assuming no clouds. I have seen video on youtube, and it looks like one would
need at least good binoculars. TIA
Looking into the sun is fraught with danger, more so using binoculars! Do you want to be blinded? I suggest projecting the sun's image onto a a piece of paper, maybe with a simple pinhole camera.

Last fiddled with by paulunderwood on 2019-10-17 at 16:12
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Old 2019-10-17, 16:19   #4
xilman
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Originally Posted by paulunderwood View Post
Looking into the sun is fraught with danger, more so using binoculars! Do you want to be blinded? I suggest projecting the sun's image onto a a piece of paper, maybe with a simple pinhole camera.
True. However, if you use a filter suitable for the task, it's fine.

I've observed the sun many times through 15x80 binoculars, including the 1999 98% partial eclipse visible from Oxford.

If you don't know what constitutes a suitable filter, don't observe the sun through a telescope or binoculars.
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Old 2019-10-17, 16:22   #5
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Quote:
Originally Posted by paulunderwood View Post
I suggest projecting the sun's image onto a a piece of paper, maybe with a simple pinhole camera.
That worked for Venus, but Mercury is too small. Its angular diameter will be five times smaller than Venus, so the dot will have 25 times less area.

Compare these images:

https://en.wikipedia.org/wiki/Transi...us_Transit.JPG (Venus)

https://en.wikipedia.org/wiki/Transi..._9th,_2016.png (Mercury)

Last fiddled with by GP2 on 2019-10-17 at 16:25
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Old 2019-10-17, 16:30   #6
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Quote:
Originally Posted by GP2 View Post
That worked for Venus, but Mercury is too small. Its angular diameter will be five times smaller than Venus, so the dot will have 25 times less area.

Compare these images:

https://en.wikipedia.org/wiki/Transi...us_Transit.JPG (Venus)

https://en.wikipedia.org/wiki/Transi..._9th,_2016.png (Mercury)
I see. Or rather I did not! The image of Mercury's transit was indistinguishable between the dots of filth on on my 1080p monitor,
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Old 2019-10-17, 18:31   #7
ATH
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Quote:
Originally Posted by xilman View Post
IAll the rest is left as a simple exercise in geometry for the reader. You didn't expect me to do all your work for you, did you?
You can also look up on heavens-above that the Mercury diameter is 9,95 arc seconds on Nov 11th.
But it also says the Mercury distance is 0.676 AU that day, and wikipedia informs us Mercury's radius is 2439.7 km, so we can double check:

Mercury diameter: 3600 arc seconds / degree * 2 * arctan( 2439700 m / (0.676 AU * 149597870700 m/AU)) ~ 9.95 arc seconds

The Sun distance is 0.9899949 AU that day and the Sun radius is 696,342 km:
Sun diameter: 60 arc minutes / degree * 2 * arctan( 696342000 m / (0.9899949 AU * 149597870700 m/AU)) ~ 32.33 arc minutes
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Old 2019-10-18, 19:12   #8
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On May 9, 2016 (previous transit) I was in Escalante, Utah. I didn't even know it was going to happen. The National Park Service visitor center had a little viewing setup (maybe a small Celestron with appropriate filter?) and it was an interesting experience to see this.

Here is the Wikipedia image of that event.
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Old 2019-10-18, 22:12   #9
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During the 2012 Venus transit, I was barely able to see Venus through just eclipse shades. I had to really squint to see it. And I couldn't see any of the sunspots.

Once I projected it through binoculars onto a piece of paper, both Venus and the sunspots were clear as day.

No way in hell would I be able to see Mercury - which would be even smaller than the sunspots.

Last fiddled with by Mysticial on 2019-10-18 at 22:18
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Old 2019-10-18, 23:00   #10
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Quote:
Originally Posted by Mysticial View Post
Once I projected it through binoculars onto a piece of paper, both Venus and the sunspots were clear as day.
I tried that method with Mercury in 2016 and couldn't see it. It worked with Venus in 2004 and 2012.

The dot for Mercury is so small that you probably need the focus to be exact, and that's hard to do when you're projecting onto paper.

Last fiddled with by GP2 on 2019-10-18 at 23:01
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Old 2019-10-19, 02:10   #11
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When I was a kid, sunglasses were referred to as smoke glasses in Persian (now they are called Sun glasses). At the time, people would use the black residue of smoke from a candle (Soot) to darken transparent glass to look at a solar eclipse. I assume this is the origin of the prank were someone is given eye glasses which leave dark rings around the eyes when removed.
In any case if you use smoked glass you still risk eye injury if you don't smoke the glasses dark enough to be safe.

Last fiddled with by a1call on 2019-10-19 at 02:14
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