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09 Sep 2017 11:44

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
 
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Watsisname
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09 Sep 2017 16:38

Lol, horizontal hail would be pretty terrifying.
 
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09 Sep 2017 20:06

I want to see megacryometeors one day :)  I read about a particularly alarming one that fell in Portugal back in the 1800s the size of an elephant!  I also want to experience ball lightning.  How does it pass through walls and spin and last for so long?  In laboratory experiments they've only managed to make it last for fractions of a second.

In the 1935 Labor Day hurricane the wind was so intense that the friction of it on the sand caused fires to occur mid-air!
 
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09 Sep 2017 22:28

A-L-E-X wrote:
Source of the post I read about a particularly alarming one that fell in Portugal back in the 1800s the size of an elephant!


A-L-E-X wrote:
Source of the post In the 1935 Labor Day hurricane the wind was so intense that the friction of it on the sand caused fires to occur mid-air!


Where and by whom were these documented?
 
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10 Sep 2017 07:49

https://books.google.com/books?id=OLbvX ... ne&f=false

http://archives.chicagotribune.com/1935 ... ere-killed

http://www.storm2k.org/phpbb2/viewtopic.php?t=23205

I'm surprised you hadn't heard of it before, the violent winds causing the sand to cause fire sparks in the air was compared to a Van De Graaf generator.  

Documentation is in the footnotes.

https://en.wikipedia.org/wiki/Megacryometeor

. Jesús Martínez-Frías, a planetary geologist and astrobiologist at Institute of Geosciences (Spanish: Instituto de Geociencias, IGEO) in the Spanish National Research Council (Spanish: Consejo Superior de Investigaciones Científicas, CSIC)[1] in Madrid, pioneered research into megacryometeors in January 2000 after ice chunks weighing up to 6.6 pounds (3.0 kg) rained on Spain out of cloudless skies for ten days.

Contents  [hide] 
1 Mass and size
2 Formation
3 References
4 External links
Mass and size[edit]
More than 50 megacryometeors have been recorded since the year 2000. They vary in mass between 0.5 kilograms (1.1 lb) to several tens of kilograms. One in Brazil weighed in at more than 50 kilograms (110 lb).[2] Chunks about 2 m (6 ft 7 in) in size fell in Scotland on 13 August 1849.[3]

Formation[edit]
The process that creates megacryometeors is not completely understood, mainly with respect to the atmospheric dynamics necessary to produce them. They may have a similar mechanism of formation to that leading to production of hailstones.[4] Scientific studies show that their composition matches normal tropospheric rainwater for the areas in which they fall. In addition, megacryometeors display textural variations of the ice and hydro-chemical and isotopic heterogeneity, which evidence a complex formation process in the atmosphere.[5][6][7] It is known that they do not form from airplane toilet leakage because the large chunks of ice that occasionally do fall from airliners are distinctly blue due to the disinfectant used.

Some have speculated that these ice chunks must have fallen from aircraft fuselages[4] after plain water ice accumulating on those aircraft through normal atmospheric conditions has simply broken loose. However, similar events occurred prior to the invention of aircraft.[8][9] Studies indicate that fluctuations in tropopause, associated with hydration of the lower stratosphere and stratospheric cooling, can be related to their formation.[5] A detailed micro-Raman spectroscopic study made it possible to place the formation of the megacryometeors within a particular range of temperatures: −10 to −20 °C (14 to −4 °F).[10] They are sometimes confused with meteors because they can leave small impact craters.

Interesting stuff about ball lightning too- apparently the great Nikola Tesla could reproduce them in the lab

https://en.wikipedia.org/wiki/Ball_ligh ... cteristics
https://en.wikipedia.org/wiki/Ball_ligh ... _lightning
 
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10 Sep 2017 14:38

A-L-E-X wrote:
Source of the post I'm surprised you hadn't heard of it before, the violent winds causing the sand to cause fire sparks in the air was compared to a Van De Graaf generator.

But there is a big difference between sparks from static electricity and actual flames from friction.
 
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10 Sep 2017 14:59

Mr. Abner wrote:
A-L-E-X wrote:
Source of the post I'm surprised you hadn't heard of it before, the violent winds causing the sand to cause fire sparks in the air was compared to a Van De Graaf generator.

But there is a big difference between sparks from static electricity and actual flames from friction.

Sorry I meant sparks of fire not something akin to a forest fire lol.  Needless to say, but it scared numerous people- of course they had never witnessed a Cat 5 in action before.
 
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Watsisname
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10 Sep 2017 16:24

A-L-E-X wrote:
Source of the post Sorry I meant sparks of fire not something akin to a forest fire lol.

Be careful of one's wording. :)  Sparks of electricity are not the same as sparks of fire, either.
There can also be electric discharges in the ash clouds of volcanic eruptions.

Be careful of one's sources, too.  Just because it is on wikipedia does not mean it is reliable, even if it has citations.  Check the citations, too.  The very large cryometeor in Brazil (second citation) is a broken link for example, and I can't find anything else about that event online. Some of the other reports seem more credible though.

Basically, I'm just trying to get you to apply cautious skepticism to everything you read online.  Critically reviewing a claim is an important part of science regardless of whether or not you think the claim is true.
 
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12 Sep 2017 10:01

Watsisname wrote:
A-L-E-X wrote:
Source of the post Sorry I meant sparks of fire not something akin to a forest fire lol.

Be careful of one's wording. :)  Sparks of electricity are not the same as sparks of fire, either.
There can also be electric discharges in the ash clouds of volcanic eruptions.

Be careful of one's sources, too.  Just because it is on wikipedia does not mean it is reliable, even if it has citations.  Check the citations, too.  The very large cryometeor in Brazil (second citation) is a broken link for example, and I can't find anything else about that event online. Some of the other reports seem more credible though.

Basically, I'm just trying to get you to apply cautious skepticism to everything you read online.  Critically reviewing a claim is an important part of science regardless of whether or not you think the claim is true.

I completely agree with you, Wat (I wish I knew your real name, I find it weird calling someone Wat :P)  I agree with you about wikipedia too, I researched the footnotes and that's how I found the Nature articles.  About the megacryometer issue, I'm not sure how accurate it is (I've seen scientists on both sides of the issue) but I at least thought it was worthy of discussing because the scientist in Spain has done some in-depth research on  it and there was an article in Discovery magazine about it too (I also thought it was worthy of discussing because a scientific mechanism for why it might be occurring was outlined- many outlandish claims can't be taken seriously because there isn't a mechanisjh described for why it might happen (like some who want to draw a connection between solar activity and hurricanes- I can't find any kind of mechanism that would make that possible, however there is a possible mechanism for how TC's could lead to more tremors, which is what the Nature articles were about.  That's what made that research credible. I also found some of the ball lightning accounts amazing, but it seems like it's been viewed by so many reliable sources and somewhat replicated in the lab- but not for the amount of time or size it's been seen in the field- so there are still some mysteries surrounding it, but we do probably have a scientific mechanism for how and why it happens.)
 
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26 Sep 2017 12:07

CPU: Intel Core i7-5820K 4.2GHz 6-Core Processor - RAM: G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 - GPU: EVGA GeForce GTX 1080 Ti SC Black Edition
Quando omni flunkus, moritati
 
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27 Sep 2017 22:47

I have a question to ask abut binoculars.  I'm going on a trip to the mountains in a couple of weeks and I want to have a good set of binoculars with me.  Basically, I have three requirements 1) I have a tripod but I don't want to lug it around all the time so even if it's just for brief moments, I want it to be at least somewhat handholdable 2) I want to be able to see all of M31 and her satellite galaxies in one FOV and the dark dust lanes too and 3) I want to at least be able to make out the rings of Saturn.  I already have a pair of Bushnell 10x50 I've had since high school but I want something bigger that I can handhold at least for a few minutes.  Should I get the Celestron 15x70 (fov 4.4 degrees, weight 3 pounds) or the Celestron 25x70 (fov 2.7 degrees, weight 3.3 pounds)?  At first blush I thought I'd get the 25x70 since 15x70 already seems to be pretty close to the 10x50 I already own.  Also, are 20x80 (fov 3.6 degrees, weight 4.7 pounds) at all handholdable?  And I take it I should stay far away from any zoom binoculars?
 
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28 Sep 2017 18:21

A-L-E-X, I would recommend staying away from 25x70.  Your 10x50 would be better, or try the 15x70 if you like them.  To put it briefly, bigger numbers are not always better, and often quite the opposite.

The first number is the magnification, and the second number is the aperture.  What 25x70 does for you compared to 15x70 is take the same amount of light (70mm aperture) and spread it out more ((25/15)^2 = 2.8x more area), which will only make the view of faint objects like galaxies worse.  Higher magnification on hand-held binoculars also makes it more difficult to maintain a steady image, and most people find this uncomfortable or annoying -- a lesson learned over and over by bird watchers.

The most important thing for viewing M31 is a wide enough field of view (at least 3 degrees FOV sounds good), and light gathering power (larger aperture size).  15x70 will gather about twice as much light as 10x50, while also magnifying 50% more, so it roughly balances out to give a larger image with about the same surface brightness.  20x80 gathers 2.5x more light but spreads it over 4x as much area, so that is also worse than the 10x50.  4.7 pounds also does seem a bit heavy.

Finally, with viewing M31, what you mostly see even with a large telescope is the bright central region of the galaxy, and it's fairly featureless.  The spiral bands and dust lanes are visible but they're a lot fainter.  I'm not sure how we'll you'll be able to spot them with the binocs, but your 10x50 or the 15x70 sound like your best choices.

Hope that helps. :)
 
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29 Sep 2017 04:05

Watsisname wrote:
A-L-E-X, I would recommend staying away from 25x70.  Your 10x50 would be better, or try the 15x70 if you like them.  To put it briefly, bigger numbers are not always better, and often quite the opposite.

The first number is the magnification, and the second number is the aperture.  What 25x70 does for you compared to 15x70 is take the same amount of light (70mm aperture) and spread it out more ((25/15)^2 = 2.8x more area), which will only make the view of faint objects like galaxies worse.  Higher magnification on hand-held binoculars also makes it more difficult to maintain a steady image, and most people find this uncomfortable or annoying -- a lesson learned over and over by bird watchers.

The most important thing for viewing M31 is a wide enough field of view (at least 3 degrees FOV sounds good), and light gathering power (larger aperture size).  15x70 will gather about twice as much light as 10x50, while also magnifying 50% more, so it roughly balances out to give a larger image with about the same surface brightness.  20x80 gathers 2.5x more light but spreads it over 4x as much area, so that is also worse than the 10x50.  4.7 pounds also does seem a bit heavy.

Finally, with viewing M31, what you mostly see even with a large telescope is the bright central region of the galaxy, and it's fairly featureless.  The spiral bands and dust lanes are visible but they're a lot fainter.  I'm not sure how we'll you'll be able to spot them with the binocs, but your 10x50 or the 15x70 sound like your best choices.

Hope that helps. :)

Thanks Wat! The 15x70 definitely has much better reviews on Cloudy Nights.  Exit pupil between 4-5mm (aperture/magnification) seems to be the sweet spot, Wat.  I was only thinking of the 25x because I also wanted to see the rings of Saturn, but I guess they look like "ears" on either of them.  At any rate, I could always mount the 15x70 on a tripod and do afocal photography and zoom in further with the camera lens, right?
Found out some interesting things from the reviews- 1) none of these 70mm binoculars actually have an aperture of 70mm.  The 15x70 model is actually 63mm (exit pupil 4.2mm) and the 25x70 actually has an aperture of 62mm (exit pupil 2.5mm, actual fov is only 2.4 degrees!)  Even 20x80 binoculars were found to only have an aperture of 72mm.  2) I did read that you could see M32 and M110 with averted vision with the 25x70 but that M31 actually looked bigger and brighter with the 15x70. 3) Because they are dual-lensed, a pair of binoculars has 1.4142 (square root of 2) times as much reach as a telescope of the same aperture- does this make sense to you?  In other words, a 70mm pair of binoculars should be able to see stars as dim as what a 100mm telescope can see.  Read that with the 15x70 binoculars the limiting magnitude is around 11.7 or 11.8  They also said that for some reason- increased magnification allows you to see dimmer stars (I don't see how that could be if the overall image is dimmer- but they might be referring to point source stars vs extended objects like M31-- they said it was something like 0.1 mag for every 10% increase in power, so since 25/15=0.67, theoretically I should be able to see point source stars 0.7 mag dimmer with the 25x- this might help with finding stars in light pollution but does nothing for extended objects like M31.) 4) with any of these binoculars, the fov is only sharp for the center 70%, so that is another thing in favor of a fov as wide as possible- like the 4.4 degrees of the 15x70- which becomes 3.1 degrees or almost exactly the apparent size of M31 ( if you only count the center 70% of the fov.)
With my telescopes too, I find that lower power is better.  I was wondering if in light pollution the 25x would perform better, but the 2.5mm exit pupil is really small........
 
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12 Oct 2017 23:42

They just send me this in email
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13 Oct 2017 00:54

I had a related question to the above, how do the views from a 70mm 400 f.l. refractor compare to those of 15x70 binoculars (if a similar power to the binoculars is used with an eyepiece with the refractor)

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