(meteorobs) blind spots and black meteors

[Norman W. McLeod III]

>Unless you have a companion(or video evidence) who is also seeing the same 
>black meteors, I'll assume you are noticing a mechanism of the eye.

That makes sense.


>Norman is probably seeing the blind spots in the center of his eyes.

I just did a fairly good measurement of my blind spots.  For left eye 
looking at Saiph (left foot of Orion), Sirius is about 18 degrees to the 
left.  With Sirius on the meridian both stars were at about the same 
elevation.  But Sirius is in my blind spot, which measured 5 degrees wide 
and 7 degrees tall.  The ellipse of blindness is centered about 2 degrees 
above Saiph.

For the right eye I used Bellatrix - Aldebaran but had to turn my head a 
bit to get them on a horizontal line of sight.  Just about the same 
measurements came out.  The blind spots are thus 18 degrees away from 
central vision.  No binocular blindness, thank goodness, or else we would 
all have a dark spot in otherwise good vision.  The spots would be centered 
about 36 degrees apart straddling central vision.

Finding out how large my blind spots are and where they are located, I 
wonder how they would be connected with black meteors.  The meteors have 
always been points at or near central vision.  Floaters don't move nearly 
fast enough for me to be satisfied with that explanation either.  While 
lying down your floaters would be moving even slower.  In standing up, the 
floaters tend to sink downwards with gravity.  I haven't logged enough 
hours in planetariums to see a black meteor there.  So, it's still up in 
the air...

Norman




>It's nearly impossible to keep your eyes from moving, so as Norman notices 
>the blind spot it moves across his vision and a black spot appears to move 
>across the star field.
>
>One of the most dramatic experiments to perform is the demonstration of 
>the blind spot
>http://faculty.washington.edu/chudler/chvision.html
>
>http://www.exploratorium.edu/snacks/blind_spot.html
>http://coglab.wadsworth.com/experiments/BlindSpot/
>http://library.thinkquest.org/J002330/
>
>need more?
>http://www.dogpile.com/info.dogpl/search/web/%2527blind%2Bspot%2527%2Beye
>
>Charlie
>
>Norman W. McLeod III wrote:
>
>>At 09:39 AM 11/20/2004, you wrote:
>>
>>>Could you "discuss" the black meteor briefly again Norman; or anyone else.
>>>I've read and long thought that this was simply something similar to a 
>>>floater in the eye.  Thanks.
>>>
>>>Long trains,
>>>      Jeff W.
>>
>>
>>Here is a partial repost I did on 7 Feb 1999 concerning black 
>>meteors.  Their frequency seems less that what I originally wrote.  I 
>>have heard several possible explanations for them but am not satisfied 
>>with any.  Repost begins next :
>>
>>I watched the Perseids of 1960 for a couple of hours at max with my best 
>>friend at the time.  Late in the second hour I was astonished to see what 
>>looked like a meteor with no color at all, and my announcement of having 
>>just  seen a black meteor got us both laughing.  It wasn't 
>>fatigue-induced either, for I was fully alert.
>>Turns out I have generally seen one, sometimes two, during most of my 
>>observing sessions.  Over the years the appearance of black meteors has 
>>been linked to fatigue a number of times, but that hasn't been the case 
>>with me.  Too bad I haven't been recording them.
>>
>>Our reasoning with joviality  was that meteors come in all colors, so why 
>>not black ones?  The ones I see are generally Geminid speed with the 
>>moving body visible as a point.  I even get an impression of magnitude 
>>from them,  perhaps from the size of the black spot compared to the size 
>>of star glare.  The majority are magnitudes  +1 to +3 and travel an 
>>average of 10 degrees.  I have never seen one move so fast that only a 
>>streak was visible (as in the majority of short fast meteors), nor have I 
>>ever seen one leave a train (black or otherwise.)  They seem very real to 
>>me, but all these years the situation has been a joke.  Perhaps it's time 
>>to reconsider?
>>
>>Nebulous meteors are plenty real.  Most of them have a bright central 
>>body surrounded by an ethereal envelope, and the ones that are also 
>>carrying a wake look like moving comets.  Very rare are the ones that 
>>have an appearance like a moving planetary nebula with no central 
>>body.  In nearly all cases the meteors are slow.  I always mention these 
>>in my notes.
>>
>>Norman
>>
>>
>>
>>Norman W. McLeod III
>>Staff Advisor
>>American Meteor Society
>>
>>Fort Myers, Florida
>>nmcleod at peganet.com
>>
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>>
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>
>
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Norman W. McLeod III
Staff Advisor
American Meteor Society

Fort Myers, Florida
nmcleod at peganet.com
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