[APML]: Re: Eclipse

["C. Hernandez" <herdel@sol.racsa.co.cr>]

David Williams wrote:
> 
>     Mr. Hernandez:
> 
>     Thank you for writing back to me about the eclipse coming up.  Do
> you know what time of day on this Thursday that it should happen?
> Since I live in Paris, Illinois, in the midwestern part of the U.S., I
> might not even be able to tell that the eclipse is happening.  Also
> I'll have to check the weather reports to see if it will be clear.
> 
>     Are you going to try to take a picture of it?  I think that it
> would be neat to get a picture of the total eclipse or even part of
> it.  My mom, sister, and niece are out west in Phoenix, Arizona on a
> trip now and will be there on Thursday too.  But when I looked at the
> map it showed that it wouldn't be much better out there either.  Well
> I better get ready for school so I won't be late.  Good bye.
> David
> 
To the ASTRO-PHOTO, ATM, SHALLOW-SKY and ASTRO mailing lists:

I am posting to the lists this e-mail to David Williams, so any of you
can help him to enjoy the eclipse as much as I expect to do, altough it
might be a little bit off the main subjects of the lists. My apologies
for this  but he might need all the help he can, for his safety.

Hi David,

Yes I am planning to take some pictures of the eclipse, if the weather
cooperates, because it has been cloudy the past few days. I will let you
know how they turn out.

I am glad to tell you that you will be able to get some of the incoming
eclipse in Illinois (I don't know where Paris is, though I used to visit
the Windy City many times while living in Oconomowoc, Wisconsin). In
fact, you'll get to see more of the eclipse than your folks traveling
South to Phoenix, this because the penumbra shifts to the North as the
time of the eclipse goes by. 

As an example, the eclipse in Phoenix attains its maximum at 9:55 am and
people there will see only 2% of the Sun covered by the Moon. People in
Chicago will see about 5% of the Sun covered around 11:55 am (just great
for lunch break) and people in Boston will get to see a nice 20% of
coverage around 1:25 pm.

So check your weather, ask for an early lunch break at school, or better
yet, take your whole class with you, and enjoy the tiny bit of eclipse
you are going to get. 

But please, DO NOT LOOK AT THE SUN WITHOUT PROPER FILTERING. Please do
not use any of the following materials as filters, they are dangerous:

        CD's
        Floppy disks
        Processed photographic film, neither color or B&W
        Mylar wraps (such as those used in food packaging)
        Polarizing filters
        Sun glases
        Smoked glass

Many of these, altough will permit you to view the Sun, will allow a lot
of fatal UV or infrared light through that will burn your retina. And
the worst of it, you won't feel any pain because the retina has no pain
receptors. If you can get a hold to it, there is an excellent article on
this subject by Ralph Chou int the Feb. issue of S&T.

Use only aluminized Mylar designed to view the Sun or welding filters
from #12 up. The first ones you can probably get at photo shops and the
second ones at hardware stores.

If you are not sure of a material, please ask beforehand, either to me
or to someone at any of the mailing lists you are subscribed to. I am
sure that many folks at the ATM list through which you found me will be
more than glad to help as would people from other lists.

Let me know about your experience afterwards. I sure will write to you
about mine.

Carlos Hernandez
Heredia Costa Rica