Greetings and welcome to the
Introduction to Astronomy.
One of the things that I like
to do in each of my introductory
astronomy classes is to begin
the class with the astronomy
picture of the day from
the NASA website that is
APOD.NASA.GOV/APOD.
And today's picture for
August the 17th of 2019.
Well, it is titled 1901
Photograph: The Orion Nebula.
So what do we see here?
Well, this is an
image taken back
in 1901 of the Orion nebula.
Now, if you think
about that 1901
was still part of the
early days of photography
starting in the mid 1800s.
Photography did exist, but it
was also a very time consuming
and difficult thing to do.
And at around that time or
even a little earlier than most
things were done by hand.
So people an astronomer would
look through the telescope
and would sketch
out what they saw.
And that is how things were
done from the beginning
of the telescope at
the time of Galileo
until photography
became efficient enough
to be able to be used.
And at the time.
This one.
This is actually what they
call a photographic plate.
So we're used to today,
digital photographs.
So just a digital string
of numbers that record.
And then are converted into
an image at this point,
it was actually a piece of glass
with a photographic emulsion
on it, which would then
be exposed to the sky
and in this case, a 50
minute long exposure
to be able to bring out the
Orion nebula that we see here.
So an object that
we've seen many times.
But this time, has
taken over 100 years ago
now more recently many of these
images have been digitized.
So scanned and put
into a digital format
for ease of use and sharing
across various areas.
And that's one, of
course advantages
of digital photography is that
it's very easy to share images
whereas when you have a piece
of glass with your image on it.
It's very difficult
to share and to store
storage requires very important
controlled temperature
and controlled
humidity conditions
in order to keep that
emulsion and that image
from deteriorating over time.
So in this case, we now
have the digital images
and a lot of these
are being converted
so that they can still be used.
And in fact, having a
lot of these old images
is important to be able to go
back and look what things were
like 100 years ago or more.
So what.
How had things
changed in astronomy.
We look at things and things
don't change very quickly.
But there are some
cases where we
want to see what were
things like 100 years ago.
And this is a chance to
be able to go and see
and to go back to look at the
old archives of these images
and of course, the
advanced to photography
was a very important
one for astronomy
to go from sketching
things to photography
was very important because
you went from something that
was subjective something people
do to something that is more
objective just the image
so that everyone would
see the same image.
So anyone looking at this image
today is seeing the same thing,
essentially.
Whereas if 10 different people
had sketched the Orion nebula
on this day you would have
10 different images of what
it looked like everyone
would be a little bit
different because everybody
sees things slightly differently
and would be able to give us
would highlight different areas
may see something else as
more or less important.
So it's one of
the things that is
going on to look at these
images to study them
and to bring them up
into the digital age.
So that was our picture of
the day for August the 17th
of 2019.
It was titled 1901
Photograph: The Orion Nebula.
We'll be back again tomorrow
for the next picture previewed
to be Human Spaceship.
So we'll see what that
is about tomorrow.
And until then have a
great day, everyone.
And I will see you in class.
