2019 October 14 – Andromeda Before Photoshop


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
October the 14th of 2019. While it is titled
Andromeda Before Photoshop. So what do we see here? Well, this is an image of the
Andromeda Galaxy the nearest large spiral galaxy to our own
and only a couple of million light years away. So very close by
galactic standards. And we see the structures within
the galaxy the central nucleus and then the dust
lanes in the outer – as we go towards
the outer layers. Now the Andromeda Galaxy
is often photographed and we see lots of
images of it, but I quite like the one we see today. This is kind of the
beginning of the image. What do we see when
we’re first done. Now, this is actually
a combination of hundreds of different
images put together and stacked together. But what you get to see is all
of the little imperfections that do occur when you
are taking things taking images of things out in space. And that is because our
skies are not crystal clear and there are lots of other
things going on there as well. And in fact, we see some
artificial phenomena here. In fact, a lot of
these are either airplane trails or
satellite trails as they move across the sky. So if they happen to go
across your field of view, you’re going to
get them and have to have them removed in order
to get your nice image of just the sky. So there are some things
that are artificial created here on earth. There are other things that
are natural phenomena that occur all the time things like
meteor trails can also come up through this image
and would cause would cause a distortion to it. Sometimes we see a meteor and
showing up in one of our images which of course, is something
that cannot be planned for. And we can also get
cosmic ray trails again, high energy particles
from space that are coming through the Earth’s atmosphere. And finally cameras
are not perfect. There are pixels within
them that are bad. So you can see. You’ll get to see
some of those as well. Now what would it look
like after processing. Well, what you need to do is to
move the mouse over the image and all of the
processing is then done. And you can see what
has been removed. All of these long
streaks have been removed to get rid of this. And I mentioned the bad
pixels, you can see some cases, there where it looks like
a star is being removed. It’s not that the
star was being removed that that was a bad pixel
within the camera detector. The charge coupled device
that detects the light and sometimes there
are certain bad pixels and those can be removed and
you can find that as well here. So when you have the
mouse over the image you get the final image. Once it has been processed
and all of the other things have been removed all of the
airplane and satellite trails meteors you can
actually remove all that to be able to see
what Andromeda would look like through a pristine sky. So that’s what we
get to see here in our image of the day for
the great Andromeda Galaxy. So that was our picture of
the day for October the 14th of 2019. It was titled Andromeda
Before Photoshop. We’ll be back again tomorrow
for the next picture previewed to be The Galaxy Above. So we’ll see what that
is about tomorrow. And until then have a
great day, everyone. And I will see you in class.

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