Salutations, celestial sight-seers! I'm David Fuller with Eyes on the Sky. What's up this week?
Neptune! The eighth planet reaches opposition on September 1st and you can see the
planet with simple binoculars. That's right! You don't even necessarily need a
telescope to be able to spy the farthest planet in our solar system. Ok it's not
really the furthest planet - we all know that Pluto is actually the furthest one
right? That's ok you can still see this and it doesn't take a lot of
magnification to do so. So let's switch over to Stellarium so you can see where
in the sky to start looking for it. We're generally facing southeast not long
after it gets dark, and I've highlighted where Neptune is in the sky. And as you
can see it's a rather star poor region in the constellation of Aquarius.
But we're actually going to start looking from Capricornus. However even those stars are not
terribly bright, so we're going to start in a few brighter ones to make sure that we're looking in
the right location. So let's begin at Pegasus which is going to be this square
shape over towards the east it's gonna look a little bit more like a diamond as
its on each side sorta like this. We're going to follow that across this way
over towards into Aquarius. Once we get to Aquarius we're gonna kind of hop along
Aquarius, and then down towards Capricornus.
But, let's take off all these helpful star constellation lines and hop this way
without having to actually look at those as a crutch. This star right here is
Alpheratz, in Andromeda. We're gonna go diagonally across the great square of
Pegasus that's about twenty degrees of sky. You can measure it simply just by
holding your fists together at arm's length and the two stars should be about on
either side of where your fists are. We're gonna keep going that same direction out
this way - now,
don't get confused by these stars which are the head and neck of Pegasus. We're
gonna go under the head and neck to this star another twenty degrees which is
going to be Alpha
Aquarii. And now we can drop a fist away it'll just go ten degree distances
where to go from Alpha Aquarii, to Beta Aquarii. Turn ourselves about 90
degrees down towards the horizon and wind up at Deneb Algiedi in Capricornus.
And if we zoom-in on this area of the sky we can see that there's a fair number of stars
to be able to guide our way over to where we want to see Neptune. But,
measuring that we can see that it's a good 14 degrees of sky across. So since
binoculars are only about seven degrees or so that's a long way to go
just hoping that we find it there. And then once we get there, how do we know
for sure that we found the planet? So let's turn off our measuring tool and we'll turn on
the ocular view, which you can see up here in Stellarium, which is very useful you can
set the field of view and magnification you want to use for a given eyepieces and
telescopes. And I've got this set for binoculars. So this green circle is a seven
degrees field of view. And when you have Deneb Algiedi centered, remember you're gonna do that 20 - 20 - 10 -10 to find it
this star, Nashira, which is a - almost fourth magnitude star - is going to be in
the same field of view as Deneb Algiedi, which is third magnitude. So you'll be able to
find those fairly simply. These are dimmer stars above it, we've got some dimmer stars below. So go
with these brighter ones and now go on the same direction as these two stars
opposite of Nashira. So we're gonna go this way and you have this star coming into your field of view
just as Nashira leaves while Deneb Algiedi is still there.
This star is going to be about fourth magnitude, and it is Iota Aquarii. So that should still be fairly easy to
see with most any binoculars. Now this is where it gets a little bit tricky tricky
as part of the star hop. Imagine this is the apex of a pyramid that's on its side
so if we look at these stars here and here and then there's some dim one here
and then another bright-ish one here and then a dim one there. There's sort of this long
line that's a base, but sorta makes a pyramid angled off on its side. that pyramid
is where we're going to go through but we're gonna draw our line again - Nashira,
Deneb Algiedi through Iota to this star so on the same line so the brighter of
these two stars but the inner one and that will bring us to 42 Aquarii. So as
Iota is getting ready to leave the field of view we're gonna bring another star
into our field of view over on this side. So we passed through the base of our
pyramid and now gone on from 42 to this star which is Sigma Aquarii and
that's a 4.8 magnitude star. So that's also a 5th magnitude star. But with this one centered neptune is
now in our field of view of binoculars. So the planet is actually there. And once
we actually center Neptune, we can also see that there's this other star Lambda Aquarii is
gonna be over on this side. And that star is a 3.7 magnitude star. So things start to
brighten up you know you've got a little bit too far. But the way to find Neptune
for sure is looked for this quadrilateral shape of stars. Neptune is actually
very near another star right here. So they're these four, 7th magnitude stars
between Sigma and lambda over here and Neptune is at the end of this
quadrilateral set of stars here. Now you've got other stars as well but neptune is
pretty close to in the middle of them as of this date. However, if we bring up our
date and time window and go through time you can see that Neptune is going to move
closer to Sigma and away from where Lambda is - but the Moon will of course interfere towards the
end of September and then couple days later into October, then we'll have
Neptune really into this quadrilateral shape of stars. I said I would also
show you how to find this with a reversed view. And so will back our way out
and get over to Deneb Algiedi again
and as you can see I kinda went backwards that way so you can see the
direction we're going to go because now Nashira is on this side
of Deneb Algiedi, so it's it's still the same way in the sky but it's going to
reverse it the way you look at it through your finder scope field of view.
So you have to mentally reverse the image. But if you've already done the
hop once with binoculars, you have a pretty good idea of what to look for and
be able to mentally reverse that as you watch the view in your finder scope. So
opposite of Nashira, away from there from Deneb Algiedi, and then we're
going to go over to Iota Aquarii, Deneb Algiedi leaves our field of view and as
that happens we bring this skewed pyramid shape into the field of view. We'e
gonna look for the brighter two stars and choose the inner one which is 42
Aquarii, as that goes across, and we leave Iota on the other side of the
field of view. We're going to bring Sigma Aquarii into our field of view, and as
we do
Neptune arrives - we center that - we now have Sigma on one side we've got Lambda
the other side and Neptune is centered so then we can look that, with our
telescope, take off
the crosshairs and Neptune would be visible in a telescopic field of view.
Now, Neptune is interesting to look at your telescope is even though it's blue
white and kind of a pale, blue color. It doesn't look like a blue-white star does
and that's because as you could see up here over in the upper left-hand corner
of Stellarium it shows that its 2.4 arc seconds
diameter. So you really can see a little tiny bit of disk to the planet. You won't see any
detail, but you can see the disc which is different than a star which is always
going to be point-like in nature.
Plus the planet displays reflected sunlight a little bit differently than a
star looks. So you really can tell that you're looking at a planet and not a
star and that's a pretty neat thing to be able to see for the farthest planet
away from us in the solar system - except for Pluto,
of course. Right? That's all for this week!
Keep your eyes on the sky and your outdoor lights aimed down so we can all see
what's up.
I'm David Fuller, wishing you clear, and dark, skies.