Hello! Have you ever wanted to do some science with your telescope and
astronomical camera or maybe just a standard DSLR without a telescope at all?
It's really easy to do. I'd like to introduce you to this which is the Star Analyser
grating. Now the grating comes mounted in this filter cell which you
then just screw directly onto your eyepiece or your static FITS camera or
astronomical video camera or, as I said, just a plain DSLR. When you do that, it
splits the light so that you can study the stars just like professional
scientists do. Now before I show you how we mount this grating,
let's take a look at some of the results that you can easily get.
Let's start with one of my favorites.
Each of these Star Analyser spectra is a different OBAFGKM star.
At the top are the hot type B stars and at the bottom are the cool type M stars.
This was captured with just a 9 inch telescope and an astronomical video
camera. But you could do the same with a DSLR or FITS camera too. Notice that each
star spectrum is a little different because they're all different temperatures.
For example, this hydrogen beta line is strongest on this type A star, which is
our familiar alpha Lyra.
Now don't worry, you don't need to become an astrophysicist to do this kind of thing.
It's really pretty simple and there's a lot of help on the web. And, you know what?
This kind of thing makes a great high school science project.
Ok. Let's look at a different example now. This is a very hot star called a Wolf Rayet
star. Because it's at the end of its life, it's shedding its outer shell.
That means we can see into the core of the star. With just a DSLR and
a Star Analyser, you can capture this star spectrum.
You'll be able to see the glowing carbon from the core. And you can detect the
effects of the massive stellar winds as the star blows off its outer shell.
My experience is that when I capture this kind of data, my understanding of
the stars grows in leaps and bounds.
Now here's an example that's much closer to home. With a Star
Analyser on almost any astronomical camera, it's easy to detect...
the methane in the atmosphere of Neptune.
Just a few decades ago, this kind of thing was only possible with professional instruments.
Now, all it takes is a small telescope and astronomical camera.
So this is an animation of an exploding star. A Type II supernova happens when
the star's internal furnace runs out of fuel and its core collapses under the
force of gravity. A shock wave from the implosion rushes outward
and the the star explodes. For a short while it's brighter than all of the stars in the galaxy.
With just an eight inch telescope and a cooled FITS camera, just 15 minutes of
integration time will capture the supernova spectrum.
You can easily determine what type of supernova it is
and, by observing the Doppler shift in the spectrum, you can measure how many
millions of miles per hour its shell is racing towards us.
Ok, so here's our last example.This one is a
quasar: a black hole with an accretion disk.
It's four trillion times brighter than the Sun ... but it's also billions of
light-years away.
It's so distant that we can detect the red shift due to the cosmological
expansion of the universe. With the same equipment you'd use on a supernova,
you can easily capture the quasar spectrum and then measure its redshift.
From that you can determine its distance.
So ... this stuff isn't hard. Amateurs do it all the time...
And those are some pretty exciting examples, aren't they?! Now just for a moment,
let's look at how we use the Star Analyser grating to get these kinds of
results
So this is a typical wide-field view of Orion's belt when viewed through the
Star Analyser grating. We can see the individual stars. And on each star we can
see a rainbow called a "spectrum." The Star Analyser grating and splits the
starlight (just like a prism would do) to create each spectrum.
And each spectrum contains information about the star. Once we've captured that
image, we then look at it in software.
We're going to look at a program named RSpec here. Now there on the left is
the star. And on the right is the spectrum. Now you don't need to use a
color camera. That just happens to the image that we are using here.
We're pretty far zoomed in. Now what the software does is plot the intensity of
this region over in the graph here on the right. That peak there is the star.
And this region over here is the spectrum. We won't get into a lot of
detail here, but that dip right there in the graph corresponds to a gap in the
rainbow here. And by analyzing this graph, we can tell all sorts of information
about the star: its temperature, some of the materials that are on it,
the star type.
It's really easy to use.
You know, what always amazes me is just how easy it is for amateurs with such
simple equipment to capture and interpret the spectra of stars.
It doesn't require dark sky sites or a lot of aperture.
I've seen amateurs do this with a six inch refractor and a webcam. So I've got here
an astronomical video camera.
The neat thing about this camera is that when you use a video camera with the
RSpec software, the spectrum is live.
That means you've got a lot of opportunity to do public outreach and
education.
So, when we take the Star Analyser grating, we just screw onto the nose
piece of our camera. Most cameras come with the nose piece that's about the
right length. There's nothing exact about [It doesn't have to be exactly placed.]
Now you might be using a static, cooled FITS camera
It may have a nose piece that works for you ... or perhaps you're using a filter
wheel. You can mount the grating in a filter wheel and the site talks more
about how to mount it so it's approximately the right distance from
your sensor. And finally we've got our beloved DSLRs. Now it's easy and there's
two ways to use a DSLR. The first is to use this thread adapter and thread it on
to our camera's lens cap threads and then just thread our grating
right onto it
Now we're ready to go! We can capture spectra. We can piggyback the camera.
We could even use the camera on a static tripod without tracking and capture the
spectra of bright stars.
Now there is a second way that a lot of us use our cameras and of course that's
without the lens - we're using our telescope as the lens. And for that, if
you have your t-ring on the camera already, you just use a different adapter
that we have that goes into the t-ring threads. And then you thread the SAtar
Analyser into it and then mount this on your telescope.
So like I said when we started, wouldn't YOU like to do some science with your
telescope or your DSLR?!
It's easy to do and it's inexpensive. Check out our site. We love to answer
questions and I look forward to hearing from you that you've captured your first
star spectrum!