Episode: 3243
Title: HPR3243: Pictor - free and open radio astronomy
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3243/hpr3243.mp3
Transcribed: 2025-10-24 19:30:56

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This is Haka Public Radio episode 3243 for Wednesday the 6th of January 2021.
Today's show is entitled,
Victor, Free and Open Radio Astronomy.
It is hosted by Andrew Conway and is about 48 minutes long and carries a clean flag.
The summary is, discussion with the people that created the Victor Radio Telescope.
This episode of HBR is brought to you by an honest host.com.
Get 15% discount on all shared hosting with the offer code HBR15.
That's HBR15.
Better web hosting that's honest and fair at An Honesthost.com.
Hello and welcome to another episode of Haka Public Radio.
With me, Mike Nalu, who's from known as Andrew.
And I'm sort of on my own turf talking about astronomy today.
But I'm not the one that's going to be saying the interesting things, not that I would ever do.
I'm actually joined by two guests who run a very interesting and novel
radio telescope projects.
So would you like to introduce yourself to our listeners?
Sure, so my name is Apostolos.
I am studying computer science at the University of Firavs in Greece.
Me and Vasyls actually work on several RF and radio astronomy projects.
One of them is the Victor Radio Telescope, which we will discuss mostly today.
I hope the listeners enjoy our conversation or chat.
So my name is Vasyls.
I'm a Apostolos brother.
I'm a graduate student of European International Studies in University of Firavs.
And now I'm a postgraduate student in Technical University of Athens in Environment and Development.
As Apostolos told you, we are running Victor.
And I hope you have a great podcast.
Thank you very much guys.
So we should say how we met in that we were both at Fosden earlier this year.
And we just came up to the HDR table.
Somehow we're introduced to me and you told me about your Pictor Telescope.
And that's how we got to this episode.
So before we go any further, can you just explain to people who maybe you're not that familiar
with astronomy or even radio telescopes what a radio telescope does?
Yeah, sure.
So a radio telescope is basically like an optical telescope.
But it's actually instead of observing in visible wavelengths,
it's actually built for detecting radio signals.
So one thing many people are not aware of is that
objects in space do not only meet visible wavelengths, but there are many objects that
emit radio waves.
So like neutral hydrogen, for example, several atomic and molecular spectro lines,
mesors, pulsars, radio galaxies, quasars.
I mean, there's a whole variety of objects that emit radio waves.
And so a radio telescope is basically an instrument used to detect such objects.
So it's basically opening up a window to the invisible universe in a way.
Yeah, that's a great, that's a great little description.
You mentioned mesors there.
That's actually something that I worked on.
And it's really surprising if you don't know mesors is like a naturally occurring
microwave version of a laser, but we get them in our own star of the sun.
So it's just, it's, I haven't heard that word for a while, really interesting.
Yeah, it's interesting.
Yeah, so now your telescope, the pictorial radio telescope, it's special
because as I understand it, it's open source.
So could you see how it came about and how we decided to make it an
open source project, both in software and hardware, I understand.
Yeah, sure. So we wanted to build a radio telescope at the beginning, like for personal use.
But then we decided, you know, why not?
We built the telescope. We've invested a lot of time into it, both in terms of hardware and software.
So why not put it online for everyone to use it for free?
So one part of this, because it's based on the same philosophy, is to put it up open source.
Now every project we work on in radio astronomy is like everything we do is open source on,
so you can find everything on GitHub. And the good thing about this is that
many people have actually came to the project, copied the source code and worked on their own
projects. Some of them either use it for digital signal processing, for data analysis.
And some just even applied the whole code to their telescopes.
So that's pretty good. That's pretty cool. And also we have the contributors.
So you check out GitHub, you'll see some poll records and contributions. So it's definitely like
a win-win situation in a way.
At every point, an open source standard information can spread around people very easily and can
definitely help you back at some point. So that's why we release everything at GitHub.
Excellent. And what language are you coding in?
So we mainly use Python. So pick for is basically based on Python. For the web server, we use PHP.
So I use our sensor request. It gets passed to via PHP to a page that the Raspberry Pi computer on
the telescope can access via Python and basically fits the observation parameter. So it just runs
the observation from there and sends the data to the user via email. And it doesn't just send
the row data because it wouldn't be super convenient for the user, you know. Basically the user
has to do no work, basically just fills in the form, sends the data, sends the parameter to the
observation and receives an email with an image file. So that image file basically contains all
the plots, all the data. And can anyone use it?
Yeah, yeah, yeah. That's why we decided to create an online remote radio telescope with
everyone could use totally for free, no matter where they leave the educational background.
That was the main reason we decided to create an instrument, a SATA specter. And actually another
reason was that radio astronomy, particularly in Greece, is not very popular at least compared to
optical astronomy. And to be honest, this does make sense to a certain point because astronomy
at visible wavelengths works pretty much like, alright, do you have a lens, you have an optical
sensor? So it's very easy to understand what you're observing and how everything works. And on
the other hand, a radio astronomy is a different thing because human does not have a radio sensor
to detect a radio signal. So it's difficult for someone to understand how everything works at
a very first time point. Right, okay. I mean, that's some, that's, that's some. So,
anyone can use it. And you're looking for contributors to the project in terms of like developing the
code or anything like that? Yeah, sure. I mean, everything is open. So if anyone wants to
contribute, make a pull request. Of course, absolutely. We are actively looking for people who
wish to help. You don't have to contribute to use Victor, obviously. But, you know, if you've
got programming knowledge or have some ideas you wish to implement, which has already been done.
Like certain people have come on GitHub said, okay, Victor is cool, but I want to improve it.
So here's a code snippet. You could apply to, for example, send me some of the data in a row format.
So I can do further analysis or whatever. And yeah, pretty much you can contribute. You don't have
to, of course, but any, any contribution is of course appreciated. Yeah, great. So I mean,
you do have an audience right now of people who are, certainly have the skills to contribute,
people who are interested in, you know, consort software, people I know that are interested in,
you mentioned Python, you also mentioned Raspberry Pis, that's another topic that comes up quite a lot
in the hack-up public radio. So, yeah, so the focusening, you know, you might want to take a look
and see if there's something you can offer here. And so, anyone can use it.
And I've, I've been looking at your website. Your very website is actually very clean,
nice introduction. It's not, you know, if you're going to be even someday at school,
it's not going to scare you off. I don't think it's nice, nice, gentle introduction
to the world radio astronomy. And you've got a PDF that you can download that introduces you as well,
which I thought was really nice. I've not read the whole thing yet, but the beginning of it looks
really good. And so, do you have any hopes of particular people who would be using it? Are you
wanting schools to use it or you just want general people of interest to start using it, maybe developing
their own projects? Any thoughts on that front? Yeah, I think, first of all, thank you for your
kindly words. Kind of words. Yeah, at the beginning, it was mostly friends and people around
their work who just wanted to use a radio telescope. But now, we have a lot of, let's say,
proposals from some schools or even universities who want to use Victor as an educational project.
And that makes us really happy because we have the feeling that we can contribute at some point
to a radio astronomy education. And that's really awesome.
It does indeed, yeah. So, I mean, I can think of quite a few groups that I would know would
be interesting using it. There's one problem we have with astronomy, and I'm here in Scotland,
and like the whole of the UK, really, our weather is not great. In fact, I've got about the worst
weather in the country. So, we only get what may be 30, 40, 50 nights a year, where it's clear,
so we can use normal telescopes, optical telescopes. So, actually, we've got the ideal climate for
radio astronomy because radio astronomy, it's not bothered about clouds, is it? You can see straight
two clouds. Yeah, exactly. That's a very, very big advantage of radio astronomy, comparing to
optical astronomy. But even here, actually, optical astronomy, of course, it's something very,
very popular. We're also working on optical astronomy as well. But, yeah, in some northern
countries, like Scotland or Belgium, for example, things are much more difficult for optical astronomy,
because it's like 90% of the year cloudy. So, yeah, radio astronomy is the only way there.
Yeah, so I don't know. I confess, I've worked in the theoretical side of things,
like I've mentioned measures, but I've never actually worked. I actually used a radio telescope
before, but feeling that's about to change once I get to know your telescope a little bit.
So, now, I imagine that you've got a lot of work into this from the looks of it.
Whether any particular challenge is along the way that you had to deal with, that you found
difficult to deal with. Yeah, it's definitely been a lot of work, like from the very beginning,
until, like, even before and after everything works, you know, you're still making improvements.
So, it's definitely quite challenging, but, you know, as I said, users don't have to worry about
this. The code is ready, and they can apply to their telescopes and everything. So, some of the
challenges, I remember one time, like, at the early beginning, we had obtained this dish,
seemingly for 2.4 gigahertz, I mean, at least that's what the manufacturer claimed it to work at.
And basically, it didn't work. We had built the feed home, we had measured everything,
we had pretty much tried everything. And the problem was that this dish had actually got,
it was like a grid, sort of, dish, like with holes. And so, the wavelength, the 21 centimeter
wavelength, was basically too short for these holes. So, what we ended up doing is, like, I remember
being out on one morning, and I just said, okay, why not? Let me just try to turn the feed home around,
to point directly to Zenith. And it actually worked, like, like magic, I see the hydrogen line,
barley, but, yeah. So, what we ended up doing is, this was a problem with the dish, just
take all the aluminum foil from the kitchen, just wrap it around the dish, among the
Plycro. So, that ended up being the dissolution. Obviously, we cannot have a piece of aluminum foil
running 24-7 in the rain and things like that. So, we just took a little mesh and cut it around the
dish. So, that's basically, sort of, more permanent solution. We do have a lot of fun stories
about picture issues. For example, in FOSDAM, there was a very, very, there is a very, very interesting
story. We've made a lot of talks in Greece, all over Greece, and no problem ever happened,
and everything worked very well. And I'm talking about problems because,
a picture, as we said, it's a remote radio telescope. And of course, when we have a talk,
we make a presentation about how picture works, and of course, we are doing a non-line observation,
a remote observation. And in Greece, everything worked like a charm, everything went perfect.
But when we were in, in FOSDAM, lots of miles away from, from a picture control,
just before our presentations, we realized that we have a problem connecting to the telescope,
because, of course, we always do a test observation before a talk to be sure that everything
works perfectly. And we had a problem. We had no connection with the telescope, and we didn't
know what to do. Fortunately, we tried to contact at home Greece, and tell to someone to just
restart the control panel of the picture, because there's something went weird with the voltage.
At the very, very last minute, we saw the problem, and everything went fine.
Oh, that's what I'm glad to hear it. So, as I said, I missed the talk at FOSDAM, because I was,
one day I was stuck to the HPR table, and the other day I was just overwhelmed with talks I wanted
to go to. But yeah, that's absolutely, you mentioned in the, well, part of the reason I asked that
question is because I really want people to realize that when you go into the website, imagine
it looks fairly, I mean, it does look fairly easy and straightforward. But it's good to appreciate
how much work goes behind these things. It's not just a few buttons on the web page, and there's
a little aerial stuck out of windows somewhere. This is quite a bit more work, quite a bit more
serious work than that. And I think that's the point I really want folks to understand.
Now, you mentioned the 21 centimeter line. Now, for listeners who don't know that, is the wavelength
that neutral normal hydrogen emits that, and that is the line that we map out our galaxy after
that's how we know we are in the spiral galaxy, and that's how it was first measured. So, you can
actually examine our own galaxy at that 21 centimeter line. Yeah, yeah, exactly.
For our listeners who are not familiar, our radio astronomy basically neutral hydrogen atoms
tend to emit radio waves under specific conditions. We won't get into the quantum physics,
how this works. But for those interested it's called the spin flip 21 centimeter transition.
So, basically, these atoms of hydrogen emit radio waves. They emit radio waves at a very
specific wavelength at 1420.405 megahertz. And so, our galaxies, of course, vary rich in hydrogen.
So, when you point a radio telescope to the galactic plane, you will almost certainly pick up,
not almost, you will certainly pick up some signal at 1420 megahertz. And based on the Doppler
shift, that is how fast the object is moving relative to you, whether it's approaching you or
traveling away from you, you will get a bit of a shift in the frequency. So, in the frequency
domain in the spectrum. So, from these, like, if you take many, many measurements of the sky,
you end up with plenty of Doppler shift measurements. So, to put it quite simply, you can actually map
the Milky Way from, with a radio telescope, and even map out the, like, block the rotation
curve of the galaxy, which is basically evidence for the existence of a black matter.
And that's interesting with hydrogen line observation, because in optical astronomy, of course,
you can see the Milky Way, but you cannot see behind the Milky Way, and you can understand
how spiral galaxy can be, at least without seeing all the galaxies. But, yes, in radio astronomy,
you can see, thanks to Doppler shift, the peaks from other galaxy arms, and do a map on that.
Yeah, it's like looking at the Prisbee from the side.
Yeah, that's very clearly explained. So, let's see for a project,
or maybe there's a skeptic out there who doesn't believe the shape of our galaxy is a spiral,
and it's rotating in the way they say. They don't believe in dark matter, you know. Could they use
your telescope to do measurements and test and produce results that we show this Doppler shift?
Yeah, yeah, absolutely. If you observe, even right now, probably, you might see more than one
peak. You might see, for example, two or three distinct peak peaks. So, the Doppler shift,
like, because, okay, you see one peak, and then one to the right, and then another one to the right,
maybe, this is because the different spiral arms in the galaxy move at a different velocity,
relative to the Sun over the Earth. So, an observer can use Picroteloscope to observe
this Doppler shift, then, yeah, it's pretty much evidence, like, beyond any doubt that we do
indeed live in a spiral galaxy. Yes, and in dark matter, you mentioned that, that came about because
we could, there's a galaxy we can see, and if we just look at that, and then applying Newton's laws,
then we would expect the galaxy to rotate in a certain way, but it doesn't, when we did,
when we looked at the 21 centimeter line, we found that it rotates in a different way, a different
speeds as you go up from the center of the galaxy. And that is the dark matter, which you see,
we can actually look for that with your telescope. That's excellent.
Essentially, yeah, for the dark matter, for people who are not familiar with,
whether you have a dish, how can this prove a dark matter? Basically,
basically, you take some measurements of the sky, and given the Doppler shifts,
you end up combining the data, and basically produce a rotation curve. So,
what a rotation curve is, is basically the velocity of the objects orbiting a certain body. So,
for example, in the solar system, planets move in a certain motion. And this follows Kepler's
through law of motion, but when you try to apply this to galaxies, you get a completely different
shape. And so, the main theory, basically, behind this agreement, they're in the, in the expected,
with the natural rotation curve, because this is actually seen in pretty much every galaxy,
not only the Milky Way. This is basically evidence that there has to be more mass in our galaxy.
And so, that's the hypothesis of the theory, that dark matter is really there.
Yeah. Yeah. And so, what else could you be observing? Is there anything, for example,
that we could observe in our solar system with Pectora?
Yeah. So, you can theoretically detect the sun. It's a very bright radio source in the sky.
Now, Pectora is mostly intended for hydrogen line work. So, you know, we could, of course,
turn it to do solar drift scans. But, you know, obviously, this would be, because we have such a huge
user base, it would be a bit difficult to see, to sort of coordinate, like, okay,
is everyone, does everyone want to see the sun? Because I think detecting hydrogen
clouds is a bit more interesting for people from what we've seen. So, that's the main, like,
intended source, basically, galactic hydrogen, like the hydrogen line, basically.
Well, most users who try to build their first telescope, they, of course, will do tests
with the sun or the moon. And actually, when we started hosting Pectora, we realized
that sun and moon, or even Jupiter, are quite popular observing that. And hydrogen line
was a little bit difficult than all the others. So, that's why we focus on hydrogen line.
Okay, you know, that makes perfect sense. I think that's an excellent way to
to draw people in to the subject, actually. So, you're going back to this more technical aspects.
Are there, are there any things that, are there any developments or improvements that you're
working on, or is everything just a stable state and you're maintaining it that way, just now?
Yeah, so, okay. So, both of the web been replaced, as well as the processing software is
constantly getting improved, like, even yesterday, last night I was doing improvements
on the software. So, yeah, there's tons of improvements on, tons of updates, tons of
GitHub comments you will see. And this is mostly on the software. So, it allows the user to do more
more specific data analysis. So, for example, if there is radio frequency interference, which is
a big problem already, strongly, you can sort of, the software helps you sort of carry it out a
bit, mitigate the RFI. So, yeah, there's definitely lots of updates and improvements, almost every day,
really. I think the most difficult part on setting a remote radio telescope is,
itself, the remote thing. As you find out how this works, all the other stuff,
it's not that difficult. I mean, of course, I'm going to do improvements and even on the hardware,
but the remote stuff, it's the most difficult thing, because from as I told you, in some situations,
you cannot have control, even if the software about the RFI are working great, if there are issues
with the remote stuff, then everything can go like a mess. So, we're always trying to see if there
are still improvements on the remote stuff, and then come everything else. Yeah, imagine that's
actually quite, yeah, I can see that's why that's the most difficult part, automated telescope,
because it's quite hard, because there's lots of little details that you have to, if it's
contend with, and you mentioned interference, what sources of interference have you had to
contend with? Yeah, so, okay, so there's basically two types of radio frequency interference. One
is, one is curious sort of interference, and the other is, or unintended, and the other is
intended interference. So, what this means is that, for example, your cell phone, when you're in
a coal, emits some radio waves to communicate with the cell tower, and of course, this can
contaminate your signal. What we actually had to deal with, and this is another interesting story,
is unwanted emissions. So, for example, a Raspberry Pi may emit radiation due to the electronic
circuits. So, this is completely unwanted and unintentional, but unfortunately, it happens.
So, I remember, for example, when we, because the first time, just tested it with my laptop, and
saw the hydrogen line, but then, you know, we wanted to automate everything, make it available in
line, things like that. And so, we placed the Raspberry Pi near the disk, and just all of a sudden,
like so much noise and interference popped up. So, the simple solution is just to build a
thirdicage, which is basically a metal box, which basically shields you from radiation,
from interference. So, you know, the Raspberry Pi is in a metal box, so it can't really contaminate
the telescope. Actually, interference is a very, very harmful story in RF. We had so, so much
we are stuff going on on the spectrum. For example, I remember a time when we had some tests,
and opposed to telling me for a couple of hours that we have a very, very weird interference.
And it was very, very difficult to understand what was that. And at the end of it, we realized that it was
a computer. It was the power source of a computer, a power adapter, and it was making interference.
And it was, it's something that you cannot imagine at the very first stage.
Yes, I always, there's a story here in, well, not here, but in Wales, which is, if you don't know,
the next England. Philosophers are not familiar. In this little village, they had their broadband
installed some years ago. And every morning at 7 a.m., the broadband in the village would go down,
it would just stop working. Like, nobody knew why. It worked perfectly overnight, and in the
most early evenings. But at 7 a.m., it would always go down. And it turned out that one
villager had this old fashioned cathode ray tube television from the 1970s, and he turned it on
to watch the news at 7 a.m. on the door every day. And that created so much radio interference
that it destroyed the, the, the, the microwave transmitter to the village. Yeah, it's absolutely
funny. Yeah. Yeah. So, but for radio telescopes, it's just a serious stuff, because you're doing,
well, yeah, you could ruin your, you could ruin all your observations of somebody switched on
a television like that or, you know, like PowerPack, like you said, of a, of a computer. So you
mentioned that you've got software that can, as you mentioned, the FanideKage, which is a hardware
solution, but you also said that you've got software solutions to removing interference and noise
in the signal. Yeah, yeah, yeah, absolutely. So generally with a radio frequency interference,
you, you try to mitigate as much as possible. One, one segment of that is a hardware, as you mentioned,
but there's also software solutions. They don't always work, of course, but they can definitely help.
One, like to get into the mathematics a little bit, one way we, we remove a narrow bond,
radio frequency interference. Our feature is with a median operation. So you'll play a median to
the spectra, and suddenly the, the peaks just disappear. So that's, for example, one way you can
get rid of a radio frequency interference, and that's also good for a picture, because it's,
it's not a supervised method of removing interference. So I don't have to be on my computer,
waiting for every single observation to analyze. That will be pretty difficult. But for manual,
like if you have more, more annoying sort of interference, that it's, it's, it's contaminant,
it's contaminant, your data, like it gets your data very contaminated. Then you can do some
manual or supervised processing and data analysis to remove, to get rid of the interference
in software. So you can do this by, for example, in a non-py array for people familiar with Python,
you can just blank the channels. And the interference basically disappears like that. It's not always
very easy, because you know, sometimes interference is really, really, really close to your signal,
like the, like the hydrogen line, for example, but it can definitely help.
Okay, yeah, I can, yeah, I'm just a lot of interference to, to contend with. So I just,
I haven't actually submitted a request to do an observation yet. I should have done, I keep
looking at the page and then thinking, well, no, maybe I should read the instructions. I'm,
I'll confess, I'm from an old school of the manual first.
Luckily your manual is easy to read. So I haven't yet used it, but I'm, I'm definitely going to.
So I'm looking at the page right now and it's a few fields.
Right, right. Yeah, don't worry, we'll get through it. It generally takes one minute to submit
an observation, not one's thinking. One thing we want to mention is that there is actually no
request. It's just a submit. When someone wants to make an observation, there is no request for us
to say, okay, stuff like that. It's just a submission and the telescope automatically does the observation
for you. All right. So when I, if I take to the, if I take to the request, then you're not
sitting there going, oh, no, it's Andrew and Scott on making a stupid observation request again.
It's going to bring the telescope, band him. You know, that doesn't happen.
You make sure that I can't do anything stupid.
Okay, I don't worry. There's no way to break it. That's why I told you the, the most of stuff is to,
to get secure with the remote with everything that has to do with the remote to, to avoid any,
problems due to, for example, wrong controls and stuff like that. So yeah, there are no requesting
or needs only submissions. Okay, right. Okay. That gives me a lot more confidence to go in.
I was going to say try and break it. I'm sure I'm sure I'm going to fail if I did try.
So I noticed when it says, so it says, would you like to see if you're your raw data as a CSV file?
Yes or no, could, could you describe briefly what would you get back? What information we would get
back after some material request? Yeah, yeah. So whether you select yes or no on this, on this
field, you get a plot file. Usually, for most users, including you, a plot file,
any much file is sufficient. So you can just say no there. But if you wanted to get the raw data,
so get like, because you usually just get an image file. If you want the raw data to sort of
play around a bit, then you can of course, select yes. So it's up to you. Either way, you will
get the data you need. So you can select no, no, anything you want. For the users that visit
Picrotelscope for the first time, we suggest to use the no option because the raw data can confuse
them. So I think it's, it's easier to, to play on with a no option.
Okay. Well, while you were talking, I submitted my first request. So I hope that wasn't too spammy
of me, but I thought I would since it was so easy. I thought I would get my go.
And I really have to say to people, don't be scared off by this. I mean, literally, there's a few
fuels you can take the default values to, you know, is extremely friendly. It's not scary at all.
I would have no problems sitting my nine-year-old daughter in front of it, you know, and you know,
in a few, in a matter of minutes, I could explain to her what she should, she should do.
I'm explaining to her what the results mean. Well, I'm not so sure I could, I could do that
quite so quickly. But yeah, yeah, it looks, looks very straightforward. I have to say,
um, great win and to read your astronomy. So, um,
so you submitted the observation, uh, I don't know, was it like 10 seconds, 20, uh, you
you should receive it as soon as it finished. It was 10 seconds, yeah. Oh yeah, it's a short
option. Yeah. Okay, yeah, you should receive the observation, uh, if you take your emails,
probably. Yeah, there it is.
Wow, I've got a nice little PNG file with a spectrum radio velocity. So, is that me,
is this radio velocity curve? I see my email. That is of our galaxy. Yeah, yeah,
this little peak that you're saying is actually the, uh, the Milky Way. It's a spiral,
it corresponds to spiral arm in our galaxy. Um, and you can see the radial velocity, uh,
both, uh, I've put a secondary axis there. So it automatically, um, you know, you see exactly
at both velocity, the gas, the, um, the hydrogen clouds are moving at a relative to, to you.
Um, so, uh, if you observe it some other time, you will see a different, um, a different sort
of Doppler shift because you're obviously pointing to a different location in the Galactic
plane. Um, so you're sort of exposed to different spiral arms, but, uh, yes, sometimes you even
see two or three peaks there. So, um, it's definitely, uh, an interesting thing to try. Yeah, I've
got, I've got, I've got three peaks actually. So I presume that may be looking through three
different hydrogen clouds, perhaps in different spiral arms in the galaxy. Are you looking at
the left plot or the top center? The, oh, I'm looking at the left one. Yeah. Sorry, that's the,
is that the role we're looking at? That's a signal to noise ratio. Sorry. Yeah. Yeah. So,
so the left one is basically the, the row spectrum. Um, and this is where digital signal processing
and the software comes into play because this is the row data. Um, this is what the SDR receives.
It's not what the actual sky looks like. Um, because, you know, this three humps, the big ones,
the wide ones are actually, uh, uh, are caused by the SDR basically. So what we do is,
okay, we point to the sky when the Milky Way is not at the zenith, so at the horizon.
So we don't get any contamination and we calibrate the telescope. So we say, okay,
this is what the sky looks like without hydrogen. And then we, we basically subtract or divide
the, this factor. So, so it's basically the, the row data divided by the calibration data.
So if you look at the top center, it becomes more flat. Um, so basically the, the sort of SDR
artifacts, um, basically cancel out. And what you end up with is this hydrogen pit, uh,
it should be at 14, 20.5 megahertz. Yeah. And this is basically the hydrogen.
This is the true sky signal. Um, okay. And something you might see on the right, very narrow one.
This is, this is probably really frequent interference. Um, notice, uh, I mentioned the
median earlier, the median operation. Uh, this is the red curve that you're seeing. So, uh,
if you, if you look on the right where this narrow peak exists, uh, which does contaminate the
data, of course, but applying it median operation, basically, uh, if you look at the red curve along,
there's no interference at all. So that, that's basically the logic behind, uh, median operations.
And it's applied automatically. You don't have to worry about, uh, what factor we'll use on
the, on the race room for nothing like that. What, what do we want to make clear is that, uh,
for a beginner observer, uh, the, the, the window that, um, uh, she's called,
concentrate is the center one, the calibrated spectrum. Uh, there, it's, there is the,
there is the easiest way to, to see the, the hydrogen line, uh, the powervious versus time,
the waterfall, uh, or the average spectrum, uh, are things that, uh, not so important on all that.
I mean, uh, are some, uh, some data for, uh, for users who, who want to know more about, uh,
how all this stuff is working on and how we calibrated that about, um, the main part is the
calibrated spectrum. Yes, yes, I see that. Yeah. I always, I always need to look at the wrong one.
So, um, yeah, so I do see one peak, and I see that, uh, at, at 1420 megahertz, and then a much
larger, spiky one that's slightly higher frequency. Yeah, yeah, that's, that is excellent. So from,
the listeners, um, I'll put this image that I'm looking at. We're discussing now in the show notes,
so you can actually see, um, what's being discussed, um, and of course you can run your own
observations, but they'll be different. I will put this specific observation that I just got.
One other question, the, the bottom time series graph, uh, of relative power, the, it shows a
decreasing trend over the 10 seconds of observation. Why, why, why is it decreasing, do you know?
Yeah, yeah, that's a good, uh, question. That's, that's a good observation of you because, um,
it's actually not that clear compared to other observations. Uh, but it's, it's not a sky effect.
It's, um, it's completely, uh, NSDR thing. So if you get, for example, the different SDR, uh,
it might be more flat from the beginning. Um, it has to do with, uh, we're getting into more
technical stuff here, but it has to do with, uh, sort of the temperature variation, as soon as the
observation begins. Uh, if you observe for like, uh, uh, for like 10 hours, of course, you won't see
a constant decrease in power after like 30 minutes or so, it will start to flood it out. Um,
so it's completely an, uh, NSDR, uh, effect. Okay. And you mentioned the SDR before, what is SDR
stand for? Uh, SDR is software defined radio. So, uh, it's basically, uh, as, as, as,
expect from there, like, uh, a device that you feed your, uh, RF signal in, uh, like you do with,
for example, a TV decoder. Um, so NSDR is basically a very, very versatile, um,
and modable sort of device that you plug into your computer. It's, it's literally a, a USB
stake, uh, usually most of the times. And, uh, with the new radio, which is an open source, uh, uh,
framework for, uh, radio work, uh, you can sort of program what you want your rest there to do, like,
okay, you acquire some data. Um, and then you pass the data, the row data to, uh,
digital signal processing pipeline. So this is basically what NSDR does. It's, it's basically a
receiver that lets you do, uh, pretty much anything. All right. Okay. Yeah. I'd never come across that
before. Uh, yeah. So that's, um, obviously, it's my training in radio astronomy was theoretical
and, um, before USB was invented. So that's why I'm not proud of that. Okay. That's, that's,
that's all, that's all great. So, um, it's, I think we're sort of getting towards the end of the
episode. Is there anything else that you'd like to mention that we've not managed to cover so far?
Um, yeah, well, I don't know if we mentioned this. Uh, we did, uh, send you like, uh, we mentioned
it in, uh, the email, but for people who want to see, okay, uh, you have this telescope, uh,
with, uh, with over 3,000 observations on the archive from, uh, over 700, uh, user from all around
the world. Um, one, one thing we, we actually managed to do quite recently is, uh, obtain the very
first radio image in Greece. Uh, we obviously, we obviously mentioned how, um, uh, you know,
how, how radio astronomy is not that popular in Greece, but, uh, you know, we're happy to basically,
help with a little bit of contribution. So what we've done is, uh, like to, to, to basically
advance radio astronomy in Greece, what we've done is actually, um, with picture telescope, we've
actually obtained the very first radio image, uh, of the sky. So it's, uh, an northern sky,
hydrogen line survey, uh, that, uh, user can find, uh, a lot of listeners can find on, uh,
on the GitHub as well. Okay, yes. So that's, uh, what I mean, Paul, as you did send me that, uh,
email I forgot to mention, I was right at the beginning, and I'll put that image, your first
image, um, from Greece. I'll make sure that goes in the show notes too for our listeners to look at.
Excellent. Um, so I said one last question. How did you choose the name Pector? Where did that come
from? Uh, Pector. So, so on the southern, uh, sky, uh, and there's, uh, there's already a call,
galaxy called Pector A. So, um, that's basically very, uh, where it originated from.
All right. Okay. I didn't, uh, didn't make the connection there, but yeah, okay. I have, I have
visually heard of that. Yeah. It sounds very popular, galaxy, but, uh, yeah. Actually, we wanted to have,
a unique name because the most, uh, ceramic project, uh, uh, is, uh, have a very, very similar
names like constellations, uh, or something like a cosmos or a raster and stuff like that. And,
we want to make something that, uh, that is a little bit unique. So that's why we choose Pector.
Yeah. No, it's a good name. Nice and short, memorable, easy to spell. Yeah, it's got all that.
And it's something to do with radio astronomy as well, so much. Yeah, exactly.
Well, um, I'd like to thank you both very much for taking the time, uh, to talk to me. I've got a
feeling that we, you know, that, uh, I'm going to go off and play with this and, I don't know,
I think folk will find this interesting. And as I said, as we said earlier, if you've got some
skills that are relevant and an interest, go in, contribute to this project, it sounds like an
excellent project. And I do congratulate both of you on your work on it. Um, yeah, so maybe we'll
do a follow-up show, um, if there's further questions or there's more we'd like to discuss, um, but,
yeah, thank you very much, uh, both for your time. Yeah, that will be very, very interesting. So,
yeah, thank you for social, Matt. Yeah, it's, uh, our pleasure. Uh, if, uh, listeners want to do
a second part, uh, absolutely. Why not? Yeah, great. Okay, thank you. Yeah, okay. And thanks to our
listeners for tuning in. And of course, if you have an interest in astronomy, radio astronomy,
or anything like that, or you do some interesting, uh, observations with the Victoria Telescope,
please do record an HPR show about it and let us all know. Thank you very much for listening. Bye-bye.
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