PICTOR: An Open Source Low Cost Radio Telescope based on RTL-SDR

PICTOR is an open source and open hardware radio telescope that aims to promote radio astronomy on a budget. It consists of a 1.5 meter parabolic dish antenna, 1420 MHz feedhorn, a two stage low noise amplifier (LNA), high pass filter, and from what we gather, an RTL-SDR. Future designs may also use higher bandwidth SDRs. Currently there doesn't seem to be much information about the build and exact components used in their design, but we're hoping that those details will come in time.

The radio telescope allows a user to measure hydrogen line emissions from our galaxy. Hydrogen atoms randomly emit photons at a wavelength of 21cm (1420.4058 MHz). The emissions themselves are very rare, but since our galaxy is full of hydrogen atoms the aggregate effect is that a radio telescope can detect a power spike at 21cm. If the telescope points to within the plane of our galaxy (the milky way), the spike becomes significantly more powerful since our galaxy contains more hydrogen than the space between galaxies. Radio astronomers are able to use this information to determine the shape and rotational speed of our own galaxy.

PICTOR also has a very interesting web based interface which can be used to let users from anywhere in the world access the telescope and log an observation. The first PICTOR telescope is currently online and observations can be created simply by going to their website, and clicking on the "Observe" link. Users can then enter the frequency and other parameters for their observation, and the resulting graph will be emailed to you after the observation. The software source is available on their GitHub page, and is based on a GNU Radio flowgraph and Python plot script.

For more information about PICTOR, logging an observation, and radio astronomy in general, we recommend checking out their PDF guide. We test ran a short observation at the hydrogen line frequency, and we received a graph with the hydrogen line peak clearly visible (spliced in to the photo below). We note that the wavy shape is due the to shape of the filters they used.

PICTOR Radio Telescope
PICTOR Radio Telescope


  1. Steve

    Hi Guys,

    Great telescope, when not in use it can double as a barbecue!

    I subscribed twice and I haven’t received an email. I guess it’s just gone down again.

    Have a good day.

    Kind regards,


    • Apostolos

      Hi Steve,

      Yes, we’ve pulled the plug for safety reasons due to heavy snow. We expect the weather to improve in the next 1-2 days though, so stay tuned. Sorry for the inconvenience!

      • Steve

        Hi Apostolos,
        We in Britain always thought you had year-round sunshine in Athens ☀️😊.

        Do you have a link to the design of your feed horn? Your whole setup is very aesthetically simple and clean.

        I’m trying to do a similar project with an old 139cm dish.



            • Steve

              Hi Apostolos,
              So I bought a length of coated steel piping 15cm x 50cm. I’m proposing to operate without the choke, so I imagined that the length should bu cut to 27+10 ie 37-38, but then underneath it says without the choke length = 18 cm. Why is that?

              Secondly, to mount at the focal point, do I mount the pipe opening at the focal point or the monopole at the focal point.

              Hope the snow has cleared.



              • Anonymous

                Hi, sorry for the late reply (for more direct contact, feel free to use GitHub issues: https://github.com/0xCoto/PICTOR/issues)

                I don’t quite remember the logic for stating length = 18 cm. Perhaps incorrect calculation? The way I state it isn’t very clear either. In any case, you can get rid of the choke and keep the length to ~27.8 cm. That length isn’t super critical, and neither is the choke for simple observations.

                The opening end of the feed should be at the focal point. Super precise adjustments shouldn’t be noticeable anyway, but that should be a good spot. Remember that if you were to place the monopole at the focal point, the waves arriving from the edges of the dish would end up hitting the outer end of the can and would not actually reach the monopole. So this can affect your aperture efficiency a bit.


  2. Anonymous

    Sorry, I guess my message was misunderstood, I didnt told that YOU are harvesting emails.
    Just that I have seen many times good sites manipulated for this reason.
    Glad that it have been solved and all the best for you.

    • Coto

      Yeah, no worries. The site was never hacked (there was just a network misconfiguration (our mistake!) that redirected pictortelescope.com to a different page), and the emails are hidden from the public. They are also not stored on the site, so even if a hacker managed to somehow gain access to the entire website’s files, there is a chance they would only have access to the last observation’s email (not everyone’s email), so it’s not even worth trying to hack the website for 1 email, but the website is secure nonetheless.

    • Anonymous

      I do set up an observation too, also no email with results.
      Maybe the hack was deeper as expected, let me be a little paranoid and think about email harvesting

      • Anonymous

        “Please note the telescope may be undergoing some maintenance so you might not be able to make observations right now.”

        Seems like they are aware of the issue. And I sincerely doubt that they are harvesting emails.

      • Coto

        There was never a hack, there was just a network misconfiguration (our mistake!) that redirected pictortelescope.com to a different page. Everything is fixed now and seems to be working properly, and we do not harvest any email addresses/share it with third parties.

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