My first step into hydrogen line observing

[Victor Boesen]

Ever since I found out it was possible to map the hydrogen intensity in the Milky Way I was really excited to try it out myself at some point. Fast foward about 6 months and I've finally gotten a dish that suits my current living situation (apartment, no possible permanent mount and etc.). This morning I received a 100X60cm wifi grid dish, which I modded for lower frequencies by flipping the dipole reflector on the feed arm.

Here's the antenna with the flipped reflector.

My main use for the dish is weather satellite image transmission at 1.7GHz but I also want to H-line observing from time to time, and perhaps even write my own software for mapping the Milky Way when I finish school this summer. After I'd tried receiving a couple of weather satellites earlier today I finished by pointing the dish towards Cygnus, which is rich in hydrogen, and I noticed a small "hump" right at 1420MHz. I'm using an Airspy mini and an externally powered Nooelec SAWbird+ H1 which seem to work great at bringing out the otherwise faint hydrogen-line. I didn't get to do any sampling at longer periods (for improved detail), but I was able to spot the H-line easily on the spectrum in SDR#:

I'm really excited to dive deeper into H-line astronomy, and I have many projects in mind although not the corresponding amount of time... I know I'm somewhat limited by the size of the dish but it's sufficient for calculating doppler shift at most regions in the Milky Way.
If you, for some reason, are interested in my weather images as well, they can all be found on my twitter:)
https://twitter.com/victor_boesen

Thanks for looking!

Victor

Edited January 2, 2021 by Victor Boesen
Image disappeared. Added again:)

[CraigT82]

I know precisely nothing about anything you mentioned but it does sound fascinating! 

[Victor Boesen]

1 minute ago, CraigT82 said:

I know precisely nothing about anything you mentioned but it does sound fascinating! 

Neither did I just one year ago, but the fascination has kept me going;)

I'll try to explain it as good as I can

Hydrogen atoms consist of an electron and proton whom can both have a "spin" in one direction. Depending on the spin, the atom can be in different energy states. If the spin is flipped and the atom drops to a lower energy state, the surplus energy is transmitted at a frequency of 1420MHz (can be calculated from the change in energy and planck's constant, E=h*f). This is extremely rare but since hydrogen is the most basic atom in our universe there's an immense amount of it out there. By looking at the intensity at 1420MHz one can determine the concentration of hydrogen in that area.

By looking at the offset from the theoretical frequency (calculated with the E=h*f equation) you can calculate the doppler shift and from that, the velocity at which hydrogen is travelling towards or away from us in that direction.

[Carl Reade]

Hi good work! There is a plugin for SDR# called IF Averager which will bring out more detail. There is another which flattens out the spectrum but can't remember what it was.

Carl

[Marvin Jenkins]

On 11/12/2020 at 19:01, Victor Boesen said:

Neither did I just one year ago, but the fascination has kept me going;)

I'll try to explain it as good as I can

Hydrogen atoms consist of an electron and proton whom can both have a "spin" in one direction. Depending on the spin, the atom can be in different energy states. If the spin is flipped and the atom drops to a lower energy state, the surplus energy is transmitted at a frequency of 1420MHz (can be calculated from the change in energy and planck's constant, E=h*f). This is extremely rare but since hydrogen is the most basic atom in our universe there's an immense amount of it out there. By looking at the intensity at 1420MHz one can determine the concentration of hydrogen in that area.

By looking at the offset from the theoretical frequency (calculated with the E=h*f equation) you can calculate the doppler shift and from that, the velocity at which hydrogen is travelling towards or away from us in that direction.

I can only echo CraigT82 Still do not have a clue what you are talking about. You started with a second hand sat dish on a balcony in a block of flats and finished with an equation. Worst still equations in the middle and spinning particles in different energy states.

It is late in the evening and I have work in the morning despite it being Sunday, what are you trying to do to my brain. If I have a sleepless night it is your fault.😂

Marvin

[Victor Boesen]

4 hours ago, Carl Reade said:

Hi good work! There is a plugin for SDR# called IF Averager which will bring out more detail. There is another which flattens out the spectrum but can't remember what it was.

Carl

Thank you!! I gave it another go today with a software called "astrospy". The result is a lot better in my opinion:)

This also clearly shows the signal is doppler shifted with an offset of about 350-400KHz and therefore a relative velocity towards Earth of about 84500m/s.

[Victor Boesen]

2 hours ago, Marvin Jenkins said:

I can only echo CraigT82 Still do not have a clue what you are talking about. You started with a second hand sat dish on a balcony in a block of flats and finished with an equation. Worst still equations in the middle and spinning particles in different energy states.

It is late in the evening and I have work in the morning despite it being Sunday, what are you trying to do to my brain. If I have a sleepless night it is your fault.😂

Marvin

I'll say sorry in advance😅

[Ed astro]

Hi Victor,

Nice result! Congratulations!

19 hours ago, Victor Boesen said:

Thank you!! I gave it another go today with a software called "astrospy". The result is a lot better in my opinion:)

This also clearly shows the signal is doppler shifted with an offset of about 350-400KHz and therefore a relative velocity towards Earth of about 84500m/s.

The hydrogen line is at 1420.405752 MHz, and the main peak in your spectrum seems to be really close to that frequency. So I think the frequency offset is at most a few tens of KHz instead of 350-400 KHz

Anyway, well done and keep up the good work.

Best regards,

Eduard

[Victor Boesen]

9 minutes ago, Ed astro said:

Hi Victor,

Nice result! Congratulations!

The hydrogen line is at 1420.405752 MHz, and the main peak in your spectrum seems to be really close to that frequency. So I think the frequency offset is at most a few tens of KHz instead of 350-400 KHz

Anyway, well done and keep up the good work.

Best regards,

Eduard

Ahhh I guess I rounded off the frequency by a little too much there 

Judging from your profile picture it seems you have quite some experience with radio yourself!! Thank you very much for your compliments:))

[Ed astro]

On 13/12/2020 at 19:20, Victor Boesen said:

Judging from your profile picture it seems you have quite some experience with radio yourself!! Thank you very much for your compliments:))

Well I have some experience with radio, I did my first detection of the hydrogen line two and a half years ago, in june 2018.

It is always great to see more amateur astronomers working on radio astronomy/ hydrogen line detection.