See The Sun Part I

I Want To See The Sun Part I

Much like my other series of posts about seeing atomic particles, this is the first in a sporadic series of posts about using different devices to "see" the sun. From a simple radio telescope to solar viewing filters to a purpose-made solar telescope I'm going to do what you were always warned not to do: stare at the sun! I'll probably throw in some info about my homemade UV and infrared goggles too.

So, what do you need to make a radio telescope? An old satellite TV dish, 8 AA batteries with holder, an rf choke, a satellite finder, and some other odds and ends like solder, tape, a tripod, coax cable and coax terminators. Less than twenty dollars worth of stuff from Radio Shack (and your neighbor's garbage).

Simple instructions from the NRAO (National Radio Astronomy Observatory) are available here: 

http://www.aoc.nrao.edu/epo/teachers/ittybitty/procedure.html

Big caveat: the 0.1Mhz rf come on all the online plans don't seem to exist. Use any smallish RF choke. They may have meant milli or microHenrys (mH) but not Megahertz (Mhz). It's an honest mistake considering Mr Hertz is the guy that discovered radio waves. He used a spark gapped radio antenna, like a bug zapper for radio waves! So many of the things I experiment with are like bug zappers. Alpha particle on my spark detector-zap! Gamma or X-ray on a Geiger tube: zap! On or off electrically. Zap or no zap. 

With this radio telescope we're dealing with something more subtle: quantity. Not just yes or no, but how much? One decibel or two? A flat or peaked curve? Twenty MHz (yes we actually are taking Hertz now) means a solar flare. Ten to forty MHz and you could be looking at Jupiter, but Jupiter's magnetic storms are best monitored between eighteen and twenty-eight MHz. A wide swath between forty and eighty MHz with a plan around sixty MHz? That's Saturn my friend! Two and a half GHz-that's my Hot Pockets in the microwave oven. Of course you add voltage to the mix when interpreting too: frequency, an amplification, amplitude,  voltages, standing wave ratio...all sorts of things used in everyday devices like stereos, phones, cb radios, etc. It's all just electromagnetic waves. 

Setup is to aim at blue sky, dial decibel knob just barely to zero. Point at sun and itll6read around 6. How to aim at sun? Get the shadow of the LMB (pointy part) just barely onto the disk. Trace shadow on dish with marker once needle jumps up:

I ditched the dangerously unbalanced mounting bracket and spun the dish upside-down. There was a hole there that allowed the standard camera mounting screw to fit through, and as luck would have it the nuts from the dish bracket fit the screw. Mounting was easy!

I'm pondering getting a longer coax cable to attenuate the signal and help the RF smooth noise away. It might be possible to coil it on the tripod to create a balun. A balun is just a coil that helps a system cross from a balanced state to an unbalanced on (such as coax cabling).

Update: I did rearrange everything farther from the dish and coiled up a make-shift balun.

The red plastic cup holds the 8 AA battery pack. The second output from the LNB (low noise block converter) is capped off with a gold-plated coax terminator. The LNB is the brains of the dish which is basically a radio received. The actual dish is just a waveguide-badically an receiver in your car, only this received and translates microwaves from satellites instead of AM/FM waves. Simple!

So what am I looking at? Radio waves from our Sun. It turns out that the huge nuclear inferno above our heads melting 600 million tons of hydrogen into helium every second makes quite a lot of radiowaves! Here's a nice video of me aiming at the Sun and then slightly away a few times.

If I tame all the RF interference (probably by just moving the battery pack away) and plug this into my oscilloscope it should be easy to detect other things: like people walking past the dish or cars driving by. According to the NRAO a cellphone signal is a billion times more powerful than the cosmic rays detected by larger radio telescopes, so a radio-people-detector is very plausible (I've seen it done actually) even though this design is referred to as an Itty Bitty Radio Telescope.

My set up procedure now is to point to clear sky and dial up the gain on the meter until it almost squeals. Then I point out at the sun. If I really crank it up I can tell when the telescope scans past the sun, to the quieter open sky and then much quieter on the neighbor's tall chimney.

With the tripod locked the sun moves out of the dish's narrow focus rather quickly. The moon would do the same as it slides into the path of the sun's light the moon will get brighter in the sky-and on the radio telescope's meter. Think about it, when the moon is dark its surface is -243° Fahrenheit but when the sunlight hits it the surface rapidly heat up to a little over +250° Fahrenheit! Wow! It happens whether we can see the moon or not in the sky, on bright days you could search for the moon in a blue sky. I found it:

I'll revisit this with the oscilloscope data at some point, but lugging this weird device around my neighborhood during the day is embarrassing enough without an additional wheeled cart hauling crazy looking electrical boxes and wires. 

It will give me something more productive to at oscilloscope practice than just trying to write my name with it...cause that's what oscilloscopes are for right? M I K E!

Itty Bitty Radio Telescope? Looks more like an Itty Bitty Kitty Detector to me! I'll just mash my face all over it to be sure. Can it see me? Does it know it's mine now? Meow!