Solar Transit Educational Project (STEP)

Finding local solar noon using a TV satellite dish

Michael A. Barlow

January 2008

There are a great number of Radio Astronomy projects myself and others are working on individually within the club.  I'm interested in learning all I can and experiment with every part of the radio spectrum.  The majority of experiments I am interested in are specific to solar studies but there's lots of room for studies a bit closer to home as well as distant object studies.  Below is a project I've been working on that is very similar to what I have found on the Internet that others have completed but different in that nobody has used it in the way I am proposing.

Using the “Itty Bitty Telescope” designed by Chuck Forster, a member of the Society of Amateur Radio Astronomers (S.A.R.A.), and the Radio Skypipe software from Radio Sky Publishing one can detect the Moment of Local Solar Noon and the changes to local solar noon each day through out the year. Local Solar Noon is the moment when the Sun is centered on the celestial meridian for an observer and is different from Local Civil Noon that is displayed on the clocks on the wall.

You can read all about the history of the Itty Bitty Telescope on the S.A.R.A. web site. The IBT is essentially an eighteen inch (~46cm) off axis television satellite dish you see on the roofs of many houses. The intended function is to receive television programming signals from a satellite in geosynchronous orbit in the 12GHz band. The Sun emits radiation in many frequencies including the microwave band and to the dish its nothing more than another satellite.

The Radio Skypipe is essentially a pen on chart recorder computer software application. This software will read input values from almost any open port and plot them on an X and Y graph where X is a time stamp value. This software also has the ability to upload the data to a web page as it is being collected and the ability to automatically save each days data collection as a public or private downloadable file.

For the STEP project we are after a voltage difference as the Sun crosses the field of view of the dish. The Radio Skypipe software with the help of an Analog to Digital converter will record this voltage difference, as the voltage increases and decreases so does the pen across the chart. This will create something resembling a bell curve with voltage on the Y axis. Assuming the dish is pointed at the local meridian and allowing the solar disk to drift through the beam, one can obtain this Moment of Local Solar Noon by finding the highest voltage recorded at the very top of that bell curve.

This project will display on a web page the Moment of Local Solar Noon each day using the Radio Skypipe chart showing the Sun moving into, through, and out of the Itty Bitty Telescope's field of view. By displaying this graph on a daily basis with the ability for the general public to view will help educate the general public of the daily changes to local solar noon and help educate anybody who wishes to setup such a system at their home on how a dish works in relation to Radio Astronomy. Of most importance to me is the educational value of this project.

I am unsure how to overcome these issues since there are very few accurate optical references on the dish such as a high power finder scope to align the dish and vibrations to the system from wind may also skew the results. A final issue, of which I am unsure at this moment if it is an issue, is reading the graph during very active moments of solar activity where a false peak reading may occur.

One extra step related to this project would be to have multiple “Itty Bitty Telescope” setup at two or more longitudinal distances to show the differences in “Local” solar noon over that or those distances.

Other References;

National Radio Astronomy Observatory:

Radio Astronomy Projects, Third Edition by William Lonc

Key words and phrases for an internet search engine;
Itty Bitty Telescope
12 GHz
Radio Astronomy

Addendum; 05-10-08
This system is also in essence a Sundial. One can learn more about the STEP project and how Solar Noon is different from Local Noon by reading up on Sundials.

Addendum; 05-11-08
This system is also a stepping stone to learn Celestial Navigation. This may be an unusual way to start but once one learns the difference between Solar and Local Noon and can easily figure out how to find Solar Noon for any given specific spot on the Earth one will find it far easier to understand Celestial Navigation and then to Celestial Mechanics.

Addendum; 05-31-08
Doing a Goggle search on May 31st, 08 using the key phrase "Radio Sun at 12Ghz" netted me a whole lot of information including this particular experiment but still not the way I'm putting it together, so I guess I's still safe to say "this is MY project" :-)

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