[Moon] August 21st solar eclipse

Peter Blair g3ltf at btinternet.com
Wed Aug 2 13:41:39 CEST 2017


I’m sure all the NA community are aware of the solar eclipse coming on August 21st, for coverage see  https://eclipse2017.nasa.gov/eclipse-maps During the 2015 eclipse in NW Europe a number of stations were able to make some quite nice measurements of effective solar diameter at microwave frequencies by plotting sun noise against time. The sun is less active now and so there is less chance of sunspot flares influencing the measurements. I gave a paper on this at the 2015 Swedish EME meeting, see
http://moonbouncers.org/Eclipse%20measurements.pdf  but please note I am NOT an expert on this and for the full background you should refer to the references at the end, F1EHN and DL0SHF. My paper gives the basic maths that are needed and you can get the moon-sun separation from several programmes. If you cant make a full series of measurements (and it is a working day!) then the pre-eclipse level of sun noise to quiet sky, the time of first on-set and the level and time of maximum drop in noise are the most interesting data set. 

I think there could be quite a few microwave stations within range of at least a 60% sun obscuration. Measurements above 13cm would be most useful but its a fun thing to do at any band. I dont know how many people still use sun or moon noise to measure their systems these days, probably most of the operators on 13cm and above do so.

A few hints. The NASA site has lots if information and its easy to find the exact optical obscuration level for your location. You really need a wideband receiver such as an SDR or a noise meter, examples are  http://www.vk3nx.com/files/Noise_Meter.pdf  or http://www.g3pho.free-online.co.uk/microwaves/noiseamp.pdf   An SDR is ideal because it it easy ( certainly with Spectravue) to record the result as a csv file. Do a trial run to make sure that it will all work for 2 hours, ideally running the dish through the sector where the measurement will be taken to check for interference, you only get one shot at this. I also strongly reccomend  doing a practice run of recording and saving the SVue csv file. I seem to remember that its very easy to lose the file in SVue. I lost mine and was only left with the 13cm screen-shot. I seem to recall that on completion you need to make a copy into a separate folder before changing anything in SV. 

Have fun! 73 GL Peter G3LTF 




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