Willowbank Observatory

located at Pennyghael on the Isle of Mull

56°22'45N  6°00'07"W


Weather Instruments


The weather station is a Davis Vantage Pro 2 weather station. The anemometer and wind vane are mounted on a short mast attached to a chimney about 5 m agl. The USB webcam, bought for £4 from the Island Castaways charity shop in Bunessan, is a Logitech HD Webcam C270, using 1280x960 resolution.

I use WeatherDisplay software, which allows the weather web pages to be automatically generated and uploaded every 10 minutes. The webcam image is only uploaded every 15 minutes during the daytime.

Both the weather station, associated PCs, SAM magnetometer and router have mains supplies via UPS; in the event of a protracted supply outage then everything with the exception of the SAM instrument is shut down. The SAM kept powered for as long as possible to keep the sensors stable.


SAM: Simple Auroral Magnetometer

The Northern Lights (or Aurora) are a stunningly beautiful, and moderately rare, natural phenomena. They are ultimately driven by events on the Sun, the frequency and severity of which vary over an approximately eleven year cycle. These solar disturbances can interact with the Earth's magnetic field as part of the process which produces auroral displays. Thus monitoring small changes in the field can help to predict auroral activity. This is of interest to radio amateurs as such events are often accompanied by HF radio propagation disturbances, and enhanced VHF popagation is possible by using the aurora as a reflector.

Some good hints on predicting the probability of a visual aurora at your own location can be found at this NASA site.

The SAM magnetometer was designed by Karsten Hansky, DL3HRT and Dirk Langenbach, DG3DA and was described in DUBUS magazine issue 2/03. It can measure small changes in one, two or all three components of the Earth's field, using fluxgate sensors that are made by Speake. For more details, see the SAM website and the SAM International website. These contain both construction information, details of kits and access to real-time data from a number of stations across Europe and the world.

The installation at Willowbank now uses three sensors, one for the vertical component (Hz), one for the E-W component (Hy) and one for the N-S component (Hx), arranged at right anles to each other. My SAM magnetometer has been modified to accept a third sensor. The magnetometer software records changes from the midnight value, in units of nanoTesla (nT) for each axis. The resulting graph is uploaded every 15 minutes. On the graph you will see a series of K values, such as K=3. This is a measure of magnetic disturbance. A knowledge of the local K value, together with your magnetic latitude, can be used to judge the likelhood of an auroral display, as the link above describes. Because the fluxgate sensors used are sensitive to temperature, they are buried some 1.7 m below ground. They are about 65 m from the house and 80 m from the road, so the effects of (the occasional) passing traffic are negligable. Records are archived and stored, so if you are interested in the magnetic records for here for any day since December 2006, they are easily available, just contact me via the e-mail link below.

My modifications to the SAM Magnetometer design, made to improve the performance with long cables are described here.


Sudden Ionospheric Disturbance (SID) Recorder

Solar (X-ray) flares, amongst other events, can cause changes in the ionosphere which result in enhanced received signal strengths during daylight hours at low frequencies (up to 100 kHz or so). My experimental SID monitoring system records the received signal strength of a LF transmitter
, DHO38, located in NW Germany, which uses a frequency of 23.4 kHz.
An active E-field antenna (details here) is used and the receiver is based on the Gyrator II design.

A home-made A-D converter and an elderly laptop are used to log and archive the data. Radio SkyPipe is used as the charting software.


Past data is freely available, email me at the address below.  
Comments, or suggestions for changes, are welcome.  

Please send them to me at : marsport@marsport.org.uk

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