Solar Telescopes

Carnarvon’s three solar telescopes were programmed to follow the Sun making daily observations.

The 15cm Razdow optical telescope (with a narrow (½-angstrom) band-pass ‘Hydrogen Alpha’ filter) set up in the roof dome recorded photos at 30-second intervals. Each day, 54m of film was produced by the Razdow telescope. This was refrigerated and shipped to NASA for professional processing; however, if the camera was serviced or new film arrived with a different batch number, a 2m-length was processed locally, densitometer readings were made, and the camera settings were standardised as necessary.

In a spherical radome a little to the north of the Span building sat the 2.55m parabolic-dish radio-telescope receiving radio emission at 1.420, 2.695 and 4.995 GHz, These were recorded on magnetic tape and a chart recorder. Solar-flare-induced particle showers could then be correlated with the previous several days of surface activity.

David Johns, Span Observer at work

In a small dome between the two main telescopes an unfiltered standard 20cm scientific reflector telescope was set up to project white light sun-spot images onto a clipboard ‘screen’ to allow the SPAN observers to trace sunspots. This was sometimes used on the roof of the Span building.

Two Australian scientific observers from the Ionospheric Prediction Service, Department of the Interior, (supported by AWA technical staff) interpreted the solar observations at CRO and made twice-daily reports to Mission Control, Houston; SPAN Control, Boulder; and to other interested bodies.

Later in the life of the station a facsimile machine was supplied to transmit observer sketches of sunspot activity to SPAN Control. The transmission were just adequate but after subtle adjustments to the electronic circuits, Carnarvon achieved a startling improvement. These adjustments were implemented by the rest of the SPAN network. (NAA: PP 538/1, C622, CPR, July/Sept1973)

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