Orwell Astronomical Society (Ipswich)

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Appulse of Saturn and SAO 79057, 11 January 1975

An appulse of Saturn and the magnitude 9.1 star SAO 79057 occurred at 04:42 UT on 11 January 1975. The event was visible as an occultation from California and Hawaii, and from the UK was seen as an approach of the planet to the star at a minimum apparent distance of 2.1 arcsec.

Although Saturn takes 29½ years to complete an orbit of the Sun, and its mean daily motion is therefore only 0.033°, this equates to 5 arcsec per hour against the background stars, so the movement of the planet relative to SAO 79057 was expected to be spectacular. In late 1974, there was considerable interest in observing the phenomenon and OASI made plans to open Orwell Park Observatory for the event.

On 10 January 1975 at 23:50 UT I arrived at the Observatory to find nobody there, thick cloud overhead, and naturally began wondering whether any other mad fool would venture out that night. I sat in the car park to ponder the matter for a while. At midnight, Nigel Gage and a friend, Mark, arrived, followed a few minutes later by Tom Cardot, Mark Howe and Charles Radley, the latter bringing a sleeping bag, crash helmet (in case of falling space debris?), several books, and some other items. For an hour or so, we four engaged in general conversation.

The second stage of the Saturn rocket that had lofted Skylab into orbit (on 14 May 1973) had been predicted to re-enter Earth's atmosphere during the evening, and there were predictions of three opportunities to see it. Unfortunately, thick cloud prevented us seeing anything in the sky.

By approximately 02:00 we sat down to play cards, hoping that the clouds would disperse but, as time passed and we ate Nigel's sandwiches, drank Tom's coffee and watched Charlie lose ever more rounds of cards, the clouds did not disappear.

Then... Eureka! It was clear!! We rushed upstairs to the dome and swung the refractor to point at Saturn. There were two objects of approximately magnitude 9 in apparent proximity to the planet: one was the giant satellite Titan and the other was the small moon Rhea. We could find no sign of the star SAO 79057.

David Bearcroft had asked to be telephoned if the weather cleared so Tom and I went downstairs into the main building to call him. David set off for Orwell Park within a few minutes of our call. By the time we returned upstairs to the dome, it had clouded over again...

The clouds persisted until 05:00 UT when we decided to quit and call it a day or, you might say, early morning.

John Deans