Jack Ells: a talented amateur astronomer

Jack Ells with his computer-controlled telescope, which could make observations automatically – by counting photons from stars – overnight while he slept.

About Jack Ells

Jack Ells (1927 – 1990), a professional engineer, was an extremely talented amateur astronomer who made several telescopes, one of which is pictured above. Many years earlier, in 1963, he made a Newtonian reflecting telescope, with a 32 cm diameter primary mirror having a focal length of 203 cm. Two examples of his observations with this latter instrument are given here: one of Jupiter, and another of Apollo 12 en route to the Moon.

1. Jupiter

Pencil drawing of Jupiter made by Jack Ells on 20 March 1966.

Jupiter is a gas giant that rotates on its axis in just less than ten hours. This causes it to be flattened at the poles and means that drawings have to be made quickly. The Great Red Spot seen in the image is a vast storm that was first identified in 1665 – it is comparable in size with the Earth! The black dot, that just happens to be seen here inside the Red Spot, is the shadow of one of Jupiter’s moons, Europa, which was discovered by Galileo. Along with every drawing, Jack made detailed notes about the position of each atmospheric feature seen on the planet’s disc.

2. Apollo 12 en route to the Moon

This unique observation requires a little explanation describing the sequence of events. The final stage of the Saturn-V rocket fired the Apollo 12 spacecraft out of its Earth orbit and on its way towards the Moon. Up to this point the Lunar Module, which was to touch-down on the Moon, was still stowed behind the Apollo spacecraft, protected by four panels. Apollo thus had to manoeuvre to pick up the Lunar Module and finally separate from the rocket. During the course of this, the four protective panels were jettisoned, and afterwards the remainder of the Saturn-V rocket, whose task was now complete, was sent into orbit around the Sun. The two figures (from NASA) illustrate these events:

The Apollo Command and Service Modules are fixed to one another as a single spacecraft, the CSM. This separates from the Saturn rocket’s final stage, and turns through 180^o. The four protective panels are ejected.

The CSM docks with the LM to form the complete Apollo spacecraft that will journey to the Moon

THE OBSERVATION, made by Jack with sons Peter and David (on 14 November 1969, between 21:25 and 22:26 Universal Time), took place less than an hour after these happenings, and is reconstructed in the sketch below, which is based on his extensive notes (unfortunately Jack’s original drawing is lost).

O₂ is a cloud of liquid oxygen, released in the course of the above manoeuvre. R is the Saturn-V rocket final-stage, which had finished its task. M is the Apollo spacecraft, including the Lunar Module. R and M were just points of light, and all of the items in the sketch moved together rapidly in relation to the fixed stars. A, B and C were lights that flashed irregularly about once every 5 to 10 seconds. At first Jack was puzzled about this, but he then realised that these were three out of the four panels mentioned above.

My father’s original notes:

A model of the observatory that was used to make these observations can be found on Oxford University’s History of Science Museum website HERE. (external link)

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