Derby and District Astronomical Society

DDAS Observing Session - Flamsteed Observatory - Saturday 16th February 2008

Report by Claire Spencer

Sinus Iridum

Saturday February 16th 2008 was a crisp, clear and bright day. It looked highly likely that the observing session was on! Would I really get my first views of the night sky from the observatory? I called Robert Seymour, a DDAS member to enquire whether a lift was available to the observatory at Brailsford. Fortunately, Robert wasn’t working his long, interminable shifts for the railways, so at a little after a quarter past seven, we set off, clutching binoculars and wrapped up against the winter chill. When we arrived, the Society’s ten inch Newtonian was already in use, observing the nine day old moon. As luck would have it, the terminator cut through Sinus Iridium (the romantically named 'Bay of Rainbows'). The valley floor was in deep shadow, but shining out like a diamond ring, the mountains behind had caught the rising sun, causing the observers looking through the business end of the scope to gasp in wonderment.

Next, the telescope was turned to Mars, still high up in the constellation of Taurus the Bull. Unfortunately, Mars was past its best, as opposition had been in December, and was now fast receding from the Earth. Its apparent diameter had in consequence shrunk to little more than 10 arc seconds. However, our excellent ten inch reflector was able to show a few dusky markings on the ochre red disc of Mars. Going outside into the cold night, a couple of new members had set up an eight inch Dobsonian reflector, and were observing the planet Saturn, which was nearing opposition in the constellation of Leo, near to the first magnitude leader of Regulus, or Alpha Leonis. A wonderful sight greeted the observer on peering into the eyepiece. Probably the most beautiful planet in the solar system unashamedly displayed its ring system and two of its brightest satellites, the planet-sized Titan and the ninth magnitude Rhea.
Meanwhile, back in the observatory, Mike Lancaster had also turned the telescope to Saturn, and some stunning views were afforded of the ringed planet. Different eyepieces were tried, increasing the magnification to around 350X, with little detriment to the observed image. Cloud belts were easily seen, as well as the shadow of the rings on the planet. Also, Cassini’s division was visible as a dark brown line on the ring system, which was truly stunning. Saturn’s largest moon, Titan was easily visible, as well as Rhea, and closer to the rings was Tethys. It is true to say that every visitor to the eyepiece expressed their amazement at the sight that greeted them. The seeing really was excellent, the air quite still. Mike explained that this was partly due to the diminishment of the jet stream over the UK. The temperatures on that night went down to –5 °C, and believe me, it felt it!


Also under scrutiny that night was M42, the Orion nebula, visible under the sword belt of the three stars of Alnitak, Alnilam and Mintaka. This was to be no disappointment, either. The multiple star system star known as the Trapezium, or Theta Orionis was an awesome sight surrounded by a greenish nebulosity. I have to say that Saturn stole the show that evening for me, and if you can make it to the observatory any time, I can guarantee in the words of Messrs Lennon and McCartney, that “A splendid time is guaranteed for all.”

Claire Spencer

Image Credits: Top left - Sinus Iridum on the 2nd February 2006 by Chris Newsome, mid-right - Mars on the 13th February 2008 by Barry Ashforth, lower left - Saturn on the 16th February 2008 by Barry Ashforth, lower right - M42 on the 17th September 2005 by Adrian Brown.

DDAS members at the observing session on the 16th February 2008.
Picture by Malcolm Neal
DDAS members at the observing session on the 16th February 2008.   Picture by Malcolm Neal.