The early morning bright planet parade continues this week with yet another conjunction of the waning lunar crescent with a prominent member of the solar system. On the mornings of 3 and 4 February, at the beginning of astronomical twilight (~6am GMT for the centre of the British Isles), it’s the turn of ringed wonder Saturn to be highlighted by the old Moon.
Saturn is at opposition on the morning of 3 June and closest to Earth the same day, when it’s disc will span 18.4 arcseconds and the magnificent ring system almost 42 arcseconds. Back to our Moon encounter mornings, Saturn is somewhat further away than its opposition distance at 10.48 astronomical units, or 974 million miles (1568 million kilometres) from Earth. Consequently, Saturn’s disc measures 15.9 arcseconds and the widest extent of the rings is a shade under 36 arcseconds. In visual terms, Saturn’s globe requires a telescopic magnification of 115x to enlarge it to the same apparent size as the Moon to the unaided eye.
While observers in the heart of the UK may care to leave their observations until the onset of nautical twilight (~6:30am GMT) to allow Saturn to rise a bit higher in the sky for seeing conditions to improve, those of you using telescopes on the morning of Thursday, 4 February may care to note that that magnitude +7.7 globular cluster Messier 9 (NGC 6333) is occulted by the Moon soon after 6am GMT. Given the low altitude, encroaching twilight and the glare of the 21 percent illuminated Moon this wll be a challenging observation, but worth making an attempt — particularly with large-aperture instruments.
Inside the magazine
Find out more about how to observe the Moon, Saturn and the other planets in the night sky in the February 2016 edition of Astronomy Now.
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