BAS Observer July 2017

12 BAS OBSERVER The sky in July by Peter Allison T he long, cool winter nights of July mean it is Sagittarius time. July is the best time to look deep into the core of our own galaxy. Dark-sky nights So . . . when will you need to have your heavy coat and gloves ready this month? From about Saturday, 15th July, the Moon starts setting late enough to give some reasonably dark observing hours before it rises late in the evening. After New Moon you will have to wait until the Moon sets to have a properly dark sky. So, 15th–24th July looks best this month. BEST DARK-SKY OBSERVING DATES FOR JULY Day Date Moonrise Dark sky from sundown until moonrise Saturday 15 th Moon rises at 10.45 p.m. Sunday 1 6 th Moon rises at 11.44 p.m. Monday 17th Moon rises after midnight. Tuesday 1 8 th Moon rises at 12.45 a.m. Wednesday 1 9 th Moon rises at 1.48 a.m. Thursday 20th Moon rises at 2.52 a.m. Friday 21st Moon rises at 3.57 a.m. Saturday 22nd Moon rises at 5.01 a.m. Moon interference until evening moonset Sunday 23rd New Moon Monday 24th Moon sets 55minutes after sunset. Alignment stars Two prominent and widely spaced stars that make good alignment stars are Antares and Alpha Crucis. (We’ve pointed out Antares before as a good alignment star. It has a distinctive bright-orange colour that is impossible to mistake for any other star in this part of the sky.) Acrux or Alpha Crucis is another good alignment star, as it is the brightest star in the easily found constellation of Crux, the Southern Cross. The star is also a wide double star, so it makes it even easier to ensure you have the correct star in the eyepiece. Scorpius Crux (Southern Cross) Alignment stars: • Antares • Alpha Crucis