Messier 20, NGC 6514, Barnard 85
|Classification:||Emission, reflection and dark nebulae (B85).|
|Apparent size:||29′ x 27′ (about Moon size).|
|Diameter:||44 light years.|
|Distance:||5,200 light years.|
|Image date:||7th September 2020.|
|Exposure:||121 x 90 sec = 181 minutes.|
|Field of View:||47.7 x 31.7 arcmin. Up is 173 degrees E of N°|
M20 is unusual because it contains three different classes of nebulosity:
- The large red emission nebula is excited by the extreme ultra-violet radiation from the hot new stars near its centre.
- The blue reflection nebula is illuminated simply by the reflected light of nearby stars. It is prominent in the north (down) but actually faintly surrounds the entire emission complex.
- The black lanes are a series of dark absorpsion nebula in front of the emission nebula.
Three for the price of one!
Here is last year’s 1X image, for reference:
The large star at the centre of the emission nebula is listed as HD 164492, a 7th magnitude double star system O type star with a 10th magnitude companion. Together with other hot nearby stars they form a multiple system of at least six stars which formed inside the nebula and are responsible for ionising the nebula.
The bright star which appears in the middle of the blue reflection nebula is 7th magnitude HD164514, an A type giant. At a distance of only 384 light years it is a foreground star, not a physical component of the Trifid complex.
No filter was employed in the main feature photo, I’ve been waiting nearly a month for a new dual-pass filter from China. I hope the current tensions between Australia and China will not delay delivery…..🥱
This is my second time out with EQMOD installed, which has greatly improved the accuracy of navigation to my targets. It integrates with the planetarium software Cartes du Ciel (left & mostly hidden) to provide greater target alignment accuracy. It is successfully operated using a game-pad controller but gets annoying if I accidentally hit the ‘vibrate’ button.
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.|
|Field flattener; 2x Powermate|
|SkyWatcher EQ6-R Pro mount; No filter; ZWO ASI120 guide camera.|
|Camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).|
|Software: EQMOD, Cartes du Ciel, PHD2, SharpCap, Gimp.|
|Observatory location: 34° South.|
See annotated image at Astrometry.net