Dark nebulae in Ophiuchus

[Martin Meredith]

Dark nebulae are some of my favourite types of object to observe. I find it almost impossible to visualise them as floating clouds of obscuring dust but instead see them as holes in the starry backcloth. Nowhere is this more apparent to me than in the group of nebulae about half a degree to the south of the famous Snake (Barnard 72), itself nearly two degrees north of theta Ophiuchi. 

(Ignore the incorrect annotation as B73… time is too precious to look up the correct designation while live observing ;-)

While the darkest of dark nebulae provides an ideal calibration point for setting the black level (as I attempted to do above), I find it also helps to bring the white point down, which in turn admits some sky noise, to improve the definition of the boundaries of these dark nebulae, and to bring out some of the dust in the star field, as in the shot below. 

At -23.5 degrees declination, these objects are quite low for many northern observers. In my case they reached nearly 30 degrees above the horizon, but barely escaped a bright light dome from an airport 10 km away. Other conditions: SQM 20.06, 18C, moon just set, windless. I collected 24x10s darks for live subtraction, and chose 10s exposures to give a virtually continuous update and improvement. The shots I'm showing are quite long stacks simply because that's when I saved them but the view is already pretty good by 30s.

A widefield 'scope would work really well here I think to catch these nebulae along with the Snake. 

cheers

Martin

[laudropb]

Lovely images. Thanks for sharing

[fredman]

Dark nebulae?

I did not know they existed.

Always learning [emoji3]

Great photos by the way, and i'll search more about them.

Thanks

[orion25]

Awesome, Martin. Taking a walk on the dark side, lol!

[Mrbloke]

Superb, clouds are in space mucking up the view too!