Barnard 133 - Dark Nebula
Barnard 133 is a "Dark Nebula" and can be found in the constellation Aquila, more precisely, only half a degree south of the planetary nebula NGC 6751.
How "dark" such a nebula is, can be indicated by the opacity scale: the higher the value, the less light the cloud lets through. Barnard 133 has the
highest level with a value of 6 and thus seems to us particularly conspicuous. In addition, the nebula is located directly in front of the bright Scutum
star cloud, which is extremely rich in stars. This also raises the contrast significantly.
The distance to dark clouds can usually only be estimated. In the case of B133, the approximate value is about 1,300 light-years. With an apparent
extent of 18x5' (arcminutes) the true size of the dark cloud can be calculated to be 7x2 light years.
-----------------------------------------------------------------------------------------------------------------------------------------------
Looking through my 20 inch f/3.2 Dobson, a "dark" area appears at 120x. This is mainly characterized by the absence of very faint stars.
Increasing the magnification to 210x, even fainter stars become visible - but only outside the dark cloud. The transition from a star-rich background to
almost complete emptiness happens quite abruptly in Barnard 133. And so the boundaries can be traced very well and the dark cloud takes the shape
of a "tear"... A beautiful object! :)
All in all, B133 is certainly one of the most beautiful and rewarding dark clouds in the sky and is definitely worth a visit.
