The sky around LDN 866 at true scale, north up and east left, with stars to magnitude 8, the Lynds bright and dark nebulae, and the NGC and IC objects in the field. The box marks a circle of the same area as the cloud; the cloud itself is irregular.
LDN 866 is a dark nebula in the constellation Cygnus. It covers 0.17 sq deg of sky, about the area of a circle 28′ across, and Lynds gave it opacity 3 of 6, faint. It is a faint cloud that shows best in wide-field photographs, and it is highest in the evening sky in September.
Dark nebula: a cold cloud of gas and dust, a few degrees above absolute zero, dense enough to block the light of the stars behind it. Dark clouds are where new stars form, and they show only by contrast against a rich star field.
Finding LDN 866 from Sadr
LDN 866 lies 3.8° southwest of Sadr, the magnitude 2.2 star. Three fingers held at arm's length cover about 5°.
A dark nebula shows only by contrast, as a patch with fewer stars than the field around it. Use the lowest power and widest field you have, from a dark site with the Milky Way high in the sky; a nebula filter does not help, because there is no light from the cloud to pass.
LDN 866 is highest in the evening in September
The chart gives its height above the horizon at 9 pm through the year, from 60°N to 40°S. It can be seen from the whole northern hemisphere and south to about 52°S, and never sets north of 52°N.
The distance to LDN 866 is not well measured
No reliable distance has been measured for it yet.
77 Lynds bright nebulae and 48 Lynds dark nebulae lie within 5° of LDN 866
