I have loved this object ever since I first saw David Malin's brilliant photograph of it in his book, "A View of the Universe", from 1995. Malin's image is gleamingly clear and detailed. It reveals successive delicate layers of dark dust and red emission nebulosity surrounding the Dark Tower's head. One little structure which is faintly seen at the extreme right of this Thomas V. Davis image even looked like a human profile seen in silhuette against a red background in David Malin's picture - it was like the Horsehead nebula, except that in this case the Horsehead was a human face!
Personally I was fascinated by the fact that the red emission nebulosity was concentrated at the very top of the tower-shaped nebula. I didn't realize back then that the red emission glow was caused by energetic ultraviolet light from the hot stars of cluster NGC 6231 hitting the topmost layers of the dark nebula and ionising the hydrogen there.
David Malin's image also clearly revealed four reflection nebulae in the dark tower: One light blue "bubble" at the top of the dark tower, one yellowish one near the "bubble", one intensely blue nebula farther down, and one small yellowish nebula below the bluest one. There were also many different-colored stars sprinkled in or in front of the dark nebula.
I have been unable to find David Malin's image of this nebula on the internet. For those lucky ones who own David Malin's book, the picture of the Dark Tower is on page 112!
David Malin didn't have a name for the nebula he had photographed, and he didn't provide his readers with the exact coordinates of it. He also didn't show a wide-angle image of the NGC 6231 region, which might have shown the exact location of the dark nebula in relation to the famous cluster. So for the longest time I was unable to find any additonal information about this dark nebula at all, or to find any other pictures of it.
So I was delighted when Robert Gendler made his own image of this object. Robert Gendler's image is here:
Robert Gendler's image is actually not quite as detailed as David Malin's but it does reveal many of the same features. In particular, you can very clearly see how the red emission nebulosity concentrates around the Dark Tower's head, where the ultraviolet light from NGC 6231 hits the dark neubla "head-on". Robert Gendler's image also shows all of David Malin's reflection nebulae: a yellowish one at far left hanging under the "nose" of the dark tower, the blue bubble being blown out of the "mouth" of it, the intesely blue reflection nebula below the "chin" of it, and a small yellowish nebula at the "collarbone" of it. Because the color balance of Gendler's image is really quite blue, his picture also reveals a diffuse blue reflection nebula below the "eyebrow" of the dark tower. But Gendler's picture also shows that there is no blue reflection nebulosity at the "back" of the dark tower, and here the dust looks very black.
Gendler's image suggests that there may actually be a "cluster" of young stars associated with the "head" of the dark tower. Many of these stars look blue in Gendler's picture, but since the color balance of his image appears to be a bit too blue, the stars that we see are probably mostly of spectral classes G, F and A.
Thomas V. Davis image is very much redder in overall color balance. It reveals far fewer details in the Dark Tower itself, but it brings out surrounding wisps of red emission nebulosity caused by the ultraviolet light of the NGC 6231 cluster.
Ann
The Dark Tower in Scorpius
Optical illusion I guess.
Thanks Leon! 
even though it sounds nice