B&W Efke 100 in the 3x4 '46' Anniversary Speed Graphic, with a 135mm lens, that is well proven.

Although I never set a T shot before with it. But earlier in day light, I made sure the shutter was opening correctly and closing, in this position with the cable release.
Also, although its was windy, before I tried the third shot, made sure the camera had not been jostled, by viewing through the view finder.
My thoughts, although there where stars out, with the wind, and being on the east side of Phoenix, there might have been more dust in the air than realized, and that could have been the contributing factor, with the glow of Phoenix to the west, milking out the contrast of the starts and the night. Having looked at a star studded sky's before, the milky way, and the fainter stars, where just not as much pronounced. But I was there and wanted to give it a try.

Processed the film myself.. in 1:1 D76 for 9 and a half minutes.
Unlike MF or 35 mm film, there are no, what I call 'tell tales', on sheet film.
The film and number ect... but on this particular set of film backs, there are notches, in the side slide area, that when exposed, show you which shot it was. These also did not show. So its as if there just was not enough light, to expose at f5.6.
As I related, I heard the shutter open, and heard it close two plus hours later.
As I also understand, a fully clear negative, indicates, that the film was not exposed.
When I try it again, hopefully, it will not be so windy, and I can try to set ups, with say the speed and the RB67, using B&W in both, for the first efforts.