this night later I had a little better seeing.
I used a 200/1600mm Dobson from a good friend.
I saw different darkness inside the GRS !
The BA was not strong in contrast.
I measurded his position at II 170°.
30.10.2012, 22:50 UT, V 178x and 213x without filter
I 305° II 164°
I measured the GRS after sketching again by II 183° !