Knowing the result that each star has its own extinction law, which is
therefore a local characteristic, these extinction laws will not provide
additional information about the distribution of the dark material in NGC
6611. To obtain such information we have plotted values
of 
, the foreground value being up to 
1
5, for each object as it is
located in NGC 6611, Fig. 8 (click here). This figure contains also the MS programme stars
from Thé et al. (1990). The 
values used are listed in Table 7 (click here)
and calculated
from Table 4 of Thé et al. (1990).
Although the combined sample is not high in number (88 objects), it is
clear that the most obscured objects are located near the centre (= W280)
with a distribution of very high 
values to the north and to the
northwest.
Note that the field of NGC 6611, e.g. Fig. 7 (click here)a, already shows that these regions
are relatively less crowded. This would indicate that most dark material is
distributed towards these directions
and would be the region to look for young
objects or even traces of star formation.
Indeed, most embedded sources as discussed by
Hillenbrand et al. (1993) are
distributed towards the northeast of W280. This region would then be
most important to look for on-going star formation.
Hillenbrand et al. (1993) mention that
more than 50% of the infrared objects located south or
southeast are background objects. If we then refer to their
Table 7 (click here) of embedded stars with circumstellar material,
we find that many of these objects are located to the northwest
of the stars with the highest 
values as plotted in Fig. 8 (click here).
This supports our finding and indicates that most visible
young objects seem to be distributed north-northwest of the
centre (= W280) and on-going star formation could probably be
occurring north-northeast of it.
Figure 8: Field of NGC 6111 reproduced from a Hale Observatory photograph
of plates taken in H
and [NII]
6548, 6583
with the 200 inch Hale telescope (Osterbrock 1974).
The bright HII region, M 16, is clearly visible. The central area of NGC 6611
is drawn by an overlay. We have indicated the 
values for the PMS-programme
stars and the MS-objects of Thé et al. (1990) by an intensity scale, indicated at the
right