1. Rosaria (Sara) Bonito Dipartimento di Fisica e Chimica Universita' degli Studi di Palermo INAF-Osservatorio Astronomico di Palermo THE PROBLEMS OF SKY SUBTRACTION AND OF ANOMALOUS MEMBERS IN YOUNG CLUSTERS: THE CASE OF NGC 6611

2.  FLAMES observations (HR15N setup)  NGC 6611: forthcoming observations GES NGC 6611 & GES (Bonito et al. 2013)

3.  Nebular contribution to H  emission  Strongly varying in space and time  Narrower than stellar  FWZI method (as EW and H  10% cannot be derived) SKY SUBTRACTION & H 

4. FWZI METHOD (1)  Zoom +/- 3 A around H  in sky spectra

5. FWZI METHOD (2)  Normalize: spectrum without the emission line

6. FWZI METHOD (3)  Difference or ratio original spectrum/spectrum without the emission line

7.  FWZI(H  ) sky FWZI METHOD (4) < 3 A

8.  FWZI(H  ) star >> FWZI(H  ) sky FWZI(Halpha) & ACCRETION (Bonito et al. 2013)

9.  Upper limit for EW(Li) using other features in the Li spectral region (Randich et al. 2009)  Median sky subtraction (Jeffries & Oliveira 2005) SKY SUBTRACTION AND Li (1)

10.  Spurious absorption lines due to [SII] 6717 A SKY SUBTRACTION AND Li (1)

11. SKY SUBTRACTION AND Li (2)  No Li  No veiling  Age  Membership

12.  NGC 6611: forthcoming observations   Vel  NGC 2264  NGC 6530 IMPLICATION FOR GES

13. BWE STARS IN NGC 6611 (Bonito et al. 2013) +: members from the Guarcello et al. (2010) catalog : all the targets observed with FLAMES : BWE stars (with disk)

14. BWE STARS: WHY?  > 50 %: members (Bonito et al. 2013)  old members? (De Marchi, Panagia, Guarcello, Bonito et al. 2013)  also in other clusters completeness age spread? GES

15. CONCLUSIONS  Sky subtraction  FWZI(H  method  Spurious absorption lines (Li)  Blue with excesses (BWE) stars  completeness  age spread  other clusters (GES)