[vsnet-chat 2496] (fwd) Re: ST6 - IR Blocking Filter

[Taichi Kato <tkato>]

Date: Tue, 28 Dec 1999 18:46:13 -0600 (CST)
From: Rafael Costero <costero@astroscu.unam.mx>
Subject: [vsnet-chat 0] Re: ST6 - IR Blocking Filter

Dear Stan and Arne:

Regarding the halo Stan gets on I images: couldn't it be just fringing?
We do have that problem with a back-illuminated 2K Thomson CCD when using
narrower band-pass filters at 700 nm and longer wavelengths. Maybe the halo
is produced by the ST6 itself and some near-infrared lines: There is a Na I
doublet, VERY strong, in high- and low-pressure Sodium lamps at 818 nm (see 
Fig. 3 in Osterbrock et al., 1976; PASP, 88, 349). If there are such lamps in
Awanui and Kaitaia, that could by the cause of the halo.

Best regards and wishes to everyone in VSNET,
Rafael Costero
Instituto de Astronomia, UNAM
Mexico

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