WFPC2 Instrument Handbook for Cycle 10

Redshifted [OII] Quad Filters

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The redshifted [OII] quad filter was designed to map onto a four-faceted WFC configuration. A partial SOFA wheel rotation of -33° is required to move filter quadrant 1 (3763Å) into WF2 and WF3, with some vignetting of both camera fields. The projections of the redshifted [OII] filter settings FQUVN and FQUVN33 onto the field-of-view are essentially identical to those of the POLQ and POLQN33 filters, respectively (Figure 3.6). The vignetted regions are similar, and the location of aperture FQUVN33 is identical to that of POLQN33.

The nominal and rotated filter wheel positions for the redshifted [OII] quad filter are each associated with different filter names. This allows pipeline calibration and database retrievals to proceed smoothly. The filter names are summarized in Table 3.9.

The required central wavelength is selected by filter name and aperture location. Filter element FQUVN (Filter Quad UltraViolet Narrow) has three possible apertures, each of which is nominally centered in one of the three WF channels and associated with a unique central wavelength. The filter element FQUVN33 corresponds to a single central wavelength. In addition to the filter name and aperture, a central wavelength is also requested in the proposal instructions in order to provide a consistency check. Aperture names are discussed further in Apertures.

Table 3.9: Redshifted [OII] Quad Filter Elements

Filter Name	Aperture Name	FOV Location	Quad	Mean Wavelength (Å)	Effective Width (Å)	Comments
FQUVN	WF2	WF2	D	3992	64	Nominal filter wheel position
FQUVN	WF3	WF3	C	3912	60	Nominal filter wheel position
FQUVN	WF4	WF4	B	3829	57	Nominal filter wheel position
FQUVN33	FQUVN33	WF2	A	3763	73	Filter rotated -33°