WFC3 Instrument Handbook for Cycle 24
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Wide Field Camera 3 Instrument Handbook for Cycle 24 > Chapter 2: WFC3 Instrument Description > 2.4 Detector Read-Out Modes and Dithering

2.4
The detectors in both channels offer subarray readout capability; see Section 6.4.4 (UVIS) and Section 7.4.4 (IR) for full details. The UVIS channel also allows 22 and 33 on-chip binning of full-frame images. Finally, a variety of dithering patterns can be requested using the Astronomer’s Proposal Tool (APT) software. Predefined patterns have been established to address common requirements, such as sub-pixel dithering to improve PSF sampling or dithering to achieve large areal coverage while also sampling the inter-chip gap (Appendix C). The post-observation pipeline software (see Appendix E, the WFC3 Data Handbook, and the AstroDrizzle documentation) carries out appropriate calibration of data taken in all of these configurations, and offers the option of reconstructing dithered images with a drizzling algorithm. A combination of software packages in DrizzlePac can be used to optimize the drizzling of images. If the dither pattern incorporates non-integer pixel offsets, it can effectively improve the sampling of the point-spread function (PSF). The software can also handle mosaicked images according to a set of rules or associations, rectifying them onto a cartesian pixel coordinate system.

Wide Field Camera 3 Instrument Handbook for Cycle 24 > Chapter 2: WFC3 Instrument Description > 2.4 Detector Read-Out Modes and Dithering

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