tion it deserves . In due course , efforts such as the SkyMapper Southern Sky Survey and its shallow photometric survey should make deriving photometric zero-points from separate standard star observations redundant ( as every GMOS field will contain multiple sources with catalogued u ’, g ’, r ’, i ’ and z ’ magnitudes ), but in the interim we trust that the community will find this a useful resource .
Disco-Stu — GSAOI Image Reduction Simplified
Gemini has announced the release of a new standalone software package . Called Disco-Stu ( DIStortion COrrection and STacking Utility ), it is designed to help with the analysis of images taken with the Gemini South Adaptive Optics Imager ( GSAOI ). Disco-Stu takes images that have been reduced with the Gemini Image Reduction and Analysis Facility package for GSAOI and aligns them by matching sources with the aid of a lookup table that maps the instrument ’ s static distortion . Stacking is then performed with bad pixel rejection and , if desired , inverse-variance weighting . The astrometry can be tied to an external source catalog , and the output image can be made to share the world coordinate system of another image . Performing both these steps results in an image that is perfectly aligned with an existing image , either taken with a different instrument , or with GSAOI at a different epoch .
Disco-Stu is written in Python and requires the NumPy and AstroPy packages ( which are part of the Ureka release ). SExtractor is also required for normal operation , although source catalogs can be prepared separately .
— Chris Simpson
Figure 6 . Finding chart for the GMOS-S standard star field NGC 458-AB , a star cluster in the Small Magellanic Cloud , based on the OT Position Editor display .
Figure 7 . A color mosaic of a region of the Pyxis globular cluster , produced from HST F606W and F814W images and a stack of GSAOI H-band frames . Disco-Stu was provided with one of the HST images and a source catalog constructed from that image ( culled of faint sources and objects outside the GSAOI fieldof-view ) but no further guidance was required .
October 2016 GeminiFocus
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