The art of imaging with Hubble Max Mutchler, 25 September 2008 DITHER DRIZZLE

Advanced Camera for Surveys Wide Field Planetary Camera 2 (ACS) (WFPC2)

WF2 chip Wide Field Planetary Camera 2 (WFPC2) PC1 chip WF3 chip WF4 chip

WFPC2 pointing patterns Small-scale dithers Large-scale mosaics (at the pixel level) (at the detector level)

http://www.stsci.edu/hst/wfpc2/analysis/drizzle.html

WFPC2 drizzling cookbooks

WFPC2 drizzling cookbooks Keep it simple and pragmatic; minimal explanations Set of cookbooks for various pointing strategies and target placements (PC or WF chip/s) Which files to de-archive; reference files (uref) Some tangential issues: image registration; WF4 bias correction…34th row correction? PyDrizzle and MultiDrizzle parameters (reasonable first pass) Inspecting output, iterating, optimizing: what to look for, which key parameters to experiment with Contact the Help Desk with questions

http://hubblesite.org/newscenter/archive/releases/2000/33/

Training exercise Basic work skills and habits: handling data, organizing/notes, scripting, sanity checks, filenaming conventions, version control, etc Sub-sampled, compact dither box pattern; drizzled to half-scale A test: new cookbooks, MultiDrizzle CR-rejection Visually inspecting output: what to look for? Trial-and-error iterations; experimenting (mainly with CR-rejection); knowing when to stop More of a “functional” project, rather than a “science” project, but we’ll see how they inform each other; may include… Photometry: verify rejections via more stringent comparison to Gilliland output (optional) Photometry: drizzle both V-band and I-band images, make a color-magnitude diagram (CMD) Results will help us advise GOs, review proposals…identify bugs?

WFPC2 chips

input images

input image 1 (single_sci)

input image 2 (single_sci)

clean drizzled output (drz_sci)

exposure weight map (drz_weight)

NGC 2440 at 0.10 arcsec/pixel (detector scale) http://heritage.stsci.edu/2007/09/supplemental.html

NGC 2440 at 0.06 arcsec/pixel (sub-sampling scale) http://heritage.stsci.edu/2007/09/supplemental.html