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Aligning images from different HST cameras
edited December 2014
My science program obtained images with ACS/WFC and WFC3/IR. How do I align these?
1. use tweakreg to align the images for each instrument (and for each filter if applicable)
2. For each instrument use astrodrizzle to make high signal-to-noise drizzled images.
3. Choose a reference image (from your drizzled images made in step 2) and use tweakreg to align the images from the different instruments to this reference image.
4. Use TweakBack to propagate the tweaked solutions obtained from aligning the two drizzled images back to their respective original flt.fits images.
5. Now drizzle the tweakbacked flt.fits images for each instrument (and filters as needed).
It is useful here to define a custom WCS for final output (step7a in astrodrizzle task). Choose your reference image and use this as "driz_sep_refimage".
Aligning images from different instruments is similar to aligning images in different filters from the same instrument. There is an example of this in the DrizzlePac Handbook, Example 5: