Masks, weights and flatfields

1
Masks, weights and flatfields

• Roeland Masks and weights
• Philippe Are WFI flatfields flat?
• Ewout Making a supersky?

2
Masks, for what

• Image statistics
• We could do this more often
• Making weights
• weight flat mask
• for sextractor
• for coaddition
• Other,
• cosmic ray program

3
Different Masks

• Cold pixels
• bias gt mean(bias) 5rms(bias)
• Hot pixels
• flat / convolved(flat) lt 0.95
• Cosmic rays
• Satellite tracks
• Saturated pixels
• low gain (co-addition only)

4
Current situation

• class ColdPixelFrame
• class HotPixelFrame
• class MaskFrame
• mask coldpixels hotpixels
• class MasterWeight
• weight master_flat mask_frame
• class FlagFrame
• mask thresh(weight) science.cosmic()
• class WeightFrame
• weight master_weight flag.as_mask()

5
New situation

• Add all operations
• Use eclipse.pixelmap object
• 1good, 0bad
• (de)compress on-the-fly
• clean up class-hierarchy mess
• simplify ScienceFrame.make()

6
New Situation

• class ColdPixelMap
• class HotPixelMap
• class CosmicMap
• class SatelliteMap ?
• class Weight
• weight flat coldhotcosmicsat
• weight weight thresh(science)
• weight weight thresh(weight)

7
Error maps

• Weight is relative error map
• Could make absolute error map and do proper
  propagation of errors
• Nice idea
• but, remember the applications