Why Topics

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The "why" topics are a second layer to the threads; they provide supplemental information for the user that is interested in digging deeper. Some of the topics highlight common pitfalls and subtleties in the CIAO software, others describe aspects of the Chandra Observatory and data obtained with it. The documents also provide information on why certain science decisions are made, enabling the user to tailor the analysis to a particular dataset.

Please email the CXC Helpdesk if you have suggestions for topics that you would like to see discussed here.

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Data Products

• The Aspect Solution & pcad_asol1.fits Files
• Dither
• Multi-OBI Observations
• Why combine data?

ACIS: Data Processing

• CTI Correction
• Time-dependent Gain
• PHA Randomization
• Pixel Randomization
• Sub-Pixel Event Repositioning
• Very-faint Background Cleaning
• Dead Area Correction
• QE Contamination
• Destreaking ACIS Data
• ACIS Focal Plane Temperature

ACIS: Analysis

• -110 C Observations
• Cosmic-Ray Afterglows
• Continuous Clocking Mode
• Choosing an Energy Filter
• Understanding ACIS on-orbit energy filters
• Creating ACIS RMFs with mkacisrmf
• HETG Grating Efficiency
• Systematic Errors on ACIS Response

HRC: Data Processing

• HRC PI Filtering
• HRC-I Gain Maps
• HRC-S Time-dependent Gain Corrections and PI Filter
• Degap
• AMP_SF Correction
• Secondary Science Corruption (SSC)

HRC: Analysis

• HRC-I Background Vignetting
• HRC-S QE/QEU
• HRC RMFs

Pileup

• An Overview of Pileup
• When and How to Avoid Pileup (or not!)

PSF

• The AspectBlur parameter in MARX
• Radial Profile Aperture Corrections, e.g. PSF fraction contribution in adjacent radial bins.

Miscellaneous

• Pitfalls using PIMMS for Observed Data
• Selecting a monochromatic energy. (ACIS & HRC)
• Monochromatic Energy for Low Energy Bands (ACIS)
• Timing Analysis with Lightcurves (ACIS & HRC)
• HRMA Effective Area