astro.md

Astrophotography

Calibration frames

Bias frames

• Purpose
  • fix the pattern noise the sensor produces, the inherent noise of the electronics of the sensor
• Where
  • complete darkness
• When
  • camera has to be outside long enought to become same temperature as the light frames are going to be
• How
  • cap on the sensor
• Aperture settings
  • not relevant because no light reaches the sensor since there is the cap on it
• Exposure time
  • the shortest possible
• ISO
  • same as light frames
• Count
  • at least 50

Dark Frames

• Purpose
  • correct hot pixels on the image sensor and heat noise
• Where
  • complete darkness
• When
  • with the light frames, they must match the temperature of the light frames were shot
• How
  • cap on the sensor
• Aperture settings
  • not relevant because no light reaches the sensor since there is the cap on it
• Exposure time
  • same as light frames
• ISO
  • same as light frames
• Count
  • 25-30% of the number of light frames

Flat frames

• Purpose
  • fix the vignetting effect that comes with lens-based systems
  • fix dust on sensor or lens
• Where
  • the same place and position of light frames
• When
  • doesn't matter
• How
  • take pitcures of a flat white surface, a piece of paper should work
• Aperture settings
  • same focal point and aperture as light frames
• Exposure time
  • as long as it's needed to make the bump on the histogram of the image to reach halfway of the histogram
• ISO
  • same as light frames
• Count
  • at least 50