Stacking and Calibration

Image stacking and calibration is used in digital astrophotography in order to enhance data in photos.

To put it simply these methods are used to improve the SNR (Signal to Noise Ratio), reduce long exposure and ISO noise in images taken with DSLR's.

The example shown here is not breathtaking but was obtained using these methods. This Andromeda Galaxy (M31) image lacks exposure time but that can not be increased using only a fixed tripod without showing star trails.

Image Data: Andromeda Galaxy (Messier 31)

Lens/Scope: Canon 18-55 f/3.5-5.6 EF-S Zoom IS Lens

Focal Length: 53mm

F/Stop: f/6.3

Exposure: Stack of ten 15-second exposures (150 second total exposure)

Mount: Fixed Tripod

Guiding: None

Camera: Unmodified Canon 500D (Digital Rebel T1i)

Mode: Raw

ISO: 1600

White Balance: Custom, set on sky background

In-Camera Noise Reduction: Off

Filter: None

Date: September 12, 2010

Location: Beja, Portugal

Calibration: Dark frames were subtracted from each individual light frame to remove the thermal signal.

Processing: Calibrated, aligned and stacked in DSS. Levels, curves, brightness and contrast enhancement, noise reduction, cropped, resampled in Photoshop. Carboni Tools.