Histogram Stretch & High Dynamic Range (HDR) Combination

Initial M16 H-alpha image after calibrate, align, and stack but no further processing. 18 x 10 minute with QSI 583ws, 5nm H-alpha filter, and 203mm TMB at F7.2.

Step 1 - Background Stretch

Histogram Contrast Stretch is used with the Rayleigh option to stretch the faint background detail. The bright center of M16 is over stretched.

Step 2 - Highlight Stretch

Histogram Contrast Stretch is used with the Uniform option to stretch the bright center of M16 but faint background detail is not shown well.

Step 3 - High Dynamic Range Combination

Histogram stretched background and highlight images are blended using Combine Files | HDR Add with default parameters of Tone Map Compress = 0.0 and Brightness = 1.0.

HDR combination blends background and highlight detail. Tone map compression is not increased in this case since the center of M16 has good contrast and detail.

Step 4 - Adjust Background Contrast

A mild micro curve is applied to [0.0, 16250.0] to increase the dark background contrast.

Step 5 - Adjust Highlight Contrast

Preset darker micro curve is applied to [40274.0, 65535.0] to incrase contrast at the center of M16. Preset curves are used as a starting point and can be modified using the red control points.

M16 Ha enhanced HDR combination with no smoothing or sharpening applied.

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