Processing Example

NGC 6960 - Blue Halos Reduction

by Alejandro Tombolini

Introduction

Image of cbobchin publicated in Gallery - Blue halos - Main notes: Starmask and Interchannel Curves to reduce halos. Date: August 2013.

Processing

I notice some blue halos in some stars. Looking at the channels separately, it seems that the stars in blue channel are bigger than in the others.

I try a possible solution to reduce the stars in the blue channel. For that first built a star mask.

The secuenses shows :

1. StarMask with dafault values
2. Increase of Noise threshold to prevent the inclusion of noise and increase Scale to include larger structures
3. To include the big star of the center, increase Midtones and decrease a little Truncation to increase protection in the cores of stars.
4. Finally increase Smoothness to have protection more consistent with halos.

Now protecting the nebulae with starmask, it is possibie to reduce the halos using InterchanelCurves.

Using the Value as Reference Channel and de Blue as Target Channel adjust the curve conveniently.

See before and after of the blue channel:

I tried to show the gif with color but the image is too compressed. See the separate images for comparison.