Astrophotography sits at the intersection of science and art, much of it shaped by the photographer’s creative vision. When preparing for an imaging session, it’s important to define a clear strategy based on the intended result of the final image.
This is especially important when taking images of objects that exist a steep brightness gradient of objects, for example, an open cluster with faint gas but bright stars, or a galaxy that has a bright core. There are multiple ways to deal with these objects, two of which are:
- Generating starless and star-only images
- High Dynamic Range Imaging (HRD)
Generating starless and star-only images:
Tools such as StarNet++ and StarXterminator allow you to remove stars from your astrophotography images, this creates a lot of room for adjustments. The usual problem when curving a full image was the inability to fulfill my desires for 1. Enhance as many details for starless and 2. Preventing the stars from overexposure, in this case separating them allows me to address both desires effectively. After separating them, I typically curve the starless with enhanced details, brightness, and contrast, then depending on the situation, lower the brightness of the stars slightly. Then, I recombined the image using PixelMath in Pixinsight, this is a cool function, not only can you “star + starless,” you may also “star * 0.7 + starless,” which Andrea and I attempted, and turned out pretty well.
Additionally, you may be surprised by how *aesthetic* the starless images look, here are a few:
High Dynamic Range Imaging (HRD):
Another way of approaching is High Dynamic Range Imaging (HRD), this is especially useful for scenes with both very bright and very faint features. Typically, we shoot the object with short and long exposures, with the short exposure preserving details in bright areas, and the long exposure bringing out faint details. After calibrating each set, tools such as PixInsight’s HDRComposition or Photoshop blending with masks combine the sharpness of short exposures with the faint detail of long exposures. This is useful for capturing objects like the Orion Nebula, planets, and moon with the surrounding star field, and solar imaging.
At the heart of it, balancing an astroimage is about finding harmony between what’s out there in the sky and how we choose to show it. Whether through separating stars or blending exposures, these methods help us tell a clearer visual story.