Sky Mask Editor - MergeRAW

Open the editor

For automatic merging and shooting advice, see fixed stars or star trails. To refine the result yourself, start with a Custom Mask blend below.

MergeRAW Sky Mask Editor showing Sky motion evidence with the selected sky mask overlaid in red above a mountain skyline — The Sky motion view helps distinguish sky from foreground movement. Here the red mask overlay marks the selected sky; switch to Composite to judge the photographic result.

Choose Align Stars - Sky Tracking, then Custom Mask - Fixed Stars & Foreground for pinpoint stars or Custom Mask - Star Trails & Foreground for trails. MergeRAW aligns and combines the source images, then opens the editor with an automatic mask.

The custom modes can start from the AI mask when the optional model is available, or use the basic mask without it. The editor runs locally on macOS and Windows. No photos are uploaded.

Select Composite to judge the finished boundary, or switch between the Foreground stack and Sky stack to see the two ingredients. The numbered keys shown beside the views switch between them. Changes appear immediately in the composite.

Use Mask and its density slider to inspect the colored overlay. M toggles it. The selected Sky or Foreground label is what you paint; X switches labels. Hold Option / Alt to paint the opposite label temporarily.

Selection tools

Control	What it does
Brush · `B`	Paint a known area directly. Adjust Size and Hardness; use a smaller brush around branches and fine skyline edges. Shift-click connects brush clicks with a straight line.
Quick select · `W`	Brush over a feature to grow the selection into similar neighboring pixels. Reduce Tolerance or Reach if it spills over the skyline. Smoothing reduces sensitivity to small color variations, and Fill holes closes small enclosed gaps.
Island · `I`	Click a small disconnected patch in the mask to switch it to the selected label. The size limit helps avoid changing a large connected region accidentally.

Quick select can also require the merge's evidence to agree with the brushed spot: Motion describes movement between frames, Prior is the AI sky estimate, and Trail shows star-trail density. Only available signals appear. Keep these checks on to start; relax one if it prevents a correct selection. The corresponding views help explain where the evidence is uncertain.

Inspect difficult branches against both source stacks and the Composite. A broad brush correction followed by smaller edge strokes is often easier than forcing one tolerance to handle the whole skyline.

Review & save

Preview exposure and Preview contrast help you see a dark horizon. They affect the displayed photo only; they do not change the saved mask or Lightroom settings. The preview approximates the source's develop settings.

Use [ / ] for brush size, Space + drag to pan, F to fit and 0 for 100% zoom. Undo with Cmd / Ctrl + Z; add Shift to redo.

Save, Enter, or Cmd / Ctrl + S finishes the merge and imports the DNG into Lightroom. Cancel or Esc cancels it. Check the completed image at full resolution, especially around fine branches and trail crossings.

After a successful custom merge, the edited mask is kept beside the original as <name>_MergeRawSkyMask.TIF. The next custom merge of the same set starts from that saved mask. Reset to the automatic mask returns to the fresh estimate, and can itself be undone. Canceling leaves the saved mask unchanged.

Back to Getting Started · Focus Depth Editor

Fixed stars

Choose Align Stars - Sky Tracking, then pick the blend for your scene. The Fixed Stars blends reduce noise and reject satellite and aircraft trails.

Normal - Fixed Stars: keeps stars sharp; the landscape may blur. Use it when only the sky matters.
Basic Mask - Fixed Stars & Foreground: keeps both stars and landscape sharp, without an AI model.
AI Mask - Fixed Stars & Foreground: the better choice for a complicated skyline with trees, branches or rocky ridges.
Custom Mask - Fixed Stars & Foreground: review and correct the sky/foreground boundary in the interactive editor before finishing the merge.

With a mask blend, you can include a longer exposure or light-painted frame for a brighter foreground. Check fine edges along the skyline in the result.

AI blends require an optional, one-time download of about 86 MB, with your permission. Processing stays on your computer, works offline, and sends no photos or metadata. You can disable AI or delete the model in Plug-in Manager › Ryan's Raw Tools › AI Features.

Built with DINOv3, published by Meta Platforms, Inc., under the DINOv3 License Agreement. A copy of the license is saved with the model.

Star Trails

Keep the camera on a stable tripod and minimize gaps between exposures. Choose based on foreground noise, rather than a fixed number of frames.

Choose	When to use it
No Alignment - Tripod + Lighten - Star Trails & Multi Exposure	A straightforward trail stack when individual exposures already look clean. It does not reduce foreground noise.
Align Stars - Sky Tracking + AI Mask - Star Trails & Foreground	Many short exposures with a dark or noisy landscape. Gives a cleaner foreground and preserves light painting while leaving the stars as trails.

Light painting within the normal sky sequence can contribute to both the trails and foreground. Longer foreground exposures and detached frames stay out of the trails. The AI option uses the same optional model as the Fixed Stars blend. Check the skyline around branches and other fine detail.