Beginner tutorial – how to stack comet images in Deep Sky Stacker (my work flow)

First visit to this astronomy/astrophotography blog? Well, firstly a warm welcome to you and thanks for stopping by. After reading this post, if you want to find out more about me and this blog, why not visit my introductory page at https://undersouthwestskies.blogspot.com/2025/01/welcome-to-my-new-astronomyastrophotogr.html  You can also browse other posts by using the search bar or the blog post list on the right hand side and I'd really like to hear from you via the comment boxes. Drop me a tip, an observation or a question. Take care and clear skies to you.  Steve 

 Beginner tutorial – how to stack comet images in Deep Sky Stacker (my work flow)

Ever wondered how to turn your series of faint comet frames into one crisp, detailed image? In today’s post. I’ll walk you through my step-by-step work flow for stacking comet images in Deep Sky Stacker DSS) – a free, powerful tool that’s perfect for astrophotographers who want to capture the beauty of a comet without those distracting star trails.  

In summary, the work flow order goes like this:

1.      Open picture frames

2.      Then for each image use the green comet image to select the comet’s nucleus – saving the position for every frame

3.      Entering the stacking settings, choosing a comet stacking mode (Comet only, stars only, both)

4.      Starting the process of stacking

 

So, let’s dive straight into the more detailed work-flow.

Step 1: Register all images 

First, let’s get your light frames ready.

• Open Deep Sky Stacker and click ‘open picture files’
• Select all the comet frames you want to stack
• (Select all the bias, flats and dark frames you want to add in)
• Click ‘check all’ – and then choose ‘Register checked pictures’

·       In the pop-up window, make sure to:  –

o   check ‘register already registered pictures’

o   check ‘automatic detection of hot pixels’

o   DO NOT check ‘stack after registering’.

o   Then click ‘OK’ to start the registration process

This last step makes sure DSS knows exactly how to align and handle your images before we move on to the comet itself.

 

Step 2: Mark the comet’s nucleus in each image 

Now for the fun part — telling DSS where your comet is in each shot.

• Select the first image in your list
• Click the green comet icon on the right side of the screen
• hold down the Shift key and click directly on the comet's nucleus to mark its position. A pink circle should appear around it.
• Save the changes for that image. You can click ‘save all’ so DSS keeps track of the comet position across all selected frames OR
• Repeat this process for every light frame

This step can be a little repetitive, but it’s essential — it tells DSS how the comet moves across your frames, allowing it to align the comet while still handling the star background correctly.

Tip: If you’ve seen the tutorial “How to Stack and Process Comet Images with Deep Sky Stacker,” it shows a great visual example of this process. How to Stack and Process Comet Images with Deep Sky Stacker

 

Step 3: Stack the images

With everything marked, it  is time to stack your comet.

• Click ‘Stack checked pictures’.
• When dialogue box appears, choose ‘Stacking parameters’ appears
• go to the Comet tab and choose your desired stacking mode.
• "Stars" (comet trails)
• "Comet" (star trails) or
• "Stars + Comet" (both) – my go to choice  
• Click OK to start the stacking process. 
• If another pop-up window appears called ‘stacking steps’, keep the default settings and just click ‘OK’ again.

When DSS finishes, save your stacked image as a TIFF file, ready to edit in your favourite processing software — whether that’s Photoshop, Affinity Photo, PixInsight, or any other astrophotography editor.

Want to See It in Action?

If you prefer to follow along visually, these videos do a fantastic job of demonstrating how to select and use the comet stacking modes in DSS:

How to STACK Comet in Deep Sky Stacker - Beginners Astrophotography Tutorial

How to Stack Comet Images Without Star Trails in DeepSkyStacker

Final Thoughts

Stacking comet images in DSS might feel a bit technical at first, but once you’ve done it a couple of times, it becomes second nature. The reward is absolutely worth it — a clean, vibrant image that beautifully captures the motion and structure of your comet, without losing the stars in the background.

Give it a try with your next comet data set and watch your images transform! As always, if you have a tip or an observation about my work-flow, then drop me a comment so we can improve it for all and, it goes without saying, but I will anyway – stay safe, have fun and clear skies to you all

Steve