Stacking your frames in Deep Sky Stacker
In this step by step guide, I will help you stack your Light frames, Dark Frames, Bias Frames and Flat Frames. Deep Sky Stacker will combine these images to create one RAW file ready for final processing.
We will be using the default settings in Deep Sky Stacker.
Deep Sky Stacker is not supported for Mac. If you have a Mac, check out how to stack in Siril.
Step 1 - Importing your light, dark, flat & Bias frames
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After opening Deep Sky Stacker, your window should look like the image on the left. You now need to add in your frames.
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The top left box gives you options to open picture files, dark files, flat files, dark flat files (not used often) and offset/bias files. For more information on dark, flat and bias files, click here. The picture files are your main images, the rest are calibration files. import picture files first and then work down the list.
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Once you have imported all files, click the 'check all' tab on the left hand side. Your window should now look a bit like the image on the right. Make sure all your files are checked.
Step 2 - Registering your frames for stacking
During registration, Deep Sky stacker will determine the quality of each light frame and provide you with a score for each one. The score is mainly based on how many stars are in each frame. (It also uses Sky brightness and the width of each star, but as this is a basic guide, we do not need to go into that.)
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On the left hand side, select 'Register checked pictures', this will open a new window where you need to adjust some settings based on your equipment and target.
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First uncheck 'Stack images after registering'. We want to go through our frames before we stack. The bar below will also be green if all frames have been stacked. It will be amber if you are missing one of the calibration frames and red if you only have your light frames checked.
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Go to the 'Advanced' tab at the top of the window and it will take you to star detection. Select 'Compute the number of selected stars' and see how many stars Deep sky stacker detects. You want to get as close to 100 stars as possible. If you have too many stars detected, bring the threshold up. If you have too little stars, bring the threshold down.
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Once you have a decent amount of stars detected, hit 'OK'
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Deep sky stacker will now start creating master calibration files and register your lights. Depending on how many light frames you have, this can take a while.
Step 3 - Setting reference frame and removing unwanted frames
You will now notice that each light frame has a score. Using the top righthand bar, stretch your image enough to see stars.
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Sort the score from high to low. Right click the frame with the highest score and select 'use as reference frame'. The stacking will then work from your best frame.
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Go down to you low score frames. if you notice some star trailing or clouds in your low score frames, uncheck them. We do not want bad frames in our stack as it will reduce detail in the overall image. Only your light frames will have a score. Do not worry about the N/A on the calibration frames.
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The more images you uncheck, the shorter exposure. You need to weigh up whether the frame is worth keeping for the signal or better for dumping because of the quality. In my example I have unchecked 10 light frames, each light frame is 2 mins exposure so I have lost 20 mins of exposure time. However because the star trails were pretty bad, my overall image is likely to be better than if I stacked them all.
Step 4 - Stacking your checked frames
Now the fun part! We will stack all of our checked image to product 1 single Linear RAW file.
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On the left hand side, select 'Stack checked pictures' A new window will pop up. Scroll down and check for any warnings. You may get a warning if exposures times or gain is different for certain frames. This may impact the efficiency of the stacking.
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You will see the total exposure of your stacked frames.
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You will also see how much memory Deep Sky Stacker will temporarily use. Make sure you have enough!
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Once stacked, your image will save as 'autosave' and is usually saved in the same folder as your light frames.
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Hit 'OK' and Deep Sky stacker will work its magic. (This may take some time)
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Deep Sky stacker will compute the final image and save it. There is some options to play with the histogram in Deep Sky Stacker, but I would not. We are now ready to start processing our image.
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