Discovery Astrophotography with ZWO ASTRO

ASIDeepStack: What is it and how to use it to stack files for astrophotography



A Brief Introduction

ASIDeepStack is a deep sky stacking software (only supports 16-bit fits files for now). It offers many capabilities, including image preview, stack, histogram stretching and much more. It can process various types of files such as lights, darks, flats, bias, etc. and accordingly, after stack it will also improve the image signal-to-noise ratio (SNR).


How Does It Look Like?

ASIDeepStack interface1

ASIDeepStack interface2

Area A: Setting Bar. Including settings and help.

Area B: File List Area. Including Bias, Flat, Dark, Light four tabs, empty current tab button and so on.

Area C: Stack Area. Including open save path, start stacking, and switch single/stacked display.

Area D: Histogram Setting Area

Area E: Full-screen Button

Area F: Vertical Tool Bar

Area G: Capture Display Area

Area H: Status Bar. It shows current display image info and loading progress.

Area I: Image Processing Area

A Guide On How to Stack files

① Open ASIDeepStack. Let’s start stacking with lights files, so click the “Light” tab in File List Area (Area B).

② Click the ”Select Light” button, then select the Light files that need to be stacked in the pop-up dialog.

③ The files will be imported after you choose. You can watch the progress bar at the lower right corner of Status Bar (Area H). When the importing is finished, “Load Completed” will be prompted.

Select Light

The start stacking button in Stack Area (Area C) is now available. You can click the play icon to draw forth the stack window and then start stacking, but let’s just wait for a second.

④ If you need to re-select the Light files, you can click the sweep icon in the top right corner to remove all files under the current tab.

⑤ Import other calibration frames (darks, bias, flats).

Select Dark&Flat&Bias

⑥ When done importing all calibration frames, now you are free to start stacking. As mentioned in ③, a stacking window will pop up. After you complete stacking all files, it will automatically close and then show you the stacked image.



⑦ The main adjustment options in the “Image Processing” module are brightness, contrast and saturation. You can also stretch the upper “histogram” to further process the displayed image. When processing, if you think the result is over-processed, then you can click the “Reset” button to restart.

For beginners, we recommend you use “Auto”. For advanced astrophotography enthusiasts, you can adjust the brightness, contrast and saturation by yourselves. If the image still has much noise after processing, we recommend you check “Noise Reduction”. This would help.

When all work is done, don’t forget to save the image. The next step is about how to save it.

Image Processing


⑧ Click the setting button in Area A to set the file save path.

Save Path Set


Click the save button in Area F to save. By default, jpg and FIT format files are saved in the set path.

The saved path will also be displayed in the lower left corner of the software.

Image Saved

Click the folder button in Area C to find the image file just saved.

Here is the comparison before and after stacking:

Before Stacking

After Stacking


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