How to Align and Stack Multiple Moon Pictures with Ninox and Registax

Last Updated: June 29, 2021

Align and stack multiple moon shots (or planetary shots like Jupiter for example) allows to improve the final image quality (less noise, less deformations). This post-processing task requires having a set of photographs (typically 10 to 100 for the moon) that have been acquired in the same conditions, with the same gears, and the same settings (focal length, f number, exposure time, ISO, white balance). The alignment task (before being able to properly stack the images) is mandatory in order to compensate the for relative the motion of the moon in front of the camera between the successive shots.

In the following, the raw moon pictures have been acquired with a SONY SLT-A55 DSLR combined with a SIGMA 120-400 lens and the following settings:

Focal length : 400mm (35mm equivalent: 600mm)
ISO : 200
Aperture : F/5,6

Ninox is used for a quick preliminary crop of the raw images, with an automatic centering of the brightest object in the frame (here it's the moon). This preliminary step allows to reduce the size of the images aligned and stacked later by Registax which will perform faster (and often better).

Registax is then used to perform a precise alignment of the cropped picture set, stack everything into a single image, and apply the powerful wavelet filter.

Note : This tutorial is only valid for Windows users. Linux and OSX users are required to use Wine in so far as Registax is only available for Windows.

Method 1

Method 1 of 2:
Use Ninox for preliminary images cropping

1
Create the working directories to store the intermediate image files
- Create the root working directory ('C:\lune' for example)
- Create the source folder ('C:\lune\photos_brutes' for example) and copy all your raw images in the bitmap file format (.bmp).
- Create the destination folder ('C:\lune\photos_recadrees' for example) that will be used to store the images processed by Ninox.
2
"Install Ninox by Antony Wesley"
- Download Ninox , http://www.acquerra.com.au/astro/software/ninox/
- Extract Ninox : (in the folder 'C:\lune' for example) by right-clicking the .zip archive previously downloaded.
3
Crop your images with Ninox
- Open the Command line prompt window through 'Start -> All Programs -> Accessories -> Command Prompt'
- Change the current directory by typing 'cd C:\lune\photos_brutes' and validate with the 'Enter' key
- Start Ninox by typing : 'C:\lune\ninox-2.82\ninox.exe -width=900 -height=1000 -cutx=900 -cuty=800 -qestimator -qrenumber -outdir=C:\lune\photos_recadrees' and validate with the 'Enter' key. You can adjust the cropping settings width, height, cutx et cuty to fit your images size and resolution. More details on Ninox's website (see this tutorial's 'Sources and References' section).
4
Select the best images: in the folder 'C:\lune\photos_recadrees', delete the pictures most affected by motion blur, atmospheric perturbations, ...

Method 2

Method 2 of 2:
Use Registax to align and stack the pre-processed images

1
Download and install Registax 6 from the following page: http://www.astronomie.be/registax/download.html.
2
Open Registax (you can use the shortcut created on your desktop during the installation process)
3
Import the selected cropped images (in 'C:\lune\photos_recadrees'), either by drag and drop into Registrar's window or by using the 'Select' menu.
4
Create the Alignpoints by clicking the 'Set Alignpoints' button. Depending on your image resolution, Registax will automatically create alignpoints (red circles on the current image preview) that will later be used to register each frame with the rest of the images set.
5
Click on the 'Align' button in order to start the alignment process.
6
Click on 'Limit' in order to set the quality threshold for the image stacking process. You can see, in the 'Limit Setup' frame, that the 'Lowest Quality (%)' parameter is automatically updated by Registax.
7
Click on 'Stack' to perform the stacking task with the default parameters.
8
Use Registax's wavelet filter by clicking the Wavelet tab. Move the horizontal scroll bar for each layer in order to get the picture you like most. For the moon, my filter settings were the following:
- Layer 1: 15,0
- Layer 2: 12,0
- Layer 3: 7,0
- Layer 4: 6,0
- Layer 5: 5,0
- Layer 6: 2,0
9
Then, click 'Do All' in order to make the Wavelet filter apply on the whole image (the preview just applies to the image center). You'll find more information on the wavelet filter in Registax here: http://www.astronomie.be/registax/previewv6-3.html
10
Don't forget to save the final image by clicking 'Save Image' once you are happy with the result. Click on this section's figure to compare an original single image and the final image registered and wavelet filtered with Registax 6. Pretty nice improvement, isn't it ?

Sources et References

Ninox is a free software developed by Antony Wesley. It is a command line tool whose user manual can be consulted on its website (http://www.acquerra.com.au/astro/software/ninox/).
Registax 6 is a free software developed by an international team of 9 developers. You can visit its official webpage for more information (http://www.astronomie.be/registax/index.html).
This tutorial is largely inspired by the article on the same topic written by Paul Maxon.(http://www.astronomie.be/registax/previewv6paul.html).