How to process and enhance Moon and Sun images with Autostakkert and Affinity Photo.

Observing the Moon and the Sun with a Vaonis smart telescope does not involve stacking, unlike deep-sky object observations. It is a live observation. Processing a single JPEG image yields limited results. However, you can save all the JPEG images from the observation and stack them. This approach produces an image with reduced noise and greater dynamic range, allowing for enhanced detail during post-processing.

This tutorial provides a step-by-step guide on stacking JPEG images using the free software Autostakkert, followed by an easy post-processing session with Affinity Photo.

Fig. 1 : the Moon before and after processing

Fig. 2 : the Sun before and after processing

Requirements

Autostakkert

Autostakkert is astronomy software designed for stacking planetary images. It is free for non-commercial use and can be downloaded from the official website.

Autostakkert is compatible only with Windows-based computers. However, it can also run on macOS using an emulation solution. We recommend Crossover by CodeWeavers, which allows you to run Autostakkert without installing Microsoft Windows. Crossover costs approximately $75 and offers a free trial. You can download it from the official website.

If you’re using an Apple computer, install Crossover first, then Autostakkert.

Affinity Photo

Affinity Photo is a versatile image processing software comparable to Photoshop in features but more affordable, as it requires only a one-time purchase of about $75 rather than a monthly subscription. A free trial is also available.

Affinity Photo is compatible with macOS, Windows, and iPads. Learn more and download it here.

Tutorial sample files

Download the sample images as well as the Affinity Photo working files and resulting images.

Capturing Your Images of the Moon and the Sun

Before starting your observation, make sure that live image saving is enabled:

Navigate to the instrument screen and select the image format.

After your observation, retrieve the images from the telescope’s internal memory. Copy the relevant observation folder to your computer.

For detailed instructions on accessing the telescope’s internal memory, refer to our knowledge base: How to Save My Pictures on My PC (Windows Users)

When stacking JPEG images, we recommend capturing at least 100 images. Lower-quality images will be excluded during processing, so it’s important to have a large selection. A 10-minute observation should provide enough images for the process.

Stacking Moon and Sun Images with Autostakkert

Once you’ve copied the images to your computer, launch Autostakkert.

The interface consists of two windows: one for the main settings and another for displaying the images and defining various alignment settings (necessary for stacking).

The process and settings are the same whether you are processing images of the Moon or the Sun.

Fig 3 : Autostakkert Interface

Step 1: Select the Images to Be Stacked

1. Click the  1) Open  button in the top-left corner (Fig. 4,#1).

In the pop-up window:

1. Locate and select the folder containing your images (Fig. 5, #1).
2. Ensure image and JPEG is checked in the file format list (Fig. 5, #2).
3. Select all the JPEG images (Fig. 5, #3), then click  Close and Process Data  (Fig. 5, #4).

You should now see an image of the Moon/Sun in the image viewer.

In the settings window

• Under the Image Stabilization section (Fig. 4, #2), choose Planet (COG) and enable Dynamic Background.

• In the Quality Estimator section, disable Automatic and check Global (Frame)(Fig. 4, #3).

fig. 4 : Settings

fig. 5 : File selector

Step 2: Analyze Image Quality

1. Ensure Automatic is selected under the  Reference Frame  section.
2. Click the  Analyse button (Fig. 6, #1).

During the analysis, a chart will display the distribution of images based on their quality (Fig. 6, #2).

The left side of the dark green curve represents the images with the best quality, while the right side represents those with the worst quality.

Fig. 6 : Analyse

To ensure the best results, keep only images with a quality above 50%. For better results, you can be more selective and choose to work with only the top half of the images.

Step 3: Stacking

Under the Stack Options section:

• Select TIF as the output image format (Fig. 8, #1).
• Enter the percentage of images to retain (e.g., 75%) in the Frame Percentage to Stack field (Fig. 8, #2).
• Enable Save in Folder to save output images in the same folder as the source images (Fig. 8, #3).
• Optionally, enable Drizzle x3 for Moon images (Fig. 8, #4) (not recommended for Sun images).

In the image window:

• Click Place AP Grid to generate an alignment grid (Fig. 9, #1).
• Click 3) Stack to start the process (Fig. 9, #2).

Once completed, the output image will be saved in the specified folder.

Fig. 8 : Stacking options

Fig. 9 : Placing the alignement grid

Here's the video for a step by step guide.

Post-Processing with Affinity Photo

The final output image from Autostakkert contains more qualitative data than a single JPEG but requires post-processing to reveal its full potential. Below are the steps for processing Sun and Moon images.

Open the Autostakkert output image in Affinity Photo. The screenshot below  shows the main elements of the Affinity Photo interface that we will be using.

Fig. 10 : Affinity photo user interface

Post-Processing Sun Images

Color channels

Each pixel of a color digital image is a combination of three primary colors in varying proportions: red, green, and blue. Therefore, any image can be decomposed into three color channels. When it comes to images of the Sun, the signal is primarily in the red and green channels (since the yellow color is the result of blending red and green).

Fig. 11 : the image of sun decompose into its 3 channels.

The blue channel of our image presents a weaker signal and a slight banding effect along the edge of the Sun's disc. Therefore, we will work only with the red and green channels for an optimal result.

Let’s recombine the image using these two layers.

Fig. 12 : The procédural texture filter settings.

• Click the live filter icon and choose Procedural Texture from the list. A new layer will appear in the layer panel, and a settings window will pop up (fig. 12).
• In the settings window, click the [+] icon to add a channel.
• In the corresponding field, enter R (uppercase), then click the [R] button on the right. This means we are taking the red (R) channel as the input and assigning it to the red output channel.
• Click the [+] icon again and repeat the same steps with the green channel: enter G in the field and click the [G] button on the right.

Now we have an image composed only of the red and green channels. Let’s give a little boost to the green channel, as it contains the most contrasty part of the data.

• On the second line, after the G, enter +a*G.
• At the bottom of the window, click the [0,1] button to add a variable (a).
• Gently move the slider corresponding to the "a" value to the right in order to increase the green signal.

Refer to fig. 12 to check your settings.

Detail enhancement

Let’s start by slightly reducing some noise patterns:

• From the live filter list, choose Box Blur.
• Set the radius value to 0.5 pixels and close the settings pop-up window.

There are several tools to sharpen the details. We will use the High Pass filter.

• From the live filters list, choose High Pass to add it as a new layer over the Box Blur layer.
• In the layer settings window, set the radius to 1px and change the blend mode to Linear Light. Close the filter settings window.
• Duplicate the High Pass filter layer twice. To duplicate a layer, select it in the layer panel and press "Cmd + J."
• From the live filters list, choose Clarity and set its strength to 30%.

The details in the image are now significantly sharper.

Fig. 13 : high pass and clarity settings

Color correction

Let’s give the Sun a more pleasant color.

• Click the Adjustments icon at the bottom of the layer panel, then choose Selective color from the list.
• From the top color menu, choose Yellow
• Bring the Cyan cursor to -80% and the magenta cursor to +45%

We are now done with the processing of our images of the sun. The following video shows the details of each step

Post-Processing Moon Images

Processing the Moon is simpler as it is grayscale.

Simply apply the Box Blur and High Pass live filters. As a final touch add a brightness / contrast adjustment layer.

Depending on whether you chose the Drizzle x3 option in Autostakkert, here are the settings for each filter:

The following image compares a zoomed-in view of the "Vallis Alpes" with and without the Drizzle option. We can see that enabling Drizzle x3 in Autostakkert for the Moon results in an image with finer details.

Fig. 14 : Vallis Alpes. Left : Drizzled disable, Right : Drizzle x3 abled

By following this tutorial, you can significantly enhance your Moon and Sun images. Check out our accompanying videos for a visual guide to each step!