yaaca is an application, written in Python and C, for acquisition of images/videos with the ZWO ASI series of astronomical webcam.

It depends on Numeric Python and GTK3 gi interface available for Python2. The packages needed on Arch Linux are:

pacman -S python-numpy python-gobject gtk3 gcc make libusb-1.0 python-cairo

instead on Ubuntu with python2 as defult:

apt-get install gir1.2-gtk-3.0 gcc make libusb-1.0 python-numpy python-gobject python-gobject- cairo python-gi python-gi-cairo

It is build around a C interface to the ZWO provided library. You can communicate with this via JSON (the idea is to use the same on Android Webview), see taaca_server.h for the API. The image processing engine is written in Python, but uses NumPy for speed.

There are prepackaged archives available in the packages directory.

The easiest way to get latest version is to clone from github repository and compile the C part and launch it:

git clone https://github.com/chripell/yaaca
cd yaaca
make
./yaaca.py

First of all, make sure that the correct udevd rules for the ASI cameras are installed. Otherwise you won't be able to use them as non-root user and the kernel USB buffer might be too small.

After starting yaaca, you need to open an ASI camera from the File menu. If there aren't any listened, verify the connection, exit and reenter the application. In the same menu you can find the option to save and load full camera configuration. In the same menu you can find options to snapshot what you currently see on the screen and to run an external solver for the field (solve-field must be in the path).

In the Camera menu you can find the command to start and stop the acquisition. Below There is the record toggle (this can be also activated with the r button: yaaca tries to achieve mouse-less usability). The video stream is saved in .ser files, which are supported by most astronomical software. On Linux you can use the very good ser_player to see them. Also you can use the supplied sertoppm.py to convert to single pictures. Together with the saved file you will find also a .txt file with full info from the camera. The Long Exposure toggle selects between 2 capture mode of the camera. Quite frankly, I don't see many differences.

Settings exposes all the controls for the current model of the camera. The changes to text field will be committed when you press Return, Click Apply or press Alt+A (the button accelerator). The checkbox near the text field enables or disables auto mode. If the setting is outside allowed range, it will be cropped into it when committed. Radio buttons changes are applied immediately. On the bottom you can find the Reload button that rereads the values from the camera and Close to shut down the dialog box.

Roi/Mode is similar to the Settings dialog, but focus on image format and offers also the possibility to change the prefix where to save the videos. Additionally you have the "Recenter ROI" button that allows to use the central part of the sensor for better image quality.

View menu specifies how the image will be displayed and so doesn't change the way it is saved. Zoom specifies the zoom factor of the main area. Below you can choose to do a fast debayer (4 pixels are blended in 1) or full debayer. This is useful only for color cameras of course. Next section is for enabling the cross pointer and the histogram. The cross pointer also have a boxed areas (that can be resized with keys b and n) that specifies which part of the picture will be used by various operations (like SAA and histogram).

The part part below in the view menu allows you to stack multiple images on the fly. With SAA, the area defined by the box is used to calculate the offset of the captured image to the first, reference, one. The image is then shifted and added to the reference and the result is shown. The amount of shifting is visible in the right pane. The dark frame is built while Add Dark is selected. Of course you must cover your telescope before selecting it. The reset entries zero the accumulated frames (the number of light/dark is available in the right pane).

Gamma stretch applies a gamma function to enhance the visibility of faint details. The last part of the view menu allows you to select the view mode. It can be:

• Show Processed, stretching of the histogram, gamma stretch and other processing is visible.

• Show SAA/Dark, the accumulated image with dark subtracted is shown.

• Show Raw, raw image from the camera is displayed. This is useful for slow computers or as a sanity check about what is saved (only the debayering is applied, set it to Raw if you don't want to see it as well).

The application window is dived in 2 part. The main of the left shows the image acquired (or elaborated by SAA or such) and can be zoomed via the View menu. On the right there are various sub-windows. The top one is a full view of the acquired image and shows which part that is displayed in the main one (if it doesn't entirely fit). You can click around to change the displayed area in the main window (identified by a rectangle). Below there are some important parameter about the capture and the keys needed to change them. o-p, k-l are for exposure time and q-a, w-s for gain. r turns on/off recording. Below there is the histogram of the acquired image. You can use z-x and c-v to stretch the values that you want to display (which are shown as the red part of the histogram). Next comes an information are with the position of the cross pointer, the value of the pixel beneath it and the size of the box.

Note that you can use cursor keys to send pulses to the ST4 port (and so move the telescope if it is connected).