Camera Data for the KStars Exposure Calculator

This repository holds the camera read noise data used by the Exposure Calculator in KStars/Ekos. The calculator uses it to suggest the best sub-exposure time and gain for your camera, sky and telescope.

KStars ships with a copy of these files. To get cameras added after your KStars release, open the Exposure Calculator and click + next to the camera selector.

Add your camera

Open the camera form. No XML or git is needed.

You fill in a few values, which you can usually find on the manufacturer's product page:

• the camera name as Ekos shows it, for example ZWO CCD ASI2600MM Pro,
• mono or color sensor, and how gain is set (adjustable gain, ISO, or fixed for CCD cameras),
• pixel size and peak quantum efficiency,
• the read noise chart, as gain, read noise lines.

When you submit, a bot checks your values and opens a pull request with the camera data file. If something is wrong, the bot comments on your issue: edit the issue and the check runs again. A maintainer reviews the pull request, and once it is merged, KStars users can download your camera from the Exposure Calculator.

To correct an existing camera, submit the form again with the same camera name.

Measured values

Manufacturer charts are a good start, but your own camera may differ. If you measured your camera, for example with the SharpCap sensor analysis tool, use those values and say so in the Source field.

File format

Each camera is one XML file in cameras/. The file name is the camera name as Ekos shows it, with spaces replaced by underscores: ZWO CCD ASI2600MM Pro is stored in ZWO_CCD_ASI2600MM_Pro.xml. KStars selects the file matching the active camera automatically.

<?xml version="1.0" encoding="UTF-8"?>
<ExposureCalculatorCameraData>
    <CameraDataClassVersion>1</CameraDataClassVersion>
    <CameraId>ZWO CCD ASI2600MM Pro</CameraId>
    <SensorType>MONOCHROME</SensorType>
    <GainSelectionType>NORMAL</GainSelectionType>
    <CameraGainSelections>
        <GainSelection>0</GainSelection>
        <GainSelection>460</GainSelection>
    </CameraGainSelections>
    <CameraGainReadMode>
        <GainReadModeNumber>0</GainReadModeNumber>
        <GainReadModeName>Standard</GainReadModeName>
        <CameraGainReadNoise>
            <GainReadNoiseValue>
                <Gain>0</Gain>
                <ReadNoise>3.5</ReadNoise>
            </GainReadNoiseValue>
            <!-- more gain / read noise pairs -->
        </CameraGainReadNoise>
    </CameraGainReadMode>
    <CameraPixelSize>3.76</CameraPixelSize>
    <CameraQuantumEfficiency>0.91</CameraQuantumEfficiency>
</ExposureCalculatorCameraData>

Element	Meaning
CameraDataClassVersion	Always 1.
CameraId	The camera name. Must match the file name.
SensorType	MONOCHROME or COLOR.
GainSelectionType	NORMAL (adjustable gain), ISO_DISCRETE (DSLR ISO values) or FIXED (CCD, read noise independent of gain).
CameraGainSelections	NORMAL: the minimum and maximum gain. ISO_DISCRETE: every selectable ISO value. FIXED: a single 0.
CameraGainReadMode	One read noise table per read mode, numbered from 0, with a name. Most cameras have one mode.
GainReadNoiseValue	A gain (whole number) and its read noise in electrons, in increasing gain order.
CameraPixelSize	Pixel size in microns.
CameraQuantumEfficiency	Peak quantum efficiency as a fraction, for example 0.91.

Cameras with fixed read noise store the same value at gains -1 and 1.

Rules

KStars does not check these files, so a mistake leads to wrong exposure times or a crash. Every pull request is checked automatically:

• read modes are numbered 0, 1, 2… in order,
• gains are whole numbers in increasing order within each table,
• the file name matches CameraId, which may only contain letters, digits, spaces and ( ) + -,
• read noise and pixel size are positive, quantum efficiency is between 0 and 1,
• no unknown elements.

To check files locally (Python 3, no extra packages):

python3 tools/camera_data.py validate
python3 -m unittest discover -s tests

Pull requests with hand-written files are welcome too. Run the checks above before submitting.

For maintainers

• The Camera data from issue workflow needs Settings → Actions → General → Allow GitHub Actions to create and approve pull requests enabled, and the camera-data label.
• Pull requests opened by the workflow do not trigger the Validate workflow (a GitHub restriction on the built-in token), but the workflow validates the file before opening the pull request.
• KStars bundles these files in kstars/data/cameradata. Before a KStars release, sync them with tools/sync_camera_data.sh in the KStars repository.

License

The camera data and tools are licensed under the GNU General Public License, version 2 or later, the same license under which the data was originally published in KStars. See LICENSE.