# FITS Viewer Tool

The Flexible Image Transport System (FITS) is the standard format for representing images and data in Astronomy.

The KStars FITS Viewer tool is integrated with the INDI framework for seamless display and manipulation of captured FITS images. Furthermore, the FITS Viewer can be used to post-process raw data. To open a FITS file, select Open FITS... from the File menu, or press &Ctrl;O.

FITS Viewer features:

- Support for 8, 16, 32, IEEE -32, and IEEE -64 bits formats.

- Histogram with auto, linear, logarithmic, and square-root scales.

- Image reduction tool.

- Brightness/Contrast controls.

- Pan and Zoom.

- Auto levels.

- Statistics.

- FITS header query.

- Undo/Redo.

The FITS Viewer Tool
FITS Viewer Tool

The above diagram illustrates the FITS Viewer work area and window. The tool provides basic functions for image display and processing. FITS data depth is preserved throughout all processing, open, and save functions. While the tool adhere to the FITS standard, it does not support all possible FITS features:

- Support for only one image per file.

- Support for only 2D data. 1D and 3D data are discarded.

- No support for WCS (World Coordinate System).

The following is a brief description of the tool's functional units:

- Brightness/Contrast: Adjusts brightness and contrast. The function can be CPU and memory intensive for very large FITS.

- Histogram: Displays one-channel FITS histogram. The user can rescale the image by optionally defining an upper and lower limit for the cutoff region. The rescaling operation (linear, logarithmic, or square-root) may then be applied to the region enclosed by the upper and lower limits.

- Image reduction: Removes background noise and optical anamolies from the image. Raw CCD images are often processed to remove instrument and temperature noise, in addition to aberrations inherit in the optical system. The function supports three types of raw CCD frames:

  1. Dark Frames

  2. Flat Field Frames

  3. Dark Flat Field Frames

  The user can stack up multiple frames in each category to increase the signal-to-noise ratio. Two combination methods are provided: mean and median. The two methods produce similar results most of the time, but the median method insures that the data is not skewed due to random cosmic ray hits.

- Statistics: Provides simple statistics for minimum and maximum pixel values and the their respective locations. FITS depth, dimension, mean, and standard deviation.

- FITS header: Displays FITS header information.