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Extensible Image Serialization Format (XISF) is an image file format created by PixInsight. It is a free format open to contributions of anyone interested. For more detailed information about the format itself refer to

N.I.N.A. is capable of saving images in XISF format. The XISF format offers a variety of header meta information and N.I.N.A. will populate all available information into this header. A detailed list of all available Headers and their conditions is described below. Many applications can make use of these headers (e.g. PixInsight during processing).

Standard XISF Headers#

  • Version: 1.0
  • CreationTime: Time when the file is created
  • CreatorApplication: N.I.N.A. - Nighttime Imaging 'N' Astronomy

Observation Namespace#


  • Start: UTC time at exposure start


  • Elevation: Elevation (currently taken from a connected telescope)
  • Latitude: Latitude taken from the astrometry settings
  • Longitude: Longitude taken from the astrometry settings


Requires a telescope to be connected

  • RA: Current telescope's right ascension coordinates
  • Dec: Current telescope's declination coordinates


Available when a target is set inside a sequence.

  • Name: Name of object
  • RA: Right ascension of target
  • Dec: Declination of target


Requires a weather data source to be connected

  • RelativeHumidity: Relative humidity percentage
  • AtmosphericPressure: Air pressure in hPa
  • AmbientTemperature: Ambient air temperature in Celsius
  • WindDirection: Wind direction: 0=N, 180=S, 90=E, 270=W
  • WindGust: Wind gust in kph
  • WindSpeed: Wind speed in kph

Instrument Namespace#

  • ExposureTime: Exposure duration in seconds


Requires a camera to be connected

  • Name: Name of camera
  • Gain: Electrons per A/D unit (only available for some cameras)
  • XBinning: X binning factor
  • YBinning: Y binning factor


Requires a camera to be connected

  • Temperature: actual sensor temperature (requires a cooling unit)
  • XPixelSize: Pixel size
  • YPixelSize: Pixel size


Requires a telescope to be connected

  • Name: Name of telescope
  • FocalLength: Focal length (taken from equipment options)
  • Aperture: Focal length / Focal ratio (taken from equipment options)


Requires a filter wheel to be connected

  • Name: Current active filter


Requires a focuser to be connected

  • Position: Current step position


Additionally all information that is explained in the FITS description is stored using the FITSKeyword Core Element.


N.I.N.A. offers the possibility to use compression algorithms to try to reduce the file size of your images. There are three algorithms available:

  • LZ4: This algorithm is optimized for speed. While not as potent as Zlib it is dramatically faster and will result in an acceptable amount of compression most of the time
  • LZ4HC: Basically the same algorithm as LZ4 but with a higher compression rate. A bit more computational heavy than just LZ4.
  • Zlib: This algorithm will yield the highest compression result in most scenarios, but takes a long time to process and is by far the most computational heavy algorithm.
  • The option for byte shuffling will re-arrange the actual data in an attempt to optimize it for the compression. In most scenarios this will result in a better compressed result, but is a bit more computational heavy.



For a more in depth info on how the compression works refer to the XISF Data Block Compression


This option will store a checksum value into the XISF file to be able to validate data integrity.


For a more in depth info on how the checksum works refer to the XISF Data Block Checksum