# FITS Flexible Image Transport System (FITS) format

Extensions: `.fits`, `.fit`, `.fts`

Flexible Image Transport System (FITS) is an open standard defining a digital file format useful for storage, transmission and processing of scientific and other images. FITS is the most commonly used digital file format in astronomy.

This format requires the `astropy` package.

## Parameters for reading

cachebool

  If the file name is a URL, ~astropy.utils.data.download_file is used to open the file. This specifies whether or not to save the file locally in Astropy’s download cache (default: True).

uintbool

  Interpret signed integer data where `BZERO` is the central value and `BSCALE == 1` as unsigned integer data. For example, `int16` data with `BZERO = 32768` and `BSCALE = 1` would be treated as `uint16` data.

  Note, for backward compatibility, the kwarg uint16 may be used instead. The kwarg was renamed when support was added for integers of any size.

ignore_missing_endbool

  Do not issue an exception when opening a file that is missing an `END` card in the last header.

checksumbool or str

  If True, verifies that both `DATASUM` and `CHECKSUM` card values (when present in the HDU header) match the header and data of all HDU’s in the file. Updates to a file that already has a checksum will preserve and update the existing checksums unless this argument is given a value of ‘remove’, in which case the CHECKSUM and DATASUM values are not checked, and are removed when saving changes to the file.

disable_image_compressionbool, optional

  If True, treats compressed image HDU’s like normal binary table HDU’s.

do_not_scale_image_databool

  If True, image data is not scaled using BSCALE/BZERO values when read.

ignore_blankbool

  If True, the BLANK keyword is ignored if present.

scale_backbool

  If True, when saving changes to a file that contained scaled image data, restore the data to the original type and reapply the original BSCALE/BZERO values. This could lead to loss of accuracy if scaling back to integer values after performing floating point operations on the data.