File formats

Sidralune reads and writes the standard formats of amateur and professional astronomy, all implemented in its own code without external libraries.

Contents

• Images
• Videos
• Spectra
• Catalogues, orbits and ephemerides
• Reports and exports
• Sidralune's own files
• FITS keywords Sidralune reads

Images

Format	Extensions	Read	Write	Notes
FITS	.fit, .fits, .fts	Yes	Yes	8-, 16-, 32- and 64-bit integer and 32/64-bit float data (BITPIX 8, 16, 32, 64, −32, −64), BZERO/BSCALE, primary HDU and IMAGE extensions, mono and 3-plane colour cubes, top-down row order (ROWORDER), Bayer keywords. Written as 16-bit integer or 32-bit float with the full header
XISF	.xisf	Yes	Yes	Extensible Image Serialization Format, including zlib and LZ4 (and LZ4-HC) compressed data blocks and byte shuffling. Written as 16-bit or 32-bit float, compressed
TIFF	.tif, .tiff	Yes	Yes	8-, 16- and 32-bit integer and 32/64-bit float, mono and RGB, chunky or planar, strips or tiles, uncompressed, LZW, Deflate and PackBits. Written as 16-bit or 32-bit float
DNG	.dng	Yes		Raw CFA data, including lossless-JPEG compressed tiles
Canon CRW	.crw	Yes		Raw sensor data from Canon's cameras of 2000-2004, in 10 or 12 bits (tested with the EOS D30, D60, 10D and 300D and the PowerShot G5 and Pro1; older files that do not record their sensor size are not read). Cropped to the visible area with the black level from the masked border subtracted; exposure, ISO, date and camera come from the file
Canon CR2	.cr2	Yes		Raw sensor data (lossless JPEG with slices)
Canon CR3	.cr3	Yes		Full-size RAW (tested with the EOS Ra), read with Sidralune's own decoder. The masked border is cropped off and its level subtracted as the black level; exposure, ISO, date and camera come from the file. Compressed C-RAW files, and files written with the newer revision of Canon's codec, are not read yet: convert those to DNG with Adobe DNG Converter
PNG	.png	Yes	Yes	8-bit; written with the display stretch applied
JPEG	.jpg, .jpeg	Yes	Yes	8-bit; written with the display stretch applied
BMP	.bmp	Yes

Images are held in memory as 32-bit floating point, normalised so that the full range of an integer format is 0–1. Processing can produce values outside that range; 32-bit float formats keep them.

Videos

Format	Read	Write	Notes
SER	Yes	Yes	Mono, Bayer and RGB/BGR, 8 and 16 bits, with per-frame time stamps from the trailer
AVI	Yes	Yes	Read: uncompressed RGB24/RGB32, 8-bit grey (Y800, GREY, indexed), YUY2 and MJPEG. Write: uncompressed
Image sequences	Yes	Yes	A folder or a selection of FITS, TIFF, PNG or other image files, read in name order

Spectra

Format	Read	Write	Notes
FITS 1D	Yes	Yes	Linear wavelength axis from CRVAL1, CDELT1 (or CD1_1) and CRPIX1. Written in BeSS format
Text / CSV	Yes	Yes	Two columns: wavelength (Å) and flux; comments starting with # are ignored

Catalogues, orbits and ephemerides

Format	Used for
HYG CSV (v4.x)	Star catalogue
OpenNGC CSV (semicolon separated)	Deep-sky catalogue
Stellarium constellationship.fab	Constellation lines
Stellarium constellation_boundaries.dat	IAU constellation boundaries
MPCORB / NEA (MPC 1-line orbit format, packed designations and epochs)	Asteroid orbits
MPC CometEls.txt	Comet orbits
JPL SBDB API (JSON)	Single-object orbits
CelesTrak TLE (two-line elements, with name lines)	Satellite orbits
JPL SPK (.bsp, DAF binary, Chebyshev segment types 2 and 3)	DE440s planetary ephemeris

Reports and exports

Format	Produced by
AAVSO Extended File Format	Photometry → Measure → AAVSO report…
MPC 1992 80-column format	Solar sys. → MPC astrometry
ADES PSV (pipe-separated values)	Solar sys. → MPC astrometry
BeSS FITS	Spectra → Analyse → Save
WCS in FITS header (TAN or TAN-SIP)	Astrometry → Write WCS to FITS…
CSV	Light curves, ephemerides, catalogue searches, query results, observing lists, the logbook, radio spectra, every plot (right-click → Export data as CSV…)
PNG	Sky charts, plots, images

CSV files always use a full stop as the decimal separator and a comma as the field separator, whatever the Windows language settings, so they can be exchanged between computers.

Sidralune's own files

File	Contents	Location
settings.json	Sites, equipment, observer details, preferences	%LOCALAPPDATA%\Sidralune\Settings
planner.json	Observing lists and logbook	%LOCALAPPDATA%\Sidralune\Settings
.sdstack	Deep-sky stacking file lists	Wherever you save them
.json sequence	Sequencer instruction trees	Wherever you save them
.cs	C# scripts	%LOCALAPPDATA%\Sidralune\Data\Scripts by default
Log files	One file per day, plus crash-<date>-<time>.txt reports	%LOCALAPPDATA%\Sidralune\Logs

All of these are plain text (JSON, CSV or C#) and can be backed up, versioned or edited by hand.

FITS keywords Sidralune reads

Keyword	Used for
DATE-OBS (or DATE_OBS)	Observation start time (UTC)
EXPTIME, EXPOSURE, EXP_TIME	Exposure time
RA, DEC, OBJCTRA, OBJCTDEC	Plate-solving hints
CTYPE, CRVAL, CRPIX, CD/CDELT/CROTA, A_ORDER/B_ORDER and SIP coefficients	Existing WCS
FOCALLEN, XPIXSZ, PIXSIZE1	Image scale for plate solving
BAYERPAT, XBAYROFF, YBAYROFF	Bayer pattern for debayering
FILTER, OBJECT, IMAGETYP / FRAME	Frame classification
CCD-TEMP, CCDTEMP, SENSOR-TEMP	Sensor temperature
GAIN, EGAIN	Gain
ROWORDER	Row order (TOP-DOWN images are flipped on reading)