HNS_FITS is a program to analyse (positional) astronomical images. It will convert JPEG, BMP or FITS  to FITS files with a WCS header using two manual entered star positions. With the positions of two know stars the position of each pixel/object in the image can  be determinated. The result can be saved as standard FITS. The HNSKY planetarium program will recognise these FITS files and automatically plot them at the correct place, size and orientation. The most common FITS formats supported formats including RGB or color.

hns_fits screen shot


1) Load a BMP or JPEG file.

2) Find two known star positions from a star map.

3) Click with left mouse button on first known star to get first X, Y position.

4) Enter the RA and DEC position of first known star.

5) Click with right mouse button on second known star to get the second X, Y position.

6) Enter the RA and DEC position of second known star.

7) Click on "Convert references to WCS".

8) Save result to new FITS file.

If required the image can be stretched to a larger size.

Download: HNS_FITS.ZIP   (Version 1.4.2)

The latest version can produce RGB or color FITS files using the format where the pixels are in RGB-order:

Success,  Han  Kleijn

The above M101 image in HNSKY:


The program supports monochrome FITS files with 8, 16 bit or -32 (floating point) bits pro pixel and color FITS files. Color FITs files can come in types. They are using a third dimension for the RGB color information. First type:

SIMPLE = T / Standard FITS format flag

BITPIX = 8 / Bits per pixel

NAXIS = 3 / Number of dimensions

NAXIS1 = 3 / Number of Colors

NAXIS2 = 382 / Row length

NAXIS3 = 255 / Number of rows

HNSKY uses this format for the coloured planetary images. For download these FITS see ter hnsky webpage. The JPEG or BMP files can be saved as this first type only (NAXIS1 = 3)

Note that this format is equivalent to BITPIX=24, NAXIS=2, NAXIS1=382, NAXIS3=255.

Second supported RGB format:

SIMPLE = T / Standard FITS format flag

BITPIX = 8 (or 16 or -32) / Bits per pixel

NAXIS = 3 / Number of dimensions

NAXIS1 = 382 / Row length

NAXIS2 = 255 / Number of rows

NAXIS3 = 3 (or 2 or 1) / Number of Colors in order RED, GREEN and BLUE

HNS_FITS can add the WCS header to these files. However it is not supported in HNSKY. An example file using this format is available at:

Both RGB FITS formats are also supported by the German program GIOTTO for video astronomy: