ASTAP is a free stacking
program for deep sky images. This program can view and stack
astronomical FITS images using an astrometric solution. It uses
a local version of Astrometry.net or PlateSolve2 to find the astrometric solution. With the solution the
astronomical position of each pixel can be calculated.
Double click on one of
the selected files to see it in the viewer:
images including Dark Frame and Flat Field correction
- Filtering of
deep sky images based on HFD value and average value.
call to local Astrometry.net or Platesolve2 for the astrometric solution.
- FITS viewer with swipe functionality.
- Results can
be saved to 16 bit or float (-32) FITS file
- Export to 16
or 32 bit integer TIFF files, grayscale or color or simple PNG or JPEG.
building covering large areas using the astrometric linear
solution WCS or WCS+SIP polynomial.
- Some pixel math functions and digital development process
Program requires FITS
images as input It can also process PNG, TIFF or BMP files but only in
8 bit resolution. No import facility for DSLR raw files.
A post processing
software with advanced options like noise reduction and unsharp mask.
It is only intended for convenient stacking of astronomical deep sky
The single executable astap.exe can be
used anywhere. Standard location could be at c:\program files\astap\astap.exe
Install a local copy
of Astrometry.net (via ANSVR or Astrotortilla)
or Platesolve2 including
star database as the astrometric
solver. Or laternatively if you have Win10, 64 bit Creation edition you use the new Linux sub-system
methods: average and sigma-clipping-average.. Internal calculation
floating point numbers.
- Simple and
intuitive user interface.
saving of selected options and
- Can create
master files for dark and flat & flat-darks to reduce
- Limited memory
use, independent of the number of images stacked.
algorithm for OSC cameras
for MS-Windows and in the near future Linux
ANSVR link contains a newer compilation of astrometry.net made for SGP.
It runs as a Linux program under Cygwin in MSWindows. Follow up to
installation step 9. The link you have to put in ASTAP is as follows:
Adapt "user_name" to the login name used in Windows.
The server program ANSVR is not required. Remove the ANSVR shortcut in the startup menu. Location:
Alternative Linux sub-system in Win10 64bit Creators edition
Path for the astrometry.net solver program
Program operation:Start the ASTAP program.
(In MS-Windows astap.exe, in Linux astap)
Enter the approximate
location of the images taken and the image dimensions unless the
location and dimension are already contained in the FITS file header.
You can test this by just opening one FITS file.
Call up the stack
window. Select the images, dark, flats, flat darks (bias)
Select the stacking
method, average or sigma-clip-average.
For OSC camera
select "Convert OSC images to colour". Select the
(4 options).. Test the required
pattern first in the viewer with a single image. The source images
should be raw (gray) without colour produced by
Press the stack button.
Save result as
FITS ( IEEE float (-32) or 16 bit format), or
export as 16 bit stretched, 16 bit or 32 bit TIFF.
The stretched export folllows the gamma and stretch setting
of the display.
All the program settings and file selections will be save by leaving the program or click on the stack button.
The single executable astap could be
used anywhere. Standard directory could be c:/opt/astap but also at your home folder.
You need either a local copy of astrometry.net
of Wine & PlateSolve2
Installation of astrometry.net is described at installation
To get the source: sudo apt-get install libcairo2-dev
libnetpbm10-dev netpbm libpng-dev libjpeg-dev python-numpy
python-pyfits python-dev zlib1g-dev libbz2-dev swig libcfitsio-dev
Path to the astrometry.net solver program "solve-field" could be:
PlateSolve2, install Wine first. Then extract PlateSolve2 at
$HOME/.wine/drive_c/PlateSolve2.28 The separate star
database UCAC3 could be extracted at
requires the msvbvm60.dll to run. Try to find a copy and place it in
$HOME/.wine/drive_c/PlateSolve2.28 or alternatively install winetricks
Run PlateSolve2 in Wine and set in menu File
, Configure Catalog Directories
the path to the UCAC3 star catalog.
reference of each pixel is the astronomical position. So stacking is
not done against a reference image but against an position array
set by the first image. If the oversize is set from the default 100
pixels to a large value lets say 2000 pixels, the array is
on all sides 2000 pixels larger then the first image. If
the first image is 2000x1500 pixels, the stacking array will be
6000 x 5500 pixels large. So any following image will be placed in this
6000x5500 pixel array. If the images are taken from
different areas of the sky, the stacking will result in a mosaic
as long the proceeding images are within this 6000x5500 pixels.
Here a suggested work method:
Here an example mosaic x 4 of M31 made with ASTAP:
Stacked method sigma-mean using the local Astrometry.net for solving. (option --downsampling 2)
Mosaic option ON, oversize 2500 pixels. (The orginal tile images are 2328x1760 pixels)
Crop the stacked result to about 5000x5000 pixels.
If required, applie the median-equalising filter under tab Pixel Math to equalise darker areas.
Applied DDP (digital development process) under Pixel Math to strech the mosaic.
Adjusted range and save as JPEG, 90% quality.
example of a mosaic build of DSS images:
The size can be reduced by a crop function (right mouse button) later.
Making the oversize too large could result in memory overload.
De stack menu:
a good plate solver but can’t write the plate solution to the
header using standard keywords. HNS_FV can call the
PlateSolve2 program and writes the found plate solution to the FITS
file header using standard keywords.
Working of the program:
- Load the FITS file in the
- Press the “Solve” button
- Is the solution found press
principle it should be possible to rename the program as Platesolve2
and call it instead of PlateSolve2. The solution will then written
automatically to the FITS file. The
plate solution is read from the APM file produced by PlateSolve2.
There is a big variation in FITS file keywords. If this version doesn't
work, please send me the FITS file for testing.
has a CCD inspector under tools for median HFD value and Tilt measurement. This will quickly show any focus
problem in the corners:. The squares are 5 times the HFD value. Background equalization tool:
Send a message if you like this free
program. Feel free to distribute !