Use with N.I.N.A.

N.I.N.A. runs ASTAP as a command-line program and reads the .ini file it writes. arcsec accepts the same command line and writes the same file, so N.I.N.A. can use it in ASTAP’s place with no change on N.I.N.A.’s side.

Note

N.I.N.A. is the only program tested with arcsec in ASTAP’s place. Other programs that drive ASTAP’s command-line solver may work too; that is untested, and reports are welcome. Siril cannot run an external ASTAP solver, but can use arcsec’s solutions: see Use with Siril.

Setting up

1. Install arcsec. Download the Windows .zip from the latest release, extract it and put arcsec.exe in a permanent folder, for example C:\Program Files\arcsec\. Getting started has the details.

2. Install a star catalogue for your field of view. N.I.N.A. does not tell the solver where the catalogues are, so arcsec uses its own catalogue folder. Use Which catalogue do I need?, or in PowerShell:

   arcsec catalog recommend --fov 1.2     # your field height in degrees
   arcsec catalog install d50             # what it recommended

   If ASTAP is already installed with its databases, you can use those instead and skip the download.

3. Point N.I.N.A. at arcsec. Under Options > Plate Solving, choose ASTAP as the plate solver, and as the blind solver too if you like. Set ASTAP location to the full path of arcsec.exe, for example:

   C:\Program Files\arcsec\arcsec.exe

   Type or paste the path into the field. N.I.N.A.’s file browser for this setting only shows files named astap.exe, so it cannot select arcsec.exe. After cargo install, the path is C:\Users\<you>\.cargo\bin\arcsec.exe.

4. Solve. Plate solve from N.I.N.A. as usual. It reports arcsec’s results as it would ASTAP’s.

Reusing ASTAP’s star databases

arcsec reads ASTAP’s database files directly, so one copy can serve both programs. Tell arcsec where they are by setting the ARCSEC_CATALOG_DIR environment variable to ASTAP’s folder, which is C:\Program Files\astap for a default install:

setx ARCSEC_CATALOG_DIR "C:\Program Files\astap"

A program reads its environment when it starts, so restart N.I.N.A. afterwards. Check that arcsec sees the databases with:

arcsec catalog list

The solver never modifies these files. The catalogue manager does act on the folder, though: arcsec catalog remove there would delete ASTAP’s files too. It lists what it will delete and asks first.

What N.I.N.A. passes

N.I.N.A. builds the command line from its own settings, using ASTAP’s options:

N.I.N.A. setting or value	Option	arcsec’s reading
The image to solve	-f	FITS, XISF or ASDF, recognised from the contents
Field of view, from focal length and pixel size	-fov	Image height in degrees, as ASTAP defines it
Where the telescope is pointing	-ra, -spd	RA in hours; south pole distance (90 + Dec) in degrees
Search radius	-r	Degrees around that position
Downsample factor	-z	Binning before solving; 0 means automatic
Maximum number of stars	-s	Stars used for matching

The field of view N.I.N.A. sends comes from the focal length and pixel size in its equipment settings, so if solves fail, check those first.

When arcsec finishes, N.I.N.A. reads <image>.ini next to the image: PLTSOLVD=T with the solution on success, PLTSOLVD=F on failure. arcsec writes this file on failure too, as ASTAP does.

Troubleshooting

See exactly what N.I.N.A. ran

With N.I.N.A.’s log level set to Debug, its log records the full command line it runs for each solve. The .ini file arcsec writes also records it, on the CMDLINE= line, whether the solve succeeded or not. Paste that command into PowerShell and add --progress to watch each step:

& "C:\Program Files\arcsec\arcsec.exe" -f "C:\...\image.fits" -fov 1.2 -z 0 -r 30 --progress

The exit code tells you why a solve failed: run $LASTEXITCODE straight afterwards and look it up in the exit code table. 2 means too few stars were detected, 32 that no star database was found.

“No output file found”

N.I.N.A. found no .ini file after running the solver. arcsec writes one for every solve it attempts, failed or not, so this usually means it never got that far:

• The path is wrong. Check ASTAP location points at arcsec.exe itself, including the .exe, and that the file is there.
• The image could not be read (exit code 16). Run the command from the log by hand to see the error.
• It does not start at all. Run arcsec --version from PowerShell to confirm the program runs on this PC.

N.I.N.A. will not run it with automatic downsampling

N.I.N.A. checks the version stamped into the ASTAP executable, and refuses to run one without a version with its default automatic downsampling. The release .zip always carries the version stamp. A copy built with cargo install only has it if the Windows SDK’s resource compiler was available at build time. Use the release build, or set N.I.N.A.’s downsample factor to a fixed value.

“Star database not found” (exit code 32)

arcsec found no star database in its catalogue folder. Run arcsec catalog list to see which folder it is using and what is installed there. If you set ARCSEC_CATALOG_DIR, restart N.I.N.A. so it picks up the change.

It fails on images that should solve

• Check the focal length and pixel size in N.I.N.A.’s equipment settings. A wrong field of view is the most common cause of a failed solve.
• Check the catalogue covers your field: see Which catalogue do I need?.
• Very crowded Milky Way fields and frames dominated by one bright object, such as a large nebula or a bright star, are the hardest cases for arcsec.

If a solve still fails, please open an issue with the command line, the .ini file and, if you can share it, the image.