FAQ
Installation
How do I install the astrometry.net plate solver?
The current AT installable astrometry.net solver build is very old. It is recommended to install the build made by ADG Software from http://adgsoftware.com/ansvr/ and install without starting the server. You can copy your existing index files to the location where it installs the astrometry.net solver as a cygwin environment. Typically that is under application data folder, on Windows 10 it is C:\Users\<username>\AppData\Local\cygwin_ansvr and use that as the Cygwin location in AT configuration.
The AstroTortilla installer includes the Cygwin setup, which is used to install the plate-solver software. The installer can automatically install the astrometry.net solver and dependencies. If you have an existing Cygwin installation, you can point the AstroTortilla installer either to your Cygwin installation or create a new "minimal" Cygwin for astrometry.net plate-solver.
If you have installed AstroTortilla already, you can start the Cygwin setup program with necessary options from the Start-menu under AstroTortilla. It has the AstroTortilla repository pre-selected and provides other necessary options to the Cygwin setup. If you want to install additional Cygwin packages, you have to select the main Cygwin mirror of your choice while holding the Control-key and ensure that both repositories are selected when continuing.
If you want to update the AstroTortilla related bits in Cygwin (astrometry.net and dependencies), you can run the Cygwin install from AstroTortilla installer for a fully automated run.
What do I need to run AstroTortilla?
In addition to software you will need a set of index-files based on your field-of-view.
Where can I get the index files?
You can use the AstroTortilla installer to download the indexes. The installer won't download over any existing index files, so you can use the installer safely to add new ones.
Alternately you can manually download the indexes from astrometry.net project.
Where can I get the old 200-series index-files?
The 4200-series index files are distributed under GPL license and we distribute them together with AstroTortilla.
The old USNO-based 200-series index files are not permitted to be redistributed by us. You can still ask for them from astrometry.net. Familiarize yourself with the conditions and read the instructions on how to get the files here.
Which index-files do I need?
Each index-file covers a section of sky at a certain resolution, it is recommended you download the index-files that cover features from your FoV down to 1/10th of the FoV. If you use multiple setups, you can download from the largest FoV to 1/10th of your smallest FoV and use the AstroTortilla
You can calculate your Field of View with:
- Starizona's Guide to CCD Imaging
- Sky at Night Magazine
- 12D String
- Rough estimate for telescopes:
- 57.3 * sensor_width / focal_length = FOV_degrees
- 3438 * sensor_width / focal_length = FOC_arcminutes
How do I install the index-files
Use the installer for the 4200-series indexes. For a manual process download the index files and uncompress to /usr/share/astrometry/data/ -directory in Cygwin. The "new" 4200-series index-files are compressed with BZip2, you can uncompress them with bunzip2 *.bz2 -command. The "old" 200-series index-files are in compressed tar-packages, you can user tar xjf for each file or run thru a loop. You can also use other compressed package management software such as 7zip, WinZip and WinRar for these operations.
Where's the configuration file?
The configuration file for AstroTortilla is in the application local settings directory. On Windows XP it's in %USERPROFILE%\Local Settings\astrotortilla.sf.net\AstroTortilla and on Windows 7 onwards under the %USERPROFILE%\AppData\Local\astrotortilla.sf.net\AstroTortilla -directory.
The astrometry.net plate-solver has it's own configuration file for setting various plate-solver parameters and index file locations. That file is located under Cygwin root-directory in /etc/astrometry/ and you can create multiple configuration files here for various setups and needs. In the AstroTortilla GUI you can reference to these different backend configuration files on a need-to-have basis.
User Interface
The plate-solver selection drop-down is grayed out, how do I select the plate-solver?
Currently AstroTortilla supports only the locally installed astrometry.net solver. The drop-down is disabled since there are not other options to choose from.
My image takes ages to run and doesn't always find a solution
The plate-solver settings are very system specific and may vary depending on the area of sky you are looking at, you can vary your exposure time easily for different parts of the sky.
To optimize the settings use a variety of short exposures from different parts of the sky and read them using the FileOpen camera in AstroTortilla. This way you can utilize the cloudy nights and daylight instead of dark nights to find out your optimal exposure duration and other settings.
The main item to look during parameter optimization at is the number of detected objects, the log line simplexy: Found 312 objects. tells that the star detection algorithm found 312 star-like features. This figure should be in the ballpark of 200 to 500 objects.
The two variables in the extra flags settings to adjust star detection are the --sigma N and the --objs N flags. The sigma sets the camera specific noise floor level and the objs sets how many of detected objects are to be used for plate-solving. Typical values for sigma are 10, 50 and 100, and for objs 30, 50, 100 or no flag at all. The --objs N cuts the number of stars to N.
If you are using the 4000-series indexes, you most likely want to add two more flags: -r to re-sort the discovered objects calibrated by the background flux, and -c 0.02 or higher value to relax the star pattern accuracy from the default 0.01. The odds at which the field is solved is left untouched as is the star pixel position accuracy requirement, so the trustworthiness of the solution shouldn't be adversly affected.
The plate-solver has many more parameters, and one way to try them out is using the Cygwin terminal by running time solve-field --overwrite -D /tmp/solvetest /path/to/image-file <various options> to determine how long it takes to solve the image with different parameters. The --overwrite -D /tmp/solvetest makes use of a temporary directory for storing the runtime data and overwrites any data already present in that directory.
One final set of parameters that greatly affect the normal usage (i.e. the Capture and Solve -button) is the field-of-view and area restrictions. There are four settings for setting the FOV, you should set the field minimum to about half you estimated field size, maximum to twice the size, and the scale refinement to 0.1 if you don't change setups frequently. To limit the area of search (normal starry sky usage) you can reduce the search radius to 45 degrees, as this is typically the maximum sync-limit of the telescope mounts (they refuse to sync with any larger sync offsets)
