Astrometry.net index files

The progress bar will look like it is stuck in the middle for a long time. Be patient, it will finish eventually Click Finish. You can leave both boxes checked. Now you will download the astrometric index files that you need for your setup. Referring to the table below, you should grab index files through You might find that the same number of fields solve, and faster, using just one or two of the index files in the middle of that range - in our example you might try , and For reference, we used index files alone for our SDSS tests 13x9 arcmin fields ; these are the same scale is the new files.

The small-sized ones are split into 48 healpixes. See the maps here; you might not need all of them. Copy the files to the data directory wherever you installed the Astrometry. Most CPUs these days are little-endian. If you have an Intel or AMD chip, you can skip this section.

If you have one of these, read on. The index files we are distributing are for little-endian machines. For big-endian machines, you must do the following:. Scale of the image: if you provide bounds lower and upper limits on the size of the image you are trying to solve, solving can be much faster.

When you tell solve-field the scale of your image, it uses this to decide which index files to try to use to solve your image; each index file contains quads whose scale is within a certain range, so if these quads are too big or too small to be in your image, there is no need to look in that index file. It is also used while matching quads: a small quad in your image is not allowed to match a large quad in the index file if such a match would cause the image scale to be outside the bounds you specified.

However, all these checks are done before computing a best-fit WCS solution and polynomial distortion terms, so it is possible though rare for the final solution to fall outside the limits you specified. With fewer, you risk being unable to recognize some images. With more, file sizes will be bigger. We can remove stars that are within a radius of exclusion of each other eg, double stars, or problems with the reference catalog.

The index files contain a FITS header card saying what the typical astrometric error is. We try to build a uniform set of features by laying down a fine healpix grid and trying to build a feature in each cell. We run multiple passes of this, building a total of -p features in each cell.

By default, any star can be used in at most 8 features. This prevents us from relying too heavily on any one star. This option enables a second pass where we loosen up with -R value, trying to build extra features. In order to use your new index files, you need to create a backend config file that tells the astrometry engine where to find them. You can either edit that file, or create a new. Either way, you need to add lines like:.

It is safe to include multiple sets of index files that cover the same region of sky, mix and match, or whatever. The astrometry engine will just use whatever you give it. If you edited the default backend. If you create a new index file I often put one in the directory containing the index files themselves , you need to tell solve-field where it is:.

Report successes, failures, frustrations, missing documentation, spelling errors, and such at the Astrometry. Navigation index next previous Astrometry. Building Index Files for Astrometry. The steps are: Convert your reference catalog to FITS tables Prepare your FITS tables Split the sky into pieces Building Index Files Using your shiny new index files Here are some pictures of the index-building process itself: A reference catalog: We lay down a healpix grid: And select the brightest stars in each cell: And then try to build a 4-star feature centered in each cell And again… And again, until the sky is densely tiled in features.

The real deal. Local index files. Start Prev 1 Next End 1. Local index files was created by Kevin. Not sure if others have already run into this issue and already resolved it. I was not able to plates of using the local or remote indexes with the 2. I noticed that there were two folders that were available to save the indexes. One folder did not work, so I use the second. So I found a command to change the permissions. I then moved all the index files. After doing this I was able to plates solve using either local or remote.