The definition of astrometry is, “the measurement of the positions, motions, and magnitudes of stars.” As a branch of astronomy, astrometry involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of the Solar System and our galaxy, the Milky Way.
For those who are curious about how to the history and uses cases of astrometry in general, check out this article on the subject.
There is definitely use for a website and a service for users to be able to obtain astrometric information of an image. Thankfully there is a website that can do this, called astrometry.net. As the website says, “We have built this astrometric calibration service to create correct, standards-compliant astrometric meta-data for every useful astronomical image ever taken, past and future, in any state of archival disarray. We hope this will help organize, annotate and make searchable all the world’s astronomical information.”
Functionality on the astrometry.net website include the abilities to explore other uploaded images, manually upload images, and upload images via the API. To upload new photos, one does NOT need to be a registered user; however, the benefits of being a member is that the results that one uploads can be saved in a safe and easy place for later use. The alternative is to save the links when individually uploading files. When manually uploading files for review, it can be done by either URL or file upload. The file types supported for upload are:
- JPEG, GIF, PNG, or FITS image
- FITS Binary Image
- Text List
- Tarball (.tar, .gz)
When exploring other images, one can see tags of popular objects, and view works by specific users. Using the API, one needs to first to register for an account and then an API key. After getting this API Key, one will have access to the JSON API to upload the data.
There are several great uses cases; however, we will discuss 2 of them quickly. The first use case for this would be to verify the results of constellations in an image, which would allow someone to know which specific constellation they have images to help them know which stars they have seen. Another great opportunity for astrometry.net is to help with star planning.
When we went to Cottonwood Canyon State Park in Oregon, we took a few photos, which we uploaded to astrometry.net, which can be seen below: