Welcome to api.arcsecond.io

Unified REST APIs for world-wide astronomy data

(Updated: July 2017)

arcsecond.io aims at providing browsable, unified Application Programming Interfaces (APIs) to astronomical informations.
Wouldn't the world be simpler if each piece of information is well formatted and has its own stable URL, accessible using HTTP verbs (depending on the resource)? SIMBAD, NASA Exoplanet Archive, JPL Horizons, NASA ADS, IPAC, ESO, MAST are among the sources of information that arcsecond.io intends to unify. Because we believe in the unstoppable force of integration.
Even better: your data (Observing Runs and Night Logs, but also FITS data), can be integrated and automatically be linked to every other sources. While still in beta, you can already explore and play with it, and follow the changes and improvements brought by every release.
arcsecond.io aims at becoming the place of all your observing activities.
arcsecond.io is a service of onekilopars.ec, home of iObserve, the best OS X and iOS apps for astronomers, as well as multiple open-source projects for FITS files, astronomical algorithms, VOTables, etc.

One access point: api.arcsecond.io

Our goal is to give access to as much information as possible, aggregating information with a philosophy centered around resources.
The APIs will incrementally be introduced here. To follow what's going on, read onekilopars.ec blog.
Example values are inserted below to speed up experimentation, but feel free to play with other values.

Observing Runs

Observing Runs are data created by users in www.arcsecond.io. They are collections of Night Logs, associated at an Observing Site.


Current state: ready.

Night Logs

Night Logs are data created by users in www.arcsecond.io. They are all the information of a night! Targets, exposure times, night curves, data, weather...Screenshots of upcoming releases will be made in the usual places: blog, and facebook and Twitter.


Current state: ready.


Objects will be a consolidation of what SIMBAD and NED services return.
Enter the name of a known object and press Go!


Current state: working. Integration with exoplanet host stars and astro telegrams now complete! Currently being integrated with Night Logs.


Exoplanets data will be consolidated from NASA Exoplanet Archive and exoplanet.eu. A friendly note on beta-testers: putting the name of solar-system planets will fail, these are not part of exoplanets catalogs...


Current state: sligthly unstable, and working with exoplanets.eu only. Parameter filtering pending. Integration with objects done.

Observing Sites

Observing Sites are directly managed by arcsecond.io.
You can use ?continent=<Continent Name> to filter according to continents.
Examples: 2ac73126-e183-4e56-b04a-03e4f20dced4 for La Silla,
fcfa529d-880d-45ac-82e1-579640a4e439, for Mauna Kea.


Current state: ready (95%+ covered by unit tests). Static list of iObserve observatories is in place. Dynamic addition, edition, changes by registered users etc. implemented.

Telescopes & Instruments

Telescopes & Instruments are managed directly in arcsecond.io.
Examples: e88b3ac0-6fe3-40e8-9ad8-f08113d5a0f9 for the New Technology Telescope, in La Silla.


Current state: almost ready (80%+ covered by unit tests). Static list of iObserve telescopes is in place.


Telegrams are quick publications, often related to ongoing events occuring is the sky. We intend to cover GRBs, supernovae, Circulars etc...

/telegrams/  /

Current state: partial implementation of ATels, and GCN Circulars.

Data Archives

Data Archives from ESO, MAST etc. For the moment, we only have ESO and HST programmes summary. But other archives as well as FITS data is planned.

/archives/  /

Current state: started, but a lot more to come.


Publications will integrate sources such as NASA ADS and others.


Current state: partial implementation of publications identified with bibcodes. Input with arXiv format pending. Integration with other services also pending.


The people section will regroup all the scientists, and active people in the field, present in papers, proposals, etc. Hopefully, most of them will open a arcsecond.io user account!


Current state: user accounts implementation is started. Then, will need integration will all other services.

Finding Charts

Finding charts will integrate as many sources of charts as possible: SDSS, DSS, 2MASS etc.


Current state: started with IRSA optical and NIR charts from IPAC. Integrations with objects now included.

Asteroids & Comets

Asteroids and Comets will be retrieved from the JPL Horizon service.

Current state: to be implemented, based on iObserve's know-how.


Converters are URL-based calculations. Below are an example that converts equatorial/ICRS coordinates to all other coordinates, and one that converts times in various units. Both follow definitions of astropy.


/converters/times/  /

Current state: basic coordinates support. Astropy-compliant times converter added. Fluxes / magnitudes converter started.

Organisations & Universities

Organisations & Universities will regroup all the organisations such as NOAO, ESO, ESA etc, as well as universities, or group of universities involved in observing activities.

Current state: started.

What about astropy?

astropy.org is amazing! In fact, some of the things behind arcsecond.io rely on astropy.
Even better, we intend to be as much astropy-compliant as possible.

Seamless integration with open-source SDKs

To ease the integration of arcsecond.io services into your own code, we are developing open-source SDKs (a.k.a. Software Development Kit).

For now, it is rather empty, but you can nonetheless check them out on GitHub (no account required).
The SDKs will be written at least in Python, JavaScript, and Swift.


Apart from astropy, arcsecond.io wants to aknowledge the use of the following services:


This work is making use of the SIMBAD database, operated at CDS, Strasbourg, France.
See 2000, A&AS, 143, 9, "The SIMBAD astronomical database", Wenger et al.

exoplanet.eu (Obs. Paris-Meudon)

This work is making use of fantastic work of the team, at exoplanet.eu.
(we would like to link to the catalog publication, but the link is broken...)


This work is making use of the archive of the European Southern Observatory. We also thanks E.S.O. for the amazing images available at this address. Thanks to an open licence (Creative Commons Attribution 4.0 International License), this site can have an amazing look, isn't it?


This work is making use of the Barbara A. Mikulski Archive for Space Telescopes, for the HST proposal summaries.

Astronomer's Telegram

This work is making use of the Astronomer's Telegram.
You can follow it on and .


This work is making use of NASA's Astrophysics Data System. You may have a look at their new interface.


This work is making use of NASA/IPAC Infrared Science Archive. We use IRSA for the SDSS, DSS and 2MASS Finding charts.


This work is making use of NASA/Goddard Space Flight Center. We use GCN for Gamma-Ray Bursts Circulars.