All-Sky Automated Survey for Supernovae
ASASSN-18bt: Bright Supernova Discovered in the Kepler Field! (February 2018).
ASAS-SN Variable Stars Database is now public (57,000+ bright variables, more coming) (January 2018).
Yet another new telescope, Cecilia Payne-Gaposchkin, now deployed in South Africa! (November 2017).
Another new ASAS-SN telescope, Henrietta Leavitt, now deployed in Texas! (September 2017).
A new ASAS-SN telescope, Bohdan Paczyński, was deployed in Chile! (September 2017).
Comet ASASSN, our first comet discovery! (July 2017).
All-sky, real-time ASAS-SN Sky Patrol is now public! (June 2017).
See more ASAS-SN News here.
Telescope status live (via LCO webcams):

South Africa Chile Texas Hawaii

Bright supernovae discovered: 635 (173 in 2017, 40 in 2018 so far)

ASAS-SN: Variable Stars | Sky Patrol | Transients | Supernovae | CV Patrol | ATels | Papers

Twitter | Channel | Picture of the Week | ASAS (Warsaw)

We are now partially funded by 5-year grant GBMF5490.

We are also supported by Grant AST-151592. Our telescopes are hosted by .

ASAS-SN expansion was also possible with support from:
Mt. Cuba Astronomical Foundation ,
OSU Center for Cosmology and AstroParticle Physics (CCAPP) ,
the Chinese Academy of Science South America Center for Astronomy (CASSACA),
and the Villum Foundation (Denmark).

We thank George Skestos for his generous gift to Prof. Kochanek, partially used to expand ASAS-SN.

What is ASAS-SN?

The sky is very big: even in the present day, only human eyes fully survey the sky for the transient, variable and violent events that are crucial probes of the nature and physics of our Universe. We are changing that with our "All-Sky Automated Survey for Supernovae" (ASAS-SN) project, which is now automatically surveying the entire visible sky every night down to about 17th magnitude, more than 25,000 times deeper than human eye. Such a project is guaranteed to result in many important discoveries, some of them potentially transformative to the field of astrophysics---think about ASAS-SN as the "SSST" - Small Synoptic Survey Telescope, complementing LSST and other time-domain projects by frequently observing the entire bright sky. Bright transients, Galactic and extragalactic, discovered early by our high-cadence survey, are especially valuable, as they are easy to study using relatively modest size telescopes.

ASAS-SN currently consists of 20 telescopes, distributed around the globe. ASAS-SN first unit, known as "Brutus", which also happens to be the name of the Ohio State mascot, comprises of four robotic 14-cm telescopes deployed at the Hawaii station of the Las Cumbres Observatory. ASAS-SN second unit, named "Cassius", also consists of four 14-cm telescopes deployed in Chile. In 2017, with support from the Gordon and Betty Moore Foundation grant GBMF5490, we deployed additional 8 telescopes at two other LCO sites: "Cecilia Payne-Gaposchkin", deployed in South Africa, and "Henrietta Leavitt", deployed in Texas. Finally, using a combination of funds from Mt. Cuba Astronomical Foundation, the Chinese Academy of Science South America Center for Astronomy (CASSACA), and the Villum Foundation (Denmark), in September 2017 the 5th ASAS-SN unit, "Bohdan Paczyński", was deployed in Chile. All these telescopes will allow us to survey the entire visible sky every night, and are making our network much less sensitive to weather conditions.

We are discovering numerous bright supernovae in both hemispheres (615 total, 20 so far in 2018). See below where our supernova discoveries announced so far are located on the sky (bigger symbols - smaller distance)

We continue to discover numerous bright cataclysmic variables, many of which are being intensely observed by professional and amateur astronomers.

Generally we are posting our real-time discoveries using ATel, so if you interested in being notified of our results, you should subscribe to that useful service, and also see our ASAS-SN Transients page.

See below our sky coverage plot for the last 365 days - we are observing the entire sky!

At this point we are focused on discovering bright, nearby supernovae, but we like all kinds of variable objects, so if there is an object with V-band magnitude between V~9 and V~17 that we might have in our data, send us an e-mail ( and we will check what we have. Here are some papers written by outside collaborators that have used our unique ASAS-SN data: Herczeg et al. (2016), Rodriguez et al.(2016) and others.


At Ohio State: Jon Brown, Tharindu Jayasinghe, Chris Kochanek, Josh Shields, Kris Stanek, Patrick Vallely, John Beacom, Todd Thompson;

Ben Shappee, Michael Tucker (IfA, Hawaii);

Tom Holoien (Carnegie Observatories);

José Luis Prieto (Universidad Diego Portales; MAS);

Grzegorz Pojmanski (Warsaw University Observatory);

Joseph Brimacombe (Coral Towers Observatory);

David Bersier (LJMU);

Subo Dong, Ping Chen, Subhash Bose (KIAA-PKU);

Emilio Falco (CfA);

Przemek Wozniak (LANL);

Maximilian Stritzinger, Simon Holmbo (Aarhus);

Nidia Morrell (Carnegie Observatories, Las Campanas Observatory);

Laura Chomiuk, Jay Strader (MSU);

Anna Franckowiak (DESY);

Ondřej Pejcha, Michał Pawlak (Charles University).

Udit Basu, a local (Ohio) high school student who worked with us for 3 years, is now an undergrad at Princeton Astrophysics.

We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN: we truly could not do this without your help.

An important part of our project is the follow-up effort with bigger telescopes to get confirmation imaging (our images have ~8" pixels). We are fortunate to have a number of "unpaid professional astronomers" working with us on ASAS-SN "ad hoc" SN confirmation effort, including G. Bock (BOSS), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables, France), I. Cruz (Cruz Observatory, USA), J. M. Fernandez (Observatory Inmaculada del Molino, Spain), S. Kiyota (Variable Star Observers League in Japan), R. A. Koff (AntelopeHills Observatory), G. Krannich (Roof Observatory Kaufering, Germany), P. Marples (BOSS), G. Masi (Virtual Telescope Project, Ceccano, Italy), L. A. G. Monard (Klein Karoo Observatory, Western Cape, South Africa), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France), R. Post (Post Astronomy), G. Stone (Sierra Remote Observatories), W. Wiethoff (University of Minnesota, Duluth, USA). You can see from many joint Astronomer's Telegrams we have published that it is a very fruitful collaboration - we have confirmed together more than 400 supernovae!

A large number of professional astronomers have also contributed their effort and telescope time to ASAS-SN, which we most appreciate. You can see the names of our collaborators on ASAS-SN results annouced so far on ASAS-SN papers and ATels. So when you get an e-mail from us, asking to collaborate on a new exciting ASAS-SN target, we hope you will say "yes"!

ASAS-SN Hardware:

Our team makes ASAS-SN a success, but we also need excellent hardware to aid us in our mission of studying real-time variability of the entire sky:

Since we are using relatively small telescopes (lenses), we cannnot afford to waste many photons. As our detectors we have selected ProLine PL230 CCD cameras from FLI, with back-iluminated CCD sensors, giving us high QE, low-noise and fast readout (and of course they are electrically cooled). To cover 40,000 square degrees each night, we take several hundreds of images nightly with each camera. We have been very happy with the reliability of our cameras, and as part of our 2017 expansion, we have deployed 12 more of them (for a total of 20).

To achieve large field of view with a very stable and uniform point-spread-function (PSF) across the field, we use Nikon AF-S NIKKOR 400mm f/2.8G ED VR AF lenses. We had high expectations for these lenses and were not disappointed: we obtain stable and sharp images for many nights in a row. Stability is crucial for the image subtraction method, which we employ to detect transients, to work best.

And again, all ASAS-SN telescopes are deployed and run by Las Cumbres Observatory, including their telescope hardware and software: "Many eyes - one vision".

This homepage is maintained by Kris Stanek (
Updated Mon Feb 19 11:18:24 EST 2018

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