Comet ISON spotted on August 12, 2013

Comet ISON on August 12, 2013

Comet ISON was spotted by amateur imager Bruce Gary from Arizona on the morning of August 12th at around 11:33-11:56 UT. A Celestron 11-inch telescope was used at the Hereford Arizona Observatory (G95) to take the images of ISON. ISON had been hidden behind the sun’s glare since June, and the last best images were taken in late May. ISON is currently between the orbits of Mars and Jupiter, but from Earth’s perspective, it is slowly emerging from the sun’s glare.

The stacked images from Gary show a faint ISON with an estimated magnitude of 14.3 ± 0.2. It was originally predicted that ISON should have been between magnitude 12.3 and 13.5 between August 11th and 20th.

Gary also noted three different predictions for ISON, based on three different comet model formulas. Each model describes what ISON may look like by the end of the year. Those predictions range from fairly good (red line) to lackluster (blue line) to not visible at all (green line).

If ISON follows the green line model, the comet may not reach a magnitude greater than +9.73.

Sky & Telescope‘s comet analyst John Bortle was quoted today as saying if it follows the green line model, “…then ISON has no chance of surviving its perihelion… things are looking ever more bleak for chances of any grand display to be put on by ISON come this December. Still, I wouldn’t fully commit to such until I see some actual visual observations reported.”

The good news to take out of this is that ISON was imaged several weeks earlier than expected.

Karl Battams (@SungrazerComets), wrote today on a guest post on the Planetary Society blog, “the comet looks faint in this image, but it was only a few degrees above the horizon when this image was recorded, and the images are being somewhat washed out by twilight. It’s actually a remarkable feat to have imaged ISON this close to the Sun…

We are going to need several more observations like this from different observers around the world before we are going to be willing to make an updated prediction on ISON’s future behavior, including how bright it is going to get and whether it will reach or survive perihelion, so please don’t leap on us for a week or two about that.”

Credits: Stacked images taken by Bruce Gary ( on August 12, 2013

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