Comet ISON at Perihelion (Actual vs. Predicted Paths)


I superimposed the actual footage of Comet ISON passing by the Sun onto a graphic simulating its predicted path around the Sun at perihelion. They match!

This is an animation of Comet ISON at perihelion. I superimposed the actual SOHO satellite movie footage, released Friday, Nov 29, onto a still-image sky background (created with Starry Night™ software) that shows the scene at the moment of perihelion, and that displays the predicted orbital path of ISON plus labels the stars.

You’ll see the star fields (real and simulated) register fairly closely (check Antares at lower left) around the time of perihelion. It’s neat how the comet follows its predicted path! Well, of course! Newtonian gravity stills rules the solar system.

But I am amazed at how well the simulation (which is done from the viewpoint of the surface of Earth) lines up with the real movie (which was taken by the SOHO satellite from the L1 point 1.5 million km away from Earth but in the Earth-Sun line).

Click here for a more recent version using the SOHO footage released November 30, available at my Flickr site

— Alan, November 29, 2013, revised Nov. 30 /with credit to StarryNight™/Simulation Curriculum and to NASA/ESA

Sundiving Comet ISON – A Last Look

Comet ISON C/2012 S1 (Nov 21, 2013)

Comet ISON performs its dive toward the Sun, caught in the morning twilight.

This was the infamous and much-hyped Comet ISON (C/2012 S1) as it appeared this morning, November 21, 2013, a week before it performs its hairpin turn around the Sun.

The comet was easy to see in binoculars, though the camera picks up a bit more of its faint tail. ISON was much more photogenic a week ago when it was higher in a darker and moonless sky. But this morning I had to contend with bright moonlight from a waning Moon and the brightening dawn. The inset shows a blow up of just the comet.

ISON is dropping rapidly toward the Sun, making this perhaps the last sighting I’ll have of it until it reappears – we hope! – from behind the Sun in early December. If it survives its perihelion passage it might blossom into brilliance … or fade into obscurity. No one knows.

In the photo above, you can see Mercury at left, shining much brighter than ISON. It was brilliant as it rose into the southeast sky, with the elusive planet now about as well-placed as it gets as a “morning star” for us living at northern latitudes.

Comet Lovejoy C/2013 R1 (Nov 21, 2013)

This morning I was able to shoot not one but two comets.

About half an hour before ISON hove into view I aimed the camera up almost overhead toward Ursa Major, to capture Comet Lovejoy (C/2013 R1) as a bright cyan fuzzball with a short tail. Again, the photo brings out the tail – to the eye the comet was obvious in binoculars but appeared as just a fuzzy star.

I took both shots with the same gear: a 135mm telephoto lens on the Canon 5D MkII on an iOptron SkyTracker. The Lovejoy shot is a stack of 5 x 75 second exposures. The ISON shot is a 4-second exposure, with the colours and contrast boosted for prettiness.

This is certainly proving to be a year of comets. It would be nice if just one of them got really bright!

– Alan, November 21, 2013 / © 2013 Alan Dyer