What a horrible morning. A sky perfectly clear at 4 a.m. turned nearly overcast just in time to check out this week’s impressive outburst of Comet ISON. I did say “nearly”. Driving north to find a clearing failed, so I turned the car around and sped southeast toward Lake Superior. There along the beach, a few cracks in the clouds glided across Virgo, buoying hopes that sooner or later ISON would pop through the clouds if only for a minute.
And it did. While I could have measured the amount of time spent viewing the comet on a stop watch – maybe 3 minutes total – I enjoyed every juicy second. The head of the comet, a wimpy thing on Wednesday morning, had doubled in size and burned pale blue with a bright, intense, fuzzy center.
Even through thin clouds ISON and the first half degree of its tail were easy grabs in 10×50 binoculars. Its brightness, measured on the magnitude scale, was 5.0 this morning or 2.5 magnitudes brighter than earlier in the week. That translates to a tenfold increase in brightness in just two days.
Around 5:15 a.m., the sky completely cleared around the comet for a single precious, complete minute. I dashed to the telescope for one last look at the bulbous blue head and tail that stretched at least a degree (twice the diameter of the full moon) up to the northwest. OK, it wasn’t such a horrible morning.
Today was the last for dark skies without interference from the moon. Beginning tomorrow and continuing for at least the next 10 days, the moon will light up the sky well into morning twilight and beyond. While it will make the comet difficult to see with the naked eye – assuming it doesn’t leap again in brightness – it should still be visible in binoculars. ISON is rapidly approaching the sun and will soon be difficult to see. Go out to look at it the next clear morning if you can.
You can use the map from yesterday’s blog to help you find ISON. Although low, it’s near the bright star Spica in Virgo. I’m also including a new map for amateurs willing to tackle Comet Encke, located even lower in the sky and near the planet Mercury. Encke is only a few days away from perihelion or closest to the sun. These next few days will be the last time to see the comet this apparition for northern hemisphere viewers.