2013-11-11

Double-tailed comet ISON

Last night I finally had the chance to hunt for Comet C/2012 S1 ISON again - my first time in November. The sky was not perfectly clear, a littly hazy and pretty light-polluted. Nevertheless I could spot ISON with both 14x80 and 10x50 bioculars. For the first time, ISON showed a double-tail on my images. The comet is finally ramping up!

Compared to some nearby stars I estimate ISON's brightness to be around 8.2-8.3mag. It wasn't a very impressive sight. The comet appeared as a weak, star-like spot in the 10x50, while the 14x80 revealed an extended coma. The tail was not visible, altough in the 14x80 the coma appeared to be slightly elongated. The faintest stars visible in Virgo with unaided eyes measured about 4.5mag.



The tail "bifurcation" appeared faintly even in the raw images - and clearly in the processed image. Certainly a surprise, since it was first seen only five days ago with much better equipment. ISON is obviously developing an ion tail!


As always, I used a 8" f/4 Newtonian and a Canon 450Da DSLR camera to image the comet, as well as a CLS-filter to reduce skyglow. 

The evolution of the comet is shown in the picture below. I double-checked, all of the images show the same field-of-view and were shot with the same equipment under comparable conditions.


Comet ISON is visible in the pre-dawn sky during the next days, accompanied by three other comets. It will brighten even more as it approaches the sun for perihelion on Nov. 28. What happens then - time will tell!



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