C/2014 E2 (Jacques) Returns
Posted 10 October 2014 - 11:43 AM
Posted 10 October 2014 - 03:13 PM
@ klyons--nice pic--thanks for posting. Sure is a starry background.
I'm new here, otherwise I would have replied sooner. I viewed Jacques September 1 with my Z10. It looked like a round nebula with a star in the center. I did not see a tail. The viewing was not good and it clouded up after about 20 minutes. For jollies a tried a couple of filters on it. The broadband LPR filter didn't do anything. I tried an OIII filter because in the photos I've seen it had a greenish tint. The OIII made it darker but I was still able to see it clearly. It's hard to say if it added any extra details. It was rapidly clouding up at this point. So the comet had a OIII component otherwise the filter would have completely killed it. I later saw that Lumicon has a Comet filter that passes the 501, 511 and 514 bands. My OIlI passes 496 to 501. So the OIII has other uses than nebulas.
pjsmith, welcome to CN. You're smart to experiment with filters like that. The Lumicon filter you mentioned is a Swan Band filter (they call it a comet filter) and passes the OIII line and the cyanogen lines. It helps improve the contrast of comets with ionized gas tails but doesn't do much for comets that are mainly dusty. So I guess that Jacques still has some gas to it even if you didn't see a tail.
Edited by Special Ed, 10 October 2014 - 03:22 PM.
- Aquarellia likes this
Posted 03 November 2014 - 07:59 AM
... and the cyanogen lines.
Actually there are no spectral lines due to cyanogen in the green/blue region. The cyanogen "myth" has been around for at least 15 years now and just get repeated. Various websites (e.g. NASA, Lumicon) trot it out without a reference to the source (but also like to tell you that cyanogen is a deadly poison). There was a thread in this section of CN a couple of years back discussing the comet "cyanogen" spectrum issue - http://www.cloudynig...n/#entry5215844
Cyanogen radical fluorescence has a strong line on the UV/violet border.
Green spectral lines from excited C2 radicals (carbon triple bond to carbon) is correct and these were originally discovered by William Swan in 1856 in the spectrum of butane flames.
Edited by Tonk, 03 November 2014 - 08:12 AM.