comet ison question

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  • Member since
    June, 2008
comet ison question
Posted by cjw on Tuesday, October 29, 2013 5:51 PM

Does anybody know where to find daily or at least once or twice a week accurate observations of comet ison's current magnitude.  I definitely didn't think info would be this hard to find, considering all of the hype surrounding it.  I would like a good resource just in case I get a clear morning that way I'll know what to look for.      Thanks      CW

  • Member since
    May, 2005
Posted by Centaur on Wednesday, October 30, 2013 12:03 AM
The only comet magnitude information I use that is based on empirical data are the updated magnitude elements published by NASA-JPL for entry into computer programs. I use them for my Comet C/2012 S1 (ISON) charts, ephemeris and magnitude graph that I post on my comet webpage:

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  • Member since
    March, 2013
Posted by BrooksObs on Wednesday, October 30, 2013 8:36 AM

The unfortunate situation with the NASA-JPL magnitude data is that it is usually a step or two behind the comet's current situation. C/ISON is apparently experiencing yet another slowdown in its brightening trend. The very latest reliable magnitude estimates put it at virtually no brighter than it was back in mid October. This would correspond to altering the NASA-JPL formula's absolute magnitude for C/ISON downward from M1 = 8.0 to closer to M1 = 9.0 at the moment. Unless the brightening trend quickly returns, the NASA-JPL magnitude predictions will fall further behind each day now.

Surprisingly, accurate/reliable visual magnitude estimates for C/ISON made by experienced comet observers have been amazingly few in number. This is a rather unanticipated situation for a major comet although morning comets admittedly are always less observed than evening ones. Things may improve during the dark of the moon over the next two weeks, but the comet's declining altitude by the start of morning twilight may well pose a further problem unless the observer happens to be favored with a very good view of the eastern horizon.



  • Member since
    July, 2002
  • From: Texas
Posted by chipdatajeffB on Wednesday, October 30, 2013 9:02 AM

Comet ISON has been buried in zodiacal light for the past few weeks, complicating photometric measurements as well as visual estimates. Comets are much more difficult to measure photometrically than stars,  because different observers use different means of eliminating other factors (such as zodiacal light).

I do not know whether measurements are being made from spacecraft. But even the standard photometric tricks of "subtracting our atmosphere" are compromised by the comet's current position.

The universe is not only stranger than we imagine, it's stranger than we CAN imagine. --- JBS Haldane

Come visit me at Comanche Springs Astronomy Campus (we're on Google Maps) in Texas.

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