[guide-user] Comets mag, how true?

Rolf Stadelmaier Oct 27 6:25 AM


since long I'm dealing with the question: How reliable are the given
informations by Guide concerning the magnitudes of comets? I always
thought, they must be very actual after downloading the newest data
by using MPCORB.

But: The latest pictures of ISON captured by amateurs are showing a far less
shining comet than Guide suggests. Three days ago I for my own took the
chance, to acquire a picture of this most promising comet to diagnose a very
very great difference between Guide's information and reality. Although my
local conditions for imaging had been very poor (foggy cloudy sky, gibbous
wanning moon causing reflections, optics covered with damp) the result is
obviously: ISON's magnitude compared to the magnitudes of stars in the
imaged field is far beyond the value given by Guide of mag 8.8. It seems to
correspond more to the values of stars with mag 13.4 or 14.2.
Can anyone shed some light on this confusing behavior - Bill?
Thoughts and explanations would bee much appreciated.

Rolf Stadelmaier

PS: To support my experience I uploded a picture to the Photo section.
Please have a look.