Re: [guide-user] Comet Magnitude Parameters
P. Clay Sherrod Sep 23, 2013
The magnitude will be based entirely (and many time erroneously) on the
latest MPEC that is issued for the updated elements on the comet. Rarely
is the specified magnitude anywhere close to the given magnitude, typically far
brighter (given) that the comet actually is. Note also that magnitudes
from MPC on comets are expressed as m1 (total) magnitudes which is horribly
misleading in many cases. Except in rare comets where the head, or
nucleus, of the comet is the ONLY measurable parameter (no visible outer coma
nor tail), the measurable comet will include the coma as well as the tail that
passes through the measurable semi-diameter of the coma; that entire combination
of dust and gases is what comprise the TOTAL (m1) magnitude and it is quite
difficult to ascertain, even via CCD, accurately. More often - a good case in
point at this time is comet 2P Encke - there is a distinct starlike nucleus that
should be measured rather than attempt to measure a very vague and extended
faint cloud of gas INCLUDING the nucleus. Such a measurement would be =
However, a nuclear measurement (not given on MPECs) would be the
measurement of the starlike or disklike structure of the comet structure itself,
or m2, nuclear magnitude.
In short, never rely on the given magnitudes that you see predicted by JPL
or MPC; using current comet lists like:
are far more reliable.
But - always record and report what YOU measure, not what you "think" the
comet should be or what others report....use lists only as a guide.
Arkansas Sky Observatories
MPC H45 - Petit Jean
MPC H41 - Petit Jean Mountain
MPC H43 - Conway Westhttp://www.arksky.org/
----- Original Message -----
Sent: Monday, September 23, 2013 11:23
Subject: [guide-user] Comet Magnitude
wonder it is possible to show the Comet Magnitude Parameters under More Info
when you click on a comet. It would be useful to known on what the reported
magnitude is based.
I know you can look at the comet elements text
file, but having it under More Info would be more convenient.