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Re: (meteorobs) More questions please.
>>-one way is to describe "BEGIN" and "END" in terms of Right Ascension
(hours) and Declination (degrees) which are coordinates from a celestial
map.
Right? <<
Yes, they are the positions using the coordinate system used on most star
charts.
>>-another way to describe "BEGIN" and "END" is in terms of AZIMUTH
(degrees, north = 0 or 360, and south= 180), and ELEVATION. How is
ELEVATION
in this circumstance determined? Is it horizon = zero (0) degrees and
zenith
= 90 degrees? <<
You are correct...the horizon is zero degrees; zenith is ninety.
>>Is there something like an overlay map that will help beginners learn both
these coordinating systems to then be able to transfer from one system to
the
other? I take it you all use only celestial map coordinates, yes? no? <<
None that I know of, other than some planetarium programs. For instance, Red
Shift lists positions with both systems. From fireball reports I see, folks
who participate in astronomy as a profession or a hobby tend to use right
ascension and declination. Most of the others use azimuth and altitude.
Either is fine.
>>Neither of these systems are used for reporting meteors, right? Only
radiant
and sporadic designations, right? <<
I am not sure if I understand your question here, but in visual observing,
there are two types of observing - plotting and counting. When plotting, the
meteor positions are plotted on maps or charts designed specifically for
that purpose. In that case the positions can be determined. Those who are
counting generally do not list positions, although there are some
exceptions. Most observers simply list the meteor as a sporadic or shower
member.
>>>Can I go by these listings? Is there a similar listing for planets (or
do they change during the year)? Are the numbers on some of the charts on
"NAMN: Limiting Magnitude Charts" (lm) actually magnitudes that indicate
brightness from an observers view? <<<
Most listings of the planetary magnitudes are taken as an average. The list
in the NAMN Guide is for determining meteor magnitudes and is accurate for
that purpose since they will be used for visual estimates. The LM Charts are
something different. Those are the older IMO charts in which you count the
number of stars in a predetermined area, and then match your count to
the tables. This gives you the limiting magnitude of your site. These
estimates are made frequently throughout the observation.
However, the charts on the NAMN site have been updated, and the ones there
will soon be completely removed and replaced with an entirely different set
aimed at new observers. Therefore, for the most accurate LM
estimates, I recommend you visit the IMO website at http://www.imodot net/
and look under their visual section for some charts.
Hope this helps,
Mark Davis
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