(meteorobs) Need moon magnitude help please

[Chris Peterson]

Hi Roberto-

I rarely do this, for several reasons. First, the magnitude of a fireball 
isn't usually that useful to know, unless you can actually get an accurate 
light profile. And that isn't possible with these video meteors because the 
signal is saturated. So the technique is to look at the apparent diameter of 
the saturated Moon, and compare it to the apparent diameter of the saturated 
meteor, and run that through some kind of estimation function. You're lucky 
to be accurate within a couple of magnitudes, which pretty much makes 
compensating for things like atmospheric extinction pointless.

For more distant meteors, where I have multiple station data, I do sometimes 
convert the apparent magnitude to a normalized magnitude.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Roberto G." <md6648 at mclink.it>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: Friday, October 09, 2009 1:27 PM
Subject: Re: (meteorobs) Need moon magnitude help please


>From: "Chris Peterson" <clp at alumni.caltech.edu>
>

>Hi Tom-
>
>For conventional Moon phase (0% new, 100% full), you can use this:
>
>mag = -3.33 ln(phase) + 2.79
>
>to give the zenithal magnitude of the Moon. You might want to correct that
>for zenith angle, just as you would for a meteor, although it usually isn't
>necessary when using the Moon as a brightness reference for fireballs.
>
>At the time of your event, the Moon's phase was 72%, so I'd put its
>brightness at mag -11.5. At an altitude of 50°, I wouldn't worry about any
>corrections to that. Your meteor was low enough, however, to be somewhat
>attenuated. If you are able to compare it with the Moon, you should
>probably
>increase its estimated brightness slightly to compensate for atmospheric
>extinction.
>
>Chris

For a rigorous calculation he should to correct:

1)  zenithal magnitude of the Moon

2)  zenithal magnitude of the bolid (at the maximum or better at each flare)

3) it must correct the magnitude of bolid too for the color of the bolid
    if saw visual, but it should to do the same for the CCD if he known
    the light curve of the camera

4) he should too correct for the limit magnitude of the sky in that moment.
    for a sky reference of 6,5a.

But  he can to calculate only the first 2 item.
Best greetings.
Roberto Gorelli