(meteorobs) The Moon and the 2007 Aurigids

[Bruce McCurdy]

Joe Rao wrote:

>>First . . . the correction.  The article states that next year's Aurigid 
>>shower will take place three days before a Full Moon occuring @ 02:32 UT 
>>on September 4.  In reality, the shower will peak nearly four days AFTER a 
>>Full Moon occurring @10:35 UT on August 28.
***

... and Petrus Jenniskens replied:

> I have returned from travel in Europe and am catching up
> on my e-mail. I suspect your question was answered already, but just in 
> case: you are right about the time of Full Moon. September 4 (02:32 UT) is 
> actually the time of Last Quarter. That was sloppy of me. Point is that 
> the Moon is bad for visual observations, but not too bad given that we are 
> a few days away from full Moon and the shower is expected to be rich in -1 
> to +1 magnitude
> meteors.
***

    It would have been greatly preferable if the Moon was a few days before 
Full rather than after. A Third Quarter Moon is generally in the direction 
of Earth's motion, and by extension a typical radiant, meaning that both 
Moon and radiant are likely to be in the sky at the same time. Whereas a 
waxing Moon will typically set before prime meteor time for some portion of 
the planet. This is especially significant at that time of year: in 
September the Moon is rushing northward as well as eastward from day to day 
as it passes through and beyond Full.

    In the specific case of 2007 September 01 11:37 UT, the gibbous Moon 
will reside in Aries some 45° from the radiant in Auriga (what are the exact 
coordinates of the radiant, please?). It will have reached a declination of 
+16°, meaning an early rise and a high culmination for those of us in the 
northern hemisphere. (And really, folks, who in the south will see the 
Aurigids?) It will be similarly bright, but 16° higher in the sky, as the 
waning gibbous Moon for this year's Perseids.

    That said, this year I observed Perseids at about 50% their 'normal' 
rate -- 1 every 2 minutes instead of one per minute -- and it was well worth 
my time. If as Petrus claims the Aurigid shower (squall?) is rich in zeroeth 
mag streakers, observers should be amply rewarded, and even counts reduced 
by less-than-ideal conditions will be of great scientific interest.

    Here in Edmonton at the appointed hour (5:37 a.m. MDT)  the Sun will be 
10° below the horizon, the Moon will have just crested and still be 52° high 
in the SSW, and I will be inclined at about 30° in my favourite 
chaise-longue under the darkest sky I can find.

    Bruce
    *****