(meteorobs) Please QC what I wrote.

[meteoreye at comcast.net]

Hi Rainer.

I'm enclosing an excerpt of what I wrote in this month's NAMN notes.

Could you please look it over and see if you agree on how Sirko's showers should be reported to the IMO? If you can, do it soon, se we can be sure that people report directly and the NAMN forwards reports in the form you would like.

I will also forward to you what I am going to write in the Jan NAMN notes for your approval.

Thanx

Wayne

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4.  COM and MON expanded discussion …
 
            COM--The knowledge obtained during the past decade of video observations, combined with previous photographic records and the sparse visual coverage during late December and January has been both a blessing and a curse. This is particularly acute with these two showers. In fact, this is the reason why this month’s NAMN Notes is a few days late, as I have wrestled with how to present this information in a useful and coherent manner. I apologize for the delay, since I underestimated the difficulty. For the casual observer, this is of small consequence, but for the few people who observe during these winter months, I wanted to provide the most accurate and current data possible. Typically, less than 2 dozen hours of Teff are reported between the end of the Geminids and the end of January.
 
            The video data has suggested a much more complicated situation. In fact, for 2008, in addition to shifting the peak date later in the month of December, the IMO says “The radiant ephemeris of this shower is severely questioned after the scrutinization of single-station video data showing a clear radiant with an offset of about 15 degrees to the Working List positions.” The result is given as “possible COM” in the 2008 shower calendar.
The IMO recommends the use of the old COM positions for 2007-2008, while meteors from the “possible COM” position should be noted separately.
 
            This means that for IMO reporting, the COM positions listed in the minor shower section above should be used. As to how you should report the meteors to the NAMN, I will discuss that for each of the possible COM radiants below.
 
            The video data suggests there are actually 4 radiants nearby. I’ll discuss the two radiants in December below, based on the start date of activity. All of these showers produce fast meteors, between 58 and 64 km/sec.
 
            The first is Sirko Molau’s shower 76. My research has indicated that the positions are nearly a perfect match for IAU shower #32, the December Leo Minorids (DLM). It is almost 20 degrees offset from the IMO’s COM radiant, so they should not be counted as COM meteors. Meteors from this radiant should be reported directly to the IMO as SPO, with comments indicating they are DLM, which is “possible COM”. This shower produced an outburst on December 5, 1921 of greater than 80 per hour. Since it seems likely this stream is from a long period comet (possibly C/1798 X 1 Bouvard, per Jenniskens?), and this was the only outburst, it’s hard to predict what might occur in coming years.
If you depend on the NAMN to forward your data to the IMO, that is what will happen. In the NAMN database, they will be recorded as DLM, and will be reported to the IMO as SPO with an explanation. This procedure also applies to the other showers listed below.
Here are the radiant positions:
 
Start of DLM “possible COM” Activity Dec 4; Radiant 149 (9:54) Dec +35
End of DLM “possible COM” Activity Dec 29; Radiant 169 (11:14) Dec +28
 
            The second is Sirko’s shower 81, which comes closest to the official IMO position. In fact, on the video indicated peak date (Dec 16) the radiants are identical. However on earlier days there is a considerable offset, on the 9th there is an 11 degree difference in Declination. These should be reported to the IMO and NAMN as COM. It would be worth noting which position of the radiant (official IMO or Sirko Molau’s) appears to be more accurate in describing the activity
 
(SM) COM Start of Activity Dec 9; Radiant RA 152 (10:06) Dec +23
(SM) COM End of Activity Dec 16; Radiant RA 174 (11:36) Dec +26
 
            The other two video indicated showers occur in January, so we will discuss them next month.
 
            MON—Like the Coma Berenicids, the situation with the Monocerotids after including recent video data has changed. It appears that in addition to the standard MON radiant, there is another stream about 15 degrees away. Based on my research, this seems to be IAU shower #250, the November omega Orionids (NOO). These were also reported as lambda Orionids (LOR) but with as much evidence as there is for the NOOs, they should be grouped together. This shower ends abruptly on December 5th, when the standard MON radiant suddenly begins, missing the ascending branch of activity. They should be reported to the IMO as SPO, with an explanation that they are NOO in the comment section. That is how the NAMN will forward the data.
 
(SM) NOO Activity this “Moonth” Nov 28; Radiant RA 091 (6:03) Dec +16
(SM) NOO End of Activity December 5; Radiant RA 096 (6:26) Dec +16
 
See the Minor shower section above for MON positions throughout this period.
 
            I know this is rather technical stuff for many readers, feel free to skim over this information. The situation with Major showers is easy to figure out.
These Minor showers, with rates just above the visual threshold are a challenge to see, but can teach us much about the evolution of meteor streams. For the few dedicated observers who brave winter’s chill to observe, I felt a need to provide all the things I have learned in my research. For all the positions listed above, you can extrapolate between the positions listed, or you can send me a message, and I will send you detailed information of radiant positions for any night. Ideally, future video and visual plotted observations will shed light on these showers. If nothing else, it shows the value of accurately determining the path of any meteor from these areas of the sky. That’s more support for my suggestion last month of using an alignment string for this purpose.