Quadrantids 1995: Visual Observations
team Delphinus, Biddinghuizen (Marco Langbroek & Koen Miskotte)


Dear people,

Some very preliminary results about observed Bootid activity of January 3/4 by DMS station Biddinghuizen observers.

Koen Miskotte observed a total of 675 meteors (sporadic and Bootid). His highest absolute one hour count of Bootids was between 3 and 4h UT: 112 bootids, Lm +6.7.

I observed a total of 566 meteors, of which 146 were sporadic/minor stream and 420 Bootids in 11.2 h effective observing time between 17:18 and 6:10 UT. Until 0:30 UT I used the conservative method of writing down data on paper, after 0:30 UT I used a memo-recorder. Lim. mag.'s varied between 6.8 (early part of night) and 6.0, but were mostly around 6.3-6.6. Obviously, skies were not as transparant as during the summer campaign (regular Lm. of +6.9-7.0). My highest absolute one hour count was 91 Bootids between 4:30 and 5:30 UT, Lm. +6.3.

Jaap van 't Leven (Bosschenhoofd) reports the possible observation of a double radiant structure.

Activity behaviour:
A first rough reduction (my data only) doesn't give straightforward results. There's a strange structure in the later part of the night in my data: activity seems to rise again after 4h UT! This is most probably not due to odd estimated limiting magnitudes: I have to exponentially upgrade them to unreasonably high values to get rid of the odd rising slope... I really don't know what to think of it...
The data before 4h UT give a reasonable activity behaviour. I find a peak near 0:30 UT (+/- 30 minutes), sol. long. 282.538 +/-0.03 (1950.0). This is almost inbetween IMO and DMS prediction... Rising and falling slopes have a B-value of about 2.9-3.0 (see Jenniskens 1994, astron. astroph. 287, 990-1013 for an explanation of what a 'B-value' etcetera means). Working with an assumed x=2.6, y=1.4 in radiant altitude correction and my common Cp of 0.8 I find a peak ZHR around 220 +/- 25.

As mentioned, I find a very odd activity behaviour in the later part of my data sample, but I hesitate to call it significant. I guess it isn't, though I can't explain what went 'wrong' with me in the later part of the night. From 3:30h UT onwards, activity according to my data rises (!) again, from about ZHR=90 around 3:30 UT to ZHR=230 around 6 UT. On a single log. scale, this 'rising slope' has a linear behaviour with a B-value of about 2.7, quite suggestive!

results 4/5 January:

Due to an incorrect working alarm, I didn't wake up around 3h UT as was planned, and therefore unfortunately I slept this night instead of conducting observations. But Koen Miskotte has observed from Harderwijk. His data:

____________________________________________________
UT        Nboo  Nspo    Lm    Teff (h)  ZHR   +/-
3-4       6     7       6.4   1.00      9     4
4-5       4     10      6.4   1.00      5     3
____________________________________________________
assuming x=2.6, and with y=1.4, Cp=1.2

This completes my report on preliminary results. I'm very interested in results by others, especially ZHR-behaviour after 4h UT, and position of the observed peak.

Marco Langbroek
DMS station Biddinghuizen



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Casper ter Kuile and Marco Langbroek