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|Starting to Use Your Telescope|
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|Buying a telescope for a child|
|Photographing a partial eclipse|
Visual Meteor Watches
Graham Winstanley was able to observe on three nights. Observing from Bassingham, Lincs on Aug 8-9, he saw 5 meteors, including 2 Perseids between 2336 and 0040 UT (LM 5.5). Increasing cloud hindered his observations on Aug 11-12 (Perseid maximum night), but, observing from Bishop Stortford, he saw 4 Perseids between 2207 and 2236 UT (LM 4.5). Observing from Bishop Stortford again on Aug 12-13, he saw 15 Perseids and 1 sporadic between 2125 and 2230 UT (LM 4.7).
Tom Banks (Comberbatch, Cheshire) was clouded out near Perseid maximum but was able to observe on two other nights. During the night of Aug 8-9, he saw 8 Perseids and 8 sporadics between 0125 and 0340 UT (LM 4.9). During the night of Aug 14-15, he saw 8 Perseids and 2 sporadics between 2300 and 0100 UT (LM 4.7) and then saw another 11 Perseids between 0112 and 0240 UT (LM 4.7).
Ken Meadows (High Wycombe) observed from 2136 UT on Aug 11-12 (LM 5.0), seeing 10 Perseids and 1 sporadic before cloud intervened at 2238 UT (just before the enhanced activity seen elsewhere). Later, from approx 0120 UT onwards, he saw 28 Perseids and 7 sporadics (LM 5.0-5.3), before the approaching dawn ended his observations at 0324 UT. The highlight was a mag -5 Perseid in Cepheus at 0311 UT. His observations early in the night of Aug 12-13 were severely affected by cloud, but he did see 5 Perseids in just over an hour.
Michael Kinns (Sandwich, Kent) observed between 2150 and 2330 UT on Aug 12-13, seeing 16 Perseids (LM 5), ranging in brightness from mag 0 to mag 4.
Graham Taylor (Broughty Ferry, near Dundee) observed between 2222 and 2324 UT on Aug 12-13, seeing 11 Perseids (LM 4.0).
Bill Ward has generated this bar chart based on visual inspection of his image grabs during his radio monitoring of meteor echoes near Perseid maximum.
Each bar shows the echo counts during a 30 minute interval.
A distinct isolated peak can be seen in the interval that starts at 2300 UT on Aug 11.
This ties in with the enhanced Perseid activity reported by those visual observers who had clear skies.
The graph below has been generated from Bill's colorgramme plot on the rmob website. Each bar represents the meteor echo count during a one hour period. Note that the counts may differ from those in the above graph for which Bill was able to manually check fainter echoes in the spectrogram image captures - some of these will have been ignored by the HROfft software that reports the counts for colorgramme.
Once again, the peak for the 23h-00h period on Aug 11-12 can be seen.
Also obvious is the 24 hour diurnal variation in counts with maxima near 05h UT and minima near 17h UT each day. Although meteor rates do routinely show a 24 hourly rise and fall, the hour to hour changes seen here are also influenced by the changing position of the Perseid (and other) radiants in the sky relative to the GRAVES transmitter and Bill's receiver and also by the changing activity level of the Perseids themselves.
As can be seen, overall rates are clearly higher during Aug 11-12 than during the preceding and following nights. Whether the peak near 08h UT on Aug 12 ties in with any visual activity or is just a random fluctuation is not yet clear.
Bill Ward has generated this intensity plot for the Perseid spectrum that he captured at 22:34:38 UT during a short clear spell early in the night of Aug 12-13.
As often happens, only part of the spectrum fell within the camera's field of view. Here we see the red and near infrared spectrum of this Perseid.
Bill was particularly pleased with the level of detail in this spectrum. He has compared the atmospheric emission lines (O O2, N, N2) in his spectrum with those recorded in a detailed spectrum by the (rather more expensive) VLT while observing a distant supernova in 2002.
The comparison is shown below
VLT spectrum sections are in black. The modelling done by the astronomers indicated this was the profile of an emission of 4200K at a height of 95km in our atmosphere.
Bill notes that "as the devil is in the detail, if you look closely at the model line (at around 755nm from O2) it is missing from the VLT observation but it is a distinct line in my spectrum. Another cool aspect is the "height" of the lines in the regions marked. Comparing the various scalings shows a very good ratio relation. So it would suggest that my real spectrum matches the modelling quite well. 4200K it is! "
Added by: Tracie Heywood