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Topic: ZHR

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	zhr
		In practice, the ZHR is determined from an observation by correcting the observational parameters to the "ideal" conditions listed above.
		Typically, the ZHR is expressed with error margins, the error being given as +/- ZHR/sqrt(N).
		The predicted ZHR may be used to forecast what kind of rates you'll see.
	skytour.homestead.com /zhr.html (687 words)

	IMO Results: Leonids 1998 - Final
		The ZHR profile in Figure 4 consists of 16 non-overlapping bins in the respective period which is certainly near the upper limit for resolving the small-scale structure of the shower.
		The peak ZHR of the reduced nodal maximum is 80, and the skewness is retained.
		The ZHR is an observational measure for the shower's activity as seen by an average observer on Earth.
	www.imo.net /articles/shower/leo98a.html (5040 words)

	Lunar Impact Plots for 2001 Meteor Streams (Site not responding. Last check: 2007-10-11)
		zhr = 120 34% impacts on unlit near side w/polar graze = 64 deg.
		zhr = 10 1% impacts on unlit near side w/polar graze = 5 deg.
		zhr = 8 1% impacts on unlit near side w/polar graze = -27 deg.
	www.lpl.arizona.edu /~rhill/alpo/lunarstuff/moonhits2001.htm (1093 words)

	Hourly Rates (Site not responding. Last check: 2007-10-11)
		ZHRs for known meteor showers range from 1 or 2 for the weakest showers that are detectable, to over 100 in the case of the Perseids, Quadrantids and Geminids.
		Most meteor showers have a similar ZHR from year to year, but some show a variable ZHR, depending on how close the Earth passes to the stream of dust left by the parent comet of the meteor shower.
		In 1966, a ZHR of 150,000 was estimated during the 20 minute peak of the Leonid shower.
	www.wwwtln.com /finance/95/hourly-rates.html (1009 words)

	IMO Results: Perseids 1995 and 1996
		This ZHR rise coincided with the occurrence of a number of fireballs as well, but according to the magnitude data and the population index r this part of the activity also included a large portion of fainter meteors.
		Since the ZHR of the background and core Perseids can be regarded as constant for each return, we suggest to use the width of the graph at a ZHR level above that of the other components as a measure for the width of the outburst component.
		The ascending node of the comet 109P/Swift-Tuttle is at 139.44° [6], hence the 1992 passage was the closest to the orbit of the Perseid parent comet.
	www.amsmeteors.org /imo-mirror/articles/shower/per9596.html (2271 words)

	ZHR (Site not responding. Last check: 2007-10-11)
		The supreme authority of the Association is the ZHR Congress, which chooses the Chairman of ZHR, the Girl Scout Head, the Boy Scout Head, the Supervisory Board, the Auditing Committee of the Association, and the Scout Court.
		The Management of the Association are the Leaders including: the Chairman of ZHR, the Girl Leader and Boy Leader, as well as two Deputies, the Supreme Chaplain of the Association, the General Secretary, the Treasurer, the Foreign Commissioner, and one or two members.
		The Chairman of ZHR is the supreme representative of ZHR in external affairs and directs the Association with the assistance of the Leaders.
	www.zhr.pl /drogowskazy/17_usa.htm (1091 words)

	Improved 2001 Leonid storm predictions from a better model including cumulative non
		Although we originally assumed this constant to be the same as in the distribution normal to orbital plane (that corresponds the observed shape of ZHR curve), it now appears that in the normal to plane case the value 1 is probably a better one [5].
		This spreadsheet model then calculated the ZHR values for different solar longitudes by weighting the data according to the A2-value and distribution parameter and added the direct spread effect according to principles in [1] and chapter 2 of this paper.
		Calculated ZHR values were then fitted to observed curves by adjusting two variables: a factor directly affecting all the values, and the A2 spread half strength parameter.
	www.saunalahti.fi /fmbb/astro/2001leonidstorm.htm (3603 words)

	Mark Kidger's Meteor Observing Home Page
		ZHR plots based on IMO data are shown here and here.
		As a curiosity, I have added a plot that shows the ZHR, the number of Leonids reported to the IMO so far, and the number of observers reporting data, as a function of the date.
		The very small population indices mean that the correction to the ZHR for naked eye magnitude is unusually small.
	www.iac.es /galeria/mrk/meteors.html (2137 words)

	2001 Leonids
		A meteor storm is defined as a shower with a ZHR >1000.
		The ZHR was about 340, well short of a storm but that didn't matter to observers who saw the event in its full glory.
		ZHRs were 150, 300, and 500, although observed rates were lower due to moonlight interference.
	skytour.homestead.com /leo2001.html (1050 words)

	NAMN Guide: Appendix A - List of Meteor Showers
		The peak itself is normally quite sharp, with ZHRs of 3+ noted for only a day or two to either side of the maximum.
		Velocity: 47 km/s Population Index: 3.0 ZHR: variable 3-10, usually ~2 NOTES: Occasionally, this shower produces enhanced activity with a ZHR of around 10, but on average, expect ZHRs to be 4 or less.
		Velocity: 20 km/s Population Index: 2.6 ZHR: variable NOTES: This is a PERIODIC shower which is visible during a short period before or after the perihelion passage of its parent comet, 21P/Giacobini-Zinner.
	www.namnmeteors.org /appendixA.html (4078 words)

	Glossary (Site not responding. Last check: 2007-10-11)
		For scientific comparison purposes, an observed rate is converted to a Zenith Hourly Rate by factoring out local variables such as sky conditions (limiting magnitude), cloud cover and altitude of the radiant.
		Zenith hourly rate (ZHR): An estimated number of shower meteors a single observer would see under virtually perfect conditions: zero clouds, a limiting magnitude of 6.5, and the radiant at the zenith.
		As the last of these never occurs in practice, and would be instantaneous in any event, the ZHR is always higher than the observed rate of meteors, typically by a factor of two or more depending on other restrictions such as moonlight, clouds and/or haze, and light pollution.
	members.shaw.ca /weskyscan/glossary.htm (3268 words)

	NAMN Guide: Chapter 8 - Zenithal Hourly Rate (Site not responding. Last check: 2007-10-11)
		Of course, this is the ideal condition to observe meteors under.
		To make matters worse, the human factor is a variable that makes ZHR results less precise.
		(HR) (r)6.5 - LM ZHR = ----------------------- Sine A (57) (2.6)6.5 - 5.7 = ----------------------- Sine 60 degrees (57) (2.6).8 = -----------------------.866025404 57 X 2.14 = -----------------------.866025404 121.98 = ---------------------.866025404 = 140 ZHR
	www.namnmeteors.org /guidechap8.html (245 words)

	Latest Leonid News
		ZHR levels were above 1000 from roughly 1h20m UT to 2h45m UT corresponding to 235.26 to 235.31 degrees in solar longitude.
		ZHRs are computed with a population index of 2.0, zenithal exponent of 1.0.
		ZHR levels were above 1000 from roughly 1h30m UT to 3h00m UT corresponding to 235.26 to 235.32 degrees in solar longitude.
	www.arm.ac.uk /leonid/latest.html (2469 words)

	Last predictions before 1999 Leonids
		Introduction The highest ZHR Leonid storms of the 19th and 20th centuries, as well as many other sharp outbursts, have occurred when the Earth encountered a young dust trail within the Leonid stream.
		Changes to the ZHR fit due to the error are not substantial but a new fit is done.
		Despite the uncertainty in the observed ZHR in 1966, it is probably one of the more reliable data points used in the fit and 1833 the least reliable.
	www.arm.ac.uk /leonid/last1999.html (701 words)

	Meteor observations
		Using a population index r=2, the IMO has calculated provisional ZHR values of 2350 for the first peak and 2660 for the second peak, but notes that if the shower was richer in fainter meteors, a larger population index would be applicable and the calculated ZHR values would therefore be higher.
		The ZHR values quoted in the IMO circular of Nov 22 show the ZHR at around 100 late on Nov 18, rising to around 300 by 0240UT on Nov 19 and not exceeding 1000 (i.e.
		With the revised values, the peak ZHR was found to be around 250 per hour during the early hours of Nov 17 and the secondary peak was found to have a ZHR of around 120 per hour.
	www.theastronomer.org /meteor_observations.html (4275 words)

	Zenithal Hourly Rate - TheBestLinks.com - ZHR, Apparent magnitude, TheBestLinks.com:Find or fix a stub, ...
		ZHR, Zenithal Hourly Rate, Apparent magnitude, TheBestLinks.com:Find or fix a...
		In astronomy, the Zenithal Hourly Rate (ZHR) of a meteor shower is the number of meteors an observer would see in one hour under a clear, dark sky (limiting apparent magnitude of 6.5) and if the radiant of the shower were in the zenith.
		The rate which can effectively been seen is always lower and decreases as the radiant is closer to the horizon.
	www.thebestlinks.com /ZHR.html (145 words)

	IMO Meteor Shower Calendar 1999 \| International Meteor Organization
		Recent observations show the delta-Cancrid ZHR is unlikely to rise much above 3-4, and the visual maximum may fall around lambda = 291° (1999 January 11).
		The ZHR can be rather erratic at times, a variability also seen in 1996, when rates ranged between 10-30 from hour to hour during the peak.
		ZHR: Zenithal Hourly Rate, a calculated maximum number of meteors an ideal observer would see in perfectly clear skies with the shower radiant overhead.
	www.imo.net /calendar/cal99.html (4520 words)

	CBA Belgium Website
		I made an expedition to Braeside Observatory in Flagstaff, Arizona to observe the event, and secured a maximum ZHR value of 1426 (full results here) under very good sky conditions.
		Overall, we can expect to observe ZHR values of 3500 meteors per hour (up to 6000) in the night of November 18/19th, 2002.
		Taking into account the fact that peak activity of the 1767 and 1866 dust trails is expected to yield nearly identical ZHR values over Europe (1767 trail) and the US (1866 trail), we found no evident reasons justifying a trip to the US.
	users.skynet.be /fa079980/leonids2002/Leonids2002_expedition.htm (1107 words)

	[No title] (Site not responding. Last check: 2007-10-11)
		There is no such thing as a ZHR for a single observer- a "true" ZHR requires at least a handful of observers who together yield full sky coverage.
		The storm seems to have shown a broad plateau rather than a sharp peak and rates were continuing high as dawn broke at 20.00 UT. The meteors were bright, but not comparable to the 1998 fireballs in brilliance.
		This is the filament that we should see from the UK next year, as long as the 30 minute discrepancy does not cause the predicted time to be revised too much.
	www.theastronomer.org /tacirc/2001/e1712.txt (463 words)

	MBK Team observations: 2001 Leonid meteor storms (Site not responding. Last check: 2007-10-11)
		ZHR then drops to ~700±100 at the end of observations, between 12:30 and 12:55 UT.
		Remark: ZHR values were calculated with r=2.0 and gamma=1.0.
		ZHR values might differ from those calculate by IMO due to a smaller observation sample and individual observer perception coefficients.
	www.orion-drustvo.si /MBKTeam/meteors/leo2001.htm (179 words)

	SPA Meteor Section - The 1999 Leonids
		It predicts peaks on 2001 November 18 at 10h (ZHR ~ 2500?), 17h30m (ZHR ~ 9000?) and 18h20m UT (ZHR ~ 15,000?).
		Estimates by Lyytinen and Van Flandern for the main peak ZHR flux in 2000 were closer to those seen than any of the other main proponents in that year, so their comments are worth noting.
		The highest ZHRs are unlikely to persist for more than a few tens of minutes at most, judging by previous Leonid storm events.
	www.popastro.com /sections/meteor/leonids.htm (712 words)

	Dutch Meteor Society: Leonids 1999
		The highest ZHR Leonid storms of the 19th and 20th centuries, as well as many other sharp outbursts, have occurred when the Earth encountered a young dust trail within the Leonid stream.
		A model in which ZHR/f_M (ZHR being the observed peak ZHR in past encounters) is fitted as a function of Delta a_0 and r_E-r_D, as described in [1], is done, and applied to the future years.
		One interesting change to the ZHR fit, is that the predicted ZHR in 1801 from the 2-rev trail is now 300.
	www.xs4all.nl /~dmsweb/leonids/1999/leonid5.html (1439 words)

	(meteorobs) ZHR and HR confusion (Site not responding. Last check: 2007-10-11)
		This is not equal to the Zenith Hourly Rate, which is reached by correcting the Hourly Rates observed for deviating limiting magnitude and radiant altitude.
		A zenith hourly rate (ZHR) strictly speaking is what an 'standard' observer would observe if he had the radiant in the zenith and a limiting mgnitude of +6.5.
		The Japanese observed with low radiant altitude and low Limiting magnitude due to moonlight, so their HR is much lower than the actual ZHR computed from it.
	www.meteorobs.org /maillist/msg09815.html (188 words)

	ZHR - Competition (Site not responding. Last check: 2007-10-11)
		The Slovak Association of Hotels and Restaurants (ZHR SR) incooperation with a general sponsor Nestlé Slovensko Ltd. advertise a competition "Restaurant of the year 2002".
		The entry forms to copy can be found on the internet site ZHR SR: www.zhr.sk, where the evaluation criteria for the competition are published as well.
		Written entry forms must be sent by 15 September 2002 to the address: ZHR SR, Námestie Slobody 2, 974 01 Banská Bystrica.
	www.zhr.sk /ang/sutaz.htm (430 words)

	The October Leonid Forecast for 2002 (Site not responding. Last check: 2007-10-11)
		The model of Lyytinen/Van Flandern also has very modest ZHR contribution from the 1833 Leonid trail (maximum ZHR of 160 around 06:30 UT) and that of Jenniskens has a small contribution from the same trail (maximum ZHR of 28 at 06:00 UT) and that from 1799 (maximum ZHR of 51 at 04:50 UT).
		The reader is reminded that latest Asher/McNaught forecast has much smaller maxima (1000 ZHR as opposed to 3000 for 1st peak, and 6000 opposed to 10,000 for the second).
		However, because the shape of the ZHR profile changed from a Gaussian to a Lorentzian, the fluences remain roughly equivalent (broader activity profiles).
	www.spaceweather.com /leonids (1521 words)

	C&MS: The Chi Orionids (Site not responding. Last check: 2007-10-11)
		The Northern Chi Orionids are active during November 16-December 16, with a maximum ZHR of two coming on December 10 (solar longitude=258 deg) from RA=82 deg, DEC=+23 deg.
		The Southern Chi Orionids are active during December 2-18, with a maximum ZHR of three coming on December 10 (solar longitude=258 deg) from RA=88 deg, DEC=+20 deg.
		A maximum ZHR of 2.84 came on the 11th from RA=84 deg, DEC=+25 deg.
	comets.amsmeteors.org /meteors/showers/chi_orionids.html (1059 words)

	2001 Leonid Meteor Storm (Site not responding. Last check: 2007-10-11)
		The Leonid storm of 1966 was one of the greatest in history, with a peak ZHR of about 100,000.
		Comet Temple-Tuttle reached perihelion (closest approach to the Sun) in February 1998, and the 1998 Leonids were characterized by a fireball display of unusually bright meteors peaking at a ZHR of about 350.
		The International Meteor Society estimates that the first peak ZHR was about 1400/hr.
	webpages.charter.net /alsonwongweb/20014.htm (596 words)

	British Astronomical Association - Meteor Section
		By Aug 10-11, a marked increase in activity was evident, ZHR climbing towards the mid-20s.
		Activity was certainly climbing late on the Thursday-Friday of Aug 11-12, with ZHR 60-70 towards dawn.
		Fewer data are available for Aug 14-15, but it appears that by then ZHR was falling off towards the 20s, and lower still on Aug 15-16 as the usual rapid decline set in.
	www.britastro.org /meteor (4111 words)

	Re: (meteorobs) n, HR, ZHR
		At best, you have an EZHR (estimated ZHR, usually used for high rates in short periods).
		A ZHR can be given along with this, but it's nice to know what the ZHR was calculated from.
		> > Notice that most observers give their results by ZHR, since it is the > best to compare ur results with other observers have different > observational conditions, which will be equalized after applying the ZHR > formula.
	www.meteorobs.org /maillist/msg10540.html (600 words)

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