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Mount Pinos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Pinos clear sky chart from 2003-08-01 to 2005-11-07.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	6% 5% 63%	8691
	Night	6% 5% 5% 57%	8477
Transparency	Day	6% 6% 20% 33% 32%	7105
	Night	9% 9% 22% 32% 26%	6753
Seeing	Day	15% 33% 42% 9%	638
	Night	8% 21% 34% 31%	2922

By Month

Percentage Cloud Cover
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month		Occurrence of each Forecast	Data Points
January	Day	15% 8% 6% 7% 6% 35%	535
	Night	9% 10% 8% 8% 5% 5% 6% 35%	818
February	Day	21% 11% 12% 7% 7% 5% 18%	561
	Night	21% 8% 10% 7% 5% 7% 24%	684
March	Day	7% 5% 6% 6% 7% 48%	673
	Night	7% 5% 5% 5% 5% 7% 7% 45%	688
April	Day	6% 6% 6% 6% 53%	720
	Night	5% 5% 59%	600
May	Day	5% 5% 5% 62%	789
	Night	5% 64%	574
June	Day	85%	840
	Night	5% 80%	478
July	Day	85%	822
	Night	82%	530
August	Day	6% 76%	1114
	Night	72%	929
September	Day	85%	1015
	Night	79%	930
October	Day	5% 5% 69%	636
	Night	7% 66%	728
November	Day	11% 8% 52%	469
	Night	6% 5% 6% 5% 5% 8% 45%	697
December	Day	16% 5% 7% 5% 5% 5% 41%	517
	Night	11% 6% 7% 7% 5% 43%	821

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	10% 9% 37% 36% 5%	302
	Night	12% 10% 33% 31% 12%	462
February	Day	25% 15% 20% 32% 6%	183
	Night	23% 17% 24% 24% 9%	282
March	Day	12% 13% 26% 31% 15%	449
	Night	20% 11% 28% 22% 16%	480
April	Day	12% 11% 28% 27% 19%	528
	Night	13% 12% 25% 33% 15%	464
May	Day	8% 10% 24% 35% 20%	640
	Night	11% 13% 28% 30% 15%	466
June	Day	21% 47% 24%	799
	Night	9% 28% 46% 11%	445
July	Day	16% 30% 50%	760
	Night	6% 13% 39% 38%	476
August	Day	16% 31% 45%	1000
	Night	8% 21% 34% 29%	806
September	Day	7% 26% 62%	969
	Night	9% 37% 48%	851
October	Day	9% 21% 36% 30%	794
	Night	10% 26% 24% 34%	947
November	Day	10% 9% 39% 32% 8%	384
	Night	14% 16% 25% 29% 14%	563
December	Day	9% 14% 45% 27%	297
	Night	9% 17% 38% 31%	511

Seeing (when cloud cover <= 80%)
Color Meanings: Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month		Occurrence of each Forecast	Data Points
January	Day	18% 35% 35% 10%	37
	Night	18% 29% 32% 19%	234
February	Day	42% 34% 21%	38
	Night	25% 29% 33% 11%	186
March	Day	23% 40% 30% 5%	59
	Night	8% 34% 32% 21%	239
April	Day	27% 46% 20% 5%	54
	Night	9% 31% 40% 17%	232
May	Day	21% 39% 34%	61
	Night	5% 25% 41% 24%	200
June	Day	10% 30% 47% 11%	59
	Night	13% 25% 55% 5%	120
July	Day	12% 67% 16%	62
	Night	11% 71% 14%	157
August	Day	23% 66% 7%	90
	Night	7% 33% 50% 6%	363
September	Day	11% 32% 44% 11%	89
	Night	13% 36% 44%	358
October	Day	13% 40% 31% 13%	88
	Night	20% 36% 33% 6%	366
November	Day	100%	1
	Night	12% 37% 33% 16%	249
December	Night	18% 23% 39% 15%	218

Page generated at 2008-06-05 20:07:37. Version ab11