Lockwood Valley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lockwood Valley 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	7% 5% 64%	8692
	Night	7% 5% 5% 58%	8476
Transparency	Day	5% 20% 34% 36%	7069
	Night	8% 23% 33% 31%	6712
Seeing	Day	13% 33% 43% 8%	623
	Night	9% 22% 35% 28%	2843

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	19% 6% 5% 5% 5% 6% 37%	536
	Night	15% 6% 7% 5% 5% 6% 36%	818
February	Day	27% 8% 9% 5% 7% 5% 19%	561
	Night	25% 8% 6% 6% 5% 7% 25%	684
March	Day	5% 6% 5% 7% 49%	673
	Night	5% 5% 5% 9% 5% 6% 6% 46%	687
April	Day	6% 6% 5% 6% 56%	720
	Night	6% 5% 7% 61%	600
May	Day	5% 5% 64%	788
	Night	5% 5% 66%	576
June	Day	87%	840
	Night	83%	478
July	Day	85%	821
	Night	5% 83%	530
August	Day	5% 77%	1114
	Night	5% 5% 72%	929
September	Day	85%	1016
	Night	81%	930
October	Day	6% 71%	636
	Night	5% 5% 67%	728
November	Day	11% 5% 7% 53%	470
	Night	6% 5% 5% 7% 5% 7% 48%	696
December	Day	21% 6% 5% 5% 41%	517
	Night	14% 5% 5% 7% 6% 43%	820

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	45% 38% 7%	303
	Night	5% 6% 35% 38% 13%	461
February	Day	12% 21% 25% 34% 5%	187
	Night	10% 22% 32% 21% 13%	284
March	Day	6% 13% 29% 33% 17%	448
	Night	18% 28% 25% 22%	477
April	Day	7% 10% 28% 32% 21%	527
	Night	8% 8% 28% 37% 17%	467
May	Day	10% 27% 35% 23%	638
	Night	16% 30% 27% 20%	468
June	Day	21% 42% 32%	801
	Night	7% 31% 42% 17%	447
July	Day	14% 30% 52%	754
	Night	5% 14% 37% 42%	470
August	Day	14% 31% 48%	999
	Night	7% 20% 32% 38%	809
September	Day	26% 67%	946
	Night	7% 34% 57%	836
October	Day	6% 20% 34% 36%	782
	Night	8% 23% 28% 37%	943
November	Day	9% 39% 34% 11%	382
	Night	11% 34% 29% 19%	550
December	Day	7% 12% 47% 32%	302
	Night	5% 14% 41% 36%	500

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	25% 33% 30% 11%	36
	Night	20% 29% 27% 21%	215
February	Day	40% 34% 20% 5%	35
	Night	25% 29% 33% 11%	168
March	Day	22% 43% 24% 8%	57
	Night	10% 38% 29% 18%	233
April	Day	29% 41% 25%	51
	Night	11% 33% 39% 14%	223
May	Day	16% 46% 31% 5%	60
	Night	5% 30% 38% 21%	201
June	Day	10% 27% 54% 8%	59
	Night	12% 33% 50%	120
July	Day	13% 68% 18%	60
	Night	19% 62% 15%	158
August	Day	26% 67% 6%	88
	Night	5% 39% 44% 6%	363
September	Day	12% 28% 50% 8%	90
	Night	18% 35% 39%	357
October	Day	10% 45% 32% 10%	86
	Night	6% 20% 40% 27% 5%	366
November	Day	100%	1
	Night	14% 34% 34% 15%	237
December	Night	14% 25% 41% 15%	202

Page generated at 2008-08-27 04:51:59. Version ab11