Las Cruces
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Las Cruces clear sky chart from 2005-11-05 to 2008-11-27.

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	5% 7% 61%	12236
	Night	7% 61%	12193
Transparency	Day	8% 16% 29% 30%	10492
	Night	8% 16% 31% 30%	10428
Seeing	Day	15% 25% 28% 23%	577
	Night	5% 21% 41% 26%	3817

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	5% 5% 7% 11% 53%	835
	Night	5% 5% 7% 55%	1203
February	Day	5% 70%	792
	Night	5% 69%	985
March	Day	6% 68%	1023
	Night	5% 7% 64%	1016
April	Day	6% 73%	1077
	Night	7% 69%	899
May	Day	5% 8% 65%	1141
	Night	5% 5% 5% 6% 62%	905
June	Day	10% 64%	1170
	Night	6% 6% 8% 11% 53%	810
July	Day	8% 6% 6% 7% 8% 8% 12% 30%	1208
	Night	5% 5% 10% 8% 8% 14% 32%	833
August	Day	8% 5% 5% 8% 7% 8% 8% 38%	1118
	Night	6% 6% 6% 5% 8% 13% 39%	919
September	Day	9% 6% 63%	1038
	Night	5% 6% 5% 8% 57%	937
October	Day	5% 78%	920
	Night	75%	1113
November	Day	6% 74%	1090
	Night	6% 74%	1352
December	Day	7% 70%	824
	Night	70%	1221

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	8% 10% 19% 30% 21%	714
	Night	5% 8% 20% 33% 20%	979
February	Day	5% 16% 43% 28%	691
	Night	14% 45% 28%	864
March	Day	6% 15% 33% 38%	866
	Night	5% 7% 13% 36% 33%	861
April	Day	5% 23% 62%	960
	Night	6% 5% 23% 58%	786
May	Day	9% 10% 23% 45%	1034
	Night	5% 7% 11% 26% 43%	754
June	Day	10% 12% 23% 45%	1010
	Night	5% 15% 11% 20% 45%	643
July	Day	10% 17% 22% 16% 7%	720
	Night	12% 18% 24% 17% 7%	490
August	Day	11% 17% 22% 18% 5%	896
	Night	10% 18% 26% 17%	764
September	Day	6% 19% 32% 21%	962
	Night	6% 11% 20% 27% 17%	865
October	Day	12% 34% 41%	855
	Night	13% 24% 49%	1029
November	Day	19% 43% 22%	1057
	Night	14% 41% 28%	1294
December	Day	5% 30% 38% 16%	727
	Night	20% 41% 21%	1099

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	Night	5% 31% 45% 12%	358
February	Day	100%	2
	Night	8% 34% 37% 14%	313
March	Day	27% 37% 25% 7%	81
	Night	10% 30% 45% 12%	359
April	Day	28% 47% 15%	85
	Night	9% 39% 39% 8%	264
May	Day	25% 32% 31% 7%	91
	Night	7% 29% 43% 17%	276
June	Day	8% 21% 35% 29%	89
	Night	16% 45% 33%	252
July	Day	7% 38% 41%	78
	Night	5% 35% 50% 5%	238
August	Day	6% 26% 42% 16%	87
	Night	17% 61% 11%	261
September	Day	21% 26% 37%	64
	Night	7% 46% 36%	273
October	Night	16% 41% 30% 8%	360
November	Night	13% 44% 32%	459
December	Night	5% 22% 47% 21%	404

Page generated at 2008-11-27 11:47:35. Version ab11