Starburst Meadows Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starburst Meadows Observatory 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	21% 5% 6% 5% 7% 34%	8706
	Night	23% 5% 5% 5% 6% 34%	8464
Transparency	Day	18% 16% 38% 24%	4517
	Night	18% 16% 42% 20%	4200
Seeing	Day	12% 31% 28% 21% 5%	549
	Night	16% 34% 32% 15%	2272

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	18% 6% 5% 45%	490
	Night	16% 7% 6% 5% 5% 38%	863
February	Day	15% 5% 5% 6% 46%	546
	Night	18% 7% 45%	707
March	Day	19% 5% 7% 5% 38%	664
	Night	20% 6% 5% 6% 8% 35%	700
April	Day	26% 6% 5% 5% 5% 6% 30%	751
	Night	29% 5% 5% 34%	568
May	Day	33% 5% 5% 6% 27%	825
	Night	37% 7% 6% 5% 6% 20%	529
June	Day	19% 5% 6% 7% 5% 5% 11% 28%	840
	Night	21% 5% 7% 7% 6% 7% 30%	476
July	Day	18% 5% 6% 5% 6% 8% 9% 28%	866
	Night	26% 7% 6% 9% 27%	496
August	Day	22% 5% 6% 5% 6% 9% 29%	1192
	Night	25% 6% 6% 5% 7% 27%	846
September	Day	18% 7% 49%	994
	Night	19% 5% 6% 44%	951
October	Day	26% 5% 5% 6% 6% 34%	608
	Night	30% 6% 6% 5% 9% 23%	754
November	Day	18% 6% 5% 6% 8% 35%	474
	Night	25% 6% 5% 36%	692
December	Day	24% 5% 5% 5% 5% 5% 5% 32%	456
	Night	21% 5% 6% 6% 5% 34%	882

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	11% 14% 40% 32%	274
	Night	20% 9% 43% 26%	420
February	Day	15% 13% 38% 31%	323
	Night	25% 9% 39% 23%	396
March	Day	23% 14% 48% 13%	323
	Night	26% 19% 36% 18%	341
April	Day	20% 11% 33% 32%	344
	Night	18% 12% 40% 23%	259
May	Day	23% 10% 46% 18%	314
	Night	20% 11% 36% 24% 6%	177
June	Day	20% 14% 38% 23%	395
	Night	19% 11% 48% 19%	213
July	Day	26% 13% 34% 22%	394
	Night	28% 11% 35% 22%	206
August	Day	17% 23% 32% 22%	566
	Night	14% 21% 37% 24%	374
September	Day	8% 17% 39% 31%	641
	Night	7% 15% 48% 24%	543
October	Day	14% 22% 46% 16%	447
	Night	19% 26% 44% 7%	477
November	Day	19% 15% 38% 24%	288
	Night	20% 21% 34% 23%	376
December	Day	29% 22% 25% 19%	208
	Night	15% 17% 51% 15%	418

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	26% 47% 20% 5%	212
February	Day	11% 48% 25% 11%	43
	Night	14% 49% 24% 10%	187
March	Day	15% 42% 26% 15%	52
	Night	21% 40% 27% 11%	200
April	Day	14% 33% 40% 7%	42
	Night	11% 46% 38%	150
May	Day	36% 34% 21%	41
	Night	15% 30% 35% 17%	115
June	Day	9% 33% 31% 21%	51
	Night	12% 18% 49% 19%	108
July	Day	7% 15% 47% 23% 5%	51
	Night	13% 17% 46% 17%	96
August	Day	8% 29% 26% 25% 9%	71
	Night	8% 23% 41% 26%	234
September	Day	6% 26% 23% 33% 9%	72
	Night	10% 26% 32% 28%	307
October	Day	18% 29% 21% 22% 8%	71
	Night	18% 26% 32% 18%	276
November	Day	25% 29% 21% 23%	51
	Night	18% 41% 27% 12%	196
December	Day	50% 25% 25%	4
	Night	20% 41% 26% 10%	191

Page generated at 2008-08-29 16:03:11. Version ab11