Ogden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ogden 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	14% 5% 5% 7% 45%	8717
	Night	16% 5% 5% 7% 41%	8445
Cloud Cover	Day	15% 5% 5% 7% 46%	8712
	Night	18% 5% 5% 6% 42%	8455
Transparency	Day	15% 12% 28% 29% 13%	5421
	Night	16% 16% 30% 24% 12%	4899
Seeing	Day	13% 28% 41% 16%	544
	Night	8% 20% 37% 30%	2650

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	26% 7% 6% 7% 5% 10% 20%	549
	Night	26% 7% 6% 5% 5% 6% 9% 22%	804
February	Day	27% 6% 8% 5% 6% 28%	537
	Night	29% 5% 8% 31%	717
March	Day	13% 5% 5% 5% 8% 45%	675
	Night	17% 5% 5% 8% 43%	689
April	Day	17% 5% 5% 6% 5% 6% 39%	739
	Night	15% 6% 5% 5% 7% 42%	579
May	Day	12% 5% 5% 6% 9% 42%	804
	Night	17% 5% 5% 7% 40%	549
June	Day	8% 6% 6% 8% 13% 44%	846
	Night	8% 8% 7% 9% 9% 41%	469
July	Day	5% 6% 7% 58%	813
	Night	7% 5% 7% 9% 50%	546
August	Day	6% 5% 6% 60%	1204
	Night	5% 5% 7% 8% 50%	837
September	Day	9% 5% 61%	969
	Night	7% 64%	966
October	Day	17% 7% 46%	626
	Night	20% 5% 5% 6% 42%	738
November	Day	21% 5% 7% 5% 5% 35%	453
	Night	18% 5% 6% 5% 5% 6% 5% 5% 33%	712
December	Day	32% 6% 5% 6% 27%	502
	Night	28% 5% 5% 5% 5% 6% 28%	839

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	29% 6% 5% 7% 5% 5% 27%	549
	Night	28% 7% 5% 7% 5% 6% 6% 26%	804
February	Day	29% 7% 5% 5% 30%	528
	Night	31% 5% 6% 32%	717
March	Day	15% 5% 7% 46%	674
	Night	18% 7% 44%	688
April	Day	19% 6% 6% 6% 40%	740
	Night	16% 6% 5% 5% 6% 44%	579
May	Day	13% 5% 5% 6% 8% 42%	806
	Night	19% 5% 5% 5% 6% 40%	558
June	Day	9% 6% 5% 7% 13% 44%	846
	Night	9% 8% 6% 9% 8% 41%	469
July	Day	5% 7% 59%	805
	Night	7% 5% 8% 8% 49%	546
August	Day	6% 6% 61%	1206
	Night	5% 5% 5% 5% 7% 8% 50%	837
September	Day	9% 5% 5% 61%	978
	Night	7% 5% 64%	968
October	Day	17% 6% 47%	626
	Night	21% 6% 6% 6% 41%	738
November	Day	23% 6% 5% 35%	452
	Night	21% 5% 5% 5% 7% 34%	712
December	Day	34% 5% 5% 7% 28%	502
	Night	31% 5% 5% 5% 29%	839

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	37% 26% 34%	197
	Night	31% 24% 37% 7%	309
February	Day	26% 21% 43% 8%	181
	Night	19% 19% 48% 11%	277
March	Day	24% 17% 35% 20%	395
	Night	23% 17% 32% 23%	373
April	Day	15% 11% 46% 19% 7%	371
	Night	15% 17% 36% 25%	311
May	Day	20% 9% 25% 37% 7%	462
	Night	14% 17% 30% 27% 10%	281
June	Day	12% 8% 35% 40%	569
	Night	13% 10% 35% 37%	282
July	Day	10% 16% 34% 35%	614
	Night	11% 19% 31% 32%	383
August	Day	8% 7% 15% 43% 24%	898
	Night	9% 9% 21% 36% 22%	577
September	Day	7% 8% 19% 38% 26%	715
	Night	6% 8% 25% 29% 30%	746
October	Day	14% 16% 37% 25% 6%	592
	Night	12% 16% 29% 30% 10%	683
November	Day	21% 28% 39% 10%	221
	Night	28% 29% 34%	326
December	Day	33% 31% 33%	206
	Night	31% 32% 32%	351

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	11% 21% 31% 26% 10%	200
February	Day	20% 20% 25% 35%	20
	Night	9% 23% 41% 23%	172
March	Day	21% 31% 33% 14%	57
	Night	5% 18% 49% 26%	218
April	Day	23% 32% 35% 8%	56
	Night	12% 29% 27% 25%	181
May	Day	14% 36% 45%	55
	Night	9% 32% 34% 23%	167
June	Day	14% 27% 42% 14%	102
	Night	11% 28% 37% 21%	153
July	Day	19% 58% 19%	62
	Night	8% 41% 48%	170
August	Day	13% 21% 48% 16%	91
	Night	11% 37% 45%	270
September	Day	8% 34% 37% 19%	86
	Night	19% 33% 38%	336
October	Day	6% 20% 20% 46% 6%	15
	Night	6% 17% 37% 31% 7%	329
November	Night	14% 23% 35% 24%	227
December	Night	12% 17% 47% 22%	227

Page generated at 2008-08-29 14:03:10. Version ab11