Ogden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ogden clear sky chart from 2005-11-05 to 2009-12-29.

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	10% 6% 6% 48%	16491
	Night	11% 7% 6% 48%	16464
Transparency	Day	8% 12% 18% 20% 14%	13642
	Night	6% 14% 21% 18% 12%	13564
Seeing	Day	6% 28% 39% 19%	962
	Night	19% 39% 24%	5214

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% 14% 6% 6% 5% 6% 28%	1105
	Night	20% 12% 5% 7% 33%	1592
February	Day	15% 15% 5% 5% 5% 5% 5% 5% 27%	1026
	Night	13% 11% 5% 5% 6% 38%	1368
March	Day	12% 10% 5% 6% 5% 6% 5% 5% 7% 31%	1346
	Night	13% 11% 5% 5% 8% 38%	1376
April	Day	12% 7% 5% 9% 41%	1454
	Night	14% 7% 6% 5% 5% 5% 43%	1148
May	Day	10% 5% 5% 7% 47%	1601
	Night	7% 6% 5% 54%	1098
June	Day	6% 7% 60%	1680
	Night	5% 5% 63%	943
July	Day	5% 68%	1618
	Night	5% 5% 9% 61%	1071
August	Day	5% 71%	1603
	Night	6% 67%	1116
September	Day	6% 68%	1315
	Night	5% 70%	1287
October	Day	13% 5% 6% 49%	1233
	Night	10% 5% 5% 55%	1459
November	Day	14% 7% 8% 43%	1258
	Night	11% 5% 5% 49%	1909
December	Day	18% 16% 6% 9% 5% 25%	1252
	Night	20% 10% 5% 7% 5% 30%	2097

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	16% 25% 12%	786
	Night	14% 24% 18% 5%	1188
February	Day	13% 22% 17% 6%	723
	Night	10% 20% 30% 6%	1046
March	Day	11% 23% 24% 8%	994
	Night	7% 24% 28% 8%	1064
April	Day	10% 14% 25% 22%	1176
	Night	5% 11% 28% 22%	878
May	Day	9% 8% 23% 27% 8%	1386
	Night	7% 10% 21% 31% 11%	945
June	Day	5% 7% 12% 23% 34%	1523
	Night	10% 14% 21% 33%	867
July	Day	6% 10% 21% 48%	1192
	Night	7% 9% 22% 45%	795
August	Day	11% 35% 33%	1555
	Night	5% 9% 32% 34%	1068
September	Day	6% 19% 38% 15%	1227
	Night	5% 18% 36% 25%	1190
October	Day	6% 15% 33% 16%	1106
	Night	5% 10% 33% 23%	1327
November	Day	8% 18% 26% 18%	1020
	Night	6% 18% 26% 20% 6%	1544
December	Day	12% 18% 11%	954
	Night	7% 21% 17% 5%	1652

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% 21% 37% 15% 5%	457
February	Day	10% 41% 26%	46
	Night	24% 42% 15%	414
March	Day	7% 33% 40% 10%	117
	Night	5% 21% 45% 15%	471
April	Day	12% 44% 23% 12%	113
	Night	7% 28% 33% 19%	378
May	Day	14% 28% 33% 16%	121
	Night	15% 42% 30%	360
June	Day	21% 48% 22%	199
	Night	18% 39% 33%	299
July	Day	21% 51% 25%	109
	Night	7% 37% 47%	306
August	Day	24% 52% 19%	120
	Night	14% 40% 37%	358
September	Day	29% 26% 37%	117
	Night	11% 35% 38% 8%	441
October	Day	5% 30% 35% 15%	20
	Night	18% 37% 26%	475
November	Night	19% 42% 23% 5%	584
December	Night	24% 37% 14%	671

Page generated at 2009-12-30 03:20:41. Version ab11