Columbus
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Columbus 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	16% 6% 5% 5% 5% 7% 35%	16500
	Night	17% 7% 5% 6% 36%	16431
Cloud Cover	Day	16% 6% 5% 5% 5% 7% 35%	16514
	Night	17% 7% 5% 6% 36%	16446
Transparency	Day	14% 25% 16%	12700
	Night	13% 25% 16%	12760
Seeing	Day	18% 28% 25% 12%	977
	Night	8% 27% 33% 15%	4988

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	21% 9% 6% 8% 5% 5% 5% 27%	1009
	Night	22% 10% 6% 7% 5% 5% 28%	1689
February	Day	18% 9% 6% 9% 5% 5% 5% 6% 27%	1091
	Night	20% 10% 5% 6% 6% 5% 29%	1315
March	Day	21% 10% 5% 6% 5% 6% 25%	1305
	Night	18% 8% 5% 5% 5% 5% 6% 32%	1377
April	Day	17% 7% 6% 40%	1451
	Night	16% 7% 5% 5% 6% 38%	1153
May	Day	18% 5% 6% 5% 5% 6% 36%	1603
	Night	15% 6% 5% 6% 6% 7% 36%	1107
June	Day	10% 5% 5% 7% 6% 8% 39%	1658
	Night	9% 5% 6% 8% 9% 43%	960
July	Day	11% 5% 6% 6% 6% 8% 37%	1690
	Night	11% 5% 5% 6% 5% 5% 44%	1001
August	Day	7% 5% 6% 6% 7% 9% 43%	1537
	Night	7% 5% 6% 9% 50%	1180
September	Day	13% 6% 7% 7% 43%	1334
	Night	13% 5% 5% 7% 45%	1266
October	Day	17% 5% 5% 5% 5% 7% 38%	1230
	Night	18% 6% 5% 43%	1462
November	Day	16% 8% 5% 5% 6% 38%	1299
	Night	16% 8% 5% 6% 40%	1872
December	Day	26% 13% 5% 5% 25%	1293
	Night	27% 10% 5% 7% 5% 5% 22%	2049

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	21% 9% 5% 9% 5% 5% 5% 27%	1008
	Night	22% 10% 6% 7% 5% 28%	1688
February	Day	17% 9% 6% 9% 5% 5% 5% 6% 27%	1089
	Night	19% 9% 5% 7% 6% 5% 29%	1306
March	Day	22% 10% 5% 6% 6% 6% 25%	1326
	Night	19% 8% 5% 5% 5% 5% 6% 31%	1401
April	Day	17% 7% 6% 40%	1450
	Night	17% 7% 5% 6% 38%	1153
May	Day	18% 6% 5% 5% 6% 36%	1598
	Night	16% 6% 5% 6% 6% 7% 36%	1100
June	Day	10% 5% 5% 8% 5% 5% 8% 39%	1668
	Night	8% 5% 6% 8% 9% 43%	961
July	Day	11% 5% 5% 7% 5% 6% 8% 37%	1690
	Night	11% 5% 5% 6% 5% 44%	1002
August	Day	7% 6% 6% 6% 7% 8% 43%	1532
	Night	7% 5% 5% 5% 9% 50%	1181
September	Day	13% 6% 5% 6% 7% 43%	1333
	Night	13% 5% 5% 7% 45%	1267
October	Day	17% 5% 5% 5% 5% 5% 7% 38%	1230
	Night	18% 6% 5% 43%	1462
November	Day	16% 8% 5% 5% 6% 38%	1297
	Night	16% 8% 6% 6% 40%	1872
December	Day	26% 13% 5% 5% 5% 25%	1293
	Night	27% 9% 5% 7% 5% 5% 23%	2053

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	15% 28% 9%	684
	Night	12% 29% 11%	1136
February	Day	16% 27% 7%	797
	Night	21% 27%	971
March	Day	17% 23% 9%	914
	Night	5% 18% 26% 13%	1000
April	Day	12% 30% 19%	1134
	Night	10% 26% 22% 6%	883
May	Day	6% 12% 22% 21%	1233
	Night	8% 14% 20% 17% 8%	852
June	Day	16% 28% 19%	1284
	Night	7% 19% 26% 19% 5%	788
July	Day	5% 15% 25% 16%	1096
	Night	10% 27% 17% 8%	674
August	Day	5% 11% 26% 20% 7%	1357
	Night	12% 29% 25%	1052
September	Day	11% 21% 22% 8%	1146
	Night	11% 22% 23% 9%	1096
October	Day	10% 27% 20%	1074
	Night	7% 28% 20%	1283
November	Day	15% 27% 16%	1009
	Night	13% 25% 21%	1495
December	Day	16% 19% 7%	972
	Night	16% 20% 7%	1530

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	14% 44% 25%	498
February	Night	10% 39% 30%	389
March	Day	7% 28% 32% 7%	64
	Night	12% 38% 28% 7%	432
April	Day	10% 23% 32% 16%	110
	Night	6% 31% 39% 9%	333
May	Day	17% 17% 26% 20%	111
	Night	5% 23% 32% 23%	343
June	Day	23% 38% 19% 7%	221
	Night	14% 53% 23%	325
July	Day	15% 29% 28% 14%	182
	Night	8% 47% 29%	317
August	Day	6% 22% 39% 22%	116
	Night	8% 36% 43% 5%	346
September	Day	10% 24% 33% 19%	109
	Night	13% 32% 34% 6%	409
October	Day	23% 25% 31%	64
	Night	6% 27% 32% 14%	452
November	Night	10% 29% 33% 11%	538
December	Night	12% 35% 23% 5%	606

Page generated at 2009-12-30 05:20:52. Version ab11