Columbus
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Columbus clear sky chart from 2005-11-06 to 2026-02-16.

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	12% 6% 2 6% 5% 4 5% 4 6% 8% 42%	131119
	Night	14% 7% 2 5% 4 3 3 3 5% 7% 46%	130033
Transparency	Day	38% 6% 11% 20% 16% 8%	134823
	Night	37% 5% 11% 20% 17% 10%	134380
Seeing	Day	12% 7% 19% 26% 24% 11%	16442
	Night	15% 7% 23% 34% 19% 2	26452

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 11% 3 6% 3 3 3 2 3 5% 44%	5289
	11th to 20th	Day	13% 6% 2 6% 4 3 3 2 3 5% 52%	5310
	21st to end	Day	27% 8% 3 8% 3 3 2 2 4 5% 34%	5849
February	1st to 10th	Day	20% 9% 2 5% 4 3 3 3 4 5% 41%	2100
	11th to 20th	Day	20% 9% 3 6% 5% 4 4 3 3 6% 39%	1999
	21st to end	Day	18% 8% 2 6% 4 3 3 2 5% 5% 42%	1746
March	1st to 10th	Day	13% 6% 2 7% 5% 4 5% 4 6% 7% 42%	4936
	11th to 20th	Day	13% 7% 2 7% 5% 4 3 2 4 5% 46%	4980
	21st to end	Day	18% 8% 2 6% 4 3 4 3 5% 6% 40%	5462
April	1st to 10th	Day	14% 9% 3 6% 5% 5% 5% 3 6% 5% 39%	2200
	11th to 20th	Day	16% 6% 3 7% 5% 5% 4 4 5% 6% 39%	2243
	21st to end	Day	12% 8% 3 7% 6% 5% 4 4 5% 6% 42%	2400
May	1st to 10th	Day	18% 7% 3 7% 5% 5% 5% 4 7% 8% 31%	5813
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 8% 44%	5862
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 8% 10% 37%	6434
June	1st to 10th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 10% 45%	2600
	11th to 20th	Day	6% 3 2 6% 4 5% 7% 6% 8% 11% 42%	2600
	21st to end	Day	6% 6% 3 8% 7% 7% 8% 5% 9% 10% 32%	2600
July	1st to 10th	Day	8% 6% 2 7% 6% 6% 6% 5% 7% 11% 35%	5900
	11th to 20th	Day	5% 5% 3 7% 5% 6% 7% 6% 9% 13% 34%	5900
	21st to end	Day	9% 6% 2 6% 5% 6% 5% 5% 7% 11% 36%	6422
August	1st to 10th	Day	1 1 1 3 4 4 4 4 6% 10% 62%	4234
	11th to 20th	Day	3 2 1 4 4 5% 6% 6% 10% 14% 46%	4143
	21st to end	Day	5% 3 2 8% 6% 7% 7% 5% 8% 10% 39%	3951
September	1st to 10th	Day	6% 6% 2 8% 6% 5% 5% 5% 6% 10% 40%	2200
	11th to 20th	Day	9% 7% 3 8% 5% 5% 5% 4 6% 7% 41%	2200
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 6% 8% 47%	2200
October	1st to 10th	Day	5% 3 2 4 4 4 5% 4 6% 8% 56%	2158
	11th to 20th	Day	11% 5% 2 5% 4 3 3 4 5% 6% 52%	2000
	21st to end	Day	12% 5% 2 4 4 4 4 3 4 6% 52%	2200
November	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 4 7% 48%	2058
	11th to 20th	Day	11% 6% 2 6% 4 3 4 3 5% 6% 51%	2100
	21st to end	Day	15% 7% 3 7% 4 4 4 3 6% 6% 40%	1932
December	1st to 10th	Day	26% 8% 3 7% 4 3 3 3 3 6% 36%	3030
	11th to 20th	Day	15% 8% 3 7% 4 3 4 4 4 5% 43%	3481
	21st to end	Day	14% 7% 2 6% 3 3 3 2 4 6% 49%	4587
January	1st to 10th	Night	19% 7% 2 5% 3 3 3 2 3 5% 48%	7634
	11th to 20th	Night	11% 6% 2 5% 3 3 3 2 3 5% 55%	7680
	21st to end	Night	30% 8% 2 6% 3 2 3 2 4 5% 35%	8402
February	1st to 10th	Night	20% 10% 3 5% 3 3 3 3 4 5% 42%	2525
	11th to 20th	Night	23% 8% 3 5% 3 3 2 2 4 6% 43%	2398
	21st to end	Night	23% 9% 2 6% 4 3 3 3 3 5% 40%	1881
March	1st to 10th	Night	19% 10% 2 5% 3 3 4 3 5% 6% 39%	4919
	11th to 20th	Night	19% 8% 2 5% 3 3 2 3 4 5% 45%	4980
	21st to end	Night	20% 11% 2 5% 4 3 3 3 4 5% 41%	5467
April	1st to 10th	Night	14% 8% 2 5% 4 3 4 4 6% 8% 41%	2200
	11th to 20th	Night	17% 7% 2 7% 4 3 3 3 5% 6% 43%	2105
	21st to end	Night	15% 8% 2 6% 4 3 4 4 4 6% 44%	2000
May	1st to 10th	Night	24% 10% 3 6% 4 4 4 3 5% 7% 29%	4082
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 5% 8% 45%	4053
	21st to end	Night	12% 9% 3 8% 5% 5% 5% 5% 6% 9% 33%	4443
June	1st to 10th	Night	5% 4 1 4 4 3 4 3 6% 9% 56%	1800
	11th to 20th	Night	5% 3 2 5% 3 4 4 3 6% 9% 55%	1800
	21st to end	Night	5% 5% 2 5% 5% 4 5% 5% 8% 10% 46%	1800
July	1st to 10th	Night	7% 5% 3 6% 4 4 5% 5% 8% 12% 42%	4078
	11th to 20th	Night	4 5% 1 6% 4 5% 5% 4 7% 11% 49%	4077
	21st to end	Night	7% 6% 2 6% 4 5% 4 4 6% 11% 44%	4449
August	1st to 10th	Night	1 1 2 2 2 2 2 5% 10% 72%	2926
	11th to 20th	Night	1 2 1 3 2 3 5% 4 8% 12% 59%	2911
	21st to end	Night	3 3 1 5% 3 4 5% 4 8% 12% 50%	3941
September	1st to 10th	Night	5% 5% 2 7% 4 5% 5% 4 7% 8% 48%	2200
	11th to 20th	Night	8% 6% 2 7% 5% 4 3 4 6% 8% 48%	2200
	21st to end	Night	7% 4 2 5% 4 3 4 4 6% 8% 54%	2200
October	1st to 10th	Night	4 4 1 3 3 2 3 3 5% 9% 62%	2220
	11th to 20th	Night	10% 4 1 4 3 3 3 2 4 6% 60%	2400
	21st to end	Night	11% 5% 2 4 3 3 3 2 4 4 61%	2640
November	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 6% 53%	2460
	11th to 20th	Night	11% 7% 2 6% 3 3 3 3 4 5% 53%	2520
	21st to end	Night	16% 7% 2 6% 4 3 3 3 4 6% 46%	2683
December	1st to 10th	Night	24% 10% 3 8% 4 3 3 3 4 5% 33%	4380
	11th to 20th	Night	17% 9% 3 5% 3 3 3 2 4 5% 45%	4946
	21st to end	Night	16% 7% 2 5% 2 3 3 2 3 5% 52%	6633

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	45% 4 6% 19% 19% 7%	5290
	11th to 20th	Day	37% 3 4 18% 21% 17%	5310
	21st to end	Day	53% 3 4 11% 18% 11%	5849
February	1st to 10th	Day	47% 4 5% 12% 18% 13%	2100
	11th to 20th	Day	49% 4 7% 14% 17% 9%	2009
	21st to end	Day	43% 5% 9% 15% 17% 11%	1746
March	1st to 10th	Day	40% 5% 7% 18% 15% 15%	4936
	11th to 20th	Day	40% 4 6% 9% 17% 23%	4980
	21st to end	Day	45% 4 7% 19% 19% 7%	5464
April	1st to 10th	Day	45% 6% 6% 17% 15% 11%	2200
	11th to 20th	Day	46% 5% 7% 15% 18% 10%	2243
	21st to end	Day	42% 5% 7% 20% 18% 7%	2400
May	1st to 10th	Day	47% 7% 10% 20% 12% 3	5851
	11th to 20th	Day	37% 7% 10% 21% 20% 4	5866
	21st to end	Day	38% 7% 12% 29% 12% 1	6447
June	1st to 10th	Day	31% 8% 15% 27% 17% 2	2600
	11th to 20th	Day	31% 10% 14% 24% 18% 3	2600
	21st to end	Day	41% 12% 14% 22% 10% 1	2600
July	1st to 10th	Day	39% 9% 26% 22% 3	5836
	11th to 20th	Day	37% 11% 22% 23% 7%	5831
	21st to end	Day	38% 10% 18% 24% 9% 1	6240
August	1st to 10th	Day	17% 7% 14% 42% 20%	4220
	11th to 20th	Day	24% 11% 29% 29% 6% 1	4182
	21st to end	Day	35% 12% 17% 22% 12% 1	3950
September	1st to 10th	Day	38% 10% 13% 20% 14% 6%	2200
	11th to 20th	Day	39% 9% 12% 20% 17% 4	2200
	21st to end	Day	32% 9% 11% 19% 16% 13%	2200
October	1st to 10th	Day	17% 4 6% 14% 21% 38%	3509
	11th to 20th	Day	23% 4 6% 18% 33% 17%	3240
	21st to end	Day	28% 5% 5% 20% 28% 15%	3538
November	1st to 10th	Day	36% 6% 8% 17% 23% 10%	2058
	11th to 20th	Day	34% 5% 9% 17% 21% 14%	2100
	21st to end	Day	44% 5% 7% 14% 17% 11%	1932
December	1st to 10th	Day	51% 4 5% 15% 19% 5%	3030
	11th to 20th	Day	42% 5% 7% 12% 22% 11%	3479
	21st to end	Day	37% 4 5% 18% 23% 13%	4587
January	1st to 10th	Night	41% 3 8% 18% 19% 12%	7635
	11th to 20th	Night	34% 3 3 19% 25% 16%	7680
	21st to end	Night	53% 3 4 13% 17% 11%	8402
February	1st to 10th	Night	45% 4 7% 11% 18% 15%	2525
	11th to 20th	Night	44% 4 7% 16% 18% 12%	2398
	21st to end	Night	48% 4 6% 12% 16% 13%	1881
March	1st to 10th	Night	46% 4 7% 15% 16% 11%	4919
	11th to 20th	Night	43% 4 5% 13% 14% 20%	4980
	21st to end	Night	46% 4 7% 14% 19% 9%	5467
April	1st to 10th	Night	40% 6% 10% 18% 16% 10%	2200
	11th to 20th	Night	42% 5% 9% 15% 15% 14%	2105
	21st to end	Night	41% 5% 10% 20% 17% 8%	2000
May	1st to 10th	Night	54% 6% 8% 18% 10% 4	4109
	11th to 20th	Night	36% 6% 11% 24% 17% 6%	4054
	21st to end	Night	45% 8% 14% 25% 7% 1	4452
June	1st to 10th	Night	24% 7% 17% 34% 18% 1	1800
	11th to 20th	Night	25% 7% 16% 31% 17% 4	1800
	21st to end	Night	29% 10% 21% 26% 12% 1	1800
July	1st to 10th	Night	34% 8% 30% 24% 3	4035
	11th to 20th	Night	29% 8% 25% 31% 7%	4026
	21st to end	Night	33% 9% 21% 26% 10% 1	4320
August	1st to 10th	Night	9% 4 18% 49% 19%	2916
	11th to 20th	Night	16% 8% 34% 35% 6% 1	2938
	21st to end	Night	25% 12% 23% 27% 11% 1	3941
September	1st to 10th	Night	31% 10% 18% 21% 15% 6%	2200
	11th to 20th	Night	33% 8% 15% 25% 15% 4	2200
	21st to end	Night	26% 7% 15% 22% 18% 12%	2200
October	1st to 10th	Night	15% 4 8% 17% 18% 38%	3623
	11th to 20th	Night	17% 2 8% 22% 32% 19%	3899
	21st to end	Night	21% 3 5% 23% 30% 17%	4252
November	1st to 10th	Night	32% 6% 9% 20% 22% 12%	2460
	11th to 20th	Night	34% 4 11% 17% 21% 13%	2520
	21st to end	Night	40% 4 8% 17% 18% 12%	2683
December	1st to 10th	Night	54% 4 5% 13% 16% 7%	4380
	11th to 20th	Night	43% 4 9% 9% 20% 15%	4947
	21st to end	Night	36% 4 5% 15% 29% 11%	6633

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	24% 13% 33% 22% 7% 1	330
	11th to 20th	Day	21% 15% 31% 24% 8% 1	330
	21st to end	Day	23% 15% 32% 21% 8% 1	363
February	1st to 10th	Day	25% 14% 25% 25% 9%	330
	11th to 20th	Day	25% 21% 30% 18% 6% 1	315
	21st to end	Day	27% 16% 35% 18% 4	249
March	1st to 10th	Day	20% 18% 37% 19% 5%	300
	11th to 20th	Day	16% 19% 41% 18% 5% 1	300
	21st to end	Day	19% 16% 32% 25% 7% 1	330
April	1st to 10th	Day	19% 18% 35% 20% 7%	300
	11th to 20th	Day	20% 13% 33% 25% 8% 1	361
	21st to end	Day	17% 12% 32% 27% 11% 1	500
May	1st to 10th	Day	13% 11% 39% 25% 11%	680
	11th to 20th	Day	13% 10% 27% 32% 16% 3	725
	21st to end	Day	11% 5% 26% 35% 19% 3	789
June	1st to 10th	Day	6% 2 12% 37% 32% 11%	730
	11th to 20th	Day	8% 1 12% 38% 33% 8%	730
	21st to end	Day	8% 2 9% 29% 35% 18%	730
July	1st to 10th	Day	8% 4 6% 27% 36% 20%	721
	11th to 20th	Day	4 1 5% 22% 46% 22%	718
	21st to end	Day	4 1 5% 25% 44% 22%	794
August	1st to 10th	Day	2 1 3 20% 47% 27%	726
	11th to 20th	Day	4 1 4 20% 46% 24%	700
	21st to end	Day	9% 1 4 16% 29% 41%	365
September	1st to 10th	Day	8% 1 4 23% 36% 28%	330
	11th to 20th	Day	7% 1 6% 22% 38% 26%	330
	21st to end	Day	9% 1 6% 28% 37% 19%	330
October	1st to 10th	Day	4 3 8% 30% 40% 15%	330
	11th to 20th	Day	9% 4 15% 33% 26% 13%	330
	21st to end	Day	18% 9% 20% 24% 22% 7%	363
November	1st to 10th	Day	13% 8% 18% 34% 20% 7%	330
	11th to 20th	Day	15% 7% 21% 35% 19% 3	330
	21st to end	Day	19% 15% 31% 22% 11% 3	330
December	1st to 10th	Day	20% 8% 34% 22% 12% 4	330
	11th to 20th	Day	19% 16% 28% 25% 10% 2	330
	21st to end	Day	19% 8% 35% 25% 11% 2	363
January	1st to 10th	Night	22% 9% 31% 30% 8%	1050
	11th to 20th	Night	22% 11% 30% 30% 7%	1050
	21st to end	Night	25% 10% 30% 30% 6%	1155
February	1st to 10th	Night	25% 11% 30% 29% 4	845
	11th to 20th	Night	27% 11% 31% 25% 5%	804
	21st to end	Night	28% 13% 34% 22% 3	561
March	1st to 10th	Night	22% 11% 36% 28% 3	600
	11th to 20th	Night	20% 12% 33% 30% 5%	600
	21st to end	Night	17% 9% 40% 29% 4 1	660
April	1st to 10th	Night	16% 10% 39% 31% 4	600
	11th to 20th	Night	19% 11% 34% 29% 6%	593
	21st to end	Night	18% 12% 35% 28% 7% 1	600
May	1st to 10th	Night	17% 10% 35% 31% 6%	600
	11th to 20th	Night	13% 6% 31% 38% 13% 1	591
	21st to end	Night	9% 4 29% 40% 17% 1	650
June	1st to 10th	Night	6% 2 15% 51% 27% 1	600
	11th to 20th	Night	5% 2 17% 53% 23% 1	600
	21st to end	Night	6% 1 11% 39% 37% 6%	600
July	1st to 10th	Night	7% 1 6% 39% 41% 6%	585
	11th to 20th	Night	3 1 5% 39% 47% 4	582
	21st to end	Night	4 1 5% 39% 45% 5%	657
August	1st to 10th	Night	2 4 45% 44% 5%	597
	11th to 20th	Night	3 4 39% 47% 7%	594
	21st to end	Night	5% 5% 30% 53% 8%	660
September	1st to 10th	Night	6% 1 7% 32% 47% 7%	600
	11th to 20th	Night	9% 1 5% 35% 47% 4	600
	21st to end	Night	8% 1 11% 34% 41% 5%	600
October	1st to 10th	Night	5% 1 8% 42% 39% 4	620
	11th to 20th	Night	10% 3 20% 43% 22% 2	800
	21st to end	Night	12% 8% 23% 36% 19% 2	880
November	1st to 10th	Night	12% 6% 20% 40% 20% 2	820
	11th to 20th	Night	13% 7% 23% 39% 17% 2	840
	21st to end	Night	18% 9% 26% 32% 13% 1	1003
December	1st to 10th	Night	24% 7% 26% 30% 12% 1	1050
	11th to 20th	Night	24% 12% 26% 31% 8% 1	1050
	21st to end	Night	22% 9% 30% 30% 9%	1155

Page generated at 2026-02-13 00:42:10. Version ac07

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