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 2024-11-30.

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% 5% 5% 4 6% 8% 41%	101259
	Night	13% 7% 2 5% 4 3 4 3 5% 7% 47%	98414
Transparency	Day	38% 7% 11% 20% 17% 7%	105002
	Night	35% 6% 12% 21% 17% 10%	102785
Seeing	Day	12% 7% 19% 26% 25% 11%	14879
	Night	15% 7% 23% 34% 19% 2	24780

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	16% 10% 3 6% 3 3 4 3 4 6% 43%	2847
	11th to 20th	Day	15% 7% 2 4 3 3 2 2 3 6% 52%	2850
	21st to end	Day	24% 7% 3 6% 3 3 3 3 6% 6% 36%	3144
February	1st to 10th	Day	21% 9% 2 5% 4 3 2 3 4 5% 40%	1900
	11th to 20th	Day	19% 9% 3 5% 5% 4 4 3 3 5% 40%	1849
	21st to end	Day	18% 8% 2 6% 4 3 3 2 5% 6% 43%	1661
March	1st to 10th	Day	16% 7% 3 9% 6% 4 5% 4 7% 7% 33%	3436
	11th to 20th	Day	19% 10% 3 10% 6% 5% 4 3 5% 6% 28%	3480
	21st to end	Day	17% 7% 2 6% 4 3 4 3 5% 6% 43%	3814
April	1st to 10th	Day	14% 9% 3 6% 5% 5% 4 3 6% 6% 39%	2090
	11th to 20th	Day	17% 7% 3 7% 5% 5% 4 4 5% 6% 38%	2129
	21st to end	Day	12% 8% 3 6% 5% 4 4 4 5% 6% 43%	2280
May	1st to 10th	Day	17% 8% 3 8% 6% 5% 5% 4 7% 8% 31%	4047
	11th to 20th	Day	13% 7% 2 7% 5% 4 4 4 5% 7% 40%	4082
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 8% 10% 38%	4477
June	1st to 10th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 10% 45%	2470
	11th to 20th	Day	6% 3 2 6% 4 5% 7% 6% 7% 11% 43%	2470
	21st to end	Day	6% 6% 3 8% 7% 7% 8% 5% 9% 10% 31%	2470
July	1st to 10th	Day	8% 5% 2 5% 5% 5% 6% 4 7% 12% 42%	4120
	11th to 20th	Day	5% 6% 3 8% 5% 6% 7% 6% 8% 12% 33%	4120
	21st to end	Day	12% 7% 3 7% 6% 6% 6% 5% 7% 11% 29%	4465
August	1st to 10th	Day	1 1 1 3 4 4 4 4 6% 9% 63%	4104
	11th to 20th	Day	3 2 1 4 4 5% 6% 6% 10% 14% 46%	4014
	21st to end	Day	5% 3 2 8% 6% 7% 7% 5% 8% 10% 39%	3830
September	1st to 10th	Day	6% 6% 2 8% 6% 6% 5% 5% 6% 10% 39%	2090
	11th to 20th	Day	9% 7% 3 9% 5% 5% 5% 4 6% 7% 39%	2090
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 6% 8% 46%	2090
October	1st to 10th	Day	5% 3 2 4 4 4 5% 4 6% 8% 55%	2050
	11th to 20th	Day	11% 5% 2 5% 4 3 3 4 5% 6% 51%	1900
	21st to end	Day	12% 5% 2 4 4 4 4 3 4 6% 53%	2090
November	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 4 7% 46%	1958
	11th to 20th	Day	11% 6% 2 6% 4 3 4 3 5% 6% 51%	2000
	21st to end	Day	15% 7% 3 7% 4 4 4 3 6% 6% 41%	1836
December	1st to 10th	Day	15% 8% 3 8% 5% 4 3 3 3 7% 41%	1710
	11th to 20th	Day	15% 8% 3 8% 5% 4 4 3 5% 4 42%	2161
	21st to end	Day	16% 7% 2 6% 4 3 3 2 4 5% 48%	3135
January	1st to 10th	Night	19% 8% 2 4 3 3 3 2 4 6% 45%	4108
	11th to 20th	Night	16% 7% 2 4 3 2 2 1 3 4 56%	4120
	21st to end	Night	23% 8% 3 5% 4 3 3 2 4 6% 39%	4532
February	1st to 10th	Night	19% 10% 3 6% 4 3 3 3 5% 5% 40%	2285
	11th to 20th	Night	22% 8% 2 5% 3 3 2 2 4 6% 44%	2218
	21st to end	Night	22% 8% 3 6% 4 3 3 3 3 5% 41%	1790
March	1st to 10th	Night	23% 11% 3 6% 3 3 4 3 5% 7% 32%	3419
	11th to 20th	Night	26% 10% 3 7% 4 4 3 4 5% 6% 29%	3480
	21st to end	Night	15% 8% 2 6% 4 4 3 3 4 5% 45%	3817
April	1st to 10th	Night	13% 7% 2 5% 4 4 4 4 6% 8% 41%	2090
	11th to 20th	Night	18% 7% 2 7% 4 3 3 3 5% 7% 42%	1999
	21st to end	Night	15% 8% 2 6% 4 3 4 4 4 6% 44%	1900
May	1st to 10th	Night	24% 10% 2 6% 4 4 3 3 5% 7% 31%	2839
	11th to 20th	Night	14% 7% 2 6% 4 4 3 3 5% 7% 45%	2823
	21st to end	Night	10% 8% 2 6% 5% 5% 5% 4 6% 9% 38%	3090
June	1st to 10th	Night	5% 4 1 4 4 3 4 3 5% 9% 57%	1710
	11th to 20th	Night	5% 3 2 4 3 4 4 3 6% 10% 55%	1710
	21st to end	Night	5% 5% 2 5% 5% 4 5% 5% 8% 10% 46%	1710
July	1st to 10th	Night	5% 3 2 5% 3 3 4 4 6% 12% 52%	2850
	11th to 20th	Night	4 5% 2 6% 4 5% 5% 4 7% 11% 48%	2850
	21st to end	Night	8% 8% 3 7% 5% 5% 5% 5% 6% 11% 38%	3098
August	1st to 10th	Night	1 1 2 2 2 2 2 5% 10% 72%	2836
	11th to 20th	Night	1 2 1 3 2 3 5% 4 8% 11% 59%	2820
	21st to end	Night	3 3 1 5% 3 4 5% 4 8% 12% 50%	3820
September	1st to 10th	Night	5% 5% 1 7% 4 5% 5% 4 7% 8% 48%	2090
	11th to 20th	Night	8% 6% 2 7% 5% 4 3 3 6% 8% 47%	2090
	21st to end	Night	7% 4 2 5% 4 3 4 3 6% 8% 54%	2090
October	1st to 10th	Night	4 4 1 3 3 3 3 3 6% 9% 61%	2109
	11th to 20th	Night	10% 4 1 4 3 3 3 2 4 6% 59%	2280
	21st to end	Night	11% 5% 2 4 3 3 3 2 4 4 60%	2508
November	1st to 10th	Night	11% 6% 2 6% 3 3 4 3 5% 6% 51%	2340
	11th to 20th	Night	11% 7% 2 6% 3 3 4 4 4 5% 52%	2400
	21st to end	Night	15% 6% 2 6% 4 4 3 3 4 6% 46%	2555
December	1st to 10th	Night	19% 7% 2 5% 4 4 3 3 4 6% 44%	2470
	11th to 20th	Night	18% 9% 3 6% 4 3 4 3 4 6% 41%	3036
	21st to end	Night	17% 8% 2 5% 3 3 3 2 4 6% 48%	4532

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	43% 6% 5% 14% 21% 10%	2848
	11th to 20th	Day	35% 5% 5% 21% 23% 12%	2850
	21st to end	Day	49% 3 4 12% 21% 11%	3144
February	1st to 10th	Day	48% 4 5% 13% 17% 13%	1900
	11th to 20th	Day	48% 4 7% 13% 18% 10%	1859
	21st to end	Day	43% 5% 9% 15% 17% 11%	1661
March	1st to 10th	Day	47% 7% 9% 16% 16% 5%	3436
	11th to 20th	Day	56% 6% 7% 9% 16% 7%	3480
	21st to end	Day	42% 5% 8% 18% 21% 7%	3814
April	1st to 10th	Day	45% 6% 6% 17% 15% 10%	2090
	11th to 20th	Day	46% 5% 7% 14% 18% 10%	2129
	21st to end	Day	42% 5% 7% 19% 19% 7%	2280
May	1st to 10th	Day	48% 7% 12% 18% 11% 5%	4085
	11th to 20th	Day	42% 7% 8% 18% 21% 5%	4086
	21st to end	Day	37% 8% 12% 31% 11% 1	4489
June	1st to 10th	Day	31% 8% 15% 27% 17% 2	2470
	11th to 20th	Day	31% 10% 14% 24% 18% 3	2470
	21st to end	Day	42% 12% 13% 23% 10% 1	2470
July	1st to 10th	Day	33% 9% 26% 28% 4	4056
	11th to 20th	Day	39% 11% 18% 21% 10%	4051
	21st to end	Day	45% 11% 18% 22% 4	4325
August	1st to 10th	Day	17% 7% 14% 42% 21%	4090
	11th to 20th	Day	24% 11% 29% 29% 6% 1	4053
	21st to end	Day	36% 12% 16% 22% 12% 1	3829
September	1st to 10th	Day	39% 10% 13% 20% 14% 5%	2090
	11th to 20th	Day	41% 9% 12% 18% 17% 4	2090
	21st to end	Day	33% 9% 11% 18% 16% 13%	2090
October	1st to 10th	Day	18% 4 7% 14% 19% 39%	3401
	11th to 20th	Day	23% 4 6% 18% 33% 17%	3140
	21st to end	Day	28% 5% 5% 20% 28% 14%	3428
November	1st to 10th	Day	37% 6% 8% 17% 22% 9%	1958
	11th to 20th	Day	34% 5% 9% 16% 21% 14%	2000
	21st to end	Day	43% 5% 7% 15% 17% 12%	1836
December	1st to 10th	Day	45% 5% 7% 18% 18% 7%	1710
	11th to 20th	Day	44% 5% 6% 11% 23% 11%	2159
	21st to end	Day	39% 4 5% 17% 23% 12%	3135
January	1st to 10th	Night	41% 4 6% 15% 17% 16%	4108
	11th to 20th	Night	35% 4 4 18% 26% 13%	4120
	21st to end	Night	47% 4 4 14% 21% 11%	4532
February	1st to 10th	Night	46% 4 7% 11% 17% 14%	2285
	11th to 20th	Night	43% 4 6% 15% 18% 13%	2218
	21st to end	Night	48% 4 6% 13% 16% 13%	1790
March	1st to 10th	Night	52% 5% 9% 15% 13% 6%	3419
	11th to 20th	Night	56% 6% 7% 14% 11% 6%	3480
	21st to end	Night	40% 5% 9% 14% 22% 9%	3817
April	1st to 10th	Night	40% 6% 10% 18% 15% 10%	2090
	11th to 20th	Night	43% 5% 9% 15% 15% 14%	1999
	21st to end	Night	41% 5% 9% 20% 17% 9%	1900
May	1st to 10th	Night	52% 7% 9% 17% 9% 5%	2866
	11th to 20th	Night	38% 7% 10% 20% 18% 8%	2824
	21st to end	Night	39% 10% 14% 28% 8% 1	3099
June	1st to 10th	Night	23% 7% 17% 33% 19% 1	1710
	11th to 20th	Night	24% 7% 16% 32% 16% 4	1710
	21st to end	Night	30% 10% 20% 27% 12% 1	1710
July	1st to 10th	Night	25% 8% 31% 31% 4	2805
	11th to 20th	Night	30% 9% 23% 28% 10%	2796
	21st to end	Night	39% 10% 22% 24% 5%	2999
August	1st to 10th	Night	9% 5% 18% 48% 20%	2826
	11th to 20th	Night	16% 8% 34% 35% 6% 1	2847
	21st to end	Night	24% 12% 24% 27% 12% 1	3820
September	1st to 10th	Night	31% 10% 18% 21% 16% 5%	2090
	11th to 20th	Night	34% 8% 15% 24% 14% 4	2090
	21st to end	Night	26% 7% 15% 21% 18% 12%	2090
October	1st to 10th	Night	15% 4 8% 17% 18% 39%	3512
	11th to 20th	Night	17% 2 8% 21% 32% 20%	3779
	21st to end	Night	21% 3 5% 23% 31% 17%	4120
November	1st to 10th	Night	33% 6% 9% 20% 20% 11%	2340
	11th to 20th	Night	34% 4 11% 17% 21% 14%	2400
	21st to end	Night	39% 4 8% 17% 18% 13%	2555
December	1st to 10th	Night	42% 5% 8% 20% 16% 9%	2470
	11th to 20th	Night	45% 4 6% 11% 18% 16%	3037
	21st to end	Night	39% 5% 5% 14% 27% 9%	4532

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% 11% 34% 24% 6%	270
	11th to 20th	Day	22% 14% 30% 25% 8% 1	270
	21st to end	Day	22% 15% 32% 22% 8% 1	297
February	1st to 10th	Day	29% 16% 26% 21% 8%	270
	11th to 20th	Day	24% 20% 31% 18% 6% 1	270
	21st to end	Day	26% 17% 37% 18% 2	225
March	1st to 10th	Day	21% 16% 38% 19% 6%	270
	11th to 20th	Day	18% 17% 40% 19% 5% 1	270
	21st to end	Day	20% 16% 32% 24% 7% 1	297
April	1st to 10th	Day	19% 17% 37% 20% 6%	270
	11th to 20th	Day	20% 14% 33% 24% 8% 1	327
	21st to end	Day	17% 12% 32% 27% 12% 1	460
May	1st to 10th	Day	13% 11% 38% 25% 12%	631
	11th to 20th	Day	13% 9% 26% 32% 17% 3	675
	21st to end	Day	11% 5% 26% 36% 20% 3	734
June	1st to 10th	Day	7% 2 12% 35% 34% 11%	680
	11th to 20th	Day	7% 1 11% 38% 34% 9%	680
	21st to end	Day	8% 1 9% 29% 36% 16%	680
July	1st to 10th	Day	8% 3 6% 26% 36% 21%	671
	11th to 20th	Day	4 1 5% 21% 46% 24%	668
	21st to end	Day	4 1 5% 25% 44% 21%	739
August	1st to 10th	Day	2 1 3 20% 47% 26%	676
	11th to 20th	Day	4 4 20% 47% 24%	651
	21st to end	Day	9% 2 4 17% 28% 41%	332
September	1st to 10th	Day	8% 1 4 21% 36% 30%	300
	11th to 20th	Day	8% 1 5% 22% 37% 27%	300
	21st to end	Day	10% 1 5% 27% 37% 20%	300
October	1st to 10th	Day	4 3 9% 31% 40% 13%	300
	11th to 20th	Day	9% 4 16% 33% 25% 13%	300
	21st to end	Day	18% 10% 20% 24% 21% 8%	330
November	1st to 10th	Day	14% 7% 18% 35% 19% 6%	300
	11th to 20th	Day	16% 8% 21% 34% 19% 3	300
	21st to end	Day	19% 16% 29% 21% 12% 3	299
December	1st to 10th	Day	16% 9% 32% 24% 14% 5%	270
	11th to 20th	Day	20% 17% 30% 24% 7% 1	270
	21st to end	Day	20% 7% 39% 23% 8% 2	297
January	1st to 10th	Night	21% 9% 31% 29% 9%	950
	11th to 20th	Night	23% 11% 28% 30% 8%	950
	21st to end	Night	23% 9% 31% 31% 6%	1045
February	1st to 10th	Night	25% 12% 30% 28% 4	765
	11th to 20th	Night	27% 10% 31% 27% 5%	744
	21st to end	Night	28% 14% 35% 21% 3	534
March	1st to 10th	Night	23% 10% 35% 28% 4	570
	11th to 20th	Night	20% 11% 33% 31% 6%	570
	21st to end	Night	16% 10% 41% 29% 4 1	627
April	1st to 10th	Night	15% 10% 40% 31% 4	570
	11th to 20th	Night	20% 11% 34% 29% 6%	563
	21st to end	Night	17% 12% 35% 28% 7% 1	570
May	1st to 10th	Night	17% 10% 34% 32% 6%	570
	11th to 20th	Night	12% 6% 30% 39% 13% 1	561
	21st to end	Night	9% 4 29% 40% 18% 1	617
June	1st to 10th	Night	5% 2 14% 51% 27% 1	570
	11th to 20th	Night	5% 2 17% 53% 22% 1	570
	21st to end	Night	6% 1 12% 40% 36% 6%	570
July	1st to 10th	Night	6% 1 6% 40% 41% 6%	555
	11th to 20th	Night	3 1 5% 39% 47% 5%	552
	21st to end	Night	4 1 5% 40% 45% 5%	624
August	1st to 10th	Night	2 4 46% 43% 5%	567
	11th to 20th	Night	3 4 40% 47% 6%	564
	21st to end	Night	4 5% 30% 53% 7%	627
September	1st to 10th	Night	6% 1 7% 32% 47% 7%	570
	11th to 20th	Night	9% 1 5% 34% 46% 4	570
	21st to end	Night	8% 1 11% 34% 41% 5%	570
October	1st to 10th	Night	6% 1 9% 43% 38% 4	589
	11th to 20th	Night	10% 3 20% 43% 21% 2	760
	21st to end	Night	12% 7% 23% 36% 20% 2	836
November	1st to 10th	Night	13% 5% 21% 40% 19% 2	780
	11th to 20th	Night	13% 7% 22% 39% 17% 2	800
	21st to end	Night	17% 9% 27% 32% 14% 1	955
December	1st to 10th	Night	23% 6% 26% 30% 14% 1	950
	11th to 20th	Night	24% 12% 26% 31% 7%	950
	21st to end	Night	21% 9% 30% 30% 9%	1045

Page generated at 2024-11-27 16:30:54. Version ac07

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