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 2024-03-28.

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% 9% 4 7% 6% 4 5% 5% 5% 7% 32%	79426
	Night	16% 10% 4 7% 6% 3 4 4 5% 7% 34%	80560
Transparency	Day	51% 4 11% 20% 11% 2	79149
	Night	50% 4 11% 21% 13% 2	80358
Seeing	Day	18% 9% 25% 24% 17% 8%	14246
	Night	19% 7% 25% 32% 15% 2	24145

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	19% 18% 6% 11% 7% 3 4 4 5% 5% 17%	2836
	11th to 20th	Day	16% 19% 8% 10% 7% 6% 8% 3 3 4 15%	2840
	21st to end	Day	27% 20% 9% 7% 7% 4 4 3 4 4 11%	3124
February	1st to 10th	Day	21% 14% 5% 9% 7% 4 4 3 4 5% 24%	1710
	11th to 20th	Day	17% 11% 5% 11% 8% 4 4 5% 5% 5% 24%	1833
	21st to end	Day	20% 13% 4 9% 4 3 4 3 3 6% 29%	1570
March	1st to 10th	Day	18% 11% 5% 7% 6% 3 4 5% 4 6% 31%	1979
	11th to 20th	Day	20% 10% 4 8% 7% 3 4 4 4 6% 30%	2090
	21st to end	Day	23% 9% 4 8% 6% 3 4 4 4 6% 29%	2255
April	1st to 10th	Day	15% 11% 4 7% 6% 3 5% 5% 5% 6% 35%	2028
	11th to 20th	Day	18% 8% 4 6% 6% 3 5% 5% 5% 6% 36%	2263
	21st to end	Day	20% 6% 3 7% 7% 4 5% 6% 5% 6% 31%	2340
May	1st to 10th	Day	19% 8% 3 6% 6% 3 5% 5% 5% 6% 33%	2340
	11th to 20th	Day	19% 7% 4 6% 6% 4 4 5% 7% 7% 31%	2301
	21st to end	Day	9% 5% 3 5% 6% 4 6% 6% 9% 10% 37%	2531
June	1st to 10th	Day	12% 5% 3 6% 7% 4 7% 5% 5% 9% 38%	2340
	11th to 20th	Day	11% 6% 3 6% 6% 3 5% 6% 6% 10% 39%	2349
	21st to end	Day	10% 5% 2 6% 6% 4 7% 6% 8% 11% 37%	2520
July	1st to 10th	Day	12% 6% 2 5% 6% 4 6% 5% 6% 9% 39%	2448
	11th to 20th	Day	10% 5% 3 5% 6% 3 7% 5% 7% 9% 40%	2340
	21st to end	Day	9% 5% 2 5% 5% 4 5% 7% 8% 11% 38%	2547
August	1st to 10th	Day	7% 6% 3 5% 6% 4 5% 6% 8% 10% 41%	2327
	11th to 20th	Day	9% 6% 3 6% 5% 4 6% 6% 9% 11% 35%	2303
	21st to end	Day	7% 5% 2 6% 5% 4 5% 6% 7% 10% 44%	2526
September	1st to 10th	Day	14% 5% 2 4 4 3 4 5% 6% 8% 46%	1990
	11th to 20th	Day	9% 5% 2 5% 5% 3 4 6% 5% 8% 46%	1980
	21st to end	Day	16% 6% 3 5% 5% 3 4 3 5% 6% 45%	1980
October	1st to 10th	Day	14% 6% 2 5% 6% 3 5% 4 6% 7% 42%	1935
	11th to 20th	Day	15% 6% 2 5% 5% 3 5% 5% 4 7% 41%	1800
	21st to end	Day	21% 9% 3 7% 6% 3 5% 4 4 6% 33%	1922
November	1st to 10th	Day	10% 7% 3 6% 6% 3 4 4 5% 7% 47%	1672
	11th to 20th	Day	16% 10% 4 7% 6% 3 5% 4 5% 6% 34%	1710
	21st to end	Day	19% 11% 4 7% 6% 3 4 4 4 6% 31%	1710
December	1st to 10th	Day	22% 15% 7% 10% 6% 3 4 3 5% 6% 19%	1710
	11th to 20th	Day	19% 14% 7% 8% 7% 3 4 5% 6% 6% 22%	2153
	21st to end	Day	24% 21% 6% 9% 7% 4 5% 4 4 5% 11%	3124
January	1st to 10th	Night	17% 18% 6% 12% 7% 4 4 3 5% 5% 18%	4109
	11th to 20th	Night	16% 17% 6% 14% 8% 4 5% 5% 4 5% 17%	4120
	21st to end	Night	27% 17% 8% 8% 7% 3 4 3 3 4 16%	4532
February	1st to 10th	Night	22% 12% 4 8% 7% 3 3 4 4 5% 28%	2470
	11th to 20th	Night	18% 11% 4 9% 7% 4 4 4 5% 7% 28%	2228
	21st to end	Night	20% 13% 5% 8% 6% 3 4 4 4 5% 27%	1884
March	1st to 10th	Night	18% 9% 4 7% 6% 3 4 4 4 6% 35%	2199
	11th to 20th	Night	17% 9% 3 6% 6% 3 4 4 5% 7% 37%	2090
	21st to end	Night	20% 9% 4 6% 5% 2 4 4 5% 7% 34%	2256
April	1st to 10th	Night	15% 8% 3 7% 5% 3 4 4 6% 7% 38%	1947
	11th to 20th	Night	15% 7% 2 6% 5% 3 6% 5% 6% 7% 38%	1644
	21st to end	Night	15% 7% 3 7% 6% 4 3 5% 5% 7% 37%	1620
May	1st to 10th	Night	18% 8% 3 6% 6% 5% 5% 5% 6% 6% 32%	1620
	11th to 20th	Night	16% 8% 3 6% 5% 4 4 4 6% 8% 36%	1592
	21st to end	Night	8% 5% 3 4 5% 3 5% 6% 7% 11% 42%	1744
June	1st to 10th	Night	8% 4 3 4 6% 3 5% 5% 6% 8% 48%	1620
	11th to 20th	Night	9% 5% 2 4 5% 3 6% 6% 7% 10% 44%	1599
	21st to end	Night	9% 4 3 5% 4 2 5% 6% 6% 10% 46%	1440
July	1st to 10th	Night	9% 5% 2 5% 5% 3 5% 5% 6% 7% 47%	1502
	11th to 20th	Night	7% 4 2 5% 4 4 6% 6% 6% 10% 47%	1620
	21st to end	Night	9% 4 3 5% 5% 3 5% 6% 5% 8% 47%	1771
August	1st to 10th	Night	6% 4 2 6% 5% 4 6% 7% 7% 9% 44%	1611
	11th to 20th	Night	8% 5% 2 7% 5% 3 5% 5% 6% 8% 46%	1598
	21st to end	Night	7% 3 2 4 5% 3 4 5% 7% 10% 50%	1826
September	1st to 10th	Night	13% 5% 2 4 4 2 5% 3 4 6% 52%	1951
	11th to 20th	Night	9% 4 3 4 5% 2 3 4 5% 8% 54%	1980
	21st to end	Night	14% 5% 2 4 4 3 4 4 4 6% 49%	1980
October	1st to 10th	Night	10% 5% 2 5% 5% 2 4 4 6% 8% 49%	2024
	11th to 20th	Night	17% 8% 3 5% 4 2 3 4 5% 7% 42%	2160
	21st to end	Night	21% 8% 3 5% 5% 3 4 4 4 6% 37%	2433
November	1st to 10th	Night	14% 6% 2 4 5% 2 4 3 4 5% 49%	2406
	11th to 20th	Night	17% 9% 4 6% 6% 3 4 4 5% 6% 37%	2470
	21st to end	Night	19% 11% 5% 7% 5% 3 4 5% 5% 6% 30%	2470
December	1st to 10th	Night	23% 14% 5% 9% 6% 3 4 4 4 5% 24%	2470
	11th to 20th	Night	18% 13% 7% 8% 6% 3 4 4 4 7% 26%	3042
	21st to end	Night	25% 20% 6% 8% 6% 3 3 4 4 5% 15%	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	69% 3 9% 13% 5%	2837
	11th to 20th	Day	73% 4 10% 10% 4	2840
	21st to end	Day	79% 2 8% 8% 3	3124
February	1st to 10th	Day	63% 3 9% 15% 9%	1710
	11th to 20th	Day	61% 5% 9% 17% 9%	1843
	21st to end	Day	58% 3 11% 19% 8% 2	1570
March	1st to 10th	Day	55% 3 12% 23% 5% 1	1979
	11th to 20th	Day	55% 4 10% 20% 9% 1	2090
	21st to end	Day	57% 3 10% 22% 8% 1	2255
April	1st to 10th	Day	51% 4 11% 20% 13% 1	2028
	11th to 20th	Day	48% 4 11% 20% 14% 3	2263
	21st to end	Day	52% 4 11% 20% 11% 2	2340
May	1st to 10th	Day	51% 4 13% 21% 9% 2	2340
	11th to 20th	Day	51% 5% 13% 18% 12% 1	2305
	21st to end	Day	39% 7% 15% 25% 12% 2	2531
June	1st to 10th	Day	43% 5% 12% 24% 15% 2	2340
	11th to 20th	Day	40% 6% 15% 22% 15% 1	2349
	21st to end	Day	39% 6% 16% 22% 14% 3	2520
July	1st to 10th	Day	42% 6% 12% 22% 15% 3	2383
	11th to 20th	Day	38% 6% 12% 26% 16% 1	2271
	21st to end	Day	37% 7% 14% 28% 12% 3	2405
August	1st to 10th	Day	36% 7% 14% 28% 14% 2	2314
	11th to 20th	Day	39% 6% 14% 28% 11% 1	2303
	21st to end	Day	34% 6% 15% 24% 16% 5%	2526
September	1st to 10th	Day	35% 6% 10% 24% 22% 3	1990
	11th to 20th	Day	35% 6% 10% 27% 20% 2	1980
	21st to end	Day	41% 4 8% 23% 22% 1	1980
October	1st to 10th	Day	41% 4 10% 25% 19% 1	1935
	11th to 20th	Day	42% 4 11% 24% 18% 2	1800
	21st to end	Day	53% 3 11% 22% 10% 2	1922
November	1st to 10th	Day	37% 5% 10% 27% 18% 3	1672
	11th to 20th	Day	51% 4 9% 21% 12% 3	1710
	21st to end	Day	55% 3 12% 20% 10% 1	1710
December	1st to 10th	Day	67% 3 9% 17% 3	1710
	11th to 20th	Day	63% 4 9% 18% 6%	2150
	21st to end	Day	76% 3 9% 7% 4	3124
January	1st to 10th	Night	67% 3 9% 15% 5%	4109
	11th to 20th	Night	70% 3 10% 14% 4	4120
	21st to end	Night	73% 4 8% 12% 4 1	4532
February	1st to 10th	Night	60% 3 10% 18% 8% 1	2470
	11th to 20th	Night	57% 3 10% 18% 11% 1	2229
	21st to end	Night	60% 3 10% 17% 8% 2	1884
March	1st to 10th	Night	51% 2 9% 24% 12% 1	2199
	11th to 20th	Night	48% 3 11% 26% 10% 3	2090
	21st to end	Night	50% 4 8% 24% 12% 1	2256
April	1st to 10th	Night	45% 4 12% 23% 14% 2	1947
	11th to 20th	Night	44% 4 11% 18% 19% 4	1644
	21st to end	Night	45% 5% 11% 23% 14% 2	1620
May	1st to 10th	Night	50% 6% 12% 21% 9% 3	1620
	11th to 20th	Night	46% 5% 12% 21% 13% 3	1593
	21st to end	Night	34% 7% 17% 27% 13% 3	1745
June	1st to 10th	Night	34% 6% 14% 24% 19% 3	1620
	11th to 20th	Night	33% 7% 15% 25% 17% 3	1599
	21st to end	Night	32% 7% 16% 24% 18% 3	1440
July	1st to 10th	Night	36% 4 12% 23% 21% 4	1459
	11th to 20th	Night	32% 6% 12% 28% 19% 2	1566
	21st to end	Night	35% 6% 13% 28% 16% 3	1672
August	1st to 10th	Night	33% 5% 17% 27% 16% 1	1600
	11th to 20th	Night	35% 7% 13% 26% 19% 1	1598
	21st to end	Night	28% 5% 14% 27% 20% 5%	1826
September	1st to 10th	Night	34% 4 12% 24% 20% 6%	1951
	11th to 20th	Night	29% 4 11% 27% 26% 3	1980
	21st to end	Night	37% 3 10% 22% 27% 2	1980
October	1st to 10th	Night	35% 5% 9% 28% 21% 2	2024
	11th to 20th	Night	42% 4 9% 26% 18% 2	2160
	21st to end	Night	49% 4 8% 23% 14% 2	2433
November	1st to 10th	Night	38% 3 11% 25% 20% 3	2406
	11th to 20th	Night	48% 4 8% 23% 15% 2	2470
	21st to end	Night	55% 2 12% 21% 9% 1	2470
December	1st to 10th	Night	63% 4 10% 18% 6%	2470
	11th to 20th	Night	58% 4 11% 20% 7%	3044
	21st to end	Night	73% 3 8% 13% 3	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	25% 15% 34% 18% 6% 2	270
	11th to 20th	Day	26% 19% 39% 11% 5%	270
	21st to end	Day	30% 14% 34% 15% 6%	297
February	1st to 10th	Day	30% 16% 33% 16% 5%	270
	11th to 20th	Day	25% 17% 38% 16% 4 1	270
	21st to end	Day	24% 20% 38% 16% 2	225
March	1st to 10th	Day	23% 15% 34% 21% 7%	349
	11th to 20th	Day	23% 14% 33% 21% 7% 1	460
	21st to end	Day	27% 13% 32% 21% 6%	490
April	1st to 10th	Day	20% 11% 33% 21% 12% 3	420
	11th to 20th	Day	21% 15% 25% 24% 10% 6%	412
	21st to end	Day	21% 12% 30% 24% 10% 2	420
May	1st to 10th	Day	25% 11% 26% 21% 12% 4	423
	11th to 20th	Day	21% 6% 24% 26% 17% 6%	447
	21st to end	Day	12% 5% 22% 26% 23% 12%	485
June	1st to 10th	Day	13% 3 22% 30% 22% 10%	450
	11th to 20th	Day	14% 5% 19% 27% 27% 9%	459
	21st to end	Day	12% 5% 24% 29% 22% 8%	630
July	1st to 10th	Day	12% 3 13% 23% 25% 23%	553
	11th to 20th	Day	10% 3 14% 26% 28% 19%	444
	21st to end	Day	9% 2 13% 28% 29% 19%	488
August	1st to 10th	Day	10% 3 11% 24% 32% 20%	446
	11th to 20th	Day	11% 3 19% 27% 23% 17%	439
	21st to end	Day	7% 3 12% 29% 29% 20%	495
September	1st to 10th	Day	14% 3 14% 24% 27% 18%	450
	11th to 20th	Day	10% 2 12% 21% 35% 20%	450
	21st to end	Day	17% 9% 16% 26% 20% 12%	450
October	1st to 10th	Day	12% 6% 21% 30% 21% 10%	450
	11th to 20th	Day	13% 11% 32% 27% 14% 2	450
	21st to end	Day	23% 12% 30% 26% 9% 1	437
November	1st to 10th	Day	14% 10% 31% 27% 13% 4	270
	11th to 20th	Day	19% 18% 26% 23% 13% 2	270
	21st to end	Day	26% 9% 37% 22% 6% 1	270
December	1st to 10th	Day	24% 16% 33% 19% 6% 2	270
	11th to 20th	Day	24% 13% 40% 18% 5%	270
	21st to end	Day	31% 16% 28% 19% 6%	297
January	1st to 10th	Night	22% 14% 34% 24% 5%	760
	11th to 20th	Night	28% 12% 32% 23% 4	760
	21st to end	Night	25% 11% 32% 28% 4	836
February	1st to 10th	Night	27% 10% 30% 30% 2	760
	11th to 20th	Night	24% 13% 35% 26% 2	743
	21st to end	Night	27% 11% 36% 24% 2	628
March	1st to 10th	Night	23% 10% 33% 28% 7%	760
	11th to 20th	Night	20% 12% 34% 27% 7%	760
	21st to end	Night	24% 9% 31% 26% 9%	821
April	1st to 10th	Night	19% 10% 35% 28% 7% 1	687
	11th to 20th	Night	17% 7% 34% 29% 12% 1	533
	21st to end	Night	18% 6% 39% 30% 8% 1	540
May	1st to 10th	Night	18% 8% 31% 30% 12%	540
	11th to 20th	Night	20% 4 24% 35% 16% 1	531
	21st to end	Night	8% 3 19% 37% 30% 3	584
June	1st to 10th	Night	8% 4 21% 44% 22% 1	540
	11th to 20th	Night	11% 4 16% 41% 26% 2	540
	21st to end	Night	9% 3 18% 44% 25% 2	540
July	1st to 10th	Night	11% 2 10% 39% 28% 9%	525
	11th to 20th	Night	6% 2 11% 39% 37% 5%	522
	21st to end	Night	10% 2 10% 39% 37% 2	591
August	1st to 10th	Night	8% 2 10% 41% 36% 4	537
	11th to 20th	Night	9% 3 10% 39% 35% 4	534
	21st to end	Night	8% 2 10% 37% 37% 7%	594
September	1st to 10th	Night	15% 2 14% 31% 33% 5%	691
	11th to 20th	Night	11% 2 11% 35% 35% 6%	720
	21st to end	Night	16% 5% 19% 32% 26% 2	720
October	1st to 10th	Night	12% 3 23% 36% 22% 4	720
	11th to 20th	Night	20% 6% 28% 33% 13% 1	720
	21st to end	Night	23% 9% 27% 31% 9% 1	792
November	1st to 10th	Night	18% 6% 25% 33% 16% 1	740
	11th to 20th	Night	20% 12% 31% 28% 10%	760
	21st to end	Night	24% 9% 27% 32% 8%	760
December	1st to 10th	Night	28% 9% 30% 27% 5%	760
	11th to 20th	Night	24% 9% 31% 30% 6% 1	760
	21st to end	Night	30% 13% 28% 26% 4	836

Page generated at 2024-03-24 23:37:01. Version ac07

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