Astronomy Club of Akron Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Astronomy Club of Akron Observatory clear sky chart from 2005-11-06 to 2026-06-16.

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	15% 11% 4 9% 5% 5% 5% 4 5% 7% 30%	137070
	Night	15% 12% 4 10% 5% 4 4 3 5% 6% 30%	134948
Transparency	Day	53% 5% 11% 20% 11% 1	140714
	Night	53% 4 11% 19% 11% 1	139376
Seeing	Day	20% 14% 28% 21% 12% 5%	16681
	Night	20% 10% 28% 28% 12% 1	26623

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	15% 21% 6% 21% 5% 4 3 3 4 5% 13%	5258
	11th to 20th	Day	11% 21% 9% 17% 8% 5% 5% 2 4 4 14%	5280
	21st to end	Day	19% 18% 7% 13% 9% 7% 4 2 4 4 14%	5780
February	1st to 10th	Day	17% 17% 5% 13% 6% 5% 3 3 5% 4 22%	1890
	11th to 20th	Day	16% 14% 7% 13% 8% 4 5% 3 4 5% 21%	1911
	21st to end	Day	16% 14% 5% 12% 5% 4 4 3 5% 6% 25%	1730
March	1st to 10th	Day	17% 13% 5% 12% 5% 4 4 3 5% 5% 26%	4942
	11th to 20th	Day	11% 10% 4 10% 6% 5% 4 3 4 6% 36%	5090
	21st to end	Day	20% 12% 4 9% 5% 4 4 3 5% 6% 28%	5586
April	1st to 10th	Day	15% 12% 4 9% 6% 5% 4 4 5% 8% 29%	2347
	11th to 20th	Day	17% 11% 4 8% 4 5% 4 4 5% 6% 33%	2662
	21st to end	Day	18% 11% 3 8% 4 4 4 4 5% 6% 33%	2730
May	1st to 10th	Day	20% 10% 3 8% 5% 5% 5% 4 5% 6% 28%	7616
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 8% 32%	7626
	21st to end	Day	19% 7% 2 7% 4 4 4 4 6% 6% 36%	8391
June	1st to 10th	Day	12% 7% 2 7% 5% 5% 6% 4 7% 8% 37%	2929
	11th to 20th	Day	12% 8% 3 8% 5% 4 5% 4 6% 8% 36%	2870
	21st to end	Day	11% 6% 2 5% 5% 5% 5% 5% 7% 10% 39%	2737
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 6% 10% 41%	5900
	11th to 20th	Day	10% 5% 2 7% 5% 5% 6% 5% 7% 11% 36%	5900
	21st to end	Day	11% 6% 2 7% 4 5% 6% 4 7% 9% 38%	6424
August	1st to 10th	Day	11% 9% 3 7% 5% 6% 6% 4 6% 9% 34%	4234
	11th to 20th	Day	10% 7% 3 7% 5% 4 6% 6% 8% 10% 34%	4174
	21st to end	Day	8% 5% 2 8% 5% 5% 6% 5% 7% 9% 39%	4587
September	1st to 10th	Day	13% 6% 2 6% 4 3 4 4 6% 7% 45%	2288
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 43%	2200
	21st to end	Day	19% 9% 3 6% 4 4 4 3 5% 7% 37%	2200
October	1st to 10th	Day	14% 6% 3 6% 5% 4 4 3 6% 9% 40%	2070
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 3 5% 6% 37%	2000
	21st to end	Day	21% 11% 4 7% 4 4 5% 3 5% 6% 30%	2200
November	1st to 10th	Day	12% 10% 3 7% 5% 4 4 4 5% 6% 39%	1855
	11th to 20th	Day	17% 14% 4 8% 5% 3 5% 4 6% 5% 29%	1887
	21st to end	Day	16% 18% 7% 10% 5% 4 5% 3 5% 6% 21%	1680
December	1st to 10th	Day	19% 14% 7% 16% 6% 4 3 3 4 4 19%	2680
	11th to 20th	Day	22% 18% 7% 13% 4 3 3 3 4 5% 18%	3070
	21st to end	Day	25% 22% 6% 13% 6% 5% 4 3 3 4 10%	4346
January	1st to 10th	Night	14% 18% 7% 22% 8% 5% 4 3 4 4 11%	7635
	11th to 20th	Night	11% 19% 9% 17% 9% 6% 5% 3 4 4 13%	7680
	21st to end	Night	18% 17% 6% 11% 6% 6% 5% 3 4 5% 19%	8401
February	1st to 10th	Night	20% 14% 5% 11% 6% 6% 4 2 5% 5% 21%	2730
	11th to 20th	Night	17% 14% 5% 12% 7% 5% 5% 4 5% 5% 21%	2593
	21st to end	Night	19% 15% 5% 11% 7% 5% 3 3 4 4 24%	2076
March	1st to 10th	Night	22% 13% 4 9% 4 3 3 2 3 5% 31%	5130
	11th to 20th	Night	13% 9% 3 7% 3 4 5% 4 6% 8% 38%	5090
	21st to end	Night	17% 11% 4 9% 5% 4 4 4 5% 5% 33%	5588
April	1st to 10th	Night	17% 13% 4 7% 6% 4 4 3 5% 6% 32%	2273
	11th to 20th	Night	15% 11% 3 8% 5% 4 4 4 6% 6% 34%	1925
	21st to end	Night	15% 9% 2 7% 5% 4 5% 4 5% 6% 38%	1890
May	1st to 10th	Night	24% 9% 3 8% 5% 5% 5% 3 5% 6% 27%	5237
	11th to 20th	Night	15% 9% 3 6% 4 4 4 3 5% 8% 39%	5234
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 8% 38%	5761
June	1st to 10th	Night	8% 7% 2 6% 5% 5% 5% 3 6% 7% 44%	1685
	11th to 20th	Night	10% 6% 2 6% 5% 4 5% 4 7% 10% 41%	1640
	21st to end	Night	10% 5% 3 6% 4 4 6% 4 6% 10% 42%	1654
July	1st to 10th	Night	10% 6% 2 7% 4 4 5% 4 6% 9% 44%	4058
	11th to 20th	Night	9% 5% 2 7% 5% 4 6% 4 7% 10% 40%	4057
	21st to end	Night	7% 6% 3 7% 5% 4 5% 4 6% 8% 46%	4427
August	1st to 10th	Night	9% 8% 3 8% 5% 4 4 4 6% 8% 40%	2915
	11th to 20th	Night	11% 8% 3 7% 4 4 4 4 5% 7% 44%	2875
	21st to end	Night	7% 5% 2 7% 4 5% 6% 4 7% 7% 44%	3276
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 5% 8% 49%	2109
	11th to 20th	Night	9% 4 1 5% 4 4 4 3 6% 8% 53%	2200
	21st to end	Night	16% 8% 2 7% 4 4 5% 3 5% 6% 41%	2200
October	1st to 10th	Night	13% 6% 3 5% 4 4 5% 3 5% 7% 45%	2330
	11th to 20th	Night	17% 7% 3 8% 4 5% 4 3 5% 6% 37%	2400
	21st to end	Night	20% 10% 3 7% 4 4 4 4 5% 6% 33%	2640
November	1st to 10th	Night	13% 9% 2 6% 4 5% 4 3 5% 7% 41%	2660
	11th to 20th	Night	17% 14% 4 9% 5% 4 3 3 5% 6% 30%	2730
	21st to end	Night	19% 15% 5% 8% 5% 5% 4 3 5% 6% 25%	2939
December	1st to 10th	Night	17% 15% 7% 11% 6% 5% 4 3 4 5% 22%	4720
	11th to 20th	Night	19% 18% 7% 12% 5% 4 4 3 4 5% 19%	5345
	21st to end	Night	23% 20% 7% 11% 5% 4 4 3 4 5% 14%	6845

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	76% 3 10% 8% 3	5259
	11th to 20th	Day	76% 3 7% 7% 7%	5280
	21st to end	Day	77% 3 6% 12% 3	5780
February	1st to 10th	Day	66% 4 9% 14% 7%	1890
	11th to 20th	Day	66% 5% 8% 14% 6%	1920
	21st to end	Day	60% 5% 12% 15% 6% 1	1730
March	1st to 10th	Day	60% 4 9% 21% 6%	4942
	11th to 20th	Day	49% 4 12% 25% 8% 2	5090
	21st to end	Day	57% 5% 8% 18% 12% 1	5586
April	1st to 10th	Day	53% 6% 12% 16% 11% 1	2347
	11th to 20th	Day	51% 6% 12% 17% 12% 2	2662
	21st to end	Day	51% 6% 11% 21% 10% 1	2730
May	1st to 10th	Day	56% 4 10% 19% 8% 3	7651
	11th to 20th	Day	49% 5% 12% 22% 11% 1	7630
	21st to end	Day	47% 5% 9% 18% 16% 4	8405
June	1st to 10th	Day	43% 7% 12% 23% 14% 1	2929
	11th to 20th	Day	44% 8% 13% 21% 14% 1	2870
	21st to end	Day	37% 9% 14% 23% 15% 1	2737
July	1st to 10th	Day	39% 3 12% 29% 15% 2	5835
	11th to 20th	Day	42% 4 14% 25% 15% 1	5831
	21st to end	Day	41% 4 12% 21% 19% 2	6240
August	1st to 10th	Day	46% 6% 13% 23% 12%	4221
	11th to 20th	Day	42% 5% 11% 30% 11% 1	4213
	21st to end	Day	40% 5% 13% 30% 10% 2	4587
September	1st to 10th	Day	38% 6% 13% 22% 17% 4	2288
	11th to 20th	Day	35% 7% 15% 25% 16% 2	2200
	21st to end	Day	47% 6% 10% 20% 16% 1	2200
October	1st to 10th	Day	32% 4 13% 31% 19% 1	3369
	11th to 20th	Day	46% 4 10% 20% 16% 4	3240
	21st to end	Day	43% 3 12% 25% 16% 1	3538
November	1st to 10th	Day	44% 5% 12% 22% 15% 1	1855
	11th to 20th	Day	55% 5% 10% 19% 8% 2	1887
	21st to end	Day	64% 6% 11% 14% 5%	1680
December	1st to 10th	Day	70% 3 11% 12% 3	2680
	11th to 20th	Day	71% 4 10% 12% 4	3066
	21st to end	Day	79% 4 7% 8% 2	4346
January	1st to 10th	Night	78% 3 7% 9% 3	7636
	11th to 20th	Night	77% 3 8% 8% 4	7680
	21st to end	Night	70% 2 9% 13% 6% 1	8401
February	1st to 10th	Night	65% 4 9% 15% 6%	2730
	11th to 20th	Night	63% 5% 10% 15% 6%	2595
	21st to end	Night	63% 4 9% 14% 8% 1	2076
March	1st to 10th	Night	57% 3 10% 20% 9%	5130
	11th to 20th	Night	43% 6% 14% 25% 10% 2	5090
	21st to end	Night	52% 5% 9% 19% 14% 1	5588
April	1st to 10th	Night	52% 6% 10% 18% 12% 1	2273
	11th to 20th	Night	49% 6% 12% 16% 14% 2	1925
	21st to end	Night	46% 6% 12% 19% 15% 2	1890
May	1st to 10th	Night	57% 5% 9% 17% 9% 4	5264
	11th to 20th	Night	45% 5% 11% 25% 14% 1	5235
	21st to end	Night	45% 5% 12% 22% 15% 2	5771
June	1st to 10th	Night	38% 6% 11% 24% 17% 3	1685
	11th to 20th	Night	39% 7% 14% 21% 16% 3	1640
	21st to end	Night	36% 8% 14% 24% 16% 1	1654
July	1st to 10th	Night	38% 4 12% 24% 18% 3	4015
	11th to 20th	Night	39% 4 14% 28% 13% 1	4006
	21st to end	Night	36% 4 13% 20% 25% 2	4297
August	1st to 10th	Night	42% 5% 12% 25% 14% 1	2904
	11th to 20th	Night	40% 5% 10% 29% 15% 1	2902
	21st to end	Night	37% 5% 14% 30% 13% 2	3276
September	1st to 10th	Night	34% 7% 10% 26% 18% 4	2109
	11th to 20th	Night	30% 5% 13% 27% 23% 2	2200
	21st to end	Night	43% 7% 11% 20% 19% 1	2200
October	1st to 10th	Night	31% 4 9% 29% 26% 1	3811
	11th to 20th	Night	43% 4 11% 21% 18% 3	3899
	21st to end	Night	39% 4 10% 29% 17% 2	4252
November	1st to 10th	Night	42% 5% 12% 23% 16% 2	2660
	11th to 20th	Night	55% 5% 10% 18% 10% 3	2730
	21st to end	Night	60% 5% 12% 17% 6%	2939
December	1st to 10th	Night	65% 4 10% 16% 4	4720
	11th to 20th	Night	68% 4 11% 14% 2	5348
	21st to end	Night	74% 4 10% 10% 2	6845

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	29% 22% 35% 10% 4 1	330
	11th to 20th	Day	29% 26% 34% 8% 2	330
	21st to end	Day	28% 26% 32% 11% 2	363
February	1st to 10th	Day	28% 22% 35% 14% 1 1	330
	11th to 20th	Day	29% 28% 31% 10% 2	330
	21st to end	Day	26% 31% 34% 9%	273
March	1st to 10th	Day	25% 20% 34% 16% 4	485
	11th to 20th	Day	28% 18% 33% 16% 6%	540
	21st to end	Day	30% 18% 29% 18% 4 1	594
April	1st to 10th	Day	23% 22% 31% 16% 7% 1	540
	11th to 20th	Day	26% 20% 26% 17% 8% 4	532
	21st to end	Day	24% 15% 32% 19% 8% 2	540
May	1st to 10th	Day	26% 17% 29% 17% 8% 2	543
	11th to 20th	Day	19% 12% 33% 20% 11% 5%	567
	21st to end	Day	18% 7% 26% 26% 18% 5%	617
June	1st to 10th	Day	14% 8% 31% 31% 14% 3	570
	11th to 20th	Day	17% 7% 24% 32% 15% 5%	550
	21st to end	Day	14% 8% 27% 29% 15% 6%	530
July	1st to 10th	Day	12% 3 20% 29% 23% 12%	525
	11th to 20th	Day	11% 7% 22% 28% 22% 10%	524
	21st to end	Day	12% 5% 22% 26% 25% 11%	576
August	1st to 10th	Day	11% 5% 21% 26% 27% 10%	526
	11th to 20th	Day	15% 6% 20% 27% 21% 12%	519
	21st to end	Day	10% 5% 19% 30% 23% 13%	583
September	1st to 10th	Day	15% 7% 20% 24% 22% 13%	530
	11th to 20th	Day	9% 3 15% 28% 28% 16%	530
	21st to end	Day	24% 9% 21% 22% 17% 7%	530
October	1st to 10th	Day	11% 10% 25% 26% 22% 5%	530
	11th to 20th	Day	19% 14% 36% 19% 9% 2	530
	21st to end	Day	27% 17% 30% 19% 5% 1	583
November	1st to 10th	Day	18% 21% 36% 15% 9% 2	333
	11th to 20th	Day	29% 22% 29% 14% 5% 1	327
	21st to end	Day	27% 21% 37% 13% 1	220
December	1st to 10th	Day	26% 21% 35% 13% 4 1	220
	11th to 20th	Day	25% 24% 35% 13% 3	220
	21st to end	Day	33% 22% 30% 13% 2	311
January	1st to 10th	Night	24% 20% 35% 17% 4	840
	11th to 20th	Night	29% 19% 33% 16% 3	840
	21st to end	Night	27% 18% 31% 21% 3	924
February	1st to 10th	Night	27% 16% 32% 22% 3	840
	11th to 20th	Night	25% 16% 36% 20% 3	823
	21st to end	Night	28% 16% 37% 17% 2	692
March	1st to 10th	Night	24% 15% 35% 22% 5%	840
	11th to 20th	Night	23% 14% 33% 23% 6% 1	840
	21st to end	Night	24% 11% 34% 23% 6% 1	924
April	1st to 10th	Night	24% 13% 34% 24% 5% 1	840
	11th to 20th	Night	21% 13% 34% 21% 10% 1	681
	21st to end	Night	19% 9% 34% 31% 7%	630
May	1st to 10th	Night	21% 8% 29% 32% 9% 1	630
	11th to 20th	Night	19% 6% 25% 38% 11% 2	621
	21st to end	Night	15% 2 19% 41% 20% 3	683
June	1st to 10th	Night	9% 4 27% 42% 18% 1	425
	11th to 20th	Night	12% 3 25% 45% 15% 1	410
	21st to end	Night	12% 4 22% 41% 20% 1	454
July	1st to 10th	Night	10% 2 13% 43% 29% 4	585
	11th to 20th	Night	9% 2 19% 40% 27% 3	582
	21st to end	Night	9% 1 15% 44% 29% 2	657
August	1st to 10th	Night	9% 2 16% 42% 29% 3	597
	11th to 20th	Night	12% 2 12% 40% 29% 4	594
	21st to end	Night	10% 3 15% 36% 32% 4	687
September	1st to 10th	Night	13% 4 17% 35% 26% 5%	800
	11th to 20th	Night	9% 2 14% 37% 33% 5%	800
	21st to end	Night	19% 6% 22% 31% 20% 4	800
October	1st to 10th	Night	16% 6% 22% 33% 20% 3	800
	11th to 20th	Night	22% 10% 28% 29% 9% 2	800
	21st to end	Night	25% 12% 28% 29% 7%	880
November	1st to 10th	Night	19% 10% 29% 30% 11% 1	820
	11th to 20th	Night	23% 16% 32% 22% 6% 1	840
	21st to end	Night	29% 13% 33% 19% 6%	840
December	1st to 10th	Night	30% 14% 33% 19% 4	840
	11th to 20th	Night	26% 17% 34% 21% 3	840
	21st to end	Night	28% 16% 34% 20% 2	924

Page generated at 2026-06-13 02:31:45. Version ac07

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