A.H. Stephens Memorial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the A.H. Stephens Memorial Park clear sky chart from 2005-11-06 to 2025-07-21.

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	13% 6% 2 6% 4 5% 5% 4 6% 8% 42%	120269
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 45%	118863
Transparency	Day	38% 6% 11% 20% 19% 7%	124048
	Night	36% 6% 10% 19% 21% 8%	123221
Seeing	Day	16% 10% 24% 24% 18% 8%	16014
	Night	15% 9% 23% 30% 20% 3	26058

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% 6% 2 4 3 3 4 3 4 5% 50%	4056
	11th to 20th	Day	12% 6% 2 4 2 2 3 2 4 7% 56%	4060
	21st to end	Day	19% 7% 2 7% 4 3 3 2 3 5% 44%	4466
February	1st to 10th	Day	15% 7% 3 7% 4 3 3 4 5% 7% 41%	1983
	11th to 20th	Day	21% 6% 2 5% 3 3 3 3 5% 4 44%	1948
	21st to end	Day	17% 6% 2 7% 3 3 3 3 5% 6% 44%	1650
March	1st to 10th	Day	21% 7% 3 7% 4 4 4 3 4 5% 38%	4835
	11th to 20th	Day	9% 3 2 5% 3 4 4 4 5% 7% 54%	4980
	21st to end	Day	16% 7% 3 6% 4 4 4 3 4 4 46%	5465
April	1st to 10th	Day	11% 4 2 6% 4 4 5% 4 5% 7% 49%	2200
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 5% 7% 50%	2317
	21st to end	Day	8% 4 2 5% 4 4 5% 4 6% 8% 51%	2600
May	1st to 10th	Day	12% 6% 2 7% 5% 4 5% 4 7% 10% 40%	5862
	11th to 20th	Day	18% 7% 3 7% 5% 5% 5% 5% 6% 8% 31%	5861
	21st to end	Day	11% 6% 2 6% 5% 4 5% 4 6% 8% 43%	6433
June	1st to 10th	Day	10% 5% 3 7% 6% 6% 6% 5% 8% 10% 33%	2600
	11th to 20th	Day	6% 4 2 6% 5% 5% 7% 5% 7% 11% 43%	2600
	21st to end	Day	5% 4 2 6% 6% 6% 7% 6% 9% 11% 38%	2600
July	1st to 10th	Day	10% 7% 2 8% 7% 7% 7% 6% 8% 9% 28%	4250
	11th to 20th	Day	6% 5% 2 7% 7% 7% 7% 5% 9% 12% 33%	4250
	21st to end	Day	8% 8% 3 9% 8% 8% 9% 7% 10% 12% 20%	4466
August	1st to 10th	Day	14% 6% 2 7% 7% 7% 6% 6% 9% 11% 26%	4104
	11th to 20th	Day	8% 4 2 7% 5% 5% 6% 5% 7% 11% 40%	4013
	21st to end	Day	8% 5% 2 5% 4 5% 5% 4 7% 9% 47%	4034
September	1st to 10th	Day	10% 6% 3 6% 5% 5% 6% 4 7% 9% 39%	2090
	11th to 20th	Day	15% 6% 2 7% 4 5% 4 4 5% 7% 40%	2090
	21st to end	Day	15% 6% 2 5% 4 4 4 4 5% 6% 44%	2090
October	1st to 10th	Day	14% 6% 2 5% 3 4 3 2 5% 6% 51%	2090
	11th to 20th	Day	12% 3 2 4 3 2 3 3 5% 5% 58%	1907
	21st to end	Day	10% 4 2 5% 4 4 3 3 4 5% 57%	2090
November	1st to 10th	Day	13% 6% 2 5% 3 4 3 2 4 5% 52%	1910
	11th to 20th	Day	15% 5% 2 4 2 3 3 3 4 7% 53%	1800
	21st to end	Day	12% 6% 2 4 4 4 4 3 5% 6% 49%	1800
December	1st to 10th	Day	12% 7% 2 6% 4 4 4 3 5% 5% 48%	2930
	11th to 20th	Day	15% 6% 2 7% 4 4 4 3 5% 5% 46%	3373
	21st to end	Day	21% 7% 2 5% 3 3 3 3 5% 6% 43%	4466
January	1st to 10th	Night	12% 5% 2 4 3 4 3 3 4 5% 54%	5889
	11th to 20th	Night	12% 6% 2 4 4 4 4 3 5% 7% 49%	5900
	21st to end	Night	16% 9% 2 6% 3 3 3 3 4 5% 45%	6490
February	1st to 10th	Night	15% 6% 2 6% 4 4 3 3 5% 6% 46%	2415
	11th to 20th	Night	20% 7% 2 6% 4 3 3 3 4 5% 44%	2338
	21st to end	Night	14% 6% 2 6% 4 4 4 3 5% 6% 46%	1980
March	1st to 10th	Night	20% 8% 2 6% 4 4 4 3 4 7% 38%	5016
	11th to 20th	Night	9% 4 2 3 3 3 4 4 6% 8% 55%	4980
	21st to end	Night	16% 5% 2 5% 4 4 4 3 4 6% 47%	5467
April	1st to 10th	Night	11% 4 2 5% 4 3 4 4 6% 6% 50%	2200
	11th to 20th	Night	11% 5% 1 5% 3 4 3 3 5% 8% 53%	2045
	21st to end	Night	8% 4 1 4 5% 4 4 3 5% 8% 53%	1800
May	1st to 10th	Night	8% 7% 3 6% 5% 4 5% 4 6% 10% 41%	4033
	11th to 20th	Night	18% 6% 2 6% 4 5% 5% 4 7% 9% 34%	4032
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 9% 47%	4421
June	1st to 10th	Night	8% 7% 2 7% 5% 5% 6% 5% 8% 12% 35%	1800
	11th to 20th	Night	5% 4 2 7% 6% 5% 5% 4 8% 11% 43%	1800
	21st to end	Night	6% 5% 2 6% 4 5% 6% 8% 8% 10% 40%	1800
July	1st to 10th	Night	12% 7% 3 8% 5% 5% 7% 5% 8% 11% 30%	2930
	11th to 20th	Night	5% 5% 2 7% 6% 7% 7% 7% 10% 14% 30%	2930
	21st to end	Night	10% 9% 3 9% 7% 7% 7% 6% 9% 12% 23%	3087
August	1st to 10th	Night	11% 7% 2 8% 6% 7% 6% 6% 8% 11% 26%	2825
	11th to 20th	Night	8% 5% 2 6% 5% 4 5% 5% 8% 12% 40%	2810
	21st to end	Night	6% 5% 2 6% 4 4 5% 4 7% 9% 48%	3588
September	1st to 10th	Night	10% 6% 2 7% 4 5% 5% 6% 7% 10% 39%	2090
	11th to 20th	Night	14% 7% 2 7% 5% 5% 5% 4 5% 7% 41%	2090
	21st to end	Night	13% 6% 2 6% 4 3 4 3 5% 7% 47%	2090
October	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 4 6% 52%	2090
	11th to 20th	Night	12% 5% 1 4 3 3 4 2 4 4 59%	2271
	21st to end	Night	11% 4 1 5% 3 3 3 3 4 5% 58%	2508
November	1st to 10th	Night	11% 6% 2 6% 3 3 3 2 4 6% 55%	2386
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 3 6% 52%	2600
	21st to end	Night	14% 4 2 5% 4 4 4 3 5% 6% 50%	2600
December	1st to 10th	Night	12% 7% 2 5% 3 2 3 3 4 5% 55%	4250
	11th to 20th	Night	16% 6% 2 6% 3 3 3 3 5% 7% 47%	4822
	21st to end	Night	19% 8% 2 6% 3 4 3 3 4 5% 42%	6490

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	36% 3 5% 20% 28% 9%	4057
	11th to 20th	Day	30% 3 4 19% 31% 13%	4060
	21st to end	Day	44% 3 3 18% 22% 10%	4466
February	1st to 10th	Day	42% 5% 8% 20% 17% 8%	1983
	11th to 20th	Day	43% 4 5% 20% 22% 7%	1958
	21st to end	Day	42% 4 7% 15% 23% 9%	1650
March	1st to 10th	Day	49% 3 6% 11% 23% 7%	4835
	11th to 20th	Day	29% 4 8% 15% 22% 21%	4980
	21st to end	Day	43% 3 5% 20% 21% 8%	5465
April	1st to 10th	Day	35% 5% 10% 22% 21% 8%	2200
	11th to 20th	Day	34% 5% 8% 21% 23% 9%	2317
	21st to end	Day	31% 6% 10% 26% 23% 4	2600
May	1st to 10th	Day	39% 5% 16% 24% 13% 2	5897
	11th to 20th	Day	49% 7% 15% 19% 10% 1	5865
	21st to end	Day	38% 5% 15% 21% 19% 2	6447
June	1st to 10th	Day	42% 9% 17% 20% 11% 2	2600
	11th to 20th	Day	32% 8% 19% 25% 15% 1	2600
	21st to end	Day	35% 11% 18% 20% 12% 4	2600
July	1st to 10th	Day	46% 11% 17% 19% 5% 2	4185
	11th to 20th	Day	38% 13% 24% 20% 4 1	4181
	21st to end	Day	50% 16% 17% 12% 5%	4324
August	1st to 10th	Day	47% 9% 17% 23% 3	4091
	11th to 20th	Day	35% 9% 17% 23% 14% 2	4052
	21st to end	Day	32% 8% 15% 26% 16% 4	4034
September	1st to 10th	Day	40% 8% 14% 17% 17% 4	2090
	11th to 20th	Day	44% 6% 9% 18% 21% 2	2090
	21st to end	Day	41% 5% 9% 20% 19% 6%	2090
October	1st to 10th	Day	30% 3 7% 14% 34% 12%	3480
	11th to 20th	Day	18% 2 4 16% 29% 31%	3147
	21st to end	Day	24% 3 4 21% 33% 14%	3428
November	1st to 10th	Day	35% 3 8% 16% 26% 12%	1910
	11th to 20th	Day	33% 3 7% 22% 24% 12%	1800
	21st to end	Day	35% 5% 7% 20% 25% 8%	1800
December	1st to 10th	Day	38% 4 5% 16% 26% 10%	2930
	11th to 20th	Day	40% 4 9% 19% 21% 7%	3370
	21st to end	Day	42% 3 7% 22% 23% 3	4466
January	1st to 10th	Night	32% 4 4 21% 31% 8%	5889
	11th to 20th	Night	35% 3 5% 19% 28% 10%	5900
	21st to end	Night	42% 4 4 14% 28% 8%	6490
February	1st to 10th	Night	39% 3 9% 19% 20% 9%	2415
	11th to 20th	Night	44% 3 5% 18% 22% 9%	2339
	21st to end	Night	39% 4 7% 15% 20% 13%	1980
March	1st to 10th	Night	46% 4 9% 13% 20% 8%	5016
	11th to 20th	Night	27% 4 8% 13% 28% 20%	4980
	21st to end	Night	38% 3 6% 19% 21% 13%	5467
April	1st to 10th	Night	33% 5% 10% 20% 22% 10%	2200
	11th to 20th	Night	31% 3 6% 24% 23% 11%	2045
	21st to end	Night	29% 6% 11% 26% 22% 7%	1800
May	1st to 10th	Night	38% 6% 17% 24% 13% 3	4060
	11th to 20th	Night	44% 7% 17% 19% 11% 1	4033
	21st to end	Night	33% 6% 15% 23% 21% 2	4429
June	1st to 10th	Night	39% 9% 19% 18% 13% 1	1800
	11th to 20th	Night	31% 10% 20% 24% 13% 2	1800
	21st to end	Night	32% 13% 19% 20% 12% 4	1800
July	1st to 10th	Night	45% 12% 21% 15% 5% 2	2885
	11th to 20th	Night	38% 15% 23% 20% 4 1	2876
	21st to end	Night	50% 16% 18% 12% 4 1	2988
August	1st to 10th	Night	47% 10% 21% 19% 3	2814
	11th to 20th	Night	33% 11% 23% 21% 11% 1	2837
	21st to end	Night	30% 8% 15% 26% 18% 2	3588
September	1st to 10th	Night	37% 11% 15% 17% 15% 5%	2090
	11th to 20th	Night	42% 8% 12% 16% 18% 5%	2090
	21st to end	Night	37% 6% 11% 18% 22% 7%	2090
October	1st to 10th	Night	31% 4 8% 14% 34% 8%	3480
	11th to 20th	Night	18% 3 4 15% 26% 34%	3770
	21st to end	Night	21% 3 4 20% 33% 18%	4120
November	1st to 10th	Night	33% 3 8% 17% 26% 14%	2386
	11th to 20th	Night	35% 3 6% 17% 26% 14%	2600
	21st to end	Night	35% 4 7% 18% 26% 9%	2600
December	1st to 10th	Night	33% 4 6% 16% 32% 8%	4250
	11th to 20th	Night	38% 4 12% 17% 21% 8%	4824
	21st to end	Night	45% 4 4 24% 21% 2	6490

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% 24% 38% 10% 3	300
	11th to 20th	Day	22% 24% 34% 14% 6%	300
	21st to end	Day	24% 27% 36% 9% 3	330
February	1st to 10th	Day	22% 20% 38% 16% 4	300
	11th to 20th	Day	38% 18% 30% 13% 1	300
	21st to end	Day	25% 21% 39% 12% 4	249
March	1st to 10th	Day	22% 17% 32% 22% 5% 1	448
	11th to 20th	Day	22% 15% 37% 18% 7% 1	500
	21st to end	Day	21% 18% 35% 19% 6% 1	550
April	1st to 10th	Day	19% 15% 34% 23% 8% 1	500
	11th to 20th	Day	15% 15% 30% 26% 12% 2	492
	21st to end	Day	12% 10% 27% 32% 16% 3	500
May	1st to 10th	Day	14% 12% 32% 25% 12% 5%	503
	11th to 20th	Day	17% 6% 24% 27% 18% 8%	527
	21st to end	Day	14% 7% 19% 29% 21% 10%	573
June	1st to 10th	Day	11% 4 19% 30% 27% 9%	530
	11th to 20th	Day	8% 4 16% 28% 27% 17%	530
	21st to end	Day	6% 3 15% 32% 30% 15%	530
July	1st to 10th	Day	9% 2 10% 26% 32% 21%	525
	11th to 20th	Day	8% 3 8% 24% 37% 20%	524
	21st to end	Day	8% 1 8% 31% 36% 16%	532
August	1st to 10th	Day	13% 4 16% 25% 26% 15%	486
	11th to 20th	Day	11% 3 10% 29% 32% 16%	479
	21st to end	Day	13% 3 11% 26% 31% 16%	539
September	1st to 10th	Day	12% 4 13% 28% 31% 13%	490
	11th to 20th	Day	17% 3 14% 26% 30% 10%	490
	21st to end	Day	16% 5% 16% 30% 24% 9%	490
October	1st to 10th	Day	17% 5% 25% 28% 16% 8%	490
	11th to 20th	Day	13% 9% 25% 28% 18% 7%	490
	21st to end	Day	15% 9% 26% 28% 17% 5%	539
November	1st to 10th	Day	20% 8% 27% 26% 16% 2	448
	11th to 20th	Day	19% 15% 36% 24% 4 2	300
	21st to end	Day	15% 16% 34% 22% 12% 2	300
December	1st to 10th	Day	27% 16% 34% 17% 5% 1	300
	11th to 20th	Day	27% 12% 37% 17% 6% 1	300
	21st to end	Day	31% 15% 32% 15% 5% 2	330
January	1st to 10th	Night	22% 19% 32% 21% 6%	800
	11th to 20th	Night	21% 16% 31% 25% 7%	800
	21st to end	Night	21% 17% 36% 23% 4	880
February	1st to 10th	Night	19% 15% 30% 31% 6%	800
	11th to 20th	Night	25% 16% 32% 24% 3	783
	21st to end	Night	18% 17% 36% 26% 3	660
March	1st to 10th	Night	17% 16% 31% 32% 5%	800
	11th to 20th	Night	17% 15% 32% 27% 9% 1	800
	21st to end	Night	16% 16% 34% 26% 8%	880
April	1st to 10th	Night	15% 15% 33% 27% 11%	800
	11th to 20th	Night	15% 12% 28% 29% 14% 1	709
	21st to end	Night	10% 7% 28% 39% 15% 1	600
May	1st to 10th	Night	9% 9% 26% 38% 17% 1	600
	11th to 20th	Night	12% 4 23% 35% 22% 4	591
	21st to end	Night	13% 4 15% 32% 31% 5%	650
June	1st to 10th	Night	9% 4 15% 39% 30% 4	600
	11th to 20th	Night	7% 2 16% 33% 31% 10%	600
	21st to end	Night	9% 2 11% 37% 34% 7%	600
July	1st to 10th	Night	9% 2 10% 29% 39% 12%	585
	11th to 20th	Night	7% 1 7% 30% 45% 10%	582
	21st to end	Night	7% 2 9% 32% 43% 7%	624
August	1st to 10th	Night	10% 2 8% 32% 40% 8%	567
	11th to 20th	Night	13% 1 8% 30% 41% 7%	564
	21st to end	Night	13% 3 8% 30% 39% 8%	687
September	1st to 10th	Night	12% 3 10% 31% 36% 8%	760
	11th to 20th	Night	16% 3 12% 27% 36% 4	760
	21st to end	Night	16% 3 15% 30% 32% 3	760
October	1st to 10th	Night	14% 4 18% 33% 25% 6%	760
	11th to 20th	Night	14% 7% 21% 32% 23% 3	760
	21st to end	Night	13% 9% 22% 32% 22% 2	836
November	1st to 10th	Night	14% 8% 24% 32% 19% 3	780
	11th to 20th	Night	17% 11% 28% 28% 14% 2	800
	21st to end	Night	15% 11% 29% 29% 14% 1	800
December	1st to 10th	Night	18% 15% 26% 32% 8% 2	800
	11th to 20th	Night	20% 12% 28% 28% 12% 1	800
	21st to end	Night	26% 14% 26% 28% 7%	880

Page generated at 2025-07-18 01:09:58. Version ac07

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