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 2024-04-03.

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% 5% 2 5% 5% 3 5% 5% 6% 8% 43%	79213
	Night	12% 6% 2 5% 5% 3 4 5% 5% 7% 45%	80925
Transparency	Day	39% 6% 11% 20% 19% 6%	78936
	Night	37% 6% 10% 19% 20% 7%	80721
Seeing	Day	16% 10% 24% 24% 19% 8%	14233
	Night	15% 9% 23% 30% 20% 3	24392

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% 6% 2 4 4 3 5% 5% 5% 7% 42%	2836
	11th to 20th	Day	13% 5% 2 4 3 2 4 4 4 7% 53%	2840
	21st to end	Day	23% 7% 2 6% 4 2 2 3 3 4 44%	3124
February	1st to 10th	Day	16% 6% 3 6% 5% 2 4 5% 5% 7% 41%	1883
	11th to 20th	Day	20% 6% 2 4 3 2 3 4 5% 5% 45%	1848
	21st to end	Day	18% 6% 2 6% 4 2 4 4 5% 6% 42%	1570
March	1st to 10th	Day	15% 5% 3 4 4 3 3 4 4 6% 50%	2040
	11th to 20th	Day	17% 4 2 5% 5% 3 4 4 4 7% 44%	2090
	21st to end	Day	15% 6% 2 5% 5% 3 5% 5% 5% 6% 42%	2299
April	1st to 10th	Day	11% 4 2 6% 5% 3 5% 5% 5% 7% 48%	2002
	11th to 20th	Day	11% 5% 3 5% 5% 3 4 4 5% 6% 48%	2082
	21st to end	Day	8% 3 2 4 5% 3 5% 5% 5% 8% 53%	2340
May	1st to 10th	Day	9% 4 2 4 5% 3 4 5% 6% 8% 50%	2340
	11th to 20th	Day	11% 5% 3 6% 6% 3 6% 5% 6% 8% 41%	2301
	21st to end	Day	11% 5% 2 5% 5% 3 6% 6% 6% 9% 41%	2531
June	1st to 10th	Day	10% 5% 3 6% 7% 5% 6% 7% 8% 10% 33%	2340
	11th to 20th	Day	7% 3 2 5% 6% 4 7% 7% 6% 11% 43%	2340
	21st to end	Day	5% 4 3 6% 7% 5% 7% 6% 9% 11% 37%	2340
July	1st to 10th	Day	8% 6% 2 7% 8% 5% 8% 8% 8% 9% 31%	2340
	11th to 20th	Day	8% 5% 2 7% 7% 5% 7% 6% 8% 12% 31%	2340
	21st to end	Day	6% 4 3 7% 7% 6% 7% 9% 9% 13% 30%	2547
August	1st to 10th	Day	9% 6% 2 7% 8% 6% 6% 8% 9% 11% 27%	2327
	11th to 20th	Day	11% 5% 3 7% 8% 5% 8% 7% 7% 10% 30%	2286
	21st to end	Day	14% 8% 3 6% 7% 5% 6% 6% 8% 10% 29%	2300
September	1st to 10th	Day	10% 6% 3 6% 5% 4 6% 6% 7% 9% 39%	1980
	11th to 20th	Day	14% 5% 3 6% 5% 3 5% 5% 5% 7% 41%	1980
	21st to end	Day	15% 6% 2 5% 5% 3 4 4 5% 6% 44%	1980
October	1st to 10th	Day	14% 6% 2 4 3 3 3 3 5% 6% 51%	1980
	11th to 20th	Day	13% 3 2 4 3 2 3 3 4 6% 56%	1807
	21st to end	Day	11% 4 2 4 4 3 3 4 4 5% 56%	1980
November	1st to 10th	Day	12% 5% 2 4 4 3 4 3 4 5% 55%	1813
	11th to 20th	Day	14% 5% 2 4 3 2 3 3 4 6% 54%	1710
	21st to end	Day	13% 5% 3 3 5% 3 4 4 5% 7% 48%	1710
December	1st to 10th	Day	17% 7% 3 5% 6% 3 5% 5% 6% 6% 38%	1710
	11th to 20th	Day	17% 6% 2 5% 4 3 3 3 4 6% 48%	2153
	21st to end	Day	20% 8% 3 5% 4 2 3 3 5% 6% 41%	3124
January	1st to 10th	Night	16% 6% 2 4 4 3 3 4 5% 6% 44%	4109
	11th to 20th	Night	11% 6% 2 4 5% 3 4 5% 6% 8% 46%	4120
	21st to end	Night	20% 9% 3 6% 4 2 3 4 3 4 43%	4532
February	1st to 10th	Night	16% 5% 2 5% 5% 3 3 4 5% 6% 45%	2295
	11th to 20th	Night	19% 6% 2 5% 4 2 4 3 4 5% 44%	2218
	21st to end	Night	15% 6% 3 5% 5% 3 4 4 5% 6% 44%	1884
March	1st to 10th	Night	13% 7% 2 5% 4 3 4 4 4 7% 47%	2138
	11th to 20th	Night	14% 5% 2 3 4 3 5% 4 5% 8% 47%	2090
	21st to end	Night	13% 5% 2 6% 4 3 6% 4 4 7% 46%	2299
April	1st to 10th	Night	11% 4 2 5% 5% 3 4 4 5% 7% 51%	2003
	11th to 20th	Night	12% 5% 1 4 4 2 4 3 4 8% 53%	1840
	21st to end	Night	8% 4 1 3 5% 2 4 4 5% 8% 55%	1620
May	1st to 10th	Night	6% 5% 2 4 4 3 5% 5% 5% 7% 54%	1620
	11th to 20th	Night	9% 4 2 5% 6% 4 6% 6% 7% 9% 42%	1592
	21st to end	Night	10% 5% 2 6% 6% 3 5% 6% 6% 9% 42%	1744
June	1st to 10th	Night	8% 6% 3 5% 6% 4 6% 7% 8% 13% 35%	1620
	11th to 20th	Night	5% 3 2 5% 6% 3 5% 5% 8% 12% 44%	1620
	21st to end	Night	7% 4 2 5% 5% 3 6% 9% 8% 10% 39%	1620
July	1st to 10th	Night	8% 5% 3 6% 5% 4 7% 7% 9% 12% 34%	1620
	11th to 20th	Night	5% 5% 3 6% 6% 5% 6% 8% 9% 13% 33%	1620
	21st to end	Night	6% 5% 2 5% 6% 4 7% 8% 9% 13% 36%	1771
August	1st to 10th	Night	6% 7% 2 7% 7% 6% 6% 8% 8% 10% 32%	1611
	11th to 20th	Night	11% 5% 2 5% 6% 4 5% 7% 9% 12% 34%	1609
	21st to end	Night	11% 7% 3 6% 6% 3 6% 7% 8% 10% 33%	2036
September	1st to 10th	Night	10% 5% 2 5% 6% 3 5% 7% 7% 10% 39%	1980
	11th to 20th	Night	13% 6% 2 6% 6% 3 5% 4 5% 8% 42%	1980
	21st to end	Night	12% 6% 2 5% 5% 3 4 4 5% 7% 48%	1980
October	1st to 10th	Night	12% 4 2 4 4 2 4 4 4 6% 53%	1980
	11th to 20th	Night	13% 5% 2 4 3 2 4 3 4 4 57%	2151
	21st to end	Night	11% 4 1 4 4 3 4 3 4 6% 57%	2376
November	1st to 10th	Night	10% 6% 2 4 4 2 3 2 4 6% 57%	2263
	11th to 20th	Night	14% 6% 2 4 3 3 3 4 3 6% 53%	2470
	21st to end	Night	14% 4 2 4 4 3 4 4 5% 7% 48%	2470
December	1st to 10th	Night	14% 7% 3 5% 5% 2 4 5% 5% 6% 45%	2470
	11th to 20th	Night	16% 6% 2 4 3 2 3 3 4 5% 51%	3042
	21st to end	Night	18% 9% 3 6% 5% 3 4 5% 5% 6% 37%	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	41% 5% 6% 19% 22% 7%	2837
	11th to 20th	Day	32% 3 5% 22% 27% 11%	2840
	21st to end	Day	46% 3 3 17% 23% 8%	3124
February	1st to 10th	Day	43% 5% 8% 19% 18% 7%	1883
	11th to 20th	Day	42% 4 5% 20% 22% 8%	1858
	21st to end	Day	43% 5% 7% 14% 21% 9%	1570
March	1st to 10th	Day	37% 4 6% 19% 23% 11%	2040
	11th to 20th	Day	40% 5% 10% 18% 19% 7%	2090
	21st to end	Day	42% 5% 9% 22% 18% 5%	2299
April	1st to 10th	Day	36% 5% 10% 21% 21% 7%	2002
	11th to 20th	Day	36% 5% 7% 21% 22% 9%	2082
	21st to end	Day	30% 6% 10% 27% 24% 4	2340
May	1st to 10th	Day	31% 5% 13% 24% 22% 5%	2340
	11th to 20th	Day	41% 6% 16% 21% 15% 2	2305
	21st to end	Day	37% 7% 13% 24% 17% 2	2531
June	1st to 10th	Day	42% 9% 17% 20% 11% 2	2340
	11th to 20th	Day	33% 8% 19% 26% 13% 1	2340
	21st to end	Day	36% 11% 18% 19% 11% 4	2340
July	1st to 10th	Day	42% 13% 17% 18% 9% 3	2275
	11th to 20th	Day	41% 12% 20% 18% 7% 3	2271
	21st to end	Day	39% 12% 21% 19% 8% 1	2405
August	1st to 10th	Day	45% 12% 17% 21% 5% 1	2314
	11th to 20th	Day	45% 10% 17% 18% 8% 2	2286
	21st to end	Day	49% 9% 15% 16% 9% 2	2300
September	1st to 10th	Day	40% 8% 14% 18% 17% 4	1980
	11th to 20th	Day	42% 6% 9% 18% 22% 2	1980
	21st to end	Day	41% 5% 9% 20% 19% 6%	1980
October	1st to 10th	Day	34% 4 8% 21% 26% 7%	1980
	11th to 20th	Day	30% 4 7% 24% 27% 8%	1807
	21st to end	Day	32% 4 4 17% 30% 12%	1980
November	1st to 10th	Day	33% 3 7% 17% 27% 13%	1813
	11th to 20th	Day	33% 3 7% 22% 24% 12%	1710
	21st to end	Day	36% 6% 7% 20% 24% 7%	1710
December	1st to 10th	Day	45% 5% 8% 17% 17% 7%	1710
	11th to 20th	Day	39% 4 6% 17% 25% 9%	2150
	21st to end	Day	44% 4 7% 18% 23% 4	3124
January	1st to 10th	Night	39% 5% 5% 18% 25% 8%	4109
	11th to 20th	Night	35% 4 6% 23% 23% 9%	4120
	21st to end	Night	46% 5% 3 12% 25% 8%	4532
February	1st to 10th	Night	40% 3 9% 18% 21% 9%	2295
	11th to 20th	Night	43% 3 5% 18% 22% 9%	2219
	21st to end	Night	41% 4 8% 15% 19% 12%	1884
March	1st to 10th	Night	38% 4 8% 16% 21% 12%	2138
	11th to 20th	Night	36% 6% 12% 17% 22% 8%	2090
	21st to end	Night	38% 4 9% 21% 20% 8%	2299
April	1st to 10th	Night	33% 5% 10% 21% 22% 10%	2003
	11th to 20th	Night	31% 3 7% 25% 23% 11%	1840
	21st to end	Night	28% 6% 11% 25% 23% 8%	1620
May	1st to 10th	Night	29% 6% 14% 24% 21% 7%	1620
	11th to 20th	Night	37% 8% 16% 20% 17% 2	1593
	21st to end	Night	37% 8% 12% 23% 17% 3	1745
June	1st to 10th	Night	39% 10% 19% 18% 13% 1	1620
	11th to 20th	Night	30% 10% 21% 25% 13% 2	1620
	21st to end	Night	33% 13% 20% 19% 11% 3	1620
July	1st to 10th	Night	39% 13% 21% 15% 9% 4	1575
	11th to 20th	Night	38% 13% 23% 18% 7% 2	1566
	21st to end	Night	34% 14% 25% 19% 7% 1	1672
August	1st to 10th	Night	42% 13% 19% 21% 5%	1600
	11th to 20th	Night	39% 12% 20% 18% 10% 2	1609
	21st to end	Night	44% 10% 19% 17% 9% 2	2036
September	1st to 10th	Night	37% 12% 15% 17% 16% 4	1980
	11th to 20th	Night	41% 8% 12% 16% 19% 5%	1980
	21st to end	Night	36% 6% 10% 18% 23% 7%	1980
October	1st to 10th	Night	32% 5% 9% 20% 27% 7%	1980
	11th to 20th	Night	31% 4 6% 21% 27% 10%	2151
	21st to end	Night	30% 4 5% 18% 30% 14%	2376
November	1st to 10th	Night	31% 3 7% 17% 27% 15%	2263
	11th to 20th	Night	34% 3 6% 17% 25% 14%	2470
	21st to end	Night	36% 4 7% 18% 26% 9%	2470
December	1st to 10th	Night	39% 6% 9% 19% 20% 7%	2470
	11th to 20th	Night	37% 4 7% 16% 27% 9%	3044
	21st to end	Night	47% 5% 5% 20% 19% 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	24% 24% 38% 11% 3	270
	11th to 20th	Day	21% 23% 34% 15% 6%	270
	21st to end	Day	24% 27% 37% 9% 3	297
February	1st to 10th	Day	24% 20% 37% 15% 4	270
	11th to 20th	Day	36% 18% 32% 13% 1	270
	21st to end	Day	27% 22% 39% 9% 4	225
March	1st to 10th	Day	20% 16% 33% 24% 5% 1	410
	11th to 20th	Day	21% 15% 38% 18% 7% 1	460
	21st to end	Day	21% 18% 35% 18% 7% 1	506
April	1st to 10th	Day	20% 15% 32% 22% 10% 1	428
	11th to 20th	Day	15% 17% 29% 23% 15% 2	412
	21st to end	Day	13% 11% 28% 28% 17% 4	420
May	1st to 10th	Day	13% 12% 32% 25% 13% 5%	423
	11th to 20th	Day	15% 5% 21% 29% 21% 9%	447
	21st to end	Day	14% 6% 15% 29% 24% 12%	485
June	1st to 10th	Day	11% 3 16% 29% 30% 11%	450
	11th to 20th	Day	9% 4 16% 25% 28% 18%	450
	21st to end	Day	7% 3 17% 31% 27% 15%	450
July	1st to 10th	Day	10% 1 11% 25% 32% 22%	445
	11th to 20th	Day	9% 3 9% 24% 35% 20%	444
	21st to end	Day	8% 1 8% 28% 37% 18%	488
August	1st to 10th	Day	13% 4 16% 25% 27% 16%	446
	11th to 20th	Day	12% 2 9% 28% 33% 17%	439
	21st to end	Day	15% 3 12% 25% 31% 15%	495
September	1st to 10th	Day	11% 4 12% 27% 32% 14%	450
	11th to 20th	Day	15% 3 14% 26% 32% 11%	450
	21st to end	Day	16% 4 15% 31% 24% 9%	450
October	1st to 10th	Day	18% 5% 25% 28% 16% 9%	450
	11th to 20th	Day	14% 8% 25% 26% 19% 8%	450
	21st to end	Day	17% 9% 26% 26% 17% 5%	495
November	1st to 10th	Day	17% 9% 29% 27% 17% 3	411
	11th to 20th	Day	19% 16% 35% 25% 4 1	270
	21st to end	Day	13% 15% 34% 24% 12% 2	270
December	1st to 10th	Day	28% 16% 32% 18% 6% 1	270
	11th to 20th	Day	27% 12% 39% 16% 5% 1	270
	21st to end	Day	30% 17% 32% 14% 5% 2	297
January	1st to 10th	Night	22% 19% 32% 22% 6%	760
	11th to 20th	Night	20% 16% 31% 26% 7%	760
	21st to end	Night	21% 17% 35% 23% 4	836
February	1st to 10th	Night	19% 15% 29% 31% 6%	760
	11th to 20th	Night	23% 16% 33% 25% 3	743
	21st to end	Night	19% 17% 36% 25% 3	628
March	1st to 10th	Night	16% 16% 31% 32% 5%	760
	11th to 20th	Night	18% 14% 32% 27% 9% 1	760
	21st to end	Night	16% 16% 33% 26% 8%	836
April	1st to 10th	Night	14% 15% 32% 28% 11%	729
	11th to 20th	Night	15% 12% 28% 28% 16% 1	638
	21st to end	Night	11% 7% 28% 38% 15% 1	540
May	1st to 10th	Night	9% 9% 27% 37% 17% 1	540
	11th to 20th	Night	11% 3 22% 36% 24% 4	531
	21st to end	Night	13% 3 13% 30% 34% 6%	584
June	1st to 10th	Night	9% 3 14% 39% 31% 4	540
	11th to 20th	Night	7% 1 16% 32% 32% 11%	540
	21st to end	Night	9% 2 12% 37% 33% 7%	540
July	1st to 10th	Night	10% 1 9% 29% 38% 13%	525
	11th to 20th	Night	8% 1 7% 30% 44% 10%	522
	21st to end	Night	6% 1 8% 32% 45% 7%	591
August	1st to 10th	Night	10% 1 7% 32% 41% 9%	537
	11th to 20th	Night	14% 1 7% 29% 41% 7%	534
	21st to end	Night	13% 3 8% 30% 38% 8%	650
September	1st to 10th	Night	12% 3 9% 30% 38% 9%	720
	11th to 20th	Night	15% 3 12% 28% 37% 5%	720
	21st to end	Night	16% 2 15% 30% 33% 4	720
October	1st to 10th	Night	14% 4 19% 32% 25% 6%	720
	11th to 20th	Night	14% 7% 21% 31% 23% 4	720
	21st to end	Night	14% 10% 22% 31% 21% 2	792
November	1st to 10th	Night	13% 8% 24% 33% 19% 3	740
	11th to 20th	Night	16% 11% 28% 29% 14% 2	760
	21st to end	Night	15% 10% 29% 30% 14% 1	760
December	1st to 10th	Night	18% 15% 25% 32% 8% 2	760
	11th to 20th	Night	20% 12% 28% 28% 12% 1	760
	21st to end	Night	26% 14% 26% 27% 7%	836

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