Stokes Starparty
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stokes Starparty clear sky chart from 2005-11-06 to 2026-02-16.

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	17% 7% 3 6% 4 4 4 4 5% 7% 37%	130980
	Night	17% 8% 3 6% 4 4 4 3 5% 6% 40%	129864
Transparency	Day	45% 6% 11% 22% 15% 2	134481
	Night	44% 5% 12% 22% 15% 2	134450
Seeing	Day	24% 17% 28% 19% 9% 3	16452
	Night	22% 15% 29% 25% 9% 1	25758

By Month

Percentage Cloud Cover NE (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	12% 10% 4 8% 5% 5% 4 3 6% 6% 37%	4661
	11th to 20th	Day	15% 10% 4 9% 5% 4 4 3 4 6% 36%	4650
	21st to end	Day	16% 8% 3 6% 4 4 4 4 5% 6% 40%	5660
February	1st to 10th	Day	15% 9% 3 8% 5% 5% 5% 3 5% 7% 35%	1890
	11th to 20th	Day	13% 9% 4 7% 5% 5% 4 3 5% 6% 39%	1951
	21st to end	Day	18% 10% 3 7% 4 4 4 4 5% 6% 36%	1650
March	1st to 10th	Day	22% 9% 3 6% 4 4 3 2 4 5% 39%	4476
	11th to 20th	Day	13% 7% 4 7% 5% 4 4 3 5% 7% 42%	4883
	21st to end	Day	19% 8% 2 6% 4 3 4 3 4 6% 40%	5864
April	1st to 10th	Day	19% 9% 2 6% 5% 4 5% 3 5% 6% 36%	2400
	11th to 20th	Day	18% 8% 2 5% 4 5% 4 3 4 7% 40%	2374
	21st to end	Day	18% 6% 2 7% 5% 5% 5% 4 5% 6% 38%	2400
May	1st to 10th	Day	30% 7% 2 5% 4 4 4 3 5% 7% 29%	6008
	11th to 20th	Day	23% 8% 3 7% 4 4 4 3 5% 6% 33%	6318
	21st to end	Day	21% 6% 2 6% 4 4 5% 4 7% 8% 33%	6949
June	1st to 10th	Day	15% 6% 2 7% 5% 6% 5% 5% 6% 9% 36%	2800
	11th to 20th	Day	17% 6% 3 6% 5% 5% 4 5% 7% 8% 34%	2800
	21st to end	Day	13% 5% 3 7% 6% 5% 5% 4 6% 10% 38%	2800
July	1st to 10th	Day	11% 7% 2 8% 5% 6% 5% 5% 6% 10% 35%	6360
	11th to 20th	Day	11% 7% 2 7% 5% 5% 6% 5% 8% 11% 32%	6360
	21st to end	Day	13% 7% 3 6% 5% 5% 4 4 5% 8% 41%	6926
August	1st to 10th	Day	21% 5% 2 7% 5% 5% 5% 4 7% 7% 31%	4314
	11th to 20th	Day	14% 6% 2 7% 4 4 6% 4 6% 8% 40%	3858
	21st to end	Day	14% 6% 2 4 3 4 4 3 5% 9% 46%	4312
September	1st to 10th	Day	15% 6% 2 6% 4 4 5% 4 5% 6% 44%	2400
	11th to 20th	Day	13% 5% 2 4 3 4 3 3 5% 7% 50%	2347
	21st to end	Day	18% 7% 3 7% 4 4 5% 3 5% 7% 38%	2200
October	1st to 10th	Day	20% 6% 2 6% 4 3 4 3 4 7% 41%	2031
	11th to 20th	Day	15% 7% 2 6% 4 3 4 3 5% 7% 43%	2000
	21st to end	Day	21% 7% 1 5% 4 4 5% 4 5% 6% 39%	2071
November	1st to 10th	Day	13% 7% 2 5% 3 3 3 2 4 6% 51%	1851
	11th to 20th	Day	17% 8% 2 4 4 3 3 4 6% 6% 42%	1890
	21st to end	Day	17% 9% 2 5% 5% 4 5% 5% 5% 7% 37%	1732
December	1st to 10th	Day	15% 9% 3 7% 4 5% 4 4 5% 6% 39%	2680
	11th to 20th	Day	21% 8% 3 6% 3 3 4 3 4 5% 39%	3066
	21st to end	Day	18% 11% 4 9% 5% 5% 5% 4 4 7% 30%	4048
January	1st to 10th	Night	12% 10% 3 9% 6% 5% 5% 4 6% 6% 34%	8234
	11th to 20th	Night	14% 10% 4 11% 4 4 5% 4 4 6% 34%	8235
	21st to end	Night	14% 8% 3 7% 5% 4 4 3 5% 6% 42%	8504
February	1st to 10th	Night	16% 8% 2 6% 4 4 4 3 5% 6% 40%	2730
	11th to 20th	Night	16% 8% 2 7% 4 5% 5% 4 5% 7% 38%	2446
	21st to end	Night	17% 9% 2 7% 5% 4 4 3 5% 5% 39%	1980
March	1st to 10th	Night	19% 10% 3 6% 3 3 3 3 5% 5% 40%	5364
	11th to 20th	Night	15% 7% 3 5% 3 4 4 3 5% 7% 45%	5072
	21st to end	Night	16% 8% 3 7% 4 4 4 3 5% 5% 40%	5067
April	1st to 10th	Night	18% 9% 3 7% 5% 5% 4 4 5% 7% 34%	2000
	11th to 20th	Night	19% 8% 2 6% 4 5% 4 4 5% 7% 38%	1975
	21st to end	Night	19% 7% 2 5% 4 4 4 4 5% 6% 41%	2000
May	1st to 10th	Night	31% 8% 3 5% 4 4 3 3 5% 7% 28%	3972
	11th to 20th	Night	24% 10% 2 6% 3 4 3 3 5% 5% 35%	3575
	21st to end	Night	21% 7% 2 6% 5% 4 4 3 6% 8% 34%	3926
June	1st to 10th	Night	17% 6% 2 5% 5% 5% 3 3 4 8% 43%	1600
	11th to 20th	Night	15% 6% 3 5% 4 4 5% 4 6% 8% 41%	1600
	21st to end	Night	13% 4 2 6% 4 3 4 4 6% 9% 45%	1600
July	1st to 10th	Night	12% 6% 2 7% 5% 5% 5% 3 6% 10% 40%	3600
	11th to 20th	Night	15% 7% 2 7% 4 5% 6% 4 6% 9% 36%	3600
	21st to end	Night	14% 5% 1 5% 4 4 5% 4 5% 7% 48%	3926
August	1st to 10th	Night	22% 5% 3 6% 4 5% 4 4 5% 7% 35%	2832
	11th to 20th	Night	15% 6% 2 6% 4 4 5% 3 5% 6% 42%	3157
	21st to end	Night	13% 4 2 4 4 4 3 3 5% 8% 50%	3586
September	1st to 10th	Night	16% 4 1 5% 4 3 4 3 5% 7% 47%	2000
	11th to 20th	Night	14% 4 2 4 3 4 3 3 4 6% 52%	2052
	21st to end	Night	18% 6% 3 5% 4 3 3 3 5% 7% 44%	2200
October	1st to 10th	Night	21% 6% 2 4 3 3 3 2 4 6% 44%	2365
	11th to 20th	Night	18% 6% 1 5% 3 3 3 3 4 6% 47%	2400
	21st to end	Night	21% 7% 2 4 3 2 3 3 5% 6% 44%	2767
November	1st to 10th	Night	13% 6% 2 5% 3 4 4 3 5% 7% 49%	2667
	11th to 20th	Night	18% 7% 2 5% 4 3 3 3 5% 5% 45%	2730
	21st to end	Night	14% 7% 2 7% 4 4 4 4 5% 7% 43%	2884
December	1st to 10th	Night	14% 9% 3 6% 4 4 4 3 5% 7% 42%	4720
	11th to 20th	Night	24% 8% 2 4 3 3 4 3 4 4 38%	5348
	21st to end	Night	20% 12% 3 8% 4 4 4 3 4 5% 33%	7150

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	47% 4 11% 24% 12% 2	4662
	11th to 20th	Day	48% 4 10% 19% 13% 6%	4680
	21st to end	Day	44% 4 11% 24% 16% 1	5660
February	1st to 10th	Day	49% 5% 12% 19% 14% 2	1890
	11th to 20th	Day	46% 5% 8% 21% 16% 2	1960
	21st to end	Day	49% 5% 10% 22% 12% 3	1650
March	1st to 10th	Day	48% 3 10% 19% 12% 7%	4479
	11th to 20th	Day	40% 7% 12% 28% 8% 4	4883
	21st to end	Day	46% 4 10% 11% 24% 6%	5864
April	1st to 10th	Day	49% 5% 9% 19% 14% 4	2400
	11th to 20th	Day	45% 5% 11% 20% 16% 3	2374
	21st to end	Day	46% 6% 9% 21% 15% 4	2400
May	1st to 10th	Day	55% 6% 13% 15% 10% 1	6019
	11th to 20th	Day	53% 6% 8% 20% 12% 1	6322
	21st to end	Day	47% 7% 11% 21% 12% 2	6949
June	1st to 10th	Day	44% 8% 12% 21% 14% 1	2800
	11th to 20th	Day	45% 8% 13% 22% 11% 2	2800
	21st to end	Day	42% 7% 13% 24% 14% 1	2800
July	1st to 10th	Day	44% 9% 12% 20% 14% 1	6290
	11th to 20th	Day	42% 9% 17% 22% 10%	6285
	21st to end	Day	41% 6% 10% 22% 19% 1	6728
August	1st to 10th	Day	50% 8% 13% 20% 9% 1	4300
	11th to 20th	Day	39% 7% 15% 27% 11% 1	3894
	21st to end	Day	35% 5% 11% 31% 15% 1	4312
September	1st to 10th	Day	40% 7% 11% 22% 18% 2	2400
	11th to 20th	Day	35% 4 10% 23% 24% 3	2347
	21st to end	Day	46% 6% 10% 18% 18% 2	2200
October	1st to 10th	Day	41% 5% 8% 19% 23% 4	3304
	11th to 20th	Day	32% 5% 9% 27% 24% 3	3240
	21st to end	Day	30% 4 15% 26% 22% 3	3322
November	1st to 10th	Day	36% 4 12% 25% 19% 3	1851
	11th to 20th	Day	42% 4 10% 24% 17% 3	1890
	21st to end	Day	45% 7% 12% 25% 10% 2	1732
December	1st to 10th	Day	46% 4 14% 25% 9% 1	2680
	11th to 20th	Day	47% 4 14% 21% 12% 2	3066
	21st to end	Day	53% 6% 10% 18% 13% 1	4048
January	1st to 10th	Night	49% 6% 11% 20% 12% 2	8234
	11th to 20th	Night	50% 4 12% 17% 12% 4	8280
	21st to end	Night	42% 4 9% 22% 19% 3	8504
February	1st to 10th	Night	45% 5% 13% 23% 13% 2	2730
	11th to 20th	Night	45% 5% 10% 20% 16% 4	2448
	21st to end	Night	46% 4 8% 23% 16% 3	1980
March	1st to 10th	Night	46% 4 11% 20% 13% 6%	5374
	11th to 20th	Night	38% 6% 16% 24% 12% 4	5073
	21st to end	Night	46% 4 8% 17% 21% 4	5067
April	1st to 10th	Night	50% 6% 10% 19% 13% 3	2000
	11th to 20th	Night	47% 6% 10% 19% 18% 1	1975
	21st to end	Night	43% 6% 9% 22% 17% 4	2000
May	1st to 10th	Night	56% 5% 11% 16% 10% 1	3978
	11th to 20th	Night	52% 6% 12% 16% 13% 1	3576
	21st to end	Night	47% 8% 12% 22% 10% 1	3927
June	1st to 10th	Night	41% 6% 10% 23% 19% 1	1600
	11th to 20th	Night	40% 7% 15% 26% 11% 1	1600
	21st to end	Night	34% 8% 15% 27% 14% 1	1600
July	1st to 10th	Night	40% 8% 14% 20% 16% 2	3560
	11th to 20th	Night	43% 9% 14% 21% 11% 1	3552
	21st to end	Night	36% 6% 13% 25% 19% 1	3809
August	1st to 10th	Night	49% 7% 15% 19% 9% 1	2822
	11th to 20th	Night	42% 7% 13% 27% 10%	3187
	21st to end	Night	33% 5% 11% 33% 17% 1	3586
September	1st to 10th	Night	38% 5% 11% 26% 19% 1	2000
	11th to 20th	Night	34% 5% 10% 25% 25% 2	2052
	21st to end	Night	41% 5% 9% 22% 21% 1	2200
October	1st to 10th	Night	42% 5% 10% 23% 20% 1	3872
	11th to 20th	Night	30% 4 10% 28% 26% 3	3899
	21st to end	Night	31% 5% 15% 30% 19% 1	4466
November	1st to 10th	Night	35% 5% 13% 24% 21% 2	2667
	11th to 20th	Night	41% 4 10% 22% 19% 3	2730
	21st to end	Night	41% 5% 14% 27% 12% 1	2884
December	1st to 10th	Night	43% 4 13% 30% 9% 1	4720
	11th to 20th	Night	49% 4 13% 19% 14% 2	5348
	21st to end	Night	53% 5% 11% 18% 12% 2	7150

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	31% 30% 25% 12% 2	220
	11th to 20th	Day	41% 29% 25% 4 1	220
	21st to end	Day	30% 31% 29% 6% 2 1	341
February	1st to 10th	Day	31% 31% 28% 9% 2	330
	11th to 20th	Day	37% 25% 28% 9% 1	469
	21st to end	Day	33% 25% 29% 10% 3	414
March	1st to 10th	Day	31% 24% 28% 13% 3	500
	11th to 20th	Day	29% 25% 29% 13% 4 1	500
	21st to end	Day	31% 26% 28% 9% 4 1	550
April	1st to 10th	Day	33% 25% 25% 12% 4	500
	11th to 20th	Day	29% 24% 26% 13% 7% 1	492
	21st to end	Day	29% 20% 32% 14% 5% 1	500
May	1st to 10th	Day	35% 20% 24% 13% 6% 1	503
	11th to 20th	Day	23% 21% 29% 18% 7% 2	527
	21st to end	Day	23% 10% 30% 24% 11% 2	573
June	1st to 10th	Day	18% 14% 32% 22% 12% 2	530
	11th to 20th	Day	22% 14% 25% 26% 12% 1	530
	21st to end	Day	16% 14% 31% 27% 10% 1	530
July	1st to 10th	Day	15% 7% 30% 26% 16% 5%	525
	11th to 20th	Day	11% 7% 28% 32% 18% 3	524
	21st to end	Day	14% 9% 35% 29% 11% 3	576
August	1st to 10th	Day	14% 7% 28% 29% 15% 7%	526
	11th to 20th	Day	13% 7% 25% 32% 16% 6%	519
	21st to end	Day	13% 11% 31% 23% 15% 7%	583
September	1st to 10th	Day	19% 12% 27% 23% 13% 7%	530
	11th to 20th	Day	13% 11% 26% 24% 16% 11%	530
	21st to end	Day	24% 9% 30% 23% 10% 5%	530
October	1st to 10th	Day	26% 10% 24% 20% 14% 6%	530
	11th to 20th	Day	22% 18% 29% 19% 9% 2	530
	21st to end	Day	27% 17% 29% 18% 7% 2	511
November	1st to 10th	Day	21% 20% 29% 20% 9% 2	425
	11th to 20th	Day	27% 22% 27% 18% 6%	430
	21st to end	Day	31% 24% 30% 11% 3 1	272
December	1st to 10th	Day	33% 27% 26% 9% 5%	220
	11th to 20th	Day	38% 26% 25% 9% 3	220
	21st to end	Day	32% 19% 33% 11% 5%	242
January	1st to 10th	Night	24% 24% 34% 16% 2	840
	11th to 20th	Night	27% 22% 28% 20% 3	840
	21st to end	Night	22% 24% 35% 17% 2	924
February	1st to 10th	Night	25% 20% 34% 19% 1	840
	11th to 20th	Night	28% 24% 35% 13% 1	804
	21st to end	Night	30% 21% 31% 15% 2	660
March	1st to 10th	Night	27% 22% 31% 17% 3	800
	11th to 20th	Night	26% 23% 30% 18% 4	800
	21st to end	Night	24% 22% 34% 15% 5%	880
April	1st to 10th	Night	26% 20% 33% 17% 4	800
	11th to 20th	Night	24% 19% 33% 19% 5%	791
	21st to end	Night	25% 15% 31% 24% 5%	800
May	1st to 10th	Night	28% 13% 30% 23% 6%	570
	11th to 20th	Night	21% 11% 34% 27% 6% 1	394
	21st to end	Night	17% 7% 27% 36% 11%	433
June	1st to 10th	Night	18% 7% 24% 37% 14% 1	400
	11th to 20th	Night	15% 7% 30% 37% 13%	400
	21st to end	Night	12% 7% 26% 42% 14%	400
July	1st to 10th	Night	12% 5% 23% 40% 19% 1	390
	11th to 20th	Night	12% 4 25% 42% 16% 1	388
	21st to end	Night	12% 5% 21% 45% 17% 1	438
August	1st to 10th	Night	11% 4 21% 39% 23% 2	540
	11th to 20th	Night	14% 5% 19% 36% 24% 2	762
	21st to end	Night	15% 6% 22% 36% 20% 2	880
September	1st to 10th	Night	17% 6% 25% 34% 16% 2	800
	11th to 20th	Night	15% 6% 23% 30% 21% 5%	800
	21st to end	Night	20% 8% 23% 30% 17% 2	800
October	1st to 10th	Night	24% 10% 23% 26% 15% 2	800
	11th to 20th	Night	22% 13% 28% 30% 8%	800
	21st to end	Night	25% 15% 30% 22% 8%	880
November	1st to 10th	Night	19% 16% 30% 25% 9% 1	820
	11th to 20th	Night	24% 18% 28% 22% 7% 1	840
	21st to end	Night	20% 21% 30% 23% 5% 1	840
December	1st to 10th	Night	25% 20% 30% 20% 5%	840
	11th to 20th	Night	25% 20% 32% 20% 3	840
	21st to end	Night	27% 20% 30% 20% 3	924

Page generated at 2026-02-13 01:42:12. Version ac07

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