White Star Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White Star Park clear sky chart from 2005-11-06 to 2025-02-06.

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	14% 10% 4 9% 5% 5% 5% 4 6% 7% 32%	108751
	Night	14% 11% 4 9% 5% 4 4 4 5% 6% 33%	109445
Transparency	Day	49% 7% 11% 20% 12% 1	112394
	Night	49% 6% 11% 20% 12% 1	113941
Seeing	Day	17% 11% 28% 24% 14% 6%	15755
	Night	19% 10% 29% 29% 13% 1	25675

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	14% 18% 7% 17% 6% 4 4 3 4 5% 16%	3617
	11th to 20th	Day	14% 18% 6% 15% 9% 5% 7% 3 3 4 16%	3813
	21st to end	Day	22% 16% 8% 14% 5% 5% 4 3 4 4 16%	4466
February	1st to 10th	Day	16% 16% 5% 11% 7% 5% 5% 3 5% 5% 21%	1755
	11th to 20th	Day	15% 11% 5% 12% 7% 6% 6% 4 5% 5% 24%	1815
	21st to end	Day	17% 13% 5% 9% 6% 4 4 4 5% 6% 26%	1570
March	1st to 10th	Day	20% 15% 5% 10% 5% 4 4 3 5% 6% 23%	3212
	11th to 20th	Day	13% 12% 4 9% 5% 4 5% 4 5% 6% 35%	3480
	21st to end	Day	19% 13% 5% 10% 6% 4 4 4 4 5% 26%	3815
April	1st to 10th	Day	13% 12% 4 9% 7% 5% 4 5% 6% 7% 29%	2186
	11th to 20th	Day	16% 9% 3 7% 5% 5% 5% 4 5% 7% 34%	2395
	21st to end	Day	20% 8% 3 7% 5% 4 4 3 5% 7% 34%	2470
May	1st to 10th	Day	18% 9% 3 9% 5% 4 4 4 6% 7% 31%	4082
	11th to 20th	Day	17% 8% 3 6% 5% 5% 6% 4 6% 7% 34%	4081
	21st to end	Day	10% 5% 2 7% 5% 5% 5% 4 6% 8% 42%	4476
June	1st to 10th	Day	12% 5% 3 7% 5% 6% 5% 5% 6% 8% 38%	2537
	11th to 20th	Day	10% 5% 2 6% 6% 5% 4 4 6% 8% 43%	2660
	21st to end	Day	10% 6% 2 7% 6% 5% 5% 5% 8% 9% 38%	2660
July	1st to 10th	Day	10% 6% 2 8% 6% 5% 5% 5% 6% 10% 37%	4440
	11th to 20th	Day	6% 4 2 5% 5% 5% 6% 5% 7% 12% 43%	4358
	21st to end	Day	7% 6% 2 7% 5% 6% 5% 5% 8% 8% 40%	4466
August	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 8% 9% 42%	4104
	11th to 20th	Day	8% 6% 2 6% 5% 5% 6% 5% 9% 12% 37%	4044
	21st to end	Day	8% 6% 2 7% 4 5% 5% 4 7% 10% 42%	4450
September	1st to 10th	Day	14% 6% 2 5% 4 4 5% 5% 6% 7% 44%	2132
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 5% 6% 8% 46%	2090
	21st to end	Day	17% 8% 2 5% 3 4 4 3 5% 7% 41%	2090
October	1st to 10th	Day	12% 7% 2 7% 4 5% 5% 4 6% 6% 43%	2043
	11th to 20th	Day	16% 8% 2 7% 4 5% 4 3 5% 6% 39%	1900
	21st to end	Day	18% 9% 3 8% 6% 4 5% 5% 6% 7% 30%	1970
November	1st to 10th	Day	11% 9% 3 7% 4 5% 4 3 6% 7% 41%	1762
	11th to 20th	Day	16% 13% 4 8% 5% 4 4 3 5% 6% 34%	1800
	21st to end	Day	18% 15% 4 9% 5% 4 4 4 5% 7% 26%	1800
December	1st to 10th	Day	15% 13% 6% 12% 7% 5% 5% 4 4 6% 22%	2796
	11th to 20th	Day	18% 18% 7% 11% 4 5% 4 3 4 5% 21%	3373
	21st to end	Day	24% 20% 7% 13% 5% 4 3 3 3 3 14%	4043
January	1st to 10th	Night	15% 16% 7% 16% 7% 5% 4 3 4 4 19%	6348
	11th to 20th	Night	11% 19% 8% 15% 8% 5% 5% 5% 4 4 15%	6152
	21st to end	Night	20% 16% 7% 11% 4 4 4 3 4 4 22%	6490
February	1st to 10th	Night	18% 14% 5% 10% 7% 5% 4 4 5% 5% 23%	2536
	11th to 20th	Night	14% 14% 4 10% 7% 5% 5% 4 5% 5% 27%	2247
	21st to end	Night	20% 13% 5% 9% 6% 4 4 3 4 5% 28%	1884
March	1st to 10th	Night	19% 13% 4 7% 4 3 3 3 3 5% 35%	3640
	11th to 20th	Night	11% 7% 2 6% 5% 5% 5% 4 6% 7% 41%	3480
	21st to end	Night	16% 10% 4 8% 5% 4 4 4 5% 6% 34%	3817
April	1st to 10th	Night	15% 11% 4 7% 5% 5% 4 4 6% 7% 33%	2009
	11th to 20th	Night	17% 8% 3 6% 5% 4 5% 3 6% 6% 37%	1732
	21st to end	Night	16% 8% 2 6% 5% 4 5% 5% 5% 6% 37%	1710
May	1st to 10th	Night	17% 9% 4 9% 6% 5% 5% 3 5% 7% 31%	2813
	11th to 20th	Night	16% 8% 3 7% 4 4 4 3 5% 6% 39%	2812
	21st to end	Night	9% 5% 2 6% 4 4 4 4 6% 9% 46%	3079
June	1st to 10th	Night	11% 6% 2 6% 4 4 5% 3 6% 8% 44%	1637
	11th to 20th	Night	8% 5% 3 6% 4 4 4 5% 7% 9% 44%	1520
	21st to end	Night	9% 5% 2 5% 4 5% 5% 4 8% 9% 45%	1520
July	1st to 10th	Night	9% 4 2 6% 4 4 5% 4 6% 10% 47%	2530
	11th to 20th	Night	7% 4 1 5% 4 4 5% 4 7% 11% 48%	2608
	21st to end	Night	6% 5% 2 7% 5% 5% 4 5% 7% 10% 45%	3087
August	1st to 10th	Night	11% 7% 2 6% 4 5% 4 4 6% 8% 43%	2825
	11th to 20th	Night	8% 6% 3 6% 4 4 4 4 6% 9% 45%	2785
	21st to end	Night	7% 5% 2 6% 4 5% 5% 4 6% 8% 46%	3203
September	1st to 10th	Night	10% 6% 2 6% 3 3 4 3 5% 6% 51%	2028
	11th to 20th	Night	9% 4 2 5% 4 4 3 3 4 7% 54%	2090
	21st to end	Night	13% 7% 2 6% 4 5% 4 3 5% 6% 44%	2090
October	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 5% 7% 47%	2136
	11th to 20th	Night	16% 9% 3 7% 4 4 4 3 4 7% 39%	2280
	21st to end	Night	20% 8% 2 7% 4 4 4 4 5% 7% 35%	2627
November	1st to 10th	Night	12% 9% 3 7% 4 4 5% 3 4 6% 43%	2536
	11th to 20th	Night	15% 11% 4 8% 5% 4 4 4 6% 7% 33%	2600
	21st to end	Night	19% 14% 4 9% 5% 5% 5% 3 5% 5% 27%	2600
December	1st to 10th	Night	12% 13% 5% 11% 6% 5% 5% 4 6% 7% 25%	4250
	11th to 20th	Night	17% 17% 6% 11% 5% 5% 4 3 5% 5% 22%	4822
	21st to end	Night	24% 19% 6% 10% 5% 5% 4 3 4 5% 14%	6922

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	70% 6% 9% 12% 3	3618
	11th to 20th	Day	74% 4 8% 6% 8%	3813
	21st to end	Day	74% 4 7% 9% 6%	4466
February	1st to 10th	Day	65% 5% 11% 12% 6% 1	1755
	11th to 20th	Day	61% 5% 10% 16% 7% 1	1825
	21st to end	Day	58% 6% 13% 15% 7% 2	1570
March	1st to 10th	Day	63% 6% 9% 17% 5%	3212
	11th to 20th	Day	49% 7% 13% 22% 9% 1	3480
	21st to end	Day	58% 7% 12% 16% 7%	3815
April	1st to 10th	Day	53% 7% 11% 17% 11% 1	2186
	11th to 20th	Day	49% 6% 12% 18% 13% 2	2395
	21st to end	Day	49% 6% 12% 21% 11% 2	2470
May	1st to 10th	Day	50% 8% 10% 22% 9% 1	4120
	11th to 20th	Day	46% 8% 13% 22% 9% 1	4085
	21st to end	Day	38% 8% 11% 20% 18% 5%	4489
June	1st to 10th	Day	41% 8% 10% 25% 12% 3	2537
	11th to 20th	Day	38% 7% 13% 21% 17% 3	2660
	21st to end	Day	39% 8% 14% 19% 14% 4	2660
July	1st to 10th	Day	41% 7% 12% 21% 17% 3	4371
	11th to 20th	Day	30% 9% 12% 28% 19% 2	4283
	21st to end	Day	37% 8% 14% 17% 20% 3	4324
August	1st to 10th	Day	34% 8% 16% 27% 15% 1	4091
	11th to 20th	Day	34% 9% 14% 31% 11% 1	4083
	21st to end	Day	35% 8% 12% 31% 13% 2	4449
September	1st to 10th	Day	37% 7% 13% 23% 17% 3	2132
	11th to 20th	Day	34% 7% 12% 27% 19% 2	2090
	21st to end	Day	42% 6% 12% 22% 17% 1	2090
October	1st to 10th	Day	28% 6% 13% 32% 21% 1	3394
	11th to 20th	Day	39% 6% 9% 26% 19% 1	3140
	21st to end	Day	41% 5% 11% 23% 18% 1	3220
November	1st to 10th	Day	42% 5% 12% 24% 16% 1	1762
	11th to 20th	Day	53% 4 11% 19% 11% 1	1800
	21st to end	Day	57% 5% 12% 18% 7%	1800
December	1st to 10th	Day	61% 6% 15% 14% 3	2796
	11th to 20th	Day	65% 5% 9% 16% 5%	3370
	21st to end	Day	76% 4 7% 9% 4	4043
January	1st to 10th	Night	68% 5% 7% 15% 4	6348
	11th to 20th	Night	72% 5% 8% 8% 7%	6152
	21st to end	Night	66% 4 12% 10% 8%	6490
February	1st to 10th	Night	62% 6% 11% 15% 5% 1	2536
	11th to 20th	Night	58% 6% 10% 18% 8% 1	2248
	21st to end	Night	59% 5% 10% 17% 8% 2	1884
March	1st to 10th	Night	53% 5% 11% 23% 8% 1	3640
	11th to 20th	Night	38% 8% 15% 22% 15% 1	3480
	21st to end	Night	48% 6% 10% 26% 9% 1	3817
April	1st to 10th	Night	49% 6% 11% 18% 14% 2	2009
	11th to 20th	Night	46% 6% 10% 19% 17% 2	1732
	21st to end	Night	45% 6% 11% 21% 14% 3	1710
May	1st to 10th	Night	52% 7% 9% 18% 12% 2	2840
	11th to 20th	Night	44% 8% 10% 23% 13% 1	2813
	21st to end	Night	32% 7% 12% 26% 20% 2	3087
June	1st to 10th	Night	37% 6% 11% 26% 16% 3	1637
	11th to 20th	Night	34% 8% 13% 25% 17% 3	1520
	21st to end	Night	33% 8% 14% 26% 17% 3	1520
July	1st to 10th	Night	32% 7% 12% 26% 17% 6%	2490
	11th to 20th	Night	27% 7% 17% 29% 17% 2	2560
	21st to end	Night	32% 8% 17% 21% 18% 5%	2988
August	1st to 10th	Night	38% 8% 12% 26% 15% 2	2814
	11th to 20th	Night	34% 8% 11% 28% 17% 1	2812
	21st to end	Night	33% 8% 13% 28% 17% 2	3203
September	1st to 10th	Night	34% 6% 13% 25% 18% 5%	2028
	11th to 20th	Night	29% 7% 10% 27% 26% 2	2090
	21st to end	Night	40% 7% 11% 22% 19% 2	2090
October	1st to 10th	Night	26% 5% 8% 30% 30% 1	3565
	11th to 20th	Night	36% 5% 10% 28% 20% 1	3779
	21st to end	Night	36% 5% 9% 32% 16% 3	4327
November	1st to 10th	Night	42% 5% 12% 23% 16% 2	2536
	11th to 20th	Night	49% 6% 11% 21% 11% 2	2600
	21st to end	Night	59% 5% 11% 18% 6%	2600
December	1st to 10th	Night	57% 5% 13% 18% 6%	4250
	11th to 20th	Night	63% 5% 13% 13% 6% 1	4824
	21st to end	Night	72% 6% 10% 8% 4	6922

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	22% 20% 32% 19% 5% 1	300
	11th to 20th	Day	22% 19% 45% 9% 4 1	300
	21st to end	Day	27% 17% 32% 20% 4	330
February	1st to 10th	Day	25% 18% 40% 13% 3	285
	11th to 20th	Day	24% 17% 37% 19% 3	270
	21st to end	Day	25% 21% 40% 10% 3	225
March	1st to 10th	Day	25% 15% 35% 19% 6%	323
	11th to 20th	Day	22% 15% 37% 21% 5% 1	460
	21st to end	Day	31% 13% 31% 18% 6% 1	506
April	1st to 10th	Day	19% 15% 31% 24% 11% 1	460
	11th to 20th	Day	22% 16% 32% 19% 8% 4	452
	21st to end	Day	26% 10% 32% 23% 7% 2	460
May	1st to 10th	Day	23% 10% 33% 22% 10% 2	463
	11th to 20th	Day	19% 10% 29% 22% 13% 7%	487
	21st to end	Day	11% 7% 26% 28% 18% 10%	529
June	1st to 10th	Day	12% 6% 29% 32% 17% 4	557
	11th to 20th	Day	12% 6% 29% 28% 20% 4	680
	21st to end	Day	12% 7% 28% 29% 18% 5%	680
July	1st to 10th	Day	9% 4 22% 32% 20% 12%	671
	11th to 20th	Day	8% 4 25% 29% 23% 11%	625
	21st to end	Day	9% 5% 22% 26% 27% 11%	532
August	1st to 10th	Day	10% 5% 15% 29% 25% 15%	486
	11th to 20th	Day	12% 2 17% 34% 23% 11%	479
	21st to end	Day	8% 3 19% 29% 27% 15%	539
September	1st to 10th	Day	15% 4 16% 29% 23% 13%	490
	11th to 20th	Day	10% 2 16% 23% 31% 18%	490
	21st to end	Day	19% 10% 23% 22% 18% 8%	490
October	1st to 10th	Day	13% 8% 24% 27% 21% 8%	490
	11th to 20th	Day	18% 15% 31% 24% 10% 2	490
	21st to end	Day	21% 15% 36% 22% 6% 1	419
November	1st to 10th	Day	15% 15% 35% 20% 11% 4	300
	11th to 20th	Day	24% 18% 30% 19% 8% 1	300
	21st to end	Day	25% 18% 36% 19% 3	300
December	1st to 10th	Day	19% 21% 36% 16% 8% 1	257
	11th to 20th	Day	20% 21% 37% 18% 3	300
	21st to end	Day	28% 18% 33% 18% 3	330
January	1st to 10th	Night	23% 15% 36% 20% 5%	1000
	11th to 20th	Night	27% 15% 36% 17% 4 1	909
	21st to end	Night	23% 15% 36% 23% 4	880
February	1st to 10th	Night	25% 13% 34% 24% 3	781
	11th to 20th	Night	23% 13% 36% 26% 3	743
	21st to end	Night	25% 16% 38% 19% 2	628
March	1st to 10th	Night	20% 13% 34% 27% 7%	760
	11th to 20th	Night	18% 14% 37% 24% 6% 1	760
	21st to end	Night	22% 13% 30% 28% 8%	836
April	1st to 10th	Night	20% 14% 36% 26% 4	679
	11th to 20th	Night	20% 10% 36% 26% 8% 1	563
	21st to end	Night	20% 8% 34% 28% 8% 1	570
May	1st to 10th	Night	21% 5% 30% 34% 8% 1	570
	11th to 20th	Night	19% 8% 25% 32% 15% 1	561
	21st to end	Night	11% 2 24% 39% 21% 3	617
June	1st to 10th	Night	12% 3 25% 44% 17%	570
	11th to 20th	Night	10% 3 23% 43% 19% 2	570
	21st to end	Night	13% 2 24% 38% 21% 2	570
July	1st to 10th	Night	10% 2 17% 38% 30% 3	555
	11th to 20th	Night	8% 3 20% 40% 25% 4	552
	21st to end	Night	7% 2 15% 43% 32% 2	624
August	1st to 10th	Night	8% 2 14% 43% 30% 3	567
	11th to 20th	Night	10% 2 16% 37% 31% 5%	564
	21st to end	Night	8% 2 14% 38% 35% 4	627
September	1st to 10th	Night	13% 5% 15% 36% 28% 4	698
	11th to 20th	Night	10% 2 15% 34% 34% 4	760
	21st to end	Night	16% 6% 21% 32% 22% 3	760
October	1st to 10th	Night	13% 8% 24% 32% 20% 3	760
	11th to 20th	Night	20% 13% 29% 27% 9% 1	760
	21st to end	Night	23% 12% 31% 26% 8%	836
November	1st to 10th	Night	15% 13% 33% 28% 10% 2	780
	11th to 20th	Night	21% 15% 33% 23% 7% 1	800
	21st to end	Night	26% 11% 33% 24% 5%	800
December	1st to 10th	Night	25% 14% 35% 21% 6%	800
	11th to 20th	Night	26% 13% 36% 22% 4	800
	21st to end	Night	29% 13% 34% 21% 3	1065

Page generated at 2025-02-03 03:05:53. Version ac07

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