Logan Valley Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Logan Valley Star Party clear sky chart from 2005-11-06 to 2025-11-18.

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	6% 9% 3 7% 4 4 4 3 5% 6% 48%	135763
	Night	6% 10% 3 7% 5% 4 4 4 5% 6% 45%	131926
Transparency	Day	34% 7% 9% 20% 19% 11%	130540
	Night	35% 8% 10% 20% 19% 8%	128146
Seeing	Day	14% 16% 29% 25% 12% 4	15837
	Night	13% 12% 21% 32% 19% 3	24981

By Month

Percentage Cloud Cover SW (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	8% 17% 7% 16% 6% 5% 5% 4 5% 4 22%	3639
	11th to 20th	Day	7% 14% 5% 11% 4 3 4 4 5% 4 39%	3640
	21st to end	Day	8% 17% 5% 8% 4 3 3 2 4 5% 40%	4004
February	1st to 10th	Day	9% 15% 5% 12% 6% 4 5% 4 5% 6% 29%	1780
	11th to 20th	Day	7% 18% 7% 12% 6% 6% 4 3 5% 5% 26%	1897
	21st to end	Day	6% 16% 6% 14% 9% 5% 3 4 7% 5% 25%	1650
March	1st to 10th	Day	5% 14% 6% 14% 7% 5% 5% 3 5% 6% 30%	4518
	11th to 20th	Day	7% 16% 6% 8% 5% 4 4 4 5% 5% 36%	4699
	21st to end	Day	7% 18% 6% 13% 6% 6% 6% 4 6% 6% 23%	5969
April	1st to 10th	Day	8% 14% 5% 13% 7% 6% 5% 4 5% 6% 27%	2400
	11th to 20th	Day	7% 13% 3 9% 6% 5% 5% 4 6% 5% 35%	2369
	21st to end	Day	6% 11% 4 8% 6% 6% 5% 4 5% 7% 38%	2539
May	1st to 10th	Day	6% 9% 5% 7% 4 4 4 3 4 5% 48%	6056
	11th to 20th	Day	7% 9% 2 6% 4 4 5% 4 6% 7% 47%	6277
	21st to end	Day	4 8% 3 7% 5% 4 4 4 5% 7% 49%	6902
June	1st to 10th	Day	11% 8% 4 7% 5% 5% 5% 4 6% 7% 37%	2800
	11th to 20th	Day	6% 8% 2 6% 5% 5% 5% 4 6% 7% 46%	2800
	21st to end	Day	4 4 1 4 3 4 3 4 5% 6% 63%	2800
July	1st to 10th	Day	2 2 1 2 2 2 3 3 4 4 75%	6319
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 4 79%	6320
	21st to end	Day	2 2 1 3 3 3 4 4 6% 7% 66%	6880
August	1st to 10th	Day	4 4 2 5% 4 4 4 4 6% 8% 57%	6210
	11th to 20th	Day	2 2 1 3 2 3 3 3 3 5% 73%	5585
	21st to end	Day	4 4 2 4 3 3 3 3 4 5% 64%	5984
September	1st to 10th	Day	2 3 1 5% 3 3 3 3 5% 6% 67%	2400
	11th to 20th	Day	6% 5% 2 5% 4 4 4 3 5% 6% 55%	2324
	21st to end	Day	4 6% 3 7% 4 3 4 3 4 5% 57%	2200
October	1st to 10th	Day	5% 5% 2 5% 3 2 3 2 3 6% 63%	3410
	11th to 20th	Day	6% 8% 3 6% 5% 4 4 3 4 7% 50%	3239
	21st to end	Day	10% 10% 4 8% 5% 5% 5% 4 8% 7% 35%	3200
November	1st to 10th	Day	12% 15% 4 8% 6% 4 4 4 4 8% 31%	1854
	11th to 20th	Day	11% 13% 5% 8% 5% 5% 6% 6% 6% 7% 26%	1847
	21st to end	Day	8% 12% 4 9% 6% 5% 6% 4 4 7% 35%	1600
December	1st to 10th	Day	6% 9% 4 7% 5% 3 4 3 5% 6% 49%	2620
	11th to 20th	Day	11% 22% 5% 11% 6% 4 5% 4 7% 6% 20%	3028
	21st to end	Day	10% 18% 6% 12% 7% 5% 5% 5% 6% 7% 21%	4004
January	1st to 10th	Night	7% 20% 7% 14% 7% 6% 6% 5% 5% 5% 20%	6306
	11th to 20th	Night	7% 14% 6% 9% 4 3 4 3 6% 5% 40%	6320
	21st to end	Night	8% 15% 4 8% 5% 4 4 3 4 5% 40%	6952
February	1st to 10th	Night	7% 13% 5% 11% 7% 5% 6% 5% 6% 7% 28%	2618
	11th to 20th	Night	7% 13% 5% 10% 8% 6% 6% 4 6% 6% 30%	2389
	21st to end	Night	6% 13% 4 13% 8% 5% 5% 5% 6% 7% 27%	1980
March	1st to 10th	Night	4 13% 6% 10% 5% 5% 5% 4 7% 8% 34%	5376
	11th to 20th	Night	8% 15% 3 7% 4 4 4 4 6% 5% 38%	5299
	21st to end	Night	4 14% 5% 11% 7% 7% 7% 5% 6% 7% 26%	5006
April	1st to 10th	Night	7% 10% 5% 9% 6% 6% 5% 4 6% 7% 35%	2000
	11th to 20th	Night	5% 11% 4 8% 6% 5% 4 5% 6% 5% 41%	1979
	21st to end	Night	6% 8% 3 7% 5% 5% 6% 6% 7% 9% 38%	1860
May	1st to 10th	Night	5% 8% 4 8% 4 4 5% 4 4 4 50%	3899
	11th to 20th	Night	3 7% 2 4 3 4 4 5% 7% 5% 54%	3616
	21st to end	Night	5% 7% 3 6% 4 3 3 3 4 5% 56%	3972
June	1st to 10th	Night	8% 9% 2 6% 4 4 4 5% 7% 8% 43%	1600
	11th to 20th	Night	5% 6% 2 7% 4 4 3 3 6% 7% 54%	1600
	21st to end	Night	3 4 1 5% 4 2 4 4 4 5% 65%	1600
July	1st to 10th	Night	2 2 1 3 2 2 3 2 3 6% 75%	3640
	11th to 20th	Night	1 1 2 1 2 2 2 3 4 82%	3640
	21st to end	Night	4 3 1 4 3 4 4 3 5% 5% 66%	3970
August	1st to 10th	Night	3 2 2 4 3 3 5% 4 6% 8% 60%	3582
	11th to 20th	Night	2 2 1 3 2 2 3 2 4 5% 74%	4270
	21st to end	Night	3 4 2 4 3 3 3 3 5% 6% 65%	5015
September	1st to 10th	Night	3 2 1 3 2 3 3 3 4 6% 70%	2000
	11th to 20th	Night	3 3 1 5% 4 4 4 3 6% 7% 60%	2075
	21st to end	Night	5% 5% 2 4 3 3 4 3 5% 7% 61%	2200
October	1st to 10th	Night	3 4 2 4 3 2 3 2 4 5% 68%	3787
	11th to 20th	Night	5% 5% 2 6% 5% 4 4 4 7% 7% 52%	3917
	21st to end	Night	5% 7% 4 7% 5% 5% 5% 5% 7% 7% 44%	4600
November	1st to 10th	Night	12% 10% 3 9% 6% 5% 6% 4 5% 6% 35%	2665
	11th to 20th	Night	11% 12% 4 10% 6% 6% 5% 5% 6% 6% 30%	2705
	21st to end	Night	8% 12% 4 9% 6% 5% 5% 4 6% 6% 35%	2800
December	1st to 10th	Night	6% 7% 3 6% 4 4 3 3 5% 7% 51%	4560
	11th to 20th	Night	12% 19% 6% 11% 7% 6% 5% 4 5% 5% 20%	5176
	21st to end	Night	12% 16% 4 10% 7% 6% 6% 5% 7% 6% 22%	6952

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	55% 12% 11% 12% 8% 1	3639
	11th to 20th	Day	43% 7% 9% 27% 11% 2	3640
	21st to end	Day	45% 9% 9% 11% 19% 8%	4004
February	1st to 10th	Day	52% 10% 14% 17% 7% 1	1780
	11th to 20th	Day	54% 10% 11% 14% 9% 2	1907
	21st to end	Day	53% 11% 12% 13% 9% 2	1650
March	1st to 10th	Day	47% 9% 9% 20% 11% 5%	4518
	11th to 20th	Day	43% 7% 11% 28% 11%	4699
	21st to end	Day	51% 12% 14% 16% 6%	5969
April	1st to 10th	Day	51% 8% 13% 18% 7% 2	2400
	11th to 20th	Day	42% 9% 12% 21% 13% 2	2372
	21st to end	Day	41% 9% 11% 21% 17% 1	2539
May	1st to 10th	Day	32% 7% 9% 24% 25% 2	6056
	11th to 20th	Day	30% 6% 10% 28% 22% 5%	6280
	21st to end	Day	27% 8% 12% 34% 16% 2	6904
June	1st to 10th	Day	40% 9% 10% 27% 13% 1	2800
	11th to 20th	Day	31% 8% 10% 23% 22% 6%	2800
	21st to end	Day	20% 5% 8% 24% 31% 12%	2800
July	1st to 10th	Day	13% 3 3 13% 25% 43%	6251
	11th to 20th	Day	12% 1 3 8% 19% 56%	6245
	21st to end	Day	16% 3 4 19% 31% 26%	6681
August	1st to 10th	Day	23% 3 4 14% 27% 28%	4524
	11th to 20th	Day	15% 3 4 15% 41% 23%	4045
	21st to end	Day	18% 3 5% 25% 26% 24%	4311
September	1st to 10th	Day	17% 4 5% 21% 30% 23%	2400
	11th to 20th	Day	27% 4 8% 21% 27% 13%	2324
	21st to end	Day	27% 5% 8% 23% 25% 12%	2200
October	1st to 10th	Day	24% 4 6% 19% 37% 11%	3410
	11th to 20th	Day	33% 4 12% 27% 21% 4	3239
	21st to end	Day	44% 6% 8% 23% 19% 1	3200
November	1st to 10th	Day	47% 7% 14% 19% 12% 1	1854
	11th to 20th	Day	50% 11% 13% 18% 7% 1	1847
	21st to end	Day	44% 9% 12% 19% 12% 3	1600
December	1st to 10th	Day	34% 7% 10% 27% 20% 1	2620
	11th to 20th	Day	61% 7% 15% 12% 4	3028
	21st to end	Day	57% 11% 12% 12% 7%	4004
January	1st to 10th	Night	56% 12% 12% 12% 7% 1	6306
	11th to 20th	Night	41% 8% 9% 24% 15% 3	6320
	21st to end	Night	43% 9% 9% 13% 14% 11%	6952
February	1st to 10th	Night	48% 13% 14% 16% 8% 1	2618
	11th to 20th	Night	47% 11% 14% 15% 10% 3	2390
	21st to end	Night	46% 13% 13% 15% 9% 3	1980
March	1st to 10th	Night	39% 9% 10% 22% 15% 6%	5376
	11th to 20th	Night	40% 8% 9% 28% 16%	5299
	21st to end	Night	45% 15% 14% 20% 5% 1	5006
April	1st to 10th	Night	41% 9% 15% 24% 10% 1	2000
	11th to 20th	Night	36% 11% 13% 24% 13% 2	1979
	21st to end	Night	33% 12% 15% 23% 16% 1	1860
May	1st to 10th	Night	27% 9% 11% 24% 26% 3	3896
	11th to 20th	Night	23% 5% 10% 34% 27% 1	3616
	21st to end	Night	26% 8% 11% 38% 16%	3972
June	1st to 10th	Night	34% 10% 13% 28% 13% 1	1600
	11th to 20th	Night	27% 6% 13% 28% 20% 5%	1600
	21st to end	Night	20% 5% 8% 30% 29% 8%	1600
July	1st to 10th	Night	13% 2 3 15% 25% 41%	3600
	11th to 20th	Night	7% 2 3 12% 25% 52%	3592
	21st to end	Night	21% 2 3 18% 33% 23%	3857
August	1st to 10th	Night	20% 3 5% 16% 31% 25%	2601
	11th to 20th	Night	14% 3 3 17% 42% 21%	3081
	21st to end	Night	14% 3 5% 25% 30% 24%	3608
September	1st to 10th	Night	15% 4 5% 22% 30% 25%	2000
	11th to 20th	Night	20% 7% 8% 22% 29% 15%	2075
	21st to end	Night	21% 6% 8% 24% 29% 12%	2200
October	1st to 10th	Night	19% 4 6% 19% 38% 13%	3787
	11th to 20th	Night	28% 5% 15% 21% 29% 3	3917
	21st to end	Night	33% 7% 9% 25% 23% 2	4600
November	1st to 10th	Night	43% 10% 12% 18% 15% 2	2665
	11th to 20th	Night	48% 9% 13% 18% 11%	2705
	21st to end	Night	43% 9% 12% 16% 15% 5%	2800
December	1st to 10th	Night	29% 7% 10% 25% 27% 2	4560
	11th to 20th	Night	62% 8% 9% 15% 5% 1	5176
	21st to end	Night	55% 11% 13% 12% 8% 1	6952

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	30% 15% 25% 16% 12% 3	200
	11th to 20th	Day	25% 17% 25% 14% 17% 4	200
	21st to end	Day	15% 15% 34% 21% 11% 4	220
February	1st to 10th	Day	20% 29% 29% 16% 5% 2	380
	11th to 20th	Day	21% 23% 32% 17% 6%	469
	21st to end	Day	23% 20% 30% 21% 6%	414
March	1st to 10th	Day	21% 25% 32% 17% 5%	500
	11th to 20th	Day	21% 19% 31% 20% 7% 2	500
	21st to end	Day	24% 23% 27% 19% 5% 1	550
April	1st to 10th	Day	23% 19% 26% 19% 11% 2	500
	11th to 20th	Day	19% 25% 28% 16% 8% 3	492
	21st to end	Day	15% 19% 32% 24% 8% 1	500
May	1st to 10th	Day	15% 21% 29% 23% 9% 4	503
	11th to 20th	Day	20% 18% 27% 22% 9% 4	528
	21st to end	Day	16% 12% 24% 27% 17% 5%	573
June	1st to 10th	Day	12% 18% 29% 23% 12% 7%	530
	11th to 20th	Day	16% 18% 30% 22% 11% 2	530
	21st to end	Day	3 14% 32% 31% 15% 5%	530
July	1st to 10th	Day	5% 8% 37% 34% 15% 2	526
	11th to 20th	Day	4 10% 33% 33% 14% 5%	524
	21st to end	Day	3 8% 30% 35% 18% 5%	575
August	1st to 10th	Day	8% 6% 28% 37% 16% 6%	527
	11th to 20th	Day	4 6% 28% 33% 21% 9%	517
	21st to end	Day	6% 11% 26% 32% 17% 7%	583
September	1st to 10th	Day	5% 9% 27% 36% 18% 6%	530
	11th to 20th	Day	10% 10% 25% 32% 18% 5%	530
	21st to end	Day	9% 11% 31% 28% 16% 5%	530
October	1st to 10th	Day	12% 15% 28% 26% 16% 4	530
	11th to 20th	Day	15% 14% 28% 26% 14% 5%	520
	21st to end	Day	15% 17% 27% 24% 14% 3	363
November	1st to 10th	Day	24% 15% 25% 25% 10% 1	330
	11th to 20th	Day	20% 16% 26% 26% 10% 2	313
	21st to end	Day	15% 16% 29% 28% 11% 3	200
December	1st to 10th	Day	23% 16% 21% 19% 13% 10%	200
	11th to 20th	Day	29% 21% 26% 16% 8% 1	200
	21st to end	Day	20% 21% 25% 21% 11% 1	220
January	1st to 10th	Night	19% 16% 22% 24% 16% 3	800
	11th to 20th	Night	21% 14% 19% 26% 17% 3	800
	21st to end	Night	17% 11% 18% 33% 19% 3	880
February	1st to 10th	Night	17% 19% 21% 29% 12% 2	800
	11th to 20th	Night	17% 14% 24% 26% 17% 2	784
	21st to end	Night	17% 15% 25% 28% 13% 2	660
March	1st to 10th	Night	15% 18% 23% 29% 14% 2	800
	11th to 20th	Night	17% 14% 22% 29% 18% 2	800
	21st to end	Night	16% 18% 22% 30% 12% 1	880
April	1st to 10th	Night	14% 14% 25% 30% 15% 3	800
	11th to 20th	Night	13% 18% 23% 26% 17% 4	791
	21st to end	Night	11% 16% 25% 33% 14% 1	660
May	1st to 10th	Night	12% 15% 29% 24% 17% 2	516
	11th to 20th	Night	12% 10% 22% 29% 23% 4	394
	21st to end	Night	11% 9% 21% 31% 24% 4	433
June	1st to 10th	Night	11% 9% 22% 37% 20% 2	400
	11th to 20th	Night	9% 13% 26% 37% 15% 2	400
	21st to end	Night	4 6% 23% 42% 24% 2	400
July	1st to 10th	Night	5% 4 22% 47% 19% 2	390
	11th to 20th	Night	2 4 27% 48% 18% 1	388
	21st to end	Night	3 3 22% 46% 26% 1	438
August	1st to 10th	Night	4 3 18% 45% 27% 3	398
	11th to 20th	Night	2 2 21% 38% 31% 6%	681
	21st to end	Night	4 5% 20% 40% 28% 3	880
September	1st to 10th	Night	4 4 17% 39% 33% 4	800
	11th to 20th	Night	6% 5% 13% 37% 32% 8%	800
	21st to end	Night	8% 8% 16% 33% 27% 8%	800
October	1st to 10th	Night	8% 7% 21% 34% 25% 6%	800
	11th to 20th	Night	12% 12% 17% 33% 22% 6%	800
	21st to end	Night	14% 10% 18% 36% 17% 5%	880
November	1st to 10th	Night	17% 13% 19% 32% 17% 1	820
	11th to 20th	Night	19% 16% 17% 31% 14% 3	828
	21st to end	Night	16% 15% 17% 29% 16% 6%	800
December	1st to 10th	Night	19% 11% 21% 28% 17% 5%	800
	11th to 20th	Night	22% 12% 20% 30% 14% 2	800
	21st to end	Night	23% 19% 21% 26% 10% 2	880

Page generated at 2025-11-14 21:55:57. Version ac07

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