Galbreath Wildlands Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galbreath Wildlands Preserve clear sky chart from 2005-11-06 to 2026-04-17.

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	9% 4 1 3 2 3 3 3 4 6% 61%	140450
	Night	12% 6% 1 4 3 3 3 3 4 6% 55%	139202
Transparency	Day	25% 4 8% 20% 24% 19%	135325
	Night	30% 4 8% 18% 21% 18%	135332
Seeing	Day	13% 11% 25% 27% 18% 6%	17190
	Night	14% 7% 18% 30% 25% 6%	26520

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	21% 9% 2 5% 4 4 5% 4 6% 7% 34%	5119
	11th to 20th	Day	16% 5% 2 5% 3 2 3 3 4 5% 54%	5340
	21st to end	Day	17% 6% 3 6% 4 4 4 3 5% 7% 42%	5843
February	1st to 10th	Day	21% 7% 2 6% 4 4 4 3 4 5% 41%	1890
	11th to 20th	Day	18% 8% 2 6% 4 5% 3 4 6% 8% 37%	1845
	21st to end	Day	20% 8% 2 5% 3 3 4 3 5% 7% 39%	1751
March	1st to 10th	Day	22% 13% 2 5% 4 3 4 3 5% 6% 34%	5062
	11th to 20th	Day	17% 7% 2 5% 4 5% 3 3 4 6% 43%	5110
	21st to end	Day	22% 9% 2 6% 5% 5% 5% 4 7% 8% 29%	5607
April	1st to 10th	Day	16% 7% 2 6% 5% 4 3 3 6% 7% 40%	2504
	11th to 20th	Day	12% 5% 2 6% 4 3 3 4 6% 7% 47%	2442
	21st to end	Day	8% 5% 2 4 3 4 3 4 6% 9% 51%	2422
May	1st to 10th	Day	4 3 1 3 2 2 2 2 4 6% 72%	5880
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 6% 75%	5879
	21st to end	Day	3 2 1 2 1 1 2 2 3 7% 78%	6902
June	1st to 10th	Day	6% 4 2 3 2 3 3 3 5% 7% 61%	2800
	11th to 20th	Day	2 2 1 2 2 1 2 2 4 6% 77%	2800
	21st to end	Day	3 1 1 2 1 1 2 2 2 5% 81%	2800
July	1st to 10th	Day	1 1 1 1 1 1 1 2 3 89%	6278
	11th to 20th	Day	1 2 1 1 1 1 2 4 85%	5880
	21st to end	Day	1 1 1 1 1 1 1 3 5% 84%	6402
August	1st to 10th	Day	1 1 1 1 1 2 2 4 5% 82%	5777
	11th to 20th	Day	1 1 1 1 1 1 1 2 4 86%	5722
	21st to end	Day	1 1 2 1 2 2 2 4 6% 79%	5984
September	1st to 10th	Day	1 1 1 1 1 1 2 2 3 5% 81%	2400
	11th to 20th	Day	3 3 1 3 3 2 3 2 4 7% 69%	2342
	21st to end	Day	3 2 1 3 2 2 2 2 3 5% 75%	2134
October	1st to 10th	Day	5% 2 1 2 1 2 2 2 3 6% 73%	3280
	11th to 20th	Day	9% 3 1 3 2 2 2 2 4 7% 64%	3261
	21st to end	Day	8% 3 1 6% 3 4 5% 3 7% 8% 51%	3558
November	1st to 10th	Day	12% 5% 2 4 4 3 4 3 6% 9% 49%	2059
	11th to 20th	Day	15% 8% 2 6% 4 4 4 4 5% 7% 41%	1797
	21st to end	Day	14% 5% 2 4 4 3 4 3 5% 6% 50%	1680
December	1st to 10th	Day	12% 5% 1 3 3 3 5% 4 7% 9% 49%	2700
	11th to 20th	Day	30% 9% 2 6% 5% 5% 5% 4 6% 7% 23%	3108
	21st to end	Day	27% 10% 3 7% 4 4 5% 5% 6% 7% 23%	4092
January	1st to 10th	Night	23% 10% 2 6% 4 4 4 4 6% 7% 30%	7791
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 5% 51%	7650
	21st to end	Night	18% 8% 2 7% 5% 4 4 3 5% 6% 37%	8371
February	1st to 10th	Night	19% 6% 2 5% 3 4 4 3 5% 6% 43%	2730
	11th to 20th	Night	17% 9% 2 6% 4 4 4 4 6% 7% 36%	2662
	21st to end	Night	16% 7% 2 4 4 3 3 2 4 7% 46%	2050
March	1st to 10th	Night	19% 17% 3 6% 3 4 4 3 4 6% 31%	5052
	11th to 20th	Night	19% 9% 1 4 3 3 3 3 3 6% 47%	5110
	21st to end	Night	19% 14% 2 5% 4 4 4 4 6% 7% 31%	5610
April	1st to 10th	Night	12% 7% 2 6% 5% 4 4 3 5% 7% 44%	2116
	11th to 20th	Night	10% 6% 2 5% 3 4 4 3 5% 7% 50%	2039
	21st to end	Night	7% 5% 1 3 3 3 4 3 6% 7% 59%	1975
May	1st to 10th	Night	4 4 1 3 2 1 1 2 3 6% 72%	4100
	11th to 20th	Night	4 2 1 3 2 3 2 2 4 5% 72%	4028
	21st to end	Night	2 1 1 2 1 2 2 3 5% 80%	3972
June	1st to 10th	Night	4 5% 2 3 3 5% 3 4 6% 8% 60%	1600
	11th to 20th	Night	2 1 2 1 2 2 2 4 5% 78%	1600
	21st to end	Night	2 2 1 2 2 1 2 2 2 3 80%	1600
July	1st to 10th	Night	1 1 1 1 1 1 1 2 91%	3678
	11th to 20th	Night	1 1 2 2 2 2 1 1 3 84%	4100
	21st to end	Night	1 1 2 1 1 2 2 3 6% 81%	4472
August	1st to 10th	Night	1 1 1 1 1 2 1 3 4 84%	4035
	11th to 20th	Night	1 1 1 1 1 1 3 4 86%	4116
	21st to end	Night	1 2 1 2 1 1 2 1 2 4 82%	5015
September	1st to 10th	Night	1 1 1 2 1 2 1 3 5% 83%	2000
	11th to 20th	Night	4 2 2 3 2 3 3 2 5% 7% 67%	2054
	21st to end	Night	3 3 1 2 2 2 2 2 4 5% 75%	2265
October	1st to 10th	Night	3 3 1 3 2 2 2 2 3 4 75%	3920
	11th to 20th	Night	5% 6% 2 4 3 2 3 3 4 6% 62%	3897
	21st to end	Night	8% 5% 1 5% 3 4 4 3 5% 7% 55%	4253
November	1st to 10th	Night	12% 6% 2 4 3 4 5% 4 6% 8% 45%	2460
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 6% 8% 39%	2819
	21st to end	Night	14% 5% 2 5% 4 3 3 3 4 7% 49%	2940
December	1st to 10th	Night	13% 4 1 4 4 3 3 3 5% 7% 51%	4700
	11th to 20th	Night	30% 8% 2 6% 4 5% 4 3 6% 6% 25%	5316
	21st to end	Night	35% 9% 2 5% 4 4 4 3 4 5% 26%	7106

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	46% 6% 12% 19% 10% 6%	5120
	11th to 20th	Day	34% 3 5% 9% 22% 27%	5340
	21st to end	Day	42% 3 8% 17% 13% 17%	5843
February	1st to 10th	Day	44% 4 8% 16% 18% 9%	1890
	11th to 20th	Day	44% 5% 10% 18% 18% 5%	1854
	21st to end	Day	43% 5% 11% 22% 13% 6%	1751
March	1st to 10th	Day	49% 5% 6% 18% 19% 2	5062
	11th to 20th	Day	40% 5% 13% 22% 12% 9%	5110
	21st to end	Day	49% 8% 13% 20% 9% 1	5607
April	1st to 10th	Day	41% 4 13% 24% 14% 3	2504
	11th to 20th	Day	34% 5% 15% 24% 16% 5%	2445
	21st to end	Day	27% 5% 16% 29% 20% 4	2422
May	1st to 10th	Day	14% 4 10% 25% 31% 16%	5880
	11th to 20th	Day	11% 3 8% 33% 33% 11%	5882
	21st to end	Day	9% 3 7% 38% 40% 3	6904
June	1st to 10th	Day	22% 5% 12% 27% 30% 5%	2800
	11th to 20th	Day	10% 3 10% 22% 37% 17%	2800
	21st to end	Day	10% 2 5% 16% 37% 30%	2800
July	1st to 10th	Day	5% 1 2 9% 28% 56%	6210
	11th to 20th	Day	7% 1 2 7% 19% 65%	5811
	21st to end	Day	7% 2 5% 16% 34% 36%	6217
August	1st to 10th	Day	8% 3 3 13% 28% 45%	4206
	11th to 20th	Day	6% 2 2 17% 41% 32%	4145
	21st to end	Day	8% 3 5% 18% 36% 30%	4311
September	1st to 10th	Day	7% 2 4 14% 31% 42%	2400
	11th to 20th	Day	16% 3 8% 28% 34% 11%	2342
	21st to end	Day	13% 2 6% 23% 33% 24%	2134
October	1st to 10th	Day	15% 2 3 15% 23% 41%	3280
	11th to 20th	Day	22% 3 6% 23% 32% 13%	3261
	21st to end	Day	28% 5% 9% 23% 25% 11%	3558
November	1st to 10th	Day	31% 5% 10% 26% 17% 10%	2059
	11th to 20th	Day	40% 5% 12% 20% 15% 8%	1797
	21st to end	Day	33% 4 11% 18% 21% 13%	1680
December	1st to 10th	Day	31% 4 6% 22% 27% 9%	2700
	11th to 20th	Day	59% 4 8% 14% 12% 4	3108
	21st to end	Day	57% 5% 10% 18% 8% 2	4092
January	1st to 10th	Night	48% 8% 14% 16% 11% 4	7791
	11th to 20th	Night	35% 4 5% 12% 20% 24%	7650
	21st to end	Night	46% 5% 7% 11% 16% 16%	8371
February	1st to 10th	Night	39% 5% 9% 18% 18% 11%	2730
	11th to 20th	Night	43% 6% 10% 21% 15% 6%	2664
	21st to end	Night	37% 5% 13% 23% 17% 5%	2050
March	1st to 10th	Night	50% 7% 8% 17% 14% 4	5052
	11th to 20th	Night	38% 4 10% 21% 19% 7%	5110
	21st to end	Night	47% 8% 16% 18% 10% 2	5610
April	1st to 10th	Night	38% 6% 14% 22% 16% 4	2116
	11th to 20th	Night	31% 5% 15% 24% 17% 7%	2039
	21st to end	Night	22% 6% 13% 33% 21% 4	1975
May	1st to 10th	Night	15% 3 6% 24% 34% 19%	4097
	11th to 20th	Night	15% 5% 7% 27% 31% 16%	4029
	21st to end	Night	9% 3 8% 36% 40% 5%	3972
June	1st to 10th	Night	21% 6% 10% 25% 30% 8%	1600
	11th to 20th	Night	10% 3 9% 22% 38% 19%	1600
	21st to end	Night	11% 2 6% 14% 34% 33%	1600
July	1st to 10th	Night	4 1 1 8% 27% 59%	3638
	11th to 20th	Night	9% 1 2 7% 17% 63%	4046
	21st to end	Night	8% 2 4 15% 27% 44%	4345
August	1st to 10th	Night	10% 2 3 10% 25% 50%	2929
	11th to 20th	Night	4 2 3 13% 41% 36%	2980
	21st to end	Night	10% 3 3 15% 32% 37%	3608
September	1st to 10th	Night	6% 2 3 15% 30% 44%	2000
	11th to 20th	Night	15% 4 8% 21% 37% 15%	2054
	21st to end	Night	14% 2 7% 20% 28% 29%	2265
October	1st to 10th	Night	15% 2 5% 12% 22% 44%	3920
	11th to 20th	Night	22% 6% 7% 21% 31% 14%	3897
	21st to end	Night	27% 5% 6% 23% 24% 15%	4253
November	1st to 10th	Night	33% 6% 12% 22% 16% 11%	2460
	11th to 20th	Night	39% 6% 14% 19% 16% 6%	2819
	21st to end	Night	34% 4 9% 19% 20% 13%	2940
December	1st to 10th	Night	31% 4 5% 23% 24% 12%	4700
	11th to 20th	Night	57% 5% 7% 14% 14% 4	5316
	21st to end	Night	60% 4 10% 15% 8% 3	7106

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	36% 14% 22% 13% 13% 2	357
	11th to 20th	Day	23% 12% 22% 18% 20% 4	430
	21st to end	Day	20% 11% 22% 26% 16% 4	473
February	1st to 10th	Day	24% 14% 22% 20% 17% 3	430
	11th to 20th	Day	29% 17% 22% 19% 12% 1	425
	21st to end	Day	23% 17% 23% 25% 10% 2	443
March	1st to 10th	Day	29% 19% 25% 16% 9% 1	540
	11th to 20th	Day	26% 14% 28% 19% 10% 3	540
	21st to end	Day	22% 21% 30% 18% 6% 2	594
April	1st to 10th	Day	20% 18% 29% 21% 9% 4	540
	11th to 20th	Day	18% 17% 31% 19% 11% 4	517
	21st to end	Day	14% 19% 33% 20% 10% 4	500
May	1st to 10th	Day	12% 19% 32% 23% 12% 3	503
	11th to 20th	Day	14% 17% 31% 19% 13% 5%	528
	21st to end	Day	10% 14% 30% 27% 15% 5%	573
June	1st to 10th	Day	8% 13% 30% 30% 15% 4	530
	11th to 20th	Day	7% 15% 35% 29% 12% 2	530
	21st to end	Day	2 7% 29% 34% 23% 6%	530
July	1st to 10th	Day	2 5% 27% 39% 21% 6%	526
	11th to 20th	Day	1 2 23% 41% 27% 7%	524
	21st to end	Day	1 2 15% 44% 29% 10%	575
August	1st to 10th	Day	2 4 25% 39% 23% 7%	527
	11th to 20th	Day	2 4 24% 35% 26% 9%	517
	21st to end	Day	1 3 19% 40% 28% 8%	583
September	1st to 10th	Day	3 5% 22% 37% 24% 8%	530
	11th to 20th	Day	5% 8% 21% 34% 24% 7%	530
	21st to end	Day	6% 7% 24% 31% 22% 10%	530
October	1st to 10th	Day	9% 8% 24% 26% 23% 10%	530
	11th to 20th	Day	11% 11% 18% 25% 25% 10%	530
	21st to end	Day	12% 8% 23% 26% 22% 8%	583
November	1st to 10th	Day	13% 13% 19% 23% 24% 6%	535
	11th to 20th	Day	19% 11% 15% 22% 24% 9%	285
	21st to end	Day	17% 8% 20% 22% 22% 11%	220
December	1st to 10th	Day	21% 9% 19% 23% 17% 11%	220
	11th to 20th	Day	30% 10% 16% 21% 14% 9%	220
	21st to end	Day	31% 12% 18% 21% 14% 4	242
January	1st to 10th	Night	27% 7% 16% 28% 18% 4	840
	11th to 20th	Night	22% 7% 15% 31% 20% 6%	840
	21st to end	Night	20% 6% 16% 31% 22% 5%	924
February	1st to 10th	Night	22% 8% 16% 32% 19% 3	840
	11th to 20th	Night	23% 9% 22% 27% 15% 5%	824
	21st to end	Night	21% 9% 23% 30% 15% 2	692
March	1st to 10th	Night	25% 11% 20% 27% 14% 3	840
	11th to 20th	Night	22% 9% 20% 30% 17% 3	840
	21st to end	Night	22% 9% 27% 27% 13% 2	924
April	1st to 10th	Night	18% 11% 26% 25% 17% 3	840
	11th to 20th	Night	13% 13% 25% 28% 16% 5%	815
	21st to end	Night	9% 14% 29% 24% 19% 3	775
May	1st to 10th	Night	9% 9% 29% 28% 21% 4	600
	11th to 20th	Night	6% 7% 27% 31% 25% 4	572
	21st to end	Night	8% 11% 24% 29% 24% 3	433
June	1st to 10th	Night	6% 10% 26% 33% 24% 1	400
	11th to 20th	Night	3 12% 30% 35% 19% 1	400
	21st to end	Night	4 3 21% 42% 30% 2	400
July	1st to 10th	Night	1 5% 19% 35% 35% 5%	402
	11th to 20th	Night	1 15% 32% 42% 10%	582
	21st to end	Night	1 11% 31% 44% 12%	657
August	1st to 10th	Night	2 1 14% 35% 37% 11%	597
	11th to 20th	Night	2 17% 31% 39% 11%	619
	21st to end	Night	2 1 12% 31% 46% 8%	880
September	1st to 10th	Night	1 3 12% 34% 39% 11%	800
	11th to 20th	Night	5% 5% 15% 36% 31% 9%	800
	21st to end	Night	5% 5% 17% 29% 34% 10%	800
October	1st to 10th	Night	6% 5% 16% 33% 32% 8%	800
	11th to 20th	Night	8% 6% 14% 29% 36% 8%	800
	21st to end	Night	13% 4 14% 30% 29% 10%	880
November	1st to 10th	Night	14% 6% 17% 26% 29% 7%	820
	11th to 20th	Night	19% 7% 14% 33% 23% 5%	840
	21st to end	Night	16% 8% 14% 33% 23% 7%	840
December	1st to 10th	Night	23% 4 16% 29% 22% 6%	840
	11th to 20th	Night	30% 7% 13% 29% 18% 4	840
	21st to end	Night	28% 10% 18% 26% 15% 3	924

Page generated at 2026-04-13 23:44:28. Version ac07

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