Dark Ranger Wasatch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dark Ranger Wasatch clear sky chart from 2005-11-06 to 2026-02-01.

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	3 7% 3 7% 4 4 4 4 5% 7% 51%	136029
	Night	3 7% 3 7% 5% 4 4 4 6% 7% 50%	133504
Transparency	Day	30% 6% 9% 20% 21% 13%	130775
	Night	30% 6% 11% 22% 20% 10%	129761
Seeing	Day	10% 16% 32% 27% 12% 3	16784
	Night	9% 7% 25% 38% 19% 2	27204

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	2 13% 7% 14% 7% 5% 4 4 6% 7% 30%	4188
	11th to 20th	Day	2 12% 6% 20% 7% 4 3 3 4 5% 33%	4190
	21st to end	Day	2 11% 6% 10% 4 3 3 3 4 7% 47%	4609
February	1st to 10th	Day	4 15% 5% 14% 7% 5% 4 4 5% 5% 31%	1800
	11th to 20th	Day	3 16% 7% 12% 7% 5% 4 4 5% 6% 32%	1805
	21st to end	Day	3 14% 5% 15% 6% 6% 6% 4 5% 7% 29%	1650
March	1st to 10th	Day	2 15% 8% 12% 5% 5% 4 3 4 6% 35%	4858
	11th to 20th	Day	2 8% 6% 9% 6% 6% 5% 5% 6% 7% 41%	5000
	21st to end	Day	3 16% 6% 13% 7% 6% 6% 4 5% 5% 28%	5486
April	1st to 10th	Day	5% 11% 5% 8% 5% 5% 5% 4 7% 7% 37%	2235
	11th to 20th	Day	5% 13% 4 8% 5% 5% 6% 4 5% 7% 37%	2513
	21st to end	Day	4 11% 4 7% 6% 4 4 4 6% 7% 41%	2600
May	1st to 10th	Day	6% 11% 3 7% 4 5% 5% 4 6% 7% 43%	5880
	11th to 20th	Day	5% 7% 2 6% 4 5% 5% 4 6% 8% 48%	5841
	21st to end	Day	3 4 2 6% 4 5% 5% 4 6% 8% 53%	6423
June	1st to 10th	Day	3 3 1 5% 5% 4 5% 3 6% 8% 56%	2775
	11th to 20th	Day	3 4 1 5% 3 3 4 3 5% 7% 62%	2800
	21st to end	Day	1 1 1 3 3 3 4 3 4 6% 70%	2718
July	1st to 10th	Day	1 1 1 3 3 3 3 3 4 5% 72%	5879
	11th to 20th	Day	1 2 1 3 3 3 4 4 6% 8% 64%	5880
	21st to end	Day	2 2 1 3 2 3 3 3 5% 7% 70%	6401
August	1st to 10th	Day	2 2 1 3 3 3 4 3 4 6% 69%	5779
	11th to 20th	Day	1 1 1 3 2 3 4 3 5% 7% 70%	5798
	21st to end	Day	2 3 1 4 4 4 5% 4 6% 7% 61%	6390
September	1st to 10th	Day	2 3 1 4 3 3 3 3 6% 6% 67%	2282
	11th to 20th	Day	4 3 1 4 4 4 4 3 5% 7% 61%	2200
	21st to end	Day	4 3 2 3 2 3 3 3 4 6% 66%	2200
October	1st to 10th	Day	4 4 1 4 3 3 3 3 4 4 67%	3412
	11th to 20th	Day	7% 6% 1 4 3 3 4 3 6% 6% 57%	3250
	21st to end	Day	4 8% 2 5% 3 4 4 3 4 6% 56%	3548
November	1st to 10th	Day	5% 8% 3 8% 5% 4 5% 4 6% 6% 46%	1855
	11th to 20th	Day	6% 11% 3 8% 5% 5% 4 4 5% 6% 43%	1890
	21st to end	Day	4 10% 4 8% 6% 5% 5% 4 5% 6% 44%	1685
December	1st to 10th	Day	2 7% 3 7% 4 4 4 3 4 6% 56%	2700
	11th to 20th	Day	3 10% 6% 12% 6% 6% 6% 6% 7% 8% 32%	3106
	21st to end	Day	3 12% 6% 13% 8% 7% 6% 4 6% 6% 30%	4403
January	1st to 10th	Night	2 12% 7% 15% 6% 4 5% 4 6% 6% 35%	5997
	11th to 20th	Night	2 11% 6% 17% 7% 4 4 3 4 6% 34%	6010
	21st to end	Night	2 10% 5% 8% 4 4 4 3 6% 7% 46%	6611
February	1st to 10th	Night	3 11% 4 11% 7% 6% 6% 5% 6% 7% 34%	2600
	11th to 20th	Night	3 11% 4 11% 7% 6% 4 4 5% 6% 39%	2480
	21st to end	Night	2 11% 4 12% 6% 5% 5% 4 6% 7% 38%	1980
March	1st to 10th	Night	3 13% 5% 11% 6% 6% 6% 5% 6% 6% 34%	5035
	11th to 20th	Night	2 9% 3 7% 5% 6% 6% 5% 7% 9% 41%	5000
	21st to end	Night	2 12% 5% 10% 6% 5% 5% 4 5% 7% 39%	5489
April	1st to 10th	Night	5% 12% 4 6% 5% 4 5% 4 5% 6% 46%	2165
	11th to 20th	Night	4 9% 2 7% 5% 4 5% 5% 6% 8% 45%	1832
	21st to end	Night	6% 9% 2 7% 6% 4 5% 5% 6% 7% 45%	1800
May	1st to 10th	Night	5% 10% 3 6% 4 4 4 4 6% 7% 49%	4100
	11th to 20th	Night	4 4 2 5% 4 3 4 4 5% 8% 57%	4074
	21st to end	Night	3 4 2 6% 4 5% 3 4 6% 8% 56%	4474
June	1st to 10th	Night	4 4 2 4 5% 5% 4 3 5% 8% 56%	1620
	11th to 20th	Night	3 2 1 4 3 4 4 3 5% 9% 64%	1600
	21st to end	Night	2 2 1 3 2 3 3 3 5% 8% 69%	1673
July	1st to 10th	Night	1 2 1 4 3 4 3 3 4 4 70%	4100
	11th to 20th	Night	1 2 2 5% 4 4 5% 4 7% 9% 58%	4100
	21st to end	Night	2 2 1 4 3 4 4 4 7% 7% 64%	4472
August	1st to 10th	Night	2 1 1 3 3 3 4 3 6% 8% 67%	4033
	11th to 20th	Night	2 2 1 4 3 3 5% 4 5% 7% 64%	4051
	21st to end	Night	2 3 1 5% 3 5% 5% 5% 6% 7% 59%	4586
September	1st to 10th	Night	2 4 1 4 3 3 4 4 4 6% 66%	2114
	11th to 20th	Night	4 3 1 4 3 3 3 3 5% 7% 64%	2200
	21st to end	Night	3 3 2 3 3 2 3 2 4 5% 70%	2200
October	1st to 10th	Night	4 3 1 3 2 2 3 3 4 5% 71%	3782
	11th to 20th	Night	5% 5% 2 4 3 4 4 4 5% 7% 56%	3898
	21st to end	Night	5% 6% 2 5% 3 4 4 4 6% 8% 53%	4252
November	1st to 10th	Night	5% 7% 3 6% 5% 3 5% 4 6% 7% 50%	2660
	11th to 20th	Night	5% 7% 3 6% 5% 6% 5% 4 6% 8% 46%	2730
	21st to end	Night	4 9% 3 8% 7% 4 4 4 6% 6% 46%	2909
December	1st to 10th	Night	2 6% 3 7% 4 3 3 3 5% 7% 56%	4710
	11th to 20th	Night	4 9% 3 8% 5% 5% 5% 5% 6% 7% 43%	5321
	21st to end	Night	3 11% 5% 13% 8% 7% 5% 4 6% 7% 31%	6846

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	48% 8% 14% 15% 13% 1	4189
	11th to 20th	Day	50% 7% 10% 19% 10% 4	4190
	21st to end	Day	37% 6% 15% 19% 21% 2	4609
February	1st to 10th	Day	51% 7% 13% 17% 11% 2	1800
	11th to 20th	Day	50% 7% 13% 18% 12% 1	1814
	21st to end	Day	48% 7% 14% 18% 11% 2	1650
March	1st to 10th	Day	44% 9% 9% 21% 11% 6%	4858
	11th to 20th	Day	36% 8% 15% 26% 15% 1	5000
	21st to end	Day	51% 8% 17% 16% 6% 1	5486
April	1st to 10th	Day	40% 7% 14% 20% 15% 4	2235
	11th to 20th	Day	43% 7% 11% 21% 17% 2	2516
	21st to end	Day	38% 6% 11% 26% 18% 1	2600
May	1st to 10th	Day	33% 10% 9% 24% 18% 5%	5880
	11th to 20th	Day	29% 6% 8% 27% 26% 4	5844
	21st to end	Day	24% 7% 8% 27% 31% 3	6424
June	1st to 10th	Day	23% 7% 10% 23% 29% 9%	2775
	11th to 20th	Day	21% 4 6% 20% 29% 19%	2800
	21st to end	Day	14% 5% 4 12% 33% 32%	2718
July	1st to 10th	Day	14% 3 4 7% 17% 55%	5816
	11th to 20th	Day	16% 5% 5% 11% 28% 35%	5811
	21st to end	Day	13% 4 5% 8% 28% 42%	6217
August	1st to 10th	Day	19% 4 5% 19% 25% 27%	4208
	11th to 20th	Day	17% 6% 4 18% 32% 24%	4197
	21st to end	Day	15% 5% 5% 16% 32% 29%	4609
September	1st to 10th	Day	17% 5% 6% 16% 30% 26%	2282
	11th to 20th	Day	21% 5% 7% 19% 29% 19%	2200
	21st to end	Day	20% 4 6% 22% 35% 14%	2200
October	1st to 10th	Day	21% 3 5% 15% 35% 20%	3412
	11th to 20th	Day	27% 4 7% 30% 26% 6%	3250
	21st to end	Day	28% 4 11% 29% 24% 4	3548
November	1st to 10th	Day	33% 7% 14% 24% 17% 5%	1855
	11th to 20th	Day	38% 4 14% 26% 17% 1	1890
	21st to end	Day	38% 6% 14% 26% 14% 3	1685
December	1st to 10th	Day	27% 5% 14% 40% 13% 2	2700
	11th to 20th	Day	44% 7% 16% 20% 12% 1	3104
	21st to end	Day	50% 7% 11% 17% 14% 2	4403
January	1st to 10th	Night	46% 7% 15% 18% 12% 2	5997
	11th to 20th	Night	50% 7% 10% 23% 9% 2	6010
	21st to end	Night	36% 8% 14% 21% 20% 2	6611
February	1st to 10th	Night	43% 10% 16% 19% 10% 2	2600
	11th to 20th	Night	42% 6% 13% 21% 16% 1	2481
	21st to end	Night	40% 8% 15% 22% 13% 3	1980
March	1st to 10th	Night	41% 9% 13% 20% 13% 4	5035
	11th to 20th	Night	33% 9% 16% 27% 15% 1	5000
	21st to end	Night	39% 8% 18% 24% 10% 1	5489
April	1st to 10th	Night	34% 7% 16% 21% 16% 5%	2165
	11th to 20th	Night	31% 6% 16% 24% 20% 3	1832
	21st to end	Night	32% 7% 16% 26% 18% 1	1800
May	1st to 10th	Night	28% 8% 14% 22% 26% 3	4097
	11th to 20th	Night	21% 8% 9% 30% 27% 5%	4075
	21st to end	Night	22% 5% 10% 29% 33% 1	4474
June	1st to 10th	Night	23% 6% 9% 24% 29% 8%	1620
	11th to 20th	Night	16% 6% 8% 20% 30% 20%	1600
	21st to end	Night	14% 3 5% 12% 32% 34%	1673
July	1st to 10th	Night	16% 3 3 8% 15% 54%	4055
	11th to 20th	Night	21% 4 4 10% 27% 34%	4046
	21st to end	Night	17% 4 6% 10% 28% 36%	4344
August	1st to 10th	Night	19% 5% 6% 16% 28% 26%	2928
	11th to 20th	Night	22% 4 7% 16% 27% 24%	2928
	21st to end	Night	13% 4 7% 14% 32% 30%	3298
September	1st to 10th	Night	18% 4 6% 18% 26% 28%	2114
	11th to 20th	Night	18% 5% 7% 21% 29% 20%	2200
	21st to end	Night	18% 3 6% 22% 35% 16%	2200
October	1st to 10th	Night	16% 3 6% 19% 35% 20%	3782
	11th to 20th	Night	26% 5% 7% 31% 25% 7%	3898
	21st to end	Night	27% 4 9% 32% 26% 3	4252
November	1st to 10th	Night	29% 6% 13% 26% 21% 5%	2660
	11th to 20th	Night	32% 6% 16% 27% 17% 2	2730
	21st to end	Night	35% 5% 14% 27% 16% 4	2909
December	1st to 10th	Night	27% 5% 12% 36% 18% 2	4710
	11th to 20th	Night	35% 7% 22% 25% 10% 1	5322
	21st to end	Night	48% 7% 15% 18% 11% 1	6846

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	18% 15% 29% 25% 11% 2	330
	11th to 20th	Day	9% 14% 40% 25% 9% 3	330
	21st to end	Day	8% 15% 36% 31% 9% 2	363
February	1st to 10th	Day	20% 22% 32% 22% 3	300
	11th to 20th	Day	15% 24% 40% 14% 6% 1	350
	21st to end	Day	12% 27% 40% 16% 4 1	414
March	1st to 10th	Day	16% 24% 38% 18% 4 1	500
	11th to 20th	Day	12% 23% 39% 19% 6%	500
	21st to end	Day	19% 25% 33% 19% 3	550
April	1st to 10th	Day	17% 23% 29% 22% 8% 1	500
	11th to 20th	Day	19% 26% 32% 16% 6%	492
	21st to end	Day	17% 25% 27% 23% 7% 1	500
May	1st to 10th	Day	13% 22% 36% 21% 7% 2	503
	11th to 20th	Day	14% 21% 28% 26% 10% 2	528
	21st to end	Day	12% 17% 31% 25% 13% 3	573
June	1st to 10th	Day	5% 14% 32% 30% 17% 3	705
	11th to 20th	Day	8% 15% 33% 28% 14% 2	730
	21st to end	Day	5% 12% 34% 32% 14% 2	648
July	1st to 10th	Day	2 10% 35% 39% 12% 2	526
	11th to 20th	Day	3 8% 34% 35% 15% 5%	524
	21st to end	Day	4 6% 31% 39% 17% 3	575
August	1st to 10th	Day	5% 11% 32% 32% 18% 3	527
	11th to 20th	Day	2 9% 31% 37% 18% 3	517
	21st to end	Day	4 11% 30% 35% 16% 5%	583
September	1st to 10th	Day	6% 10% 27% 31% 20% 6%	530
	11th to 20th	Day	8% 16% 31% 28% 13% 4	530
	21st to end	Day	7% 14% 26% 32% 16% 5%	530
October	1st to 10th	Day	11% 13% 27% 27% 16% 5%	420
	11th to 20th	Day	12% 14% 28% 25% 16% 5%	330
	21st to end	Day	10% 16% 34% 24% 13% 2	363
November	1st to 10th	Day	14% 16% 28% 27% 11% 4	330
	11th to 20th	Day	12% 12% 35% 28% 9% 3	330
	21st to end	Day	10% 10% 28% 34% 15% 3	330
December	1st to 10th	Day	12% 11% 35% 27% 11% 5%	330
	11th to 20th	Day	12% 14% 38% 26% 8% 1	330
	21st to end	Day	17% 18% 34% 21% 8% 1	363
January	1st to 10th	Night	12% 9% 30% 33% 15% 2	840
	11th to 20th	Night	11% 9% 30% 36% 13% 3	840
	21st to end	Night	9% 7% 32% 39% 11% 2	924
February	1st to 10th	Night	13% 9% 33% 35% 10% 1	800
	11th to 20th	Night	9% 9% 35% 35% 11% 1	784
	21st to end	Night	9% 11% 33% 37% 9%	660
March	1st to 10th	Night	12% 11% 31% 35% 10% 1	800
	11th to 20th	Night	6% 11% 29% 38% 15% 2	800
	21st to end	Night	11% 13% 29% 37% 10%	880
April	1st to 10th	Night	13% 12% 27% 36% 11% 1	765
	11th to 20th	Night	10% 9% 35% 34% 12% 1	593
	21st to end	Night	9% 7% 26% 39% 17% 2	600
May	1st to 10th	Night	10% 6% 28% 38% 17% 2	600
	11th to 20th	Night	9% 7% 19% 39% 24% 2	591
	21st to end	Night	10% 4 21% 36% 25% 4	650
June	1st to 10th	Night	6% 8% 16% 44% 25% 2	600
	11th to 20th	Night	5% 8% 23% 45% 20%	600
	21st to end	Night	3 4 18% 42% 32% 2	600
July	1st to 10th	Night	4 3 17% 39% 35% 3	585
	11th to 20th	Night	4 2 14% 46% 30% 3	582
	21st to end	Night	3 1 10% 40% 44% 2	657
August	1st to 10th	Night	5% 2 14% 48% 30% 1	597
	11th to 20th	Night	3 3 16% 44% 33% 1	594
	21st to end	Night	3 3 15% 44% 33% 3	660
September	1st to 10th	Night	5% 3 15% 44% 30% 3	714
	11th to 20th	Night	6% 4 18% 40% 27% 5%	800
	21st to end	Night	6% 5% 17% 38% 28% 6%	800
October	1st to 10th	Night	8% 6% 22% 40% 22% 3	800
	11th to 20th	Night	9% 5% 24% 39% 19% 4	800
	21st to end	Night	10% 4 25% 39% 19% 3	880
November	1st to 10th	Night	10% 7% 25% 39% 17% 2	820
	11th to 20th	Night	10% 6% 33% 38% 11% 3	840
	21st to end	Night	10% 10% 25% 40% 12% 3	1019
December	1st to 10th	Night	10% 6% 34% 36% 13% 1	1050
	11th to 20th	Night	13% 8% 34% 35% 9% 1	1050
	21st to end	Night	14% 13% 33% 32% 8% 1	1029

Page generated at 2026-01-28 23:21:40. Version ac07

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