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 2024-01-15.

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	4 7% 3 7% 6% 3 5% 5% 6% 7% 47%	74637
	Night	4 7% 3 6% 6% 3 5% 5% 6% 7% 48%	75163
Transparency	Day	33% 6% 11% 20% 19% 10%	74362
	Night	32% 6% 14% 22% 18% 8%	74959
Seeing	Day	10% 17% 33% 27% 11% 2	14035
	Night	9% 7% 24% 38% 19% 2	24446

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	4 13% 6% 9% 7% 4 5% 4 6% 6% 34%	1708
	11th to 20th	Day	3 13% 7% 10% 7% 4 4 4 5% 6% 36%	1660
	21st to end	Day	4 12% 8% 12% 7% 3 4 3 4 6% 36%	1782
February	1st to 10th	Day	4 13% 6% 12% 8% 4 5% 5% 5% 6% 32%	1620
	11th to 20th	Day	4 15% 7% 10% 8% 3 5% 4 5% 6% 34%	1620
	21st to end	Day	3 14% 6% 14% 8% 5% 6% 5% 5% 6% 27%	1480
March	1st to 10th	Day	3 12% 7% 10% 7% 4 5% 5% 6% 8% 33%	1933
	11th to 20th	Day	4 9% 4 7% 7% 4 7% 7% 7% 8% 36%	1980
	21st to end	Day	6% 14% 5% 11% 7% 4 6% 6% 6% 7% 29%	2178
April	1st to 10th	Day	6% 11% 5% 7% 5% 4 6% 5% 7% 8% 36%	2011
	11th to 20th	Day	6% 13% 5% 7% 7% 4 6% 5% 5% 7% 36%	2258
	21st to end	Day	5% 11% 4 6% 7% 3 5% 5% 5% 7% 43%	2340
May	1st to 10th	Day	6% 8% 3 6% 5% 4 6% 6% 8% 8% 39%	2340
	11th to 20th	Day	5% 6% 3 6% 6% 4 5% 6% 7% 9% 43%	2301
	21st to end	Day	6% 7% 3 7% 6% 5% 8% 6% 8% 7% 38%	2530
June	1st to 10th	Day	3 3 2 5% 5% 3 5% 4 6% 8% 56%	2497
	11th to 20th	Day	3 4 2 4 4 2 4 4 5% 7% 61%	2520
	21st to end	Day	2 1 1 3 3 3 3 4 5% 6% 70%	2447
July	1st to 10th	Day	2 2 1 3 4 2 4 5% 6% 8% 63%	2340
	11th to 20th	Day	3 3 1 4 4 3 4 4 6% 8% 61%	2340
	21st to end	Day	4 3 1 5% 4 3 5% 5% 6% 10% 55%	2545
August	1st to 10th	Day	3 3 1 4 5% 3 4 5% 5% 8% 58%	2328
	11th to 20th	Day	2 2 1 4 4 3 4 4 5% 7% 64%	2299
	21st to end	Day	3 3 1 3 3 3 4 4 6% 7% 63%	2548
September	1st to 10th	Day	2 3 1 3 3 2 3 4 5% 6% 68%	2054
	11th to 20th	Day	4 3 1 3 4 2 4 4 5% 7% 62%	1980
	21st to end	Day	5% 3 2 2 3 2 3 4 4 6% 66%	1980
October	1st to 10th	Day	7% 6% 3 5% 5% 3 4 5% 5% 5% 53%	1882
	11th to 20th	Day	5% 7% 2 4 3 2 4 3 6% 7% 57%	1800
	21st to end	Day	3 8% 3 6% 4 3 5% 4 4 7% 54%	1980
November	1st to 10th	Day	5% 8% 4 7% 6% 3 6% 5% 5% 6% 44%	1675
	11th to 20th	Day	6% 10% 3 6% 6% 4 5% 4 4 7% 45%	1710
	21st to end	Day	4 9% 5% 8% 7% 4 6% 5% 5% 6% 43%	1525
December	1st to 10th	Day	4 10% 5% 9% 7% 3 7% 5% 5% 6% 38%	1520
	11th to 20th	Day	5% 11% 6% 12% 8% 5% 5% 7% 6% 7% 29%	1926
	21st to end	Day	3 11% 6% 10% 8% 4 6% 5% 6% 8% 35%	3000
January	1st to 10th	Night	5% 12% 6% 9% 7% 4 4 4 5% 7% 36%	2457
	11th to 20th	Night	5% 12% 5% 9% 7% 3 4 5% 5% 7% 38%	2405
	21st to end	Night	4 13% 6% 9% 6% 4 4 5% 5% 7% 36%	2574
February	1st to 10th	Night	3 10% 4 10% 8% 4 6% 6% 6% 7% 35%	2340
	11th to 20th	Night	3 10% 5% 9% 8% 4 5% 5% 5% 6% 40%	2225
	21st to end	Night	3 10% 5% 11% 7% 4 6% 6% 6% 7% 35%	1776
March	1st to 10th	Night	4 11% 6% 8% 7% 5% 6% 6% 5% 6% 35%	2026
	11th to 20th	Night	3 7% 4 6% 7% 4 6% 5% 8% 9% 42%	1980
	21st to end	Night	4 11% 5% 7% 6% 4 5% 5% 6% 7% 39%	2178
April	1st to 10th	Night	6% 12% 4 5% 5% 3 5% 5% 4 5% 46%	1949
	11th to 20th	Night	4 8% 3 6% 5% 3 5% 5% 6% 8% 45%	1648
	21st to end	Night	6% 8% 2 5% 7% 3 4 5% 5% 7% 48%	1620
May	1st to 10th	Night	6% 7% 3 5% 6% 4 5% 6% 7% 9% 43%	1620
	11th to 20th	Night	6% 5% 2 4 5% 3 4 5% 6% 9% 50%	1594
	21st to end	Night	6% 5% 3 6% 6% 4 5% 5% 7% 10% 43%	1746
June	1st to 10th	Night	4 4 2 4 5% 4 5% 4 5% 8% 56%	1458
	11th to 20th	Night	3 2 1 3 3 3 3 4 4 9% 65%	1440
	21st to end	Night	2 1 1 3 3 2 3 3 5% 8% 69%	1505
July	1st to 10th	Night	3 2 2 4 4 3 6% 5% 6% 7% 58%	1620
	11th to 20th	Night	3 3 2 6% 5% 3 5% 4 6% 8% 55%	1620
	21st to end	Night	2 3 1 4 5% 4 5% 5% 8% 9% 54%	1773
August	1st to 10th	Night	3 2 1 4 5% 4 4 4 6% 9% 58%	1611
	11th to 20th	Night	2 3 1 4 4 3 5% 5% 7% 8% 59%	1602
	21st to end	Night	2 3 1 3 4 3 4 6% 6% 8% 60%	1807
September	1st to 10th	Night	3 4 1 3 4 2 4 4 4 6% 66%	1902
	11th to 20th	Night	4 3 1 3 3 2 4 3 6% 7% 65%	1980
	21st to end	Night	4 3 2 3 3 2 2 3 4 5% 70%	1980
October	1st to 10th	Night	6% 4 2 4 4 2 4 4 5% 6% 58%	2078
	11th to 20th	Night	5% 5% 2 4 3 3 4 4 5% 6% 59%	2160
	21st to end	Night	4 6% 2 4 4 2 4 4 4 8% 57%	2376
November	1st to 10th	Night	5% 7% 3 5% 5% 3 5% 4 6% 8% 50%	2400
	11th to 20th	Night	5% 7% 3 5% 5% 4 5% 5% 6% 8% 47%	2470
	21st to end	Night	4 9% 3 7% 8% 3 5% 4 5% 6% 45%	2631
December	1st to 10th	Night	3 9% 5% 9% 6% 4 4 5% 5% 9% 41%	2660
	11th to 20th	Night	5% 10% 5% 8% 7% 4 6% 6% 6% 8% 35%	3271
	21st to end	Night	4 10% 5% 12% 9% 4 5% 5% 6% 7% 33%	4681

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% 8% 16% 20% 8% 1	1709
	11th to 20th	Day	46% 7% 14% 19% 11% 2	1660
	21st to end	Day	49% 6% 19% 17% 7% 3	1782
February	1st to 10th	Day	50% 7% 13% 19% 10% 2	1620
	11th to 20th	Day	48% 7% 13% 19% 12% 1	1629
	21st to end	Day	52% 7% 14% 17% 9% 1	1480
March	1st to 10th	Day	45% 6% 15% 23% 9% 2	1933
	11th to 20th	Day	39% 8% 17% 22% 13% 2	1980
	21st to end	Day	49% 7% 17% 18% 7% 2	2178
April	1st to 10th	Day	41% 7% 14% 19% 14% 4	2011
	11th to 20th	Day	45% 7% 11% 19% 16% 1	2261
	21st to end	Day	38% 6% 10% 26% 19% 1	2340
May	1st to 10th	Day	35% 8% 10% 26% 18% 3	2340
	11th to 20th	Day	32% 6% 11% 26% 20% 4	2304
	21st to end	Day	37% 9% 13% 22% 16% 3	2530
June	1st to 10th	Day	24% 7% 10% 22% 28% 9%	2497
	11th to 20th	Day	22% 5% 7% 21% 28% 18%	2520
	21st to end	Day	14% 5% 4 13% 31% 33%	2447
July	1st to 10th	Day	17% 5% 6% 14% 25% 32%	2276
	11th to 20th	Day	20% 6% 7% 13% 25% 29%	2271
	21st to end	Day	22% 6% 10% 13% 23% 25%	2404
August	1st to 10th	Day	23% 5% 7% 18% 21% 25%	2313
	11th to 20th	Day	19% 5% 5% 16% 29% 25%	2299
	21st to end	Day	20% 4 5% 19% 31% 20%	2548
September	1st to 10th	Day	17% 5% 5% 15% 29% 28%	2054
	11th to 20th	Day	21% 5% 7% 20% 26% 21%	1980
	21st to end	Day	20% 4 7% 21% 36% 13%	1980
October	1st to 10th	Day	32% 5% 9% 21% 24% 9%	1882
	11th to 20th	Day	26% 4 10% 30% 24% 6%	1800
	21st to end	Day	28% 5% 15% 27% 21% 3	1980
November	1st to 10th	Day	34% 8% 14% 22% 17% 4	1675
	11th to 20th	Day	37% 4 14% 26% 18% 1	1710
	21st to end	Day	39% 6% 14% 24% 13% 3	1525
December	1st to 10th	Day	42% 7% 20% 17% 10% 4	1520
	11th to 20th	Day	46% 8% 16% 18% 11% 1	1924
	21st to end	Day	43% 8% 15% 16% 16% 3	3000
January	1st to 10th	Night	45% 7% 17% 22% 7% 2	2457
	11th to 20th	Night	44% 7% 16% 20% 10% 3	2405
	21st to end	Night	44% 7% 19% 20% 7% 3	2574
February	1st to 10th	Night	42% 9% 17% 21% 10% 1	2340
	11th to 20th	Night	42% 6% 13% 22% 17% 1	2226
	21st to end	Night	41% 8% 16% 22% 11% 2	1776
March	1st to 10th	Night	43% 8% 15% 22% 12%	2026
	11th to 20th	Night	32% 7% 18% 27% 15% 2	1980
	21st to end	Night	39% 7% 17% 25% 8% 3	2178
April	1st to 10th	Night	36% 7% 16% 20% 15% 6%	1949
	11th to 20th	Night	31% 6% 17% 24% 20% 2	1648
	21st to end	Night	31% 7% 15% 26% 20% 1	1620
May	1st to 10th	Night	32% 7% 16% 23% 19% 3	1620
	11th to 20th	Night	26% 6% 14% 27% 21% 6%	1595
	21st to end	Night	31% 7% 18% 26% 16% 2	1746
June	1st to 10th	Night	24% 6% 9% 25% 28% 8%	1458
	11th to 20th	Night	16% 6% 9% 21% 30% 19%	1440
	21st to end	Night	14% 3 5% 13% 31% 35%	1505
July	1st to 10th	Night	21% 5% 7% 15% 22% 29%	1575
	11th to 20th	Night	24% 6% 8% 14% 22% 27%	1566
	21st to end	Night	22% 6% 11% 16% 21% 24%	1674
August	1st to 10th	Night	21% 6% 10% 19% 20% 23%	1602
	11th to 20th	Night	20% 5% 9% 16% 26% 25%	1602
	21st to end	Night	18% 5% 7% 18% 30% 22%	1807
September	1st to 10th	Night	17% 4 6% 17% 25% 30%	1902
	11th to 20th	Night	18% 5% 7% 21% 27% 22%	1980
	21st to end	Night	18% 3 6% 22% 36% 15%	1980
October	1st to 10th	Night	25% 5% 11% 24% 27% 9%	2078
	11th to 20th	Night	24% 5% 8% 30% 26% 6%	2160
	21st to end	Night	24% 5% 13% 29% 24% 4	2376
November	1st to 10th	Night	29% 6% 13% 26% 21% 5%	2400
	11th to 20th	Night	31% 6% 16% 26% 18% 3	2470
	21st to end	Night	35% 6% 14% 25% 16% 4	2631
December	1st to 10th	Night	38% 8% 17% 23% 12% 3	2660
	11th to 20th	Night	40% 9% 20% 20% 11% 1	3272
	21st to end	Night	45% 8% 17% 16% 12% 2	4681

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	19% 16% 27% 24% 13% 1	270
	11th to 20th	Day	11% 15% 40% 23% 9% 1	254
	21st to end	Day	9% 18% 38% 26% 8% 2	264
February	1st to 10th	Day	17% 20% 36% 22% 4	240
	11th to 20th	Day	12% 26% 41% 14% 6% 1	285
	21st to end	Day	13% 27% 41% 15% 3 1	346
March	1st to 10th	Day	15% 25% 39% 17% 4	420
	11th to 20th	Day	11% 23% 40% 20% 6%	420
	21st to end	Day	20% 26% 34% 19% 1	462
April	1st to 10th	Day	18% 24% 29% 22% 6%	420
	11th to 20th	Day	19% 28% 32% 15% 5%	412
	21st to end	Day	18% 27% 26% 22% 7% 1	420
May	1st to 10th	Day	11% 22% 39% 21% 6% 1	423
	11th to 20th	Day	13% 19% 29% 26% 10% 2	448
	21st to end	Day	12% 18% 31% 24% 12% 3	485
June	1st to 10th	Day	5% 14% 32% 29% 17% 3	607
	11th to 20th	Day	8% 16% 31% 29% 14% 2	630
	21st to end	Day	5% 12% 32% 34% 14% 2	557
July	1st to 10th	Day	11% 34% 41% 12% 2	446
	11th to 20th	Day	3 9% 36% 35% 13% 3	444
	21st to end	Day	3 5% 31% 40% 17% 3	487
August	1st to 10th	Day	6% 10% 30% 34% 18% 2	447
	11th to 20th	Day	2 8% 31% 37% 20% 2	437
	21st to end	Day	3 10% 30% 37% 17% 4	495
September	1st to 10th	Day	5% 11% 29% 30% 19% 5%	450
	11th to 20th	Day	7% 16% 30% 30% 13% 4	450
	21st to end	Day	8% 16% 26% 33% 15% 3	450
October	1st to 10th	Day	12% 15% 26% 28% 15% 5%	352
	11th to 20th	Day	10% 16% 27% 24% 17% 6%	270
	21st to end	Day	9% 18% 38% 24% 10% 1	297
November	1st to 10th	Day	16% 16% 27% 27% 10% 3	270
	11th to 20th	Day	10% 13% 37% 27% 9% 4	270
	21st to end	Day	9% 11% 30% 31% 16% 3	270
December	1st to 10th	Day	11% 11% 37% 29% 9% 3	270
	11th to 20th	Day	12% 16% 41% 24% 6%	270
	21st to end	Day	16% 16% 38% 21% 7% 1	297
January	1st to 10th	Night	12% 8% 28% 33% 16% 2	760
	11th to 20th	Night	12% 9% 29% 35% 12% 3	740
	21st to end	Night	10% 7% 30% 38% 12% 3	792
February	1st to 10th	Night	11% 7% 34% 36% 10% 1	720
	11th to 20th	Night	9% 9% 32% 37% 12% 1	704
	21st to end	Night	9% 10% 32% 38% 10% 1	592
March	1st to 10th	Night	12% 11% 31% 35% 9% 2	720
	11th to 20th	Night	6% 9% 27% 39% 16% 2	720
	21st to end	Night	11% 13% 27% 37% 11% 1	792
April	1st to 10th	Night	14% 12% 28% 35% 11% 1	689
	11th to 20th	Night	10% 10% 33% 35% 12% 1	533
	21st to end	Night	9% 8% 24% 38% 18% 2	540
May	1st to 10th	Night	10% 5% 27% 39% 17% 2	540
	11th to 20th	Night	9% 5% 18% 39% 27% 2	531
	21st to end	Night	10% 5% 20% 36% 25% 4	584
June	1st to 10th	Night	6% 9% 15% 43% 25% 2	540
	11th to 20th	Night	4 8% 21% 45% 21%	540
	21st to end	Night	2 4 18% 41% 34% 2	540
July	1st to 10th	Night	4 4 15% 37% 37% 3	525
	11th to 20th	Night	5% 3 15% 45% 30% 3	522
	21st to end	Night	3 2 8% 38% 47% 2	591
August	1st to 10th	Night	5% 2 13% 46% 32% 1	537
	11th to 20th	Night	2 2 13% 46% 35% 1	534
	21st to end	Night	3 2 15% 42% 35% 3	594
September	1st to 10th	Night	5% 3 15% 42% 31% 3	642
	11th to 20th	Night	5% 4 17% 39% 29% 5%	720
	21st to end	Night	7% 5% 18% 36% 28% 7%	720
October	1st to 10th	Night	8% 6% 22% 39% 22% 3	720
	11th to 20th	Night	9% 5% 23% 38% 21% 4	720
	21st to end	Night	9% 4 26% 39% 19% 3	792
November	1st to 10th	Night	11% 8% 24% 38% 18% 2	740
	11th to 20th	Night	10% 6% 32% 37% 12% 3	760
	21st to end	Night	10% 11% 24% 39% 12% 3	921
December	1st to 10th	Night	11% 7% 32% 37% 12% 1	950
	11th to 20th	Night	13% 8% 32% 36% 9% 1	950
	21st to end	Night	15% 12% 33% 33% 8% 1	931

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