Red Shale Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Shale Campground clear sky chart from 2005-11-06 to 2025-08-05.

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	7% 7% 3 6% 4 4 4 4 6% 8% 48%	130076
	Night	7% 8% 3 7% 4 4 4 4 6% 7% 45%	126961
Transparency	Day	34% 4 12% 28% 18% 4	129774
	Night	38% 4 12% 26% 16% 4	126781
Seeing	Day	12% 7% 25% 32% 19% 5%	17036
	Night	12% 5% 25% 42% 14% 1	27011

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	5% 9% 7% 13% 7% 6% 6% 5% 6% 7% 30%	3638
	11th to 20th	Day	4 14% 4 8% 7% 6% 5% 4 6% 6% 35%	3640
	21st to end	Day	2 7% 4 7% 4 4 4 4 5% 6% 53%	4211
February	1st to 10th	Day	7% 16% 5% 10% 7% 5% 4 4 5% 6% 31%	1800
	11th to 20th	Day	7% 13% 4 9% 6% 4 4 4 5% 7% 37%	1755
	21st to end	Day	5% 10% 3 9% 6% 6% 6% 5% 5% 9% 37%	1635
March	1st to 10th	Day	3 9% 4 8% 4 3 4 3 5% 7% 50%	4500
	11th to 20th	Day	5% 8% 3 7% 4 4 4 4 6% 10% 45%	5000
	21st to end	Day	14% 12% 4 9% 5% 4 4 4 6% 8% 31%	5746
April	1st to 10th	Day	13% 10% 3 6% 4 5% 4 4 6% 7% 39%	2400
	11th to 20th	Day	11% 13% 4 8% 6% 5% 5% 3 6% 8% 32%	2371
	21st to end	Day	15% 9% 3 8% 5% 4 4 4 5% 7% 35%	2539
May	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 5% 7% 44%	6340
	11th to 20th	Day	10% 8% 3 6% 4 4 5% 4 6% 9% 41%	6298
	21st to end	Day	9% 5% 2 5% 3 4 5% 4 6% 9% 48%	6925
June	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 7% 9% 46%	2800
	11th to 20th	Day	7% 5% 2 5% 5% 4 5% 4 8% 9% 46%	2800
	21st to end	Day	5% 3 1 4 3 4 4 3 6% 7% 60%	2800
July	1st to 10th	Day	5% 3 1 4 3 4 4 4 7% 9% 55%	6339
	11th to 20th	Day	5% 3 1 3 2 2 3 3 4 8% 66%	6340
	21st to end	Day	4 4 2 4 3 4 5% 4 6% 9% 55%	6903
August	1st to 10th	Day	5% 3 2 5% 4 4 5% 4 7% 9% 53%	4375
	11th to 20th	Day	5% 3 1 4 3 3 4 4 7% 9% 56%	4028
	21st to end	Day	5% 2 1 3 3 3 3 3 5% 6% 65%	4190
September	1st to 10th	Day	6% 3 1 3 3 2 3 3 4 6% 64%	2280
	11th to 20th	Day	8% 3 1 4 3 3 3 3 5% 6% 59%	2280
	21st to end	Day	11% 4 1 4 3 3 2 3 5% 6% 58%	2037
October	1st to 10th	Day	8% 5% 2 4 3 2 3 2 3 4 65%	3170
	11th to 20th	Day	10% 6% 2 5% 3 2 2 2 4 5% 58%	3150
	21st to end	Day	8% 7% 2 6% 4 3 5% 4 6% 8% 47%	3196
November	1st to 10th	Day	9% 9% 2 6% 4 3 3 3 6% 8% 45%	1740
	11th to 20th	Day	8% 10% 3 7% 5% 4 3 3 6% 6% 44%	1600
	21st to end	Day	6% 9% 3 6% 4 4 5% 4 7% 8% 45%	1600
December	1st to 10th	Day	3 12% 5% 6% 3 4 4 3 6% 6% 48%	2620
	11th to 20th	Day	4 8% 3 8% 5% 5% 5% 4 6% 9% 43%	3026
	21st to end	Day	5% 9% 4 9% 6% 4 4 4 5% 6% 43%	4004
January	1st to 10th	Night	5% 12% 5% 13% 6% 5% 4 3 5% 6% 36%	6327
	11th to 20th	Night	5% 12% 6% 11% 7% 6% 5% 5% 5% 5% 33%	6340
	21st to end	Night	2 9% 4 9% 4 4 5% 3 5% 7% 48%	6811
February	1st to 10th	Night	8% 14% 4 11% 6% 6% 6% 4 5% 7% 30%	2600
	11th to 20th	Night	5% 11% 5% 11% 8% 5% 5% 4 5% 6% 33%	2532
	21st to end	Night	6% 10% 4 9% 6% 5% 4 4 5% 6% 39%	1994
March	1st to 10th	Night	5% 9% 4 7% 4 4 5% 4 6% 7% 45%	5361
	11th to 20th	Night	6% 7% 2 6% 4 4 4 4 6% 9% 47%	5000
	21st to end	Night	13% 13% 4 10% 6% 5% 5% 4 6% 8% 26%	5216
April	1st to 10th	Night	12% 11% 3 6% 5% 5% 4 4 5% 7% 37%	2000
	11th to 20th	Night	10% 11% 4 9% 5% 5% 5% 4 6% 7% 34%	1977
	21st to end	Night	14% 10% 3 5% 5% 4 4 4 5% 7% 40%	1855
May	1st to 10th	Night	14% 7% 2 4 3 4 3 3 5% 7% 48%	3640
	11th to 20th	Night	14% 8% 3 6% 4 4 4 4 6% 9% 37%	3617
	21st to end	Night	10% 5% 2 5% 4 4 4 3 6% 9% 49%	3972
June	1st to 10th	Night	10% 4 2 5% 4 5% 5% 5% 8% 9% 43%	1600
	11th to 20th	Night	9% 5% 2 5% 5% 5% 4 4 7% 9% 45%	1600
	21st to end	Night	6% 4 2 5% 3 4 4 4 6% 9% 54%	1600
July	1st to 10th	Night	4 3 1 5% 4 4 5% 5% 8% 10% 51%	3640
	11th to 20th	Night	5% 3 1 5% 4 4 5% 4 6% 8% 54%	3640
	21st to end	Night	5% 4 2 5% 4 4 5% 4 7% 10% 50%	3970
August	1st to 10th	Night	4 4 2 6% 4 4 5% 5% 7% 8% 50%	2650
	11th to 20th	Night	5% 3 2 4 3 4 5% 5% 7% 11% 52%	2811
	21st to end	Night	5% 4 1 3 3 3 3 4 6% 8% 60%	3477
September	1st to 10th	Night	7% 4 2 4 2 3 3 2 4 7% 62%	1900
	11th to 20th	Night	9% 4 2 4 3 3 4 3 6% 7% 55%	1900
	21st to end	Night	10% 5% 2 4 3 2 3 2 4 7% 56%	2142
October	1st to 10th	Night	9% 4 1 3 2 2 2 2 3 5% 66%	3800
	11th to 20th	Night	9% 7% 2 5% 3 2 3 3 5% 6% 55%	3778
	21st to end	Night	6% 7% 3 7% 4 3 4 4 6% 7% 50%	4331
November	1st to 10th	Night	9% 8% 3 7% 4 4 4 3 6% 8% 45%	2555
	11th to 20th	Night	7% 9% 3 7% 5% 5% 5% 4 6% 6% 42%	2800
	21st to end	Night	6% 8% 3 7% 4 4 5% 3 6% 8% 47%	2800
December	1st to 10th	Night	5% 10% 3 8% 5% 4 5% 4 6% 7% 44%	4570
	11th to 20th	Night	4 10% 4 9% 6% 4 5% 3 5% 7% 42%	5181
	21st to end	Night	5% 10% 4 8% 5% 5% 4 4 6% 7% 42%	6974

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	53% 3 12% 26% 5%	3639
	11th to 20th	Day	49% 3 12% 22% 12% 1	3640
	21st to end	Day	32% 3 16% 33% 16% 1	4211
February	1st to 10th	Day	55% 2 12% 20% 11% 1	1800
	11th to 20th	Day	46% 5% 15% 20% 12% 2	1764
	21st to end	Day	44% 4 12% 24% 13% 3	1635
March	1st to 10th	Day	33% 4 11% 31% 20% 1	4500
	11th to 20th	Day	35% 5% 16% 35% 9% 1	5000
	21st to end	Day	50% 5% 16% 24% 5%	5746
April	1st to 10th	Day	44% 5% 13% 26% 11% 2	2400
	11th to 20th	Day	49% 5% 13% 24% 8% 1	2374
	21st to end	Day	48% 4 13% 22% 12% 1	2539
May	1st to 10th	Day	38% 5% 10% 28% 17% 1	6340
	11th to 20th	Day	39% 4 13% 28% 14% 1	6302
	21st to end	Day	32% 5% 12% 36% 14%	6926
June	1st to 10th	Day	33% 5% 20% 27% 14% 1	2800
	11th to 20th	Day	32% 4 19% 27% 15% 3	2800
	21st to end	Day	23% 3 13% 29% 25% 7%	2800
July	1st to 10th	Day	24% 4 10% 31% 22% 10%	6271
	11th to 20th	Day	19% 3 6% 27% 33% 13%	6265
	21st to end	Day	25% 5% 9% 24% 27% 11%	6705
August	1st to 10th	Day	26% 4 10% 24% 23% 13%	4360
	11th to 20th	Day	25% 4 9% 29% 29% 5%	4067
	21st to end	Day	19% 3 9% 28% 33% 8%	4189
September	1st to 10th	Day	22% 3 6% 28% 28% 13%	2280
	11th to 20th	Day	25% 4 10% 30% 24% 8%	2280
	21st to end	Day	27% 3 10% 30% 26% 4	2037
October	1st to 10th	Day	25% 2 7% 23% 30% 13%	3170
	11th to 20th	Day	31% 2 9% 28% 27% 3	3150
	21st to end	Day	35% 4 12% 34% 14% 2	3196
November	1st to 10th	Day	37% 4 10% 27% 19% 3	1740
	11th to 20th	Day	41% 3 13% 28% 14% 2	1600
	21st to end	Day	36% 3 17% 27% 14% 2	1600
December	1st to 10th	Day	38% 3 16% 26% 15% 2	2620
	11th to 20th	Day	38% 4 22% 30% 6% 1	3024
	21st to end	Day	42% 3 10% 28% 16% 2	4004
January	1st to 10th	Night	50% 4 12% 29% 5% 1	6327
	11th to 20th	Night	52% 3 13% 18% 12% 2	6340
	21st to end	Night	37% 3 17% 28% 13% 2	6811
February	1st to 10th	Night	53% 4 13% 19% 10% 1	2600
	11th to 20th	Night	51% 4 13% 20% 10% 1	2533
	21st to end	Night	44% 5% 14% 21% 13% 4	1994
March	1st to 10th	Night	36% 5% 10% 30% 19% 1	5361
	11th to 20th	Night	33% 5% 18% 27% 17% 1	5000
	21st to end	Night	56% 5% 17% 16% 6%	5216
April	1st to 10th	Night	46% 4 13% 22% 12% 3	2000
	11th to 20th	Night	48% 4 11% 26% 10% 1	1977
	21st to end	Night	44% 4 14% 27% 11%	1855
May	1st to 10th	Night	35% 4 10% 29% 20% 1	3640
	11th to 20th	Night	44% 4 13% 28% 10% 2	3618
	21st to end	Night	32% 6% 13% 34% 15% 1	3972
June	1st to 10th	Night	35% 6% 18% 28% 11% 2	1600
	11th to 20th	Night	35% 5% 19% 23% 15% 3	1600
	21st to end	Night	27% 3 14% 28% 23% 5%	1600
July	1st to 10th	Night	26% 4 14% 31% 18% 7%	3600
	11th to 20th	Night	28% 4 9% 21% 30% 9%	3592
	21st to end	Night	28% 5% 11% 24% 24% 8%	3856
August	1st to 10th	Night	28% 5% 12% 24% 16% 15%	2642
	11th to 20th	Night	25% 5% 12% 31% 21% 5%	2838
	21st to end	Night	23% 3 8% 23% 32% 10%	3477
September	1st to 10th	Night	24% 3 4 27% 28% 14%	1900
	11th to 20th	Night	28% 4 9% 26% 24% 8%	1900
	21st to end	Night	30% 2 8% 27% 26% 6%	2142
October	1st to 10th	Night	23% 2 8% 25% 27% 15%	3800
	11th to 20th	Night	31% 3 7% 24% 32% 3	3778
	21st to end	Night	34% 4 11% 30% 15% 7%	4331
November	1st to 10th	Night	38% 4 13% 24% 16% 5%	2555
	11th to 20th	Night	40% 4 10% 29% 15% 2	2800
	21st to end	Night	36% 4 16% 28% 15% 3	2800
December	1st to 10th	Night	40% 4 17% 26% 13% 1	4570
	11th to 20th	Night	43% 4 14% 31% 8%	5182
	21st to end	Night	42% 3 8% 32% 13% 2	6974

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	11% 7% 27% 33% 16% 5%	300
	11th to 20th	Day	16% 8% 24% 33% 16% 4	300
	21st to end	Day	13% 10% 33% 30% 12% 2	330
February	1st to 10th	Day	18% 8% 33% 33% 7% 1	300
	11th to 20th	Day	16% 7% 29% 34% 13% 1	300
	21st to end	Day	14% 5% 30% 37% 14% 1	249
March	1st to 10th	Day	11% 8% 30% 32% 15% 4	300
	11th to 20th	Day	13% 9% 29% 30% 16% 3	500
	21st to end	Day	21% 8% 25% 29% 13% 4	550
April	1st to 10th	Day	21% 11% 27% 28% 12% 1	500
	11th to 20th	Day	20% 14% 34% 23% 9% 1	492
	21st to end	Day	21% 8% 22% 30% 15% 3	543
May	1st to 10th	Day	17% 9% 22% 29% 18% 6%	703
	11th to 20th	Day	18% 5% 23% 29% 20% 5%	725
	21st to end	Day	17% 6% 22% 30% 20% 5%	789
June	1st to 10th	Day	10% 7% 23% 31% 23% 7%	730
	11th to 20th	Day	11% 9% 31% 30% 17% 2	730
	21st to end	Day	8% 6% 26% 34% 21% 5%	730
July	1st to 10th	Day	5% 3 21% 39% 27% 5%	721
	11th to 20th	Day	5% 5% 26% 38% 22% 4	718
	21st to end	Day	6% 4 20% 38% 28% 5%	794
August	1st to 10th	Day	7% 3 22% 38% 23% 7%	643
	11th to 20th	Day	9% 3 24% 32% 23% 9%	477
	21st to end	Day	5% 6% 21% 32% 27% 9%	539
September	1st to 10th	Day	6% 6% 20% 33% 28% 7%	490
	11th to 20th	Day	11% 4 21% 30% 23% 11%	490
	21st to end	Day	17% 5% 23% 24% 24% 7%	333
October	1st to 10th	Day	17% 5% 20% 25% 22% 11%	300
	11th to 20th	Day	17% 7% 22% 29% 17% 8%	300
	21st to end	Day	17% 8% 26% 32% 13% 4	330
November	1st to 10th	Day	12% 11% 27% 30% 15% 5%	300
	11th to 20th	Day	14% 9% 28% 31% 16% 3	300
	21st to end	Day	11% 9% 25% 42% 13% 1	300
December	1st to 10th	Day	13% 9% 29% 33% 13% 2	300
	11th to 20th	Day	13% 6% 31% 35% 13% 2	300
	21st to end	Day	10% 6% 31% 32% 19% 1	330
January	1st to 10th	Night	12% 7% 26% 40% 15% 1	1000
	11th to 20th	Night	15% 9% 28% 35% 12% 1	1000
	21st to end	Night	11% 11% 27% 39% 11% 1	1028
February	1st to 10th	Night	13% 7% 28% 39% 13% 1	800
	11th to 20th	Night	9% 6% 31% 41% 12%	784
	21st to end	Night	11% 7% 28% 38% 14% 2	660
March	1st to 10th	Night	11% 5% 27% 43% 13% 1	800
	11th to 20th	Night	10% 5% 26% 43% 15% 2	800
	21st to end	Night	17% 6% 24% 37% 13% 2	762
April	1st to 10th	Night	20% 7% 22% 41% 10% 1	600
	11th to 20th	Night	15% 7% 30% 38% 9% 1	593
	21st to end	Night	18% 5% 25% 39% 13% 1	600
May	1st to 10th	Night	18% 3 23% 39% 16% 1	600
	11th to 20th	Night	18% 3 20% 38% 20% 1	591
	21st to end	Night	19% 3 24% 36% 17% 1	650
June	1st to 10th	Night	11% 6% 25% 38% 19% 2	600
	11th to 20th	Night	12% 6% 33% 38% 11% 1	600
	21st to end	Night	8% 6% 24% 46% 16%	600
July	1st to 10th	Night	8% 3 24% 45% 19% 1	585
	11th to 20th	Night	6% 4 29% 50% 11%	582
	21st to end	Night	4 1 23% 53% 18%	657
August	1st to 10th	Night	6% 2 21% 49% 21%	579
	11th to 20th	Night	7% 2 16% 53% 21% 1	564
	21st to end	Night	7% 3 21% 49% 19% 1	627
September	1st to 10th	Night	10% 3 17% 49% 20% 2	570
	11th to 20th	Night	11% 3 19% 44% 22% 1	570
	21st to end	Night	14% 3 21% 41% 18% 3	655
October	1st to 10th	Night	18% 3 19% 40% 19% 2	760
	11th to 20th	Night	15% 5% 20% 43% 16% 1	760
	21st to end	Night	12% 5% 27% 41% 14% 2	959
November	1st to 10th	Night	14% 6% 26% 42% 12% 1	975
	11th to 20th	Night	12% 8% 29% 41% 9% 1	1000
	21st to end	Night	9% 7% 28% 46% 9% 1	1000
December	1st to 10th	Night	10% 9% 30% 39% 12% 1	1000
	11th to 20th	Night	10% 7% 29% 42% 12% 1	1000
	21st to end	Night	14% 7% 26% 39% 13% 1	1100

Page generated at 2025-08-01 23:32:27. Version ac07

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