Eagle's Rest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle's Rest clear sky chart from 2005-11-06 to 2025-07-06.

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	17% 10% 2 6% 4 4 4 3 4 5% 41%	124212
	Night	20% 12% 3 6% 4 3 3 3 4 5% 38%	123425
Transparency	Day	44% 6% 11% 18% 14% 7%	123959
	Night	50% 6% 10% 17% 13% 5%	123265
Seeing	Day	22% 13% 26% 25% 11% 3	15574
	Night	26% 7% 15% 29% 21% 3	24598

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	33% 19% 4 9% 4 5% 3 2 3 3 15%	3639
	11th to 20th	Day	25% 13% 3 6% 4 3 3 2 2 4 35%	3683
	21st to end	Day	24% 10% 2 6% 3 3 3 3 4 5% 36%	4510
February	1st to 10th	Day	26% 14% 4 9% 5% 4 4 5% 4 6% 20%	1800
	11th to 20th	Day	25% 16% 4 8% 4 4 4 3 4 5% 22%	1755
	21st to end	Day	25% 20% 3 7% 5% 5% 3 3 3 5% 20%	1590
March	1st to 10th	Day	16% 18% 4 9% 5% 4 4 3 6% 8% 23%	4777
	11th to 20th	Day	22% 17% 3 9% 5% 4 4 3 3 3 28%	5000
	21st to end	Day	23% 15% 4 10% 6% 7% 6% 5% 5% 6% 15%	5586
April	1st to 10th	Day	27% 18% 3 9% 6% 4 4 2 4 5% 18%	2400
	11th to 20th	Day	23% 16% 4 7% 4 4 4 2 4 5% 27%	2369
	21st to end	Day	26% 11% 3 7% 4 4 4 3 5% 6% 28%	2547
May	1st to 10th	Day	17% 9% 2 6% 4 4 4 3 4 4 43%	6100
	11th to 20th	Day	18% 9% 3 7% 5% 4 4 3 5% 6% 37%	6277
	21st to end	Day	15% 8% 2 6% 4 4 4 4 6% 8% 40%	6902
June	1st to 10th	Day	23% 9% 2 6% 4 4 4 3 4 6% 35%	2800
	11th to 20th	Day	19% 7% 3 6% 4 4 5% 4 5% 7% 37%	2800
	21st to end	Day	9% 5% 1 5% 3 3 3 2 4 6% 58%	2800
July	1st to 10th	Day	3 2 1 2 1 1 1 1 2 3 82%	4491
	11th to 20th	Day	3 2 1 3 2 2 2 2 3 3 77%	4420
	21st to end	Day	3 2 1 2 2 1 2 1 3 4 79%	4706
August	1st to 10th	Day	3 3 1 4 2 2 3 2 3 5% 72%	4091
	11th to 20th	Day	4 3 1 3 2 3 3 4 5% 7% 66%	4026
	21st to end	Day	6% 4 1 3 2 2 2 2 4 6% 67%	4252
September	1st to 10th	Day	6% 3 1 3 2 2 3 3 3 5% 69%	2280
	11th to 20th	Day	11% 6% 2 4 5% 3 4 3 4 6% 52%	2280
	21st to end	Day	13% 6% 1 6% 3 3 4 3 5% 6% 51%	1996
October	1st to 10th	Day	13% 6% 1 4 3 2 3 2 3 4 57%	3180
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 5% 8% 39%	3161
	21st to end	Day	22% 9% 3 8% 5% 5% 5% 3 6% 6% 28%	3431
November	1st to 10th	Day	31% 9% 3 8% 6% 4 3 3 4 4 23%	1711
	11th to 20th	Day	28% 11% 3 9% 5% 4 4 3 5% 5% 23%	1600
	21st to end	Day	26% 11% 3 8% 5% 4 4 3 4 5% 28%	1600
December	1st to 10th	Day	18% 8% 2 5% 3 4 4 3 4 6% 43%	2620
	11th to 20th	Day	27% 14% 4 9% 5% 5% 4 4 5% 6% 16%	3028
	21st to end	Day	31% 20% 4 10% 5% 4 3 3 3 4 14%	4004
January	1st to 10th	Night	35% 18% 4 7% 4 4 3 3 4 3 14%	6306
	11th to 20th	Night	25% 14% 3 6% 3 3 2 2 3 4 34%	6276
	21st to end	Night	26% 11% 2 7% 3 3 3 2 2 4 37%	6468
February	1st to 10th	Night	24% 19% 3 8% 5% 4 4 3 4 5% 20%	2600
	11th to 20th	Night	24% 18% 4 7% 4 4 4 3 4 4 24%	2532
	21st to end	Night	24% 20% 4 6% 4 4 3 3 4 5% 23%	2040
March	1st to 10th	Night	17% 19% 5% 9% 6% 5% 4 3 6% 6% 21%	5115
	11th to 20th	Night	19% 18% 4 8% 4 5% 4 2 3 3 29%	5000
	21st to end	Night	24% 19% 4 9% 5% 5% 4 3 4 5% 18%	5388
April	1st to 10th	Night	28% 18% 4 7% 5% 4 3 3 4 4 21%	2000
	11th to 20th	Night	25% 14% 3 6% 3 4 4 4 4 4 29%	1979
	21st to end	Night	28% 13% 3 6% 3 4 4 3 4 5% 27%	1850
May	1st to 10th	Night	21% 14% 3 5% 3 3 2 3 3 4 40%	3870
	11th to 20th	Night	19% 16% 3 7% 4 3 3 2 3 3 36%	3616
	21st to end	Night	18% 10% 2 6% 4 3 3 2 4 5% 43%	3972
June	1st to 10th	Night	22% 7% 2 6% 4 3 3 3 5% 6% 37%	1600
	11th to 20th	Night	19% 9% 3 6% 3 3 3 3 4 6% 41%	1600
	21st to end	Night	12% 4 1 3 3 3 3 3 4 4 61%	1600
July	1st to 10th	Night	4 2 1 2 1 2 1 2 3 3 81%	2580
	11th to 20th	Night	3 2 1 2 2 1 2 2 2 2 80%	2540
	21st to end	Night	5% 1 1 1 1 1 1 2 2 3 81%	2844
August	1st to 10th	Night	3 2 1 3 2 3 3 2 4 5% 73%	2848
	11th to 20th	Night	3 4 1 4 3 3 3 3 5% 6% 64%	2812
	21st to end	Night	7% 4 1 4 2 2 2 2 3 3 68%	3424
September	1st to 10th	Night	7% 3 1 4 2 1 2 2 3 4 72%	1900
	11th to 20th	Night	11% 5% 2 5% 4 4 4 2 4 6% 54%	1900
	21st to end	Night	13% 6% 2 4 3 3 3 3 3 6% 52%	2179
October	1st to 10th	Night	11% 7% 2 5% 3 2 2 2 3 4 61%	3800
	11th to 20th	Night	15% 6% 2 6% 3 3 4 3 6% 8% 44%	3777
	21st to end	Night	20% 13% 4 10% 5% 4 4 3 4 5% 27%	4136
November	1st to 10th	Night	29% 10% 3 7% 5% 4 4 3 5% 5% 25%	2585
	11th to 20th	Night	31% 11% 3 7% 5% 4 4 4 4 5% 23%	2800
	21st to end	Night	24% 11% 3 7% 4 4 3 3 4 5% 31%	2800
December	1st to 10th	Night	16% 9% 2 5% 4 3 3 3 5% 6% 44%	4560
	11th to 20th	Night	30% 14% 4 9% 5% 5% 5% 3 5% 5% 16%	5176
	21st to end	Night	31% 15% 4 8% 5% 4 4 3 4 4 19%	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	75% 4 6% 8% 6% 1	3639
	11th to 20th	Day	55% 4 4 17% 16% 4	3683
	21st to end	Day	50% 6% 7% 12% 16% 9%	4510
February	1st to 10th	Day	65% 7% 10% 11% 7% 1	1800
	11th to 20th	Day	64% 7% 11% 9% 7% 3	1764
	21st to end	Day	69% 4 8% 10% 7% 3	1590
March	1st to 10th	Day	57% 7% 11% 19% 6%	4777
	11th to 20th	Day	61% 6% 7% 16% 9% 1	5000
	21st to end	Day	65% 10% 11% 10% 3	5586
April	1st to 10th	Day	69% 6% 10% 10% 5%	2400
	11th to 20th	Day	60% 6% 11% 12% 7% 2	2372
	21st to end	Day	57% 6% 13% 16% 6% 1	2547
May	1st to 10th	Day	43% 7% 11% 25% 15%	6100
	11th to 20th	Day	46% 7% 13% 23% 10%	6280
	21st to end	Day	41% 8% 26% 22% 3	6904
June	1st to 10th	Day	49% 7% 15% 22% 7%	2800
	11th to 20th	Day	46% 7% 18% 21% 8% 1	2800
	21st to end	Day	28% 4 15% 33% 15% 4	2800
July	1st to 10th	Day	11% 3 8% 16% 26% 37%	4422
	11th to 20th	Day	14% 2 5% 16% 27% 36%	4345
	21st to end	Day	11% 2 7% 25% 43% 13%	4557
August	1st to 10th	Day	16% 3 8% 23% 36% 14%	4076
	11th to 20th	Day	18% 5% 12% 35% 25% 5%	4065
	21st to end	Day	20% 4 15% 25% 25% 12%	4251
September	1st to 10th	Day	20% 3 7% 28% 28% 15%	2280
	11th to 20th	Day	33% 5% 12% 23% 18% 9%	2280
	21st to end	Day	33% 6% 12% 23% 17% 9%	1996
October	1st to 10th	Day	32% 4 7% 20% 19% 18%	3180
	11th to 20th	Day	43% 6% 14% 21% 12% 3	3161
	21st to end	Day	53% 8% 9% 15% 13% 3	3431
November	1st to 10th	Day	65% 5% 8% 13% 8% 1	1711
	11th to 20th	Day	63% 5% 9% 10% 8% 5%	1600
	21st to end	Day	58% 6% 7% 12% 12% 6%	1600
December	1st to 10th	Day	43% 5% 7% 15% 17% 13%	2620
	11th to 20th	Day	68% 6% 10% 10% 5%	3028
	21st to end	Day	75% 5% 6% 11% 3 1	4004
January	1st to 10th	Night	75% 5% 6% 8% 5% 2	6306
	11th to 20th	Night	54% 4 7% 17% 13% 4	6276
	21st to end	Night	54% 3 5% 11% 15% 12%	6468
February	1st to 10th	Night	67% 6% 9% 11% 6% 2	2600
	11th to 20th	Night	63% 6% 9% 12% 6% 3	2534
	21st to end	Night	64% 4 10% 12% 7% 2	2040
March	1st to 10th	Night	61% 7% 13% 13% 4 2	5115
	11th to 20th	Night	59% 7% 8% 16% 8% 1	5000
	21st to end	Night	67% 9% 12% 11% 2	5388
April	1st to 10th	Night	66% 6% 12% 11% 5%	2000
	11th to 20th	Night	58% 8% 12% 13% 6% 3	1979
	21st to end	Night	60% 8% 13% 12% 5% 2	1850
May	1st to 10th	Night	48% 6% 10% 23% 12% 1	3867
	11th to 20th	Night	51% 6% 11% 24% 7% 1	3616
	21st to end	Night	42% 8% 25% 21% 3	3972
June	1st to 10th	Night	48% 8% 13% 25% 5%	1600
	11th to 20th	Night	45% 6% 17% 24% 7% 1	1600
	21st to end	Night	27% 5% 17% 33% 13% 5%	1600
July	1st to 10th	Night	12% 3 8% 17% 26% 34%	2540
	11th to 20th	Night	12% 2 5% 17% 35% 28%	2492
	21st to end	Night	11% 2 8% 25% 44% 10%	2755
August	1st to 10th	Night	15% 3 8% 27% 35% 12%	2839
	11th to 20th	Night	19% 5% 15% 35% 22% 4	2839
	21st to end	Night	22% 3 12% 25% 28% 9%	3424
September	1st to 10th	Night	18% 3 9% 28% 27% 15%	1900
	11th to 20th	Night	31% 6% 11% 25% 16% 10%	1900
	21st to end	Night	34% 5% 12% 23% 15% 12%	2179
October	1st to 10th	Night	30% 4 8% 20% 24% 15%	3800
	11th to 20th	Night	39% 5% 20% 22% 11% 3	3777
	21st to end	Night	58% 6% 8% 13% 10% 4	4136
November	1st to 10th	Night	60% 7% 9% 12% 10% 2	2585
	11th to 20th	Night	63% 8% 8% 10% 7% 4	2800
	21st to end	Night	54% 7% 9% 11% 12% 7%	2800
December	1st to 10th	Night	41% 5% 7% 15% 24% 8%	4560
	11th to 20th	Night	70% 6% 10% 7% 6% 1	5176
	21st to end	Night	66% 7% 11% 12% 3 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	45% 14% 19% 16% 7% 1	200
	11th to 20th	Day	36% 12% 16% 20% 12% 4	217
	21st to end	Day	31% 13% 23% 17% 14% 3	440
February	1st to 10th	Day	33% 14% 26% 17% 9% 2	400
	11th to 20th	Day	35% 17% 25% 17% 5% 1	395
	21st to end	Day	36% 19% 18% 23% 4 1	384
March	1st to 10th	Day	33% 19% 23% 18% 7%	500
	11th to 20th	Day	34% 13% 26% 17% 8% 1	500
	21st to end	Day	36% 17% 25% 16% 5% 1	550
April	1st to 10th	Day	34% 19% 20% 19% 7% 1	500
	11th to 20th	Day	33% 17% 23% 20% 5% 3	492
	21st to end	Day	32% 17% 22% 21% 6% 2	500
May	1st to 10th	Day	23% 15% 29% 22% 7% 3	503
	11th to 20th	Day	32% 12% 24% 20% 9% 3	528
	21st to end	Day	21% 14% 26% 26% 9% 4	573
June	1st to 10th	Day	22% 13% 25% 27% 9% 4	530
	11th to 20th	Day	20% 19% 31% 22% 7% 2	530
	21st to end	Day	6% 10% 35% 32% 12% 5%	530
July	1st to 10th	Day	7% 7% 36% 34% 11% 5%	507
	11th to 20th	Day	4 8% 38% 31% 13% 6%	484
	21st to end	Day	2 5% 36% 32% 16% 8%	531
August	1st to 10th	Day	3 6% 31% 39% 14% 7%	487
	11th to 20th	Day	4 7% 27% 36% 17% 9%	477
	21st to end	Day	8% 9% 33% 31% 14% 5%	539
September	1st to 10th	Day	7% 8% 31% 32% 16% 6%	490
	11th to 20th	Day	16% 7% 28% 33% 15% 2	490
	21st to end	Day	15% 12% 29% 27% 15% 2	490
October	1st to 10th	Day	19% 10% 27% 24% 16% 3	490
	11th to 20th	Day	21% 9% 21% 27% 18% 3	490
	21st to end	Day	27% 13% 22% 22% 12% 4	534
November	1st to 10th	Day	30% 16% 19% 19% 13% 2	273
	11th to 20th	Day	30% 14% 22% 20% 12% 5%	200
	21st to end	Day	29% 13% 19% 22% 16% 2	200
December	1st to 10th	Day	30% 11% 20% 20% 12% 8%	200
	11th to 20th	Day	39% 14% 21% 20% 6% 2	200
	21st to end	Day	41% 13% 18% 20% 7% 1	220
January	1st to 10th	Night	41% 9% 20% 18% 10% 2	800
	11th to 20th	Night	32% 10% 18% 22% 15% 3	800
	21st to end	Night	30% 7% 18% 28% 15% 2	880
February	1st to 10th	Night	35% 8% 16% 30% 10% 1	800
	11th to 20th	Night	32% 10% 17% 29% 11% 1	784
	21st to end	Night	36% 10% 17% 27% 10%	660
March	1st to 10th	Night	34% 11% 16% 27% 11% 1	800
	11th to 20th	Night	28% 10% 18% 29% 14% 1	800
	21st to end	Night	36% 11% 17% 23% 13% 1	880
April	1st to 10th	Night	35% 9% 17% 24% 14% 1	800
	11th to 20th	Night	30% 9% 16% 26% 17% 2	791
	21st to end	Night	32% 9% 14% 26% 17% 2	650
May	1st to 10th	Night	25% 7% 15% 29% 21% 3	500
	11th to 20th	Night	23% 5% 12% 30% 27% 2	394
	21st to end	Night	26% 5% 14% 27% 26% 2	433
June	1st to 10th	Night	22% 6% 11% 31% 28% 2	400
	11th to 20th	Night	20% 8% 15% 33% 24% 1	400
	21st to end	Night	14% 2 9% 36% 39%	400
July	1st to 10th	Night	6% 3 7% 36% 46% 1	380
	11th to 20th	Night	5% 2 11% 44% 36% 1	368
	21st to end	Night	4 1 7% 38% 46% 4	463
August	1st to 10th	Night	5% 1 5% 33% 48% 9%	567
	11th to 20th	Night	4 1 6% 32% 48% 8%	564
	21st to end	Night	5% 3 12% 38% 37% 5%	788
September	1st to 10th	Night	7% 2 12% 33% 41% 4	760
	11th to 20th	Night	11% 4 11% 33% 34% 7%	760
	21st to end	Night	15% 4 12% 33% 30% 5%	760
October	1st to 10th	Night	17% 4 13% 36% 27% 4	760
	11th to 20th	Night	21% 5% 10% 34% 25% 4	760
	21st to end	Night	25% 9% 16% 29% 17% 5%	836
November	1st to 10th	Night	32% 8% 19% 27% 13% 2	780
	11th to 20th	Night	37% 8% 18% 25% 11% 2	800
	21st to end	Night	29% 9% 16% 31% 14% 1	800
December	1st to 10th	Night	29% 8% 19% 25% 18% 2	800
	11th to 20th	Night	40% 8% 17% 24% 11% 1	800
	21st to end	Night	44% 11% 16% 21% 7% 1	880

Page generated at 2025-07-02 22:30:17. Version ac07

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