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 2026-10-29.

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	15% 8% 2 6% 4 3 3 3 4 5% 46%	158891
	Night	18% 11% 3 6% 4 3 3 3 4 5% 41%	150624
Transparency	Day	40% 5% 11% 21% 16% 7%	153700
	Night	46% 5% 10% 19% 13% 6%	146812
Seeing	Day	22% 12% 27% 25% 11% 4	17306
	Night	25% 7% 15% 29% 21% 2	26241

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	30% 19% 4 10% 5% 5% 4 3 4 4 13%	4722
	11th to 20th	Day	19% 10% 2 5% 3 2 2 2 3 5% 46%	4797
	21st to end	Day	20% 9% 3 7% 5% 5% 4 3 6% 5% 33%	5843
February	1st to 10th	Day	25% 13% 3 9% 5% 4 4 5% 4 5% 22%	1890
	11th to 20th	Day	25% 16% 4 8% 4 4 4 3 4 5% 22%	1845
	21st to end	Day	25% 21% 3 7% 5% 5% 3 3 3 5% 20%	1667
March	1st to 10th	Day	16% 18% 4 9% 5% 4 4 3 6% 8% 23%	4883
	11th to 20th	Day	22% 16% 3 9% 5% 4 4 3 3 4 28%	5110
	21st to end	Day	23% 14% 4 10% 6% 7% 6% 5% 5% 6% 15%	5709
April	1st to 10th	Day	26% 18% 3 8% 6% 4 4 3 4 5% 19%	2520
	11th to 20th	Day	23% 16% 3 7% 4 4 4 2 4 5% 27%	2489
	21st to end	Day	25% 11% 3 7% 4 4 3 3 5% 6% 29%	2674
May	1st to 10th	Day	13% 8% 2 5% 4 4 4 3 5% 6% 46%	7910
	11th to 20th	Day	15% 8% 2 6% 4 4 4 3 5% 8% 40%	8160
	21st to end	Day	14% 7% 2 6% 4 4 4 4 6% 8% 41%	8992
June	1st to 10th	Day	22% 8% 2 6% 4 4 4 3 5% 6% 35%	2940
	11th to 20th	Day	18% 7% 3 5% 4 4 5% 4 5% 7% 39%	2940
	21st to end	Day	10% 5% 2 5% 3 3 3 2 4 6% 57%	2940
July	1st to 10th	Day	2 2 1 2 1 1 2 1 2 4 81%	8219
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 3 79%	8220
	21st to end	Day	2 3 1 3 2 2 2 2 3 4 77%	8760
August	1st to 10th	Day	2 2 1 3 2 2 2 2 3 4 76%	7547
	11th to 20th	Day	4 3 1 3 3 3 3 3 4 6% 66%	7563
	21st to end	Day	5% 4 1 3 2 2 2 3 5% 7% 65%	7884
September	1st to 10th	Day	7% 4 1 3 2 3 3 2 3 5% 67%	2520
	11th to 20th	Day	10% 6% 2 4 4 3 4 3 5% 6% 52%	2520
	21st to end	Day	12% 6% 1 6% 3 3 4 3 5% 6% 50%	2206
October	1st to 10th	Day	12% 7% 2 4 3 2 3 2 3 5% 57%	3380
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 3 5% 8% 40%	3361
	21st to end	Day	22% 9% 3 8% 5% 5% 5% 3 6% 7% 27%	3622
November	1st to 10th	Day	30% 9% 3 8% 6% 4 3 3 4 4 23%	1798
	11th to 20th	Day	27% 11% 3 10% 5% 5% 4 3 5% 5% 23%	1680
	21st to end	Day	26% 11% 3 7% 5% 4 4 3 4 5% 27%	1680
December	1st to 10th	Day	19% 8% 2 5% 3 4 4 3 4 6% 42%	2700
	11th to 20th	Day	27% 14% 4 9% 5% 5% 4 4 5% 6% 16%	3108
	21st to end	Day	31% 20% 4 10% 4 3 3 3 3 4 15%	4092
January	1st to 10th	Night	32% 19% 4 8% 4 4 4 3 4 4 13%	8172
	11th to 20th	Night	20% 11% 2 5% 3 2 2 2 3 5% 45%	8163
	21st to end	Night	21% 10% 3 9% 5% 4 3 3 3 4 35%	8371
February	1st to 10th	Night	24% 19% 3 8% 5% 4 4 3 4 5% 21%	2730
	11th to 20th	Night	24% 18% 4 8% 4 4 4 3 4 4 24%	2662
	21st to end	Night	24% 20% 4 6% 4 4 3 3 4 5% 23%	2139
March	1st to 10th	Night	17% 19% 5% 9% 6% 5% 4 3 6% 6% 21%	5229
	11th to 20th	Night	19% 18% 4 8% 4 5% 4 3 3 3 29%	5110
	21st to end	Night	25% 19% 4 9% 5% 4 4 3 4 5% 18%	5507
April	1st to 10th	Night	27% 17% 4 6% 5% 4 3 3 4 5% 22%	2100
	11th to 20th	Night	25% 14% 3 6% 3 4 4 4 4 4 28%	2079
	21st to end	Night	27% 13% 3 6% 3 4 4 3 4 5% 28%	1943
May	1st to 10th	Night	17% 13% 3 5% 3 3 3 3 4 5% 43%	5023
	11th to 20th	Night	18% 14% 3 6% 4 3 3 3 4 4 38%	4700
	21st to end	Night	18% 9% 2 5% 3 2 3 3 4 6% 43%	5181
June	1st to 10th	Night	22% 7% 2 6% 4 3 3 3 5% 6% 37%	1680
	11th to 20th	Night	18% 9% 3 6% 3 3 3 3 4 6% 42%	1680
	21st to end	Night	13% 4 1 3 3 3 3 3 3 4 60%	1680
July	1st to 10th	Night	3 2 1 2 2 2 2 2 4 4 75%	4740
	11th to 20th	Night	2 2 1 3 2 2 2 2 2 2 80%	4740
	21st to end	Night	4 2 1 2 2 2 1 2 2 3 79%	5320
August	1st to 10th	Night	3 2 1 3 2 2 2 2 3 5% 74%	5275
	11th to 20th	Night	5% 4 1 4 2 3 3 3 4 6% 65%	5292
	21st to end	Night	5% 4 1 3 2 3 2 2 4 5% 69%	6358
September	1st to 10th	Night	7% 3 1 3 2 1 2 2 3 5% 69%	2100
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 4 6% 54%	2100
	21st to end	Night	13% 6% 2 5% 3 3 3 2 3 6% 52%	2409
October	1st to 10th	Night	11% 7% 2 5% 3 2 2 2 3 4 61%	4040
	11th to 20th	Night	14% 6% 2 6% 3 4 4 2 6% 8% 44%	4017
	21st to end	Night	20% 13% 4 10% 5% 4 4 3 4 6% 27%	4364
November	1st to 10th	Night	28% 10% 3 7% 5% 4 4 3 5% 6% 25%	2718
	11th to 20th	Night	31% 11% 3 7% 5% 4 4 4 4 5% 23%	2940
	21st to end	Night	24% 11% 3 7% 4 4 3 3 4 5% 31%	2940
December	1st to 10th	Night	16% 9% 2 5% 4 3 3 3 5% 6% 43%	4700
	11th to 20th	Night	30% 14% 4 9% 5% 5% 5% 3 5% 5% 16%	5316
	21st to end	Night	30% 15% 4 8% 5% 4 4 3 4 4 19%	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	76% 4 6% 8% 5% 1	4723
	11th to 20th	Day	42% 4 3 14% 20% 16%	4797
	21st to end	Day	52% 6% 7% 12% 16% 9%	5843
February	1st to 10th	Day	63% 7% 10% 11% 7% 2	1890
	11th to 20th	Day	64% 7% 11% 9% 6% 3	1854
	21st to end	Day	69% 4 8% 9% 7% 2	1667
March	1st to 10th	Day	57% 7% 11% 19% 6%	4883
	11th to 20th	Day	61% 6% 7% 16% 9% 1	5110
	21st to end	Day	65% 10% 11% 10% 3	5709
April	1st to 10th	Day	68% 6% 10% 11% 5%	2520
	11th to 20th	Day	61% 6% 11% 12% 7% 2	2492
	21st to end	Day	56% 6% 13% 17% 6% 1	2674
May	1st to 10th	Day	38% 6% 12% 29% 14%	7910
	11th to 20th	Day	41% 7% 17% 27% 8%	8163
	21st to end	Day	39% 7% 24% 24% 6%	8994
June	1st to 10th	Day	48% 7% 15% 22% 7% 1	2940
	11th to 20th	Day	44% 7% 17% 21% 10% 1	2940
	21st to end	Day	29% 5% 14% 33% 16% 4	2940
July	1st to 10th	Day	10% 2 9% 31% 27% 20%	8151
	11th to 20th	Day	13% 2 5% 15% 30% 36%	8145
	21st to end	Day	12% 2 8% 37% 32% 7%	8563
August	1st to 10th	Day	12% 2 7% 18% 39% 23%	5976
	11th to 20th	Day	17% 5% 12% 40% 23% 4	5962
	21st to end	Day	19% 3 12% 32% 24% 9%	6187
September	1st to 10th	Day	22% 3 8% 27% 26% 15%	2520
	11th to 20th	Day	32% 6% 12% 24% 18% 9%	2520
	21st to end	Day	33% 6% 13% 23% 17% 9%	2206
October	1st to 10th	Day	32% 4 7% 20% 19% 18%	3380
	11th to 20th	Day	42% 6% 14% 22% 12% 4	3361
	21st to end	Day	53% 8% 9% 16% 12% 2	3622
November	1st to 10th	Day	64% 5% 8% 13% 8% 1	1798
	11th to 20th	Day	63% 6% 9% 10% 8% 4	1680
	21st to end	Day	57% 6% 8% 12% 12% 5%	1680
December	1st to 10th	Day	44% 5% 7% 15% 16% 13%	2700
	11th to 20th	Day	67% 6% 10% 10% 5% 1	3108
	21st to end	Day	74% 5% 6% 11% 3 1	4092
January	1st to 10th	Night	74% 5% 7% 8% 4 1	8172
	11th to 20th	Night	43% 4 6% 15% 16% 16%	8163
	21st to end	Night	54% 3 5% 10% 16% 11%	8371
February	1st to 10th	Night	66% 6% 9% 11% 6% 2	2730
	11th to 20th	Night	63% 6% 10% 12% 6% 3	2664
	21st to end	Night	64% 4 10% 12% 8% 2	2139
March	1st to 10th	Night	61% 7% 13% 13% 4 2	5229
	11th to 20th	Night	59% 7% 8% 16% 8% 1	5110
	21st to end	Night	67% 9% 12% 11% 2	5507
April	1st to 10th	Night	65% 6% 12% 12% 5%	2100
	11th to 20th	Night	59% 7% 12% 13% 6% 3	2079
	21st to end	Night	58% 8% 13% 14% 5% 2	1943
May	1st to 10th	Night	43% 6% 13% 28% 10%	5021
	11th to 20th	Night	49% 6% 12% 27% 5% 1	4700
	21st to end	Night	42% 8% 24% 24% 3	5182
June	1st to 10th	Night	48% 8% 13% 25% 6%	1680
	11th to 20th	Night	43% 6% 16% 24% 9% 2	1680
	21st to end	Night	28% 5% 17% 32% 13% 4	1680
July	1st to 10th	Night	13% 4 11% 33% 21% 19%	4700
	11th to 20th	Night	13% 2 5% 17% 36% 26%	4692
	21st to end	Night	13% 2 12% 36% 31% 6%	5205
August	1st to 10th	Night	11% 2 6% 23% 38% 20%	4169
	11th to 20th	Night	19% 5% 15% 36% 23% 3	4169
	21st to end	Night	19% 3 11% 37% 23% 6%	4977
September	1st to 10th	Night	20% 3 10% 27% 25% 14%	2100
	11th to 20th	Night	30% 6% 12% 27% 16% 9%	2100
	21st to end	Night	33% 5% 12% 23% 15% 12%	2409
October	1st to 10th	Night	29% 4 8% 20% 25% 14%	4040
	11th to 20th	Night	39% 5% 20% 22% 11% 3	4017
	21st to end	Night	58% 6% 8% 14% 10% 4	4364
November	1st to 10th	Night	60% 7% 10% 12% 10% 2	2718
	11th to 20th	Night	63% 8% 9% 10% 7% 4	2940
	21st to end	Night	54% 7% 9% 11% 12% 6%	2940
December	1st to 10th	Night	41% 5% 8% 15% 23% 8%	4700
	11th to 20th	Night	69% 6% 10% 7% 6% 1	5316
	21st to end	Night	66% 7% 10% 12% 3 1	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	45% 13% 18% 17% 6%	220
	11th to 20th	Day	33% 11% 15% 20% 16% 5%	238
	21st to end	Day	30% 12% 23% 18% 14% 2	473
February	1st to 10th	Day	32% 14% 25% 18% 10% 2	430
	11th to 20th	Day	34% 18% 26% 16% 5% 1	425
	21st to end	Day	37% 18% 18% 22% 4 1	413
March	1st to 10th	Day	32% 19% 24% 17% 7%	540
	11th to 20th	Day	34% 13% 27% 17% 8% 1	540
	21st to end	Day	35% 17% 26% 16% 5% 1	594
April	1st to 10th	Day	33% 18% 20% 20% 8% 2	540
	11th to 20th	Day	33% 17% 23% 19% 6% 2	532
	21st to end	Day	31% 17% 23% 22% 6% 2	540
May	1st to 10th	Day	22% 15% 30% 23% 7% 4	543
	11th to 20th	Day	31% 13% 24% 20% 9% 3	568
	21st to end	Day	21% 14% 26% 26% 9% 4	617
June	1st to 10th	Day	22% 14% 26% 26% 9% 4	570
	11th to 20th	Day	19% 18% 31% 23% 8% 2	570
	21st to end	Day	9% 10% 34% 31% 12% 5%	570
July	1st to 10th	Day	6% 7% 35% 35% 11% 5%	566
	11th to 20th	Day	4 9% 39% 30% 13% 6%	564
	21st to end	Day	3 6% 36% 32% 15% 8%	619
August	1st to 10th	Day	3 7% 32% 37% 14% 7%	567
	11th to 20th	Day	4 6% 28% 36% 17% 9%	557
	21st to end	Day	7% 8% 34% 30% 14% 6%	627
September	1st to 10th	Day	9% 9% 29% 32% 16% 5%	570
	11th to 20th	Day	14% 7% 28% 32% 15% 3	570
	21st to end	Day	15% 11% 28% 28% 15% 2	570
October	1st to 10th	Day	19% 11% 26% 24% 16% 5%	570
	11th to 20th	Day	20% 10% 23% 26% 17% 3	570
	21st to end	Day	27% 13% 23% 22% 11% 4	611
November	1st to 10th	Day	31% 16% 19% 20% 13% 2	300
	11th to 20th	Day	29% 12% 22% 20% 12% 4	220
	21st to end	Day	29% 13% 18% 24% 15% 2	220
December	1st to 10th	Day	32% 11% 19% 19% 12% 7%	220
	11th to 20th	Day	38% 13% 20% 19% 8% 2	220
	21st to end	Day	40% 14% 18% 19% 7% 2	242
January	1st to 10th	Night	41% 10% 19% 18% 10% 2	840
	11th to 20th	Night	30% 9% 19% 23% 16% 3	840
	21st to end	Night	28% 7% 20% 28% 15% 2	924
February	1st to 10th	Night	34% 8% 16% 31% 10% 1	840
	11th to 20th	Night	32% 10% 17% 29% 11% 1	824
	21st to end	Night	36% 11% 16% 27% 9%	692
March	1st to 10th	Night	34% 11% 16% 27% 11% 1	840
	11th to 20th	Night	28% 10% 19% 29% 13% 1	840
	21st to end	Night	36% 10% 17% 24% 13% 1	924
April	1st to 10th	Night	34% 9% 16% 25% 15% 1	840
	11th to 20th	Night	30% 9% 16% 26% 17% 2	831
	21st to end	Night	32% 9% 13% 27% 17% 2	683
May	1st to 10th	Night	25% 7% 14% 29% 22% 2	525
	11th to 20th	Night	23% 5% 12% 31% 26% 1	414
	21st to end	Night	26% 4 14% 27% 27% 2	455
June	1st to 10th	Night	23% 6% 12% 31% 27% 2	420
	11th to 20th	Night	19% 7% 15% 35% 23% 1	420
	21st to end	Night	15% 2 9% 35% 38%	420
July	1st to 10th	Night	6% 3 8% 35% 47% 2	410
	11th to 20th	Night	5% 2 12% 44% 36% 1	408
	21st to end	Night	4 1 7% 38% 45% 4	513
August	1st to 10th	Night	5% 1 5% 33% 47% 8%	627
	11th to 20th	Night	5% 2 6% 33% 47% 7%	624
	21st to end	Night	5% 3 12% 38% 37% 4	871
September	1st to 10th	Night	8% 3 13% 33% 39% 4	840
	11th to 20th	Night	11% 4 11% 34% 35% 7%	840
	21st to end	Night	15% 4 12% 34% 31% 5%	840
October	1st to 10th	Night	16% 4 12% 36% 28% 4	840
	11th to 20th	Night	20% 5% 11% 36% 24% 4	840
	21st to end	Night	25% 9% 16% 29% 16% 4	912
November	1st to 10th	Night	32% 7% 19% 27% 13% 1	820
	11th to 20th	Night	36% 8% 18% 26% 10% 2	840
	21st to end	Night	29% 9% 16% 32% 14% 1	840
December	1st to 10th	Night	30% 8% 19% 25% 17% 2	840
	11th to 20th	Night	39% 8% 18% 24% 10% 1	840
	21st to end	Night	43% 11% 17% 20% 8% 1	924

Page generated at 2026-10-26 01:37:49. Version ac07

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