Eagle Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle Lake clear sky chart from 2005-11-06 to 2024-11-04.

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 6% 2 5% 4 3 4 3 5% 6% 59%	105216
	Night	3 7% 2 6% 4 3 4 3 5% 6% 56%	102486
Transparency	Day	26% 4 9% 20% 23% 19%	104962
	Night	27% 5% 11% 21% 21% 14%	102329
Seeing	Day	10% 14% 24% 28% 19% 6%	14961
	Night	8% 8% 18% 38% 25% 4	24172

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	3 13% 5% 12% 7% 6% 7% 4 6% 7% 30%	2539
	11th to 20th	Day	4 14% 5% 12% 6% 5% 6% 4 6% 8% 30%	2586
	21st to end	Day	6% 16% 5% 11% 6% 5% 5% 4 5% 6% 30%	3146
February	1st to 10th	Day	5% 9% 4 7% 5% 4 5% 4 7% 8% 43%	1710
	11th to 20th	Day	2 10% 3 8% 5% 5% 5% 3 6% 8% 45%	1766
	21st to end	Day	3 10% 4 8% 5% 5% 5% 3 7% 7% 42%	1570
March	1st to 10th	Day	4 17% 6% 12% 8% 6% 5% 4 5% 6% 28%	3164
	11th to 20th	Day	3 9% 3 6% 4 4 3 4 4 6% 55%	3490
	21st to end	Day	4 15% 5% 10% 5% 6% 5% 4 5% 6% 34%	4008
April	1st to 10th	Day	5% 10% 4 9% 6% 4 4 4 6% 7% 42%	2280
	11th to 20th	Day	6% 10% 3 6% 4 5% 4 4 5% 7% 47%	2249
	21st to end	Day	5% 9% 2 5% 4 4 4 3 6% 6% 53%	2280
May	1st to 10th	Day	4 5% 2 4 3 3 3 3 4 6% 64%	4121
	11th to 20th	Day	3 4 2 4 3 3 3 2 4 5% 67%	4377
	21st to end	Day	5% 5% 2 5% 3 3 3 3 4 6% 59%	4813
June	1st to 10th	Day	5% 5% 2 5% 4 4 5% 5% 6% 8% 51%	2660
	11th to 20th	Day	2 3 2 4 2 3 3 3 4 6% 67%	2660
	21st to end	Day	2 2 1 3 2 2 2 3 3 4 75%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 3 3 85%	4420
	11th to 20th	Day	1 2 1 3 2 2 2 2 3 4 77%	4420
	21st to end	Day	1 1 1 2 2 2 3 2 4 5% 77%	4683
August	1st to 10th	Day	2 2 1 3 2 3 3 3 5% 5% 71%	4091
	11th to 20th	Day	1 1 1 1 2 3 2 3 4 82%	3821
	21st to end	Day	2 1 1 2 1 2 1 2 3 2 84%	4180
September	1st to 10th	Day	2 1 2 2 2 2 1 3 4 82%	2280
	11th to 20th	Day	2 2 1 4 3 3 3 3 4 6% 70%	2280
	21st to end	Day	3 3 1 3 2 2 2 2 4 5% 74%	2056
October	1st to 10th	Day	3 3 1 2 2 3 3 2 3 6% 71%	3180
	11th to 20th	Day	4 3 2 4 3 2 3 2 4 6% 66%	3161
	21st to end	Day	3 4 2 5% 4 4 4 4 5% 8% 57%	3391
November	1st to 10th	Day	7% 7% 2 7% 4 4 4 4 6% 7% 48%	1701
	11th to 20th	Day	5% 7% 2 5% 4 5% 6% 4 6% 9% 46%	1710
	21st to end	Day	2 7% 2 6% 6% 5% 4 4 6% 7% 50%	1521
December	1st to 10th	Day	5% 10% 4 9% 4 4 4 3 6% 9% 42%	1520
	11th to 20th	Day	8% 16% 4 10% 5% 6% 6% 5% 7% 7% 26%	1928
	21st to end	Day	3 9% 4 10% 6% 6% 5% 6% 9% 9% 33%	2794
January	1st to 10th	Night	3 10% 3 9% 6% 6% 6% 6% 7% 9% 35%	4406
	11th to 20th	Night	3 14% 4 9% 8% 6% 6% 4 6% 8% 30%	4358
	21st to end	Night	9% 18% 4 9% 5% 5% 4 3 5% 7% 29%	4521
February	1st to 10th	Night	4 10% 3 7% 5% 4 4 5% 6% 8% 45%	2470
	11th to 20th	Night	3 9% 3 7% 5% 5% 5% 4 6% 8% 47%	2300
	21st to end	Night	3 9% 4 8% 4 5% 5% 4 6% 8% 45%	1884
March	1st to 10th	Night	3 20% 6% 10% 5% 5% 4 3 5% 7% 32%	3705
	11th to 20th	Night	3 10% 2 6% 3 3 3 2 4 6% 56%	3490
	21st to end	Night	4 14% 5% 10% 5% 6% 5% 5% 6% 7% 33%	3643
April	1st to 10th	Night	3 9% 3 6% 6% 5% 5% 4 6% 9% 45%	1900
	11th to 20th	Night	6% 8% 3 5% 3 4 4 3 5% 7% 51%	1879
	21st to end	Night	4 6% 2 4 4 3 4 4 5% 7% 57%	1900
May	1st to 10th	Night	3 6% 2 5% 3 3 2 3 3 4 65%	2843
	11th to 20th	Night	3 3 1 4 2 2 3 3 4 4 72%	2516
	21st to end	Night	4 4 1 4 3 2 3 2 4 6% 66%	2762
June	1st to 10th	Night	4 5% 2 5% 5% 3 4 4 5% 7% 56%	1520
	11th to 20th	Night	3 2 1 3 3 2 3 3 4 4 72%	1520
	21st to end	Night	2 3 1 3 3 2 2 2 3 4 76%	1520
July	1st to 10th	Night	1 1 1 1 1 2 2 3 89%	2540
	11th to 20th	Night	2 2 1 2 1 1 2 2 3 3 81%	2540
	21st to end	Night	1 1 2 2 2 2 1 2 4 83%	2854
August	1st to 10th	Night	2 3 1 2 2 1 2 2 5% 7% 72%	2848
	11th to 20th	Night	1 1 1 2 1 1 1 1 2 3 87%	3024
	21st to end	Night	2 2 1 2 1 1 1 1 2 2 85%	3498
September	1st to 10th	Night	2 1 1 1 1 2 2 2 3 84%	1900
	11th to 20th	Night	3 2 1 3 2 2 2 2 4 5% 74%	1900
	21st to end	Night	3 2 1 2 2 2 3 2 3 6% 75%	2119
October	1st to 10th	Night	3 2 1 4 3 2 2 2 2 3 76%	3800
	11th to 20th	Night	2 2 1 4 2 2 3 3 3 6% 71%	3777
	21st to end	Night	4 4 2 5% 3 3 5% 4 5% 6% 60%	4176
November	1st to 10th	Night	6% 6% 3 5% 5% 3 4 5% 7% 8% 48%	2450
	11th to 20th	Night	4 6% 2 5% 4 4 5% 4 8% 8% 50%	2470
	21st to end	Night	2 5% 3 5% 5% 5% 5% 4 7% 8% 52%	2655
December	1st to 10th	Night	5% 9% 3 8% 4 4 4 4 6% 9% 44%	2660
	11th to 20th	Night	8% 16% 4 9% 5% 5% 5% 4 6% 9% 28%	3276
	21st to end	Night	6% 14% 4 10% 6% 5% 5% 4 7% 8% 31%	4862

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	46% 10% 15% 23% 5% 1	2539
	11th to 20th	Day	50% 9% 16% 14% 9% 2	2586
	21st to end	Day	52% 8% 12% 18% 8% 1	3146
February	1st to 10th	Day	37% 7% 14% 26% 12% 4	1710
	11th to 20th	Day	36% 6% 16% 24% 16% 2	1775
	21st to end	Day	39% 7% 14% 24% 13% 3	1570
March	1st to 10th	Day	54% 7% 10% 18% 10% 1	3164
	11th to 20th	Day	28% 5% 11% 34% 21% 1	3490
	21st to end	Day	46% 7% 13% 22% 10% 2	4008
April	1st to 10th	Day	40% 5% 14% 23% 15% 3	2280
	11th to 20th	Day	32% 6% 14% 26% 18% 4	2252
	21st to end	Day	31% 5% 14% 28% 18% 4	2280
May	1st to 10th	Day	21% 3 10% 32% 30% 4	4121
	11th to 20th	Day	18% 4 7% 19% 39% 13%	4380
	21st to end	Day	23% 5% 9% 32% 29% 3	4814
June	1st to 10th	Day	28% 5% 10% 24% 27% 6%	2660
	11th to 20th	Day	18% 3 9% 21% 34% 15%	2660
	21st to end	Day	14% 2 4 16% 34% 30%	2660
July	1st to 10th	Day	6% 2 2 6% 15% 68%	4351
	11th to 20th	Day	12% 1 3 7% 15% 61%	4345
	21st to end	Day	10% 2 2 8% 25% 53%	4535
August	1st to 10th	Day	15% 2 3 9% 19% 53%	4076
	11th to 20th	Day	7% 1 2 8% 37% 45%	3859
	21st to end	Day	8% 1 2 13% 39% 37%	4179
September	1st to 10th	Day	9% 1 2 10% 30% 48%	2280
	11th to 20th	Day	16% 3 6% 18% 32% 24%	2280
	21st to end	Day	14% 2 5% 22% 32% 24%	2056
October	1st to 10th	Day	17% 2 5% 15% 32% 31%	3180
	11th to 20th	Day	19% 3 6% 29% 35% 9%	3161
	21st to end	Day	23% 4 10% 32% 23% 8%	3391
November	1st to 10th	Day	34% 5% 12% 21% 22% 6%	1701
	11th to 20th	Day	31% 7% 16% 25% 19% 1	1710
	21st to end	Day	33% 6% 14% 23% 21% 3	1521
December	1st to 10th	Day	40% 7% 13% 22% 17% 2	1520
	11th to 20th	Day	53% 8% 11% 19% 8% 1	1928
	21st to end	Day	41% 11% 20% 18% 8% 1	2794
January	1st to 10th	Night	39% 9% 22% 23% 7%	4406
	11th to 20th	Night	47% 10% 16% 14% 9% 4	4358
	21st to end	Night	53% 5% 13% 18% 10% 1	4521
February	1st to 10th	Night	34% 5% 15% 25% 16% 4	2470
	11th to 20th	Night	33% 6% 15% 27% 17% 1	2302
	21st to end	Night	35% 8% 16% 24% 14% 4	1884
March	1st to 10th	Night	48% 7% 15% 18% 10% 2	3705
	11th to 20th	Night	28% 5% 11% 37% 19% 1	3490
	21st to end	Night	44% 8% 18% 21% 8% 1	3643
April	1st to 10th	Night	33% 8% 16% 26% 13% 4	1900
	11th to 20th	Night	30% 7% 17% 24% 17% 4	1879
	21st to end	Night	24% 7% 18% 31% 18% 3	1900
May	1st to 10th	Night	23% 4 11% 33% 23% 6%	2843
	11th to 20th	Night	17% 4 7% 21% 38% 14%	2516
	21st to end	Night	18% 6% 13% 33% 27% 3	2762
June	1st to 10th	Night	26% 7% 14% 27% 23% 4	1520
	11th to 20th	Night	16% 4 9% 23% 38% 11%	1520
	21st to end	Night	14% 3 5% 17% 33% 29%	1520
July	1st to 10th	Night	5% 1 2 8% 17% 66%	2500
	11th to 20th	Night	11% 1 3 9% 16% 61%	2492
	21st to end	Night	9% 1 2 7% 36% 45%	2764
August	1st to 10th	Night	13% 2 3 10% 22% 50%	2839
	11th to 20th	Night	7% 1 1 10% 40% 41%	3052
	21st to end	Night	9% 2 2 15% 41% 31%	3498
September	1st to 10th	Night	8% 2 2 10% 29% 49%	1900
	11th to 20th	Night	14% 3 6% 21% 30% 26%	1900
	21st to end	Night	12% 2 5% 22% 34% 24%	2119
October	1st to 10th	Night	15% 2 5% 12% 33% 33%	3800
	11th to 20th	Night	14% 4 8% 30% 34% 10%	3777
	21st to end	Night	21% 5% 10% 27% 27% 10%	4176
November	1st to 10th	Night	31% 7% 15% 21% 19% 7%	2450
	11th to 20th	Night	27% 8% 17% 24% 21% 2	2470
	21st to end	Night	27% 6% 17% 26% 20% 5%	2655
December	1st to 10th	Night	35% 8% 13% 22% 20% 3	2660
	11th to 20th	Night	50% 7% 10% 19% 13% 1	3276
	21st to end	Night	46% 8% 16% 19% 11% 1	4862

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	17% 21% 33% 21% 7% 1	180
	11th to 20th	Day	17% 15% 26% 26% 13% 2	213
	21st to end	Day	13% 14% 29% 28% 14% 3	407
February	1st to 10th	Day	13% 18% 25% 27% 14% 1	370
	11th to 20th	Day	13% 22% 27% 26% 12%	414
	21st to end	Day	12% 19% 25% 33% 10% 1	382
March	1st to 10th	Day	18% 23% 30% 20% 8% 1	460
	11th to 20th	Day	14% 20% 26% 24% 14% 2	460
	21st to end	Day	16% 23% 27% 23% 9% 1	506
April	1st to 10th	Day	15% 20% 27% 26% 11% 2	460
	11th to 20th	Day	18% 20% 25% 21% 13% 3	452
	21st to end	Day	12% 21% 24% 23% 15% 4	460
May	1st to 10th	Day	12% 17% 32% 24% 11% 3	463
	11th to 20th	Day	16% 18% 23% 22% 15% 6%	488
	21st to end	Day	11% 15% 18% 27% 22% 6%	529
June	1st to 10th	Day	8% 15% 22% 25% 20% 9%	490
	11th to 20th	Day	10% 14% 29% 26% 17% 4	490
	21st to end	Day	3 9% 21% 31% 26% 10%	490
July	1st to 10th	Day	3 5% 22% 38% 23% 10%	486
	11th to 20th	Day	1 4 22% 37% 23% 12%	484
	21st to end	Day	2 4 21% 37% 25% 12%	531
August	1st to 10th	Day	3 5% 22% 31% 27% 12%	487
	11th to 20th	Day	3 5% 20% 31% 24% 16%	477
	21st to end	Day	3 5% 24% 33% 27% 9%	539
September	1st to 10th	Day	4 4 26% 32% 27% 7%	490
	11th to 20th	Day	6% 9% 22% 30% 25% 8%	490
	21st to end	Day	5% 11% 22% 33% 25% 4	490
October	1st to 10th	Day	8% 10% 26% 27% 22% 6%	490
	11th to 20th	Day	10% 13% 18% 32% 23% 4	490
	21st to end	Day	10% 15% 25% 30% 17% 3	506
November	1st to 10th	Day	16% 13% 19% 26% 23% 3	279
	11th to 20th	Day	7% 11% 26% 29% 21% 6%	270
	21st to end	Day	10% 13% 26% 28% 18% 4	180
December	1st to 10th	Day	13% 17% 27% 21% 17% 5%	180
	11th to 20th	Day	12% 14% 28% 27% 14% 5%	180
	21st to end	Day	10% 20% 26% 25% 18% 1	198
January	1st to 10th	Night	12% 10% 22% 34% 16% 5%	760
	11th to 20th	Night	8% 10% 22% 38% 18% 4	760
	21st to end	Night	11% 6% 23% 37% 20% 4	836
February	1st to 10th	Night	11% 9% 21% 39% 18% 2	760
	11th to 20th	Night	9% 11% 21% 38% 18% 3	744
	21st to end	Night	8% 14% 20% 39% 16% 2	628
March	1st to 10th	Night	14% 13% 24% 32% 16% 3	760
	11th to 20th	Night	12% 11% 20% 32% 23% 3	760
	21st to end	Night	11% 15% 25% 33% 15% 1	836
April	1st to 10th	Night	9% 12% 24% 37% 17% 2	760
	11th to 20th	Night	12% 13% 20% 32% 19% 3	751
	21st to end	Night	8% 11% 22% 34% 22% 3	760
May	1st to 10th	Night	7% 9% 28% 35% 19% 3	566
	11th to 20th	Night	6% 7% 20% 39% 25% 4	374
	21st to end	Night	10% 7% 19% 33% 29% 2	411
June	1st to 10th	Night	6% 6% 17% 41% 27% 3	380
	11th to 20th	Night	5% 5% 21% 42% 25% 2	380
	21st to end	Night	2 2 13% 49% 33% 2	380
July	1st to 10th	Night	1 1 8% 52% 38% 1	370
	11th to 20th	Night	2 1 8% 57% 31% 2	368
	21st to end	Night	2 1 4 48% 41% 4	473
August	1st to 10th	Night	3 4 46% 42% 5%	567
	11th to 20th	Night	2 1 10% 44% 37% 5%	686
	21st to end	Night	3 1 10% 45% 38% 4	836
September	1st to 10th	Night	3 1 13% 43% 36% 4	760
	11th to 20th	Night	4 3 13% 36% 38% 7%	760
	21st to end	Night	4 4 15% 35% 35% 8%	760
October	1st to 10th	Night	6% 4 16% 39% 28% 6%	760
	11th to 20th	Night	5% 7% 13% 36% 35% 4	760
	21st to end	Night	7% 7% 17% 35% 24% 8%	836
November	1st to 10th	Night	9% 10% 17% 35% 25% 5%	754
	11th to 20th	Night	8% 8% 22% 39% 21% 3	760
	21st to end	Night	5% 9% 22% 36% 24% 4	760
December	1st to 10th	Night	11% 9% 21% 37% 19% 3	760
	11th to 20th	Night	15% 9% 20% 34% 19% 3	760
	21st to end	Night	13% 14% 23% 36% 13% 1	836

Page generated at 2024-11-01 19:47:43. Version ac07

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