White Eagle Observatory
Clear Sky Chart
History

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

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	13% 9% 3 8% 5% 4 4 4 6% 7% 37%	101358
	Night	14% 10% 4 7% 4 4 4 3 5% 6% 38%	97878
Transparency	Day	44% 5% 12% 23% 14% 2	104925
	Night	45% 4 11% 23% 15% 2	102452
Seeing	Day	18% 11% 29% 25% 13% 5%	15824
	Night	18% 9% 30% 30% 12% 1	25663

By Month

Percentage Cloud Cover SE (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	15% 13% 7% 12% 5% 5% 5% 3 5% 5% 27%	2527
	11th to 20th	Day	14% 15% 6% 16% 5% 5% 4 8% 7% 4 19%	2530
	21st to end	Day	19% 24% 7% 11% 5% 3 3 3 4 4 18%	2881
February	1st to 10th	Day	16% 14% 5% 8% 6% 6% 5% 4 5% 5% 26%	1747
	11th to 20th	Day	14% 12% 4 9% 5% 4 4 4 3 6% 34%	1848
	21st to end	Day	15% 15% 4 10% 5% 4 4 3 5% 6% 30%	1570
March	1st to 10th	Day	15% 14% 4 8% 5% 4 3 3 4 6% 34%	3120
	11th to 20th	Day	11% 6% 4 7% 5% 5% 5% 4 6% 8% 40%	3273
	21st to end	Day	20% 13% 6% 12% 6% 5% 5% 4 5% 6% 19%	4165
April	1st to 10th	Day	17% 13% 3 8% 5% 4 4 4 6% 6% 31%	2280
	11th to 20th	Day	17% 9% 4 6% 4 4 5% 4 5% 6% 36%	2254
	21st to end	Day	20% 8% 3 7% 5% 4 4 3 5% 6% 32%	2374
May	1st to 10th	Day	18% 7% 2 6% 5% 4 6% 4 6% 8% 35%	4082
	11th to 20th	Day	15% 7% 2 6% 4 4 4 4 5% 7% 42%	4299
	21st to end	Day	12% 6% 3 6% 4 4 5% 4 7% 10% 41%	4824
June	1st to 10th	Day	10% 6% 2 5% 4 5% 4 4 6% 7% 46%	2660
	11th to 20th	Day	9% 6% 2 6% 5% 4 5% 4 7% 8% 44%	2660
	21st to end	Day	11% 6% 2 7% 5% 6% 5% 6% 7% 8% 37%	2660
July	1st to 10th	Day	11% 7% 3 8% 5% 5% 6% 5% 7% 9% 34%	4440
	11th to 20th	Day	8% 4 2 6% 4 4 4 4 8% 10% 48%	4440
	21st to end	Day	8% 6% 2 7% 6% 5% 5% 5% 7% 8% 40%	4813
August	1st to 10th	Day	8% 6% 2 7% 4 5% 5% 4 7% 9% 44%	4322
	11th to 20th	Day	10% 4 2 6% 4 4 5% 4 8% 10% 42%	3729
	21st to end	Day	7% 5% 2 6% 4 4 4 4 6% 10% 47%	4180
September	1st to 10th	Day	11% 5% 2 6% 3 4 5% 3 5% 8% 47%	2280
	11th to 20th	Day	11% 4 2 4 4 3 4 3 5% 7% 52%	2162
	21st to end	Day	10% 7% 3 6% 4 4 5% 4 5% 7% 44%	2090
October	1st to 10th	Day	13% 6% 2 7% 4 3 3 3 5% 7% 47%	2033
	11th to 20th	Day	18% 8% 3 7% 5% 4 4 3 5% 7% 37%	1895
	21st to end	Day	20% 9% 2 7% 4 3 3 3 5% 6% 36%	1881
November	1st to 10th	Day	13% 9% 2 6% 4 3 4 3 5% 6% 45%	1762
	11th to 20th	Day	16% 12% 3 8% 5% 3 4 3 5% 7% 33%	1710
	21st to end	Day	19% 10% 3 9% 5% 3 4 3 4 5% 35%	1646
December	1st to 10th	Day	15% 13% 4 9% 6% 4 4 4 4 5% 31%	1520
	11th to 20th	Day	13% 14% 5% 10% 5% 5% 5% 4 5% 6% 29%	1918
	21st to end	Day	21% 22% 9% 12% 7% 3 3 2 3 4 14%	2783
January	1st to 10th	Night	15% 15% 7% 11% 5% 4 4 3 4 4 29%	4428
	11th to 20th	Night	15% 19% 7% 12% 5% 4 4 5% 6% 4 19%	4440
	21st to end	Night	22% 18% 9% 9% 4 4 3 3 4 4 21%	4784
February	1st to 10th	Night	15% 15% 5% 7% 6% 4 4 2 4 5% 32%	2432
	11th to 20th	Night	14% 12% 4 7% 4 4 4 3 5% 6% 37%	2218
	21st to end	Night	17% 12% 3 9% 4 3 4 4 5% 5% 35%	1884
March	1st to 10th	Night	18% 11% 3 6% 4 4 3 3 4 5% 40%	3733
	11th to 20th	Night	10% 7% 3 7% 5% 4 4 3 4 6% 47%	3717
	21st to end	Night	21% 11% 5% 10% 5% 4 5% 3 4 5% 27%	3466
April	1st to 10th	Night	16% 10% 3 6% 4 4 4 3 5% 7% 38%	1900
	11th to 20th	Night	19% 9% 2 6% 4 4 3 3 5% 6% 39%	1875
	21st to end	Night	18% 8% 3 7% 5% 4 4 4 5% 7% 36%	1805
May	1st to 10th	Night	16% 7% 2 7% 6% 5% 4 4 6% 7% 36%	2813
	11th to 20th	Night	13% 7% 2 5% 4 4 5% 4 6% 8% 41%	2599
	21st to end	Night	12% 7% 2 6% 4 4 5% 3 5% 7% 44%	2743
June	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 5% 7% 49%	1520
	11th to 20th	Night	8% 5% 2 5% 4 5% 5% 4 7% 8% 47%	1520
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 3 7% 8% 42%	1520
July	1st to 10th	Night	12% 6% 3 8% 4 4 5% 4 6% 7% 39%	2530
	11th to 20th	Night	6% 4 2 5% 4 4 4 4 6% 7% 55%	2530
	21st to end	Night	5% 5% 2 5% 6% 5% 6% 5% 7% 8% 46%	2750
August	1st to 10th	Night	6% 4 2 6% 4 5% 5% 4 7% 8% 49%	2599
	11th to 20th	Night	8% 4 2 6% 3 4 4 4 6% 8% 52%	3098
	21st to end	Night	8% 4 2 5% 4 4 4 3 5% 9% 53%	3476
September	1st to 10th	Night	10% 6% 3 4 4 3 3 3 6% 7% 53%	1900
	11th to 20th	Night	9% 4 2 5% 3 3 4 3 5% 6% 56%	1998
	21st to end	Night	10% 6% 2 6% 5% 4 4 4 5% 7% 46%	2090
October	1st to 10th	Night	10% 5% 3 5% 3 4 4 4 5% 6% 52%	2142
	11th to 20th	Night	17% 6% 2 6% 4 3 3 2 4 7% 46%	2284
	21st to end	Night	21% 9% 2 6% 4 3 3 3 4 6% 38%	2717
November	1st to 10th	Night	13% 7% 2 6% 3 4 3 3 4 5% 49%	2536
	11th to 20th	Night	15% 10% 3 8% 4 4 4 3 5% 6% 37%	2477
	21st to end	Night	17% 9% 3 8% 5% 4 4 3 5% 6% 37%	2531
December	1st to 10th	Night	17% 11% 3 9% 5% 4 4 3 5% 6% 32%	2660
	11th to 20th	Night	16% 13% 5% 10% 5% 4 4 3 4 5% 32%	3279
	21st to end	Night	24% 18% 6% 10% 5% 4 4 3 4 5% 16%	4884

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	61% 3 13% 16% 7%	2528
	11th to 20th	Day	65% 4 10% 13% 8% 1	2530
	21st to end	Day	70% 4 8% 13% 5%	2881
February	1st to 10th	Day	59% 5% 12% 14% 9% 2	1747
	11th to 20th	Day	52% 4 9% 24% 9% 2	1858
	21st to end	Day	55% 5% 11% 20% 7% 2	1570
March	1st to 10th	Day	52% 4 10% 21% 11% 2	3120
	11th to 20th	Day	41% 5% 13% 29% 10% 1	3273
	21st to end	Day	65% 7% 13% 12% 3	4165
April	1st to 10th	Day	53% 5% 11% 20% 11%	2280
	11th to 20th	Day	48% 5% 11% 21% 12% 3	2254
	21st to end	Day	51% 5% 12% 17% 12% 2	2374
May	1st to 10th	Day	45% 7% 13% 23% 12%	4120
	11th to 20th	Day	42% 5% 11% 27% 14%	4303
	21st to end	Day	36% 7% 12% 23% 18% 5%	4837
June	1st to 10th	Day	35% 6% 12% 27% 18% 2	2660
	11th to 20th	Day	36% 6% 11% 24% 20% 3	2660
	21st to end	Day	41% 7% 13% 23% 13% 3	2660
July	1st to 10th	Day	44% 6% 14% 23% 11% 2	4371
	11th to 20th	Day	29% 7% 16% 30% 17% 1	4365
	21st to end	Day	38% 7% 16% 16% 19% 3	4662
August	1st to 10th	Day	35% 7% 16% 29% 13% 1	4307
	11th to 20th	Day	34% 8% 11% 31% 16% 1	3765
	21st to end	Day	32% 6% 13% 28% 19% 3	4179
September	1st to 10th	Day	35% 5% 13% 25% 19% 4	2280
	11th to 20th	Day	30% 5% 11% 29% 22% 3	2162
	21st to end	Day	37% 6% 9% 26% 21% 2	2090
October	1st to 10th	Day	26% 3 8% 30% 32% 2	3384
	11th to 20th	Day	32% 4 12% 26% 25% 1	3123
	21st to end	Day	42% 4 9% 28% 14% 3	3081
November	1st to 10th	Day	40% 5% 14% 24% 16% 2	1762
	11th to 20th	Day	51% 4 12% 22% 11% 1	1710
	21st to end	Day	53% 4 11% 23% 9%	1646
December	1st to 10th	Day	55% 5% 13% 19% 8% 1	1520
	11th to 20th	Day	55% 5% 12% 19% 7% 1	1915
	21st to end	Day	77% 3 7% 9% 3	2783
January	1st to 10th	Night	60% 3 11% 17% 9% 1	4428
	11th to 20th	Night	67% 3 11% 12% 7%	4440
	21st to end	Night	67% 3 9% 14% 6%	4784
February	1st to 10th	Night	55% 3 11% 18% 11% 2	2432
	11th to 20th	Night	48% 4 11% 22% 15% 1	2219
	21st to end	Night	51% 4 11% 19% 12% 3	1884
March	1st to 10th	Night	48% 3 12% 23% 10% 4	3733
	11th to 20th	Night	38% 5% 10% 28% 17% 2	3717
	21st to end	Night	59% 4 13% 18% 6% 1	3466
April	1st to 10th	Night	45% 4 12% 25% 13% 2	1900
	11th to 20th	Night	46% 5% 8% 21% 16% 4	1875
	21st to end	Night	47% 5% 11% 21% 12% 3	1805
May	1st to 10th	Night	46% 5% 12% 21% 13% 2	2840
	11th to 20th	Night	38% 8% 17% 27% 11% 1	2600
	21st to end	Night	37% 6% 13% 18% 21% 5%	2751
June	1st to 10th	Night	34% 5% 13% 25% 20% 4	1520
	11th to 20th	Night	31% 5% 13% 25% 22% 3	1520
	21st to end	Night	39% 6% 16% 20% 17% 3	1520
July	1st to 10th	Night	43% 5% 16% 19% 13% 4	2490
	11th to 20th	Night	27% 7% 13% 32% 20% 2	2482
	21st to end	Night	32% 8% 15% 19% 22% 4	2662
August	1st to 10th	Night	31% 7% 17% 27% 17% 1	2590
	11th to 20th	Night	29% 5% 15% 30% 19% 1	3128
	21st to end	Night	29% 5% 12% 33% 17% 4	3476
September	1st to 10th	Night	30% 5% 12% 27% 23% 3	1900
	11th to 20th	Night	28% 4 8% 31% 26% 2	1998
	21st to end	Night	36% 5% 11% 29% 16% 2	2090
October	1st to 10th	Night	22% 4 7% 38% 28% 2	3571
	11th to 20th	Night	35% 4 6% 24% 29% 2	3795
	21st to end	Night	40% 3 8% 26% 19% 3	4467
November	1st to 10th	Night	38% 4 9% 27% 19% 4	2536
	11th to 20th	Night	48% 4 12% 22% 13% 2	2477
	21st to end	Night	50% 3 12% 23% 12%	2531
December	1st to 10th	Night	54% 4 11% 22% 9% 1	2660
	11th to 20th	Night	54% 4 12% 19% 9% 1	3281
	21st to end	Night	71% 4 9% 12% 4	4884

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	26% 14% 33% 22% 4 1	270
	11th to 20th	Day	26% 16% 38% 16% 4 1	270
	21st to end	Day	24% 19% 31% 21% 4 1	297
February	1st to 10th	Day	24% 19% 39% 14% 3	270
	11th to 20th	Day	26% 18% 35% 19% 3	270
	21st to end	Day	24% 21% 38% 13% 2 1	225
March	1st to 10th	Day	27% 21% 36% 15% 1	270
	11th to 20th	Day	30% 16% 34% 15% 4 1	289
	21st to end	Day	30% 14% 31% 18% 5% 2	506
April	1st to 10th	Day	25% 15% 32% 20% 6% 1	460
	11th to 20th	Day	24% 20% 25% 18% 11% 2	452
	21st to end	Day	25% 13% 30% 23% 7% 1	460
May	1st to 10th	Day	24% 12% 31% 23% 8% 2	463
	11th to 20th	Day	20% 11% 31% 24% 11% 4	614
	21st to end	Day	16% 11% 30% 23% 15% 5%	734
June	1st to 10th	Day	12% 9% 30% 30% 14% 6%	680
	11th to 20th	Day	12% 8% 31% 30% 16% 4	680
	21st to end	Day	15% 8% 33% 29% 12% 4	680
July	1st to 10th	Day	8% 4 23% 31% 21% 13%	671
	11th to 20th	Day	12% 5% 26% 29% 18% 10%	668
	21st to end	Day	7% 5% 29% 33% 20% 7%	739
August	1st to 10th	Day	8% 3 22% 34% 22% 11%	628
	11th to 20th	Day	11% 5% 20% 29% 23% 12%	479
	21st to end	Day	7% 5% 19% 32% 27% 10%	539
September	1st to 10th	Day	13% 6% 21% 33% 21% 6%	490
	11th to 20th	Day	10% 4 18% 32% 26% 9%	490
	21st to end	Day	14% 12% 23% 26% 18% 7%	490
October	1st to 10th	Day	16% 9% 26% 29% 15% 4	433
	11th to 20th	Day	19% 22% 33% 19% 7% 1	300
	21st to end	Day	31% 15% 32% 16% 6%	330
November	1st to 10th	Day	18% 17% 34% 22% 6% 3	300
	11th to 20th	Day	26% 19% 33% 14% 6% 1	270
	21st to end	Day	25% 14% 36% 20% 6%	270
December	1st to 10th	Day	20% 18% 40% 14% 8%	270
	11th to 20th	Day	22% 17% 39% 16% 5% 1	270
	21st to end	Day	28% 19% 37% 14% 2	297
January	1st to 10th	Night	20% 14% 38% 23% 5%	950
	11th to 20th	Night	24% 14% 35% 22% 5% 1	950
	21st to end	Night	21% 12% 34% 29% 4	1045
February	1st to 10th	Night	23% 13% 34% 25% 4	912
	11th to 20th	Night	21% 13% 35% 25% 5%	743
	21st to end	Night	22% 15% 38% 21% 4	628
March	1st to 10th	Night	21% 15% 35% 23% 6%	760
	11th to 20th	Night	17% 12% 37% 26% 7% 1	735
	21st to end	Night	26% 10% 34% 23% 7% 1	627
April	1st to 10th	Night	20% 13% 35% 25% 6% 1	570
	11th to 20th	Night	23% 12% 31% 27% 7%	563
	21st to end	Night	22% 8% 34% 27% 8%	570
May	1st to 10th	Night	19% 6% 36% 29% 9% 1	570
	11th to 20th	Night	18% 7% 29% 33% 12% 1	561
	21st to end	Night	13% 6% 27% 35% 18% 1	617
June	1st to 10th	Night	11% 4 28% 41% 15% 1	570
	11th to 20th	Night	10% 5% 29% 44% 12% 1	570
	21st to end	Night	11% 5% 29% 38% 16% 1	570
July	1st to 10th	Night	8% 3 16% 44% 26% 3	555
	11th to 20th	Night	7% 3 18% 42% 27% 3	552
	21st to end	Night	5% 2 17% 47% 26% 2	624
August	1st to 10th	Night	6% 3 13% 47% 29% 4	567
	11th to 20th	Night	7% 2 15% 42% 30% 5%	564
	21st to end	Night	8% 2 15% 41% 30% 3	627
September	1st to 10th	Night	12% 3 18% 38% 26% 3	570
	11th to 20th	Night	9% 4 19% 37% 27% 4	668
	21st to end	Night	13% 7% 23% 34% 21% 3	760
October	1st to 10th	Night	12% 6% 26% 35% 18% 2	760
	11th to 20th	Night	22% 10% 31% 26% 11% 1	760
	21st to end	Night	25% 12% 29% 25% 9%	836
November	1st to 10th	Night	18% 10% 37% 24% 10% 1	780
	11th to 20th	Night	20% 15% 33% 25% 7%	763
	21st to end	Night	21% 11% 37% 24% 6%	821
December	1st to 10th	Night	24% 11% 34% 25% 5%	950
	11th to 20th	Night	23% 11% 33% 27% 5%	950
	21st to end	Night	30% 14% 32% 20% 3	1045

Page generated at 2024-11-08 05:44:48. Version ac07

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