Worlds Without End Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Worlds Without End Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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	12% 7% 3 6% 4 4 4 4 5% 7% 43%	101404
	Night	13% 8% 3 6% 4 4 4 3 5% 6% 45%	98315
Transparency	Day	38% 7% 11% 24% 17% 3	105039
	Night	38% 6% 11% 24% 18% 3	102821
Seeing	Day	17% 13% 28% 24% 14% 4	15665
	Night	18% 13% 30% 26% 12% 1	25496

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	11% 13% 4 9% 4 3 4 4 5% 6% 37%	2587
	11th to 20th	Day	12% 11% 3 8% 4 4 4 3 4 5% 41%	2850
	21st to end	Day	21% 11% 5% 6% 3 3 2 3 3 5% 36%	3135
February	1st to 10th	Day	15% 10% 4 10% 5% 4 3 3 4 6% 35%	1710
	11th to 20th	Day	14% 11% 3 7% 4 3 4 4 6% 6% 38%	1796
	21st to end	Day	13% 11% 3 7% 5% 4 4 3 6% 6% 39%	1570
March	1st to 10th	Day	18% 12% 3 6% 3 3 4 2 4 4 42%	3297
	11th to 20th	Day	13% 7% 2 4 3 3 3 3 4 5% 51%	3480
	21st to end	Day	15% 9% 3 7% 5% 5% 5% 4 6% 6% 36%	3941
April	1st to 10th	Day	10% 7% 2 6% 5% 4 4 4 6% 8% 45%	2280
	11th to 20th	Day	17% 8% 2 6% 5% 4 4 4 5% 6% 41%	2254
	21st to end	Day	19% 9% 3 5% 5% 5% 4 3 5% 6% 36%	2280
May	1st to 10th	Day	14% 7% 3 7% 6% 5% 6% 4 7% 8% 33%	3782
	11th to 20th	Day	18% 6% 3 6% 4 4 3 3 5% 8% 38%	4325
	21st to end	Day	11% 7% 2 7% 5% 5% 5% 4 5% 7% 42%	4824
June	1st to 10th	Day	9% 5% 3 6% 4 4 6% 5% 7% 8% 44%	2660
	11th to 20th	Day	7% 4 1 5% 4 5% 5% 5% 6% 9% 50%	2660
	21st to end	Day	5% 3 2 5% 5% 5% 6% 4 7% 9% 49%	2660
July	1st to 10th	Day	13% 5% 2 6% 5% 4 5% 4 7% 9% 40%	4440
	11th to 20th	Day	4 4 2 5% 5% 4 5% 4 6% 11% 49%	4325
	21st to end	Day	8% 5% 3 7% 6% 6% 6% 6% 8% 9% 37%	4465
August	1st to 10th	Day	6% 4 2 4 3 3 5% 4 7% 10% 52%	4104
	11th to 20th	Day	11% 6% 2 5% 5% 5% 5% 4 6% 7% 45%	3762
	21st to end	Day	7% 5% 2 4 3 4 5% 4 7% 8% 52%	4180
September	1st to 10th	Day	12% 5% 1 4 4 4 4 4 6% 8% 49%	2280
	11th to 20th	Day	10% 6% 2 7% 4 4 4 3 5% 7% 49%	2280
	21st to end	Day	9% 5% 2 5% 4 4 4 3 6% 7% 51%	2033
October	1st to 10th	Day	9% 4 1 5% 3 4 4 3 4 6% 57%	1900
	11th to 20th	Day	13% 7% 2 6% 3 2 2 2 4 5% 54%	1900
	21st to end	Day	17% 8% 2 5% 3 3 3 2 4 5% 47%	2090
November	1st to 10th	Day	12% 6% 1 6% 4 3 4 3 3 5% 54%	1825
	11th to 20th	Day	13% 8% 3 4 4 4 3 3 4 7% 48%	1800
	21st to end	Day	15% 10% 2 5% 4 3 4 3 4 7% 44%	1700
December	1st to 10th	Day	13% 12% 2 6% 4 4 3 4 5% 7% 40%	1528
	11th to 20th	Day	13% 12% 4 8% 4 3 4 3 4 5% 39%	1918
	21st to end	Day	13% 16% 5% 9% 4 4 4 4 4 6% 30%	2783
January	1st to 10th	Night	14% 11% 5% 9% 5% 4 4 3 4 5% 36%	4364
	11th to 20th	Night	12% 9% 4 12% 6% 5% 6% 4 4 4 34%	4120
	21st to end	Night	23% 14% 5% 7% 4 3 3 2 3 4 33%	4532
February	1st to 10th	Night	16% 12% 4 8% 4 3 3 3 4 6% 36%	2470
	11th to 20th	Night	13% 9% 4 8% 5% 3 3 3 4 6% 43%	2270
	21st to end	Night	16% 10% 3 8% 4 3 3 3 5% 5% 39%	1884
March	1st to 10th	Night	20% 11% 2 5% 3 3 3 2 4 5% 43%	3586
	11th to 20th	Night	14% 7% 2 5% 3 3 4 3 4 6% 50%	3480
	21st to end	Night	15% 11% 3 7% 5% 5% 4 4 5% 6% 33%	3690
April	1st to 10th	Night	9% 6% 3 6% 3 4 3 3 6% 7% 50%	1900
	11th to 20th	Night	14% 8% 2 5% 4 3 3 3 5% 6% 45%	1875
	21st to end	Night	20% 7% 2 6% 4 3 4 3 5% 5% 41%	1900
May	1st to 10th	Night	18% 7% 2 5% 4 3 4 3 5% 6% 43%	3110
	11th to 20th	Night	14% 7% 2 6% 4 3 3 3 5% 8% 44%	2577
	21st to end	Night	11% 7% 2 8% 6% 5% 5% 4 6% 8% 39%	2743
June	1st to 10th	Night	8% 5% 2 5% 4 3 4 5% 7% 8% 49%	1520
	11th to 20th	Night	6% 4 1 3 3 3 3 3 7% 11% 55%	1520
	21st to end	Night	4 2 1 4 3 4 5% 4 6% 9% 58%	1520
July	1st to 10th	Night	12% 4 2 5% 4 3 4 4 6% 9% 46%	2530
	11th to 20th	Night	5% 3 1 4 3 3 3 3 6% 9% 60%	2641
	21st to end	Night	7% 5% 2 8% 5% 5% 5% 5% 6% 9% 43%	3098
August	1st to 10th	Night	5% 2 1 5% 3 3 4 3 5% 8% 59%	2836
	11th to 20th	Night	10% 4 2 6% 4 4 4 4 6% 8% 48%	3066
	21st to end	Night	5% 4 1 5% 3 3 3 4 5% 9% 58%	3476
September	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 4 6% 53%	1900
	11th to 20th	Night	9% 5% 1 6% 3 3 4 3 5% 8% 52%	1900
	21st to end	Night	9% 5% 2 4 3 3 5% 3 5% 6% 55%	2123
October	1st to 10th	Night	7% 3 2 4 2 3 3 3 5% 7% 62%	2280
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 4 5% 55%	2280
	21st to end	Night	19% 6% 2 4 3 3 3 2 4 5% 49%	2508
November	1st to 10th	Night	12% 6% 1 4 3 3 3 2 4 5% 56%	2471
	11th to 20th	Night	14% 6% 2 5% 4 3 3 3 4 6% 49%	2600
	21st to end	Night	16% 9% 3 6% 3 3 3 2 4 6% 45%	2695
December	1st to 10th	Night	15% 10% 3 7% 4 4 3 3 4 7% 38%	2687
	11th to 20th	Night	14% 11% 3 8% 4 4 4 3 4 5% 41%	3279
	21st to end	Night	15% 18% 5% 9% 5% 5% 4 4 5% 5% 25%	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	46% 6% 10% 25% 12% 2	2588
	11th to 20th	Day	44% 5% 9% 24% 16% 1	2850
	21st to end	Day	50% 4 10% 16% 15% 5%	3135
February	1st to 10th	Day	50% 4 11% 22% 12% 1	1710
	11th to 20th	Day	45% 5% 11% 19% 15% 4	1806
	21st to end	Day	45% 5% 9% 23% 13% 5%	1570
March	1st to 10th	Day	47% 5% 6% 20% 14% 8%	3297
	11th to 20th	Day	34% 6% 10% 27% 15% 7%	3480
	21st to end	Day	44% 9% 16% 19% 10% 1	3941
April	1st to 10th	Day	36% 6% 13% 24% 19% 1	2280
	11th to 20th	Day	44% 5% 11% 21% 16% 3	2254
	21st to end	Day	49% 6% 11% 20% 13% 1	2280
May	1st to 10th	Day	43% 11% 13% 20% 11% 1	3817
	11th to 20th	Day	43% 8% 11% 24% 13% 1	4329
	21st to end	Day	39% 9% 10% 22% 19% 1	4837
June	1st to 10th	Day	35% 9% 14% 25% 15% 2	2660
	11th to 20th	Day	29% 8% 13% 28% 19% 4	2660
	21st to end	Day	28% 9% 18% 25% 15% 5%	2660
July	1st to 10th	Day	38% 7% 13% 28% 11% 2	4371
	11th to 20th	Day	28% 7% 14% 33% 16% 2	4250
	21st to end	Day	38% 11% 16% 27% 8% 1	4325
August	1st to 10th	Day	26% 6% 17% 31% 19%	4090
	11th to 20th	Day	37% 7% 13% 25% 16% 2	3798
	21st to end	Day	28% 6% 15% 35% 12% 3	4179
September	1st to 10th	Day	32% 7% 12% 26% 18% 5%	2280
	11th to 20th	Day	34% 6% 8% 26% 24% 2	2280
	21st to end	Day	32% 7% 8% 27% 24% 3	2033
October	1st to 10th	Day	18% 3 6% 19% 45% 10%	3160
	11th to 20th	Day	23% 2 6% 21% 37% 11%	3140
	21st to end	Day	30% 4 7% 30% 25% 4	3428
November	1st to 10th	Day	35% 4 10% 23% 23% 6%	1825
	11th to 20th	Day	38% 4 8% 23% 21% 7%	1800
	21st to end	Day	42% 4 10% 26% 17% 1	1700
December	1st to 10th	Day	44% 5% 10% 26% 13% 2	1528
	11th to 20th	Day	47% 6% 8% 18% 20% 1	1915
	21st to end	Day	55% 6% 10% 15% 12% 2	2783
January	1st to 10th	Night	49% 5% 10% 21% 13% 1	4364
	11th to 20th	Night	52% 6% 9% 21% 11% 2	4120
	21st to end	Night	55% 5% 9% 20% 10% 1	4532
February	1st to 10th	Night	49% 5% 10% 21% 14% 2	2470
	11th to 20th	Night	42% 4 12% 22% 17% 3	2271
	21st to end	Night	47% 5% 9% 20% 15% 4	1884
March	1st to 10th	Night	45% 5% 8% 22% 16% 4	3586
	11th to 20th	Night	36% 6% 12% 24% 19% 4	3480
	21st to end	Night	47% 10% 13% 23% 7%	3690
April	1st to 10th	Night	32% 5% 13% 27% 19% 3	1900
	11th to 20th	Night	39% 6% 11% 23% 17% 5%	1875
	21st to end	Night	44% 6% 9% 24% 16% 1	1900
May	1st to 10th	Night	40% 8% 17% 20% 14% 2	3140
	11th to 20th	Night	40% 7% 13% 25% 14% 1	2578
	21st to end	Night	41% 9% 12% 22% 13% 2	2751
June	1st to 10th	Night	30% 9% 17% 24% 18% 3	1520
	11th to 20th	Night	22% 8% 14% 31% 21% 4	1520
	21st to end	Night	19% 9% 18% 28% 19% 7%	1520
July	1st to 10th	Night	34% 7% 15% 26% 15% 3	2490
	11th to 20th	Night	21% 6% 13% 38% 20% 2	2593
	21st to end	Night	35% 9% 16% 26% 12% 1	2999
August	1st to 10th	Night	21% 7% 20% 30% 21% 1	2826
	11th to 20th	Night	33% 7% 17% 25% 16% 3	3096
	21st to end	Night	23% 5% 16% 37% 16% 3	3476
September	1st to 10th	Night	31% 5% 10% 26% 22% 5%	1900
	11th to 20th	Night	30% 6% 11% 25% 27% 2	1900
	21st to end	Night	29% 6% 10% 24% 27% 3	2123
October	1st to 10th	Night	13% 3 7% 17% 49% 11%	3800
	11th to 20th	Night	23% 3 6% 20% 33% 15%	3779
	21st to end	Night	30% 4 7% 27% 27% 4	4120
November	1st to 10th	Night	31% 5% 11% 26% 22% 5%	2471
	11th to 20th	Night	37% 4 7% 23% 23% 6%	2600
	21st to end	Night	42% 4 9% 24% 19% 2	2695
December	1st to 10th	Night	45% 5% 11% 22% 15% 2	2687
	11th to 20th	Night	46% 4 9% 23% 16% 1	3281
	21st to end	Night	59% 8% 9% 14% 8% 2	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	27% 24% 34% 11% 2	270
	11th to 20th	Day	32% 23% 36% 9%	270
	21st to end	Day	22% 33% 32% 11% 1	297
February	1st to 10th	Day	28% 24% 34% 14% 1	270
	11th to 20th	Day	29% 29% 31% 10% 2 1	270
	21st to end	Day	32% 25% 32% 10%	225
March	1st to 10th	Day	21% 28% 39% 10% 1	270
	11th to 20th	Day	32% 21% 34% 10% 3 1	270
	21st to end	Day	34% 21% 32% 10% 2	373
April	1st to 10th	Day	21% 21% 36% 17% 5%	460
	11th to 20th	Day	26% 19% 31% 17% 5% 1	452
	21st to end	Day	27% 19% 31% 17% 5% 1	460
May	1st to 10th	Day	22% 20% 32% 20% 6%	467
	11th to 20th	Day	18% 13% 30% 25% 11% 2	675
	21st to end	Day	12% 10% 37% 24% 12% 4	734
June	1st to 10th	Day	11% 6% 27% 29% 22% 5%	680
	11th to 20th	Day	8% 4 27% 38% 20% 3	680
	21st to end	Day	6% 7% 32% 36% 15% 4	680
July	1st to 10th	Day	12% 4 19% 28% 28% 8%	671
	11th to 20th	Day	3 6% 23% 36% 27% 6%	668
	21st to end	Day	9% 4 19% 35% 26% 6%	739
August	1st to 10th	Day	11% 3 17% 41% 23% 5%	676
	11th to 20th	Day	12% 4 23% 29% 24% 7%	500
	21st to end	Day	12% 1 17% 30% 31% 9%	539
September	1st to 10th	Day	12% 6% 16% 35% 24% 8%	490
	11th to 20th	Day	8% 4 21% 33% 23% 10%	490
	21st to end	Day	12% 11% 25% 30% 16% 7%	419
October	1st to 10th	Day	12% 11% 31% 29% 13% 4	300
	11th to 20th	Day	23% 14% 35% 21% 5% 1	300
	21st to end	Day	32% 19% 29% 17% 3	330
November	1st to 10th	Day	16% 15% 40% 19% 8% 2	300
	11th to 20th	Day	25% 19% 32% 16% 6% 1	300
	21st to end	Day	32% 15% 31% 16% 5%	300
December	1st to 10th	Day	21% 24% 33% 14% 5% 2	273
	11th to 20th	Day	29% 19% 34% 14% 3	270
	21st to end	Day	28% 26% 34% 10% 2	297
January	1st to 10th	Night	23% 23% 34% 17% 3	950
	11th to 20th	Night	24% 26% 32% 15% 3	950
	21st to end	Night	21% 22% 37% 19% 1	1045
February	1st to 10th	Night	25% 20% 37% 16% 2	950
	11th to 20th	Night	23% 20% 39% 16% 2	795
	21st to end	Night	26% 22% 34% 16% 2	628
March	1st to 10th	Night	26% 17% 37% 18% 2	678
	11th to 20th	Night	25% 15% 36% 21% 3	570
	21st to end	Night	26% 16% 35% 19% 4	627
April	1st to 10th	Night	16% 19% 38% 23% 4	570
	11th to 20th	Night	21% 15% 32% 27% 5%	563
	21st to end	Night	22% 14% 39% 18% 6%	570
May	1st to 10th	Night	17% 11% 35% 29% 7%	570
	11th to 20th	Night	19% 7% 32% 26% 15% 1	561
	21st to end	Night	13% 7% 31% 31% 15% 3	617
June	1st to 10th	Night	9% 5% 22% 35% 27% 2	570
	11th to 20th	Night	7% 3 26% 41% 22% 2	570
	21st to end	Night	3 3 29% 42% 21% 2	570
July	1st to 10th	Night	12% 2 12% 36% 31% 7%	555
	11th to 20th	Night	6% 2 17% 41% 31% 4	552
	21st to end	Night	6% 3 16% 44% 28% 3	624
August	1st to 10th	Night	7% 2 14% 42% 32% 2	567
	11th to 20th	Night	8% 2 17% 39% 31% 3	564
	21st to end	Night	7% 2 16% 33% 36% 6%	627
September	1st to 10th	Night	14% 2 15% 37% 28% 5%	570
	11th to 20th	Night	13% 2 13% 39% 28% 6%	570
	21st to end	Night	12% 7% 24% 28% 24% 5%	727
October	1st to 10th	Night	8% 5% 30% 31% 23% 3	760
	11th to 20th	Night	17% 14% 33% 26% 10%	760
	21st to end	Night	23% 15% 33% 23% 6%	836
November	1st to 10th	Night	14% 11% 39% 27% 8% 1	780
	11th to 20th	Night	21% 15% 33% 23% 7%	800
	21st to end	Night	23% 19% 34% 19% 5%	895
December	1st to 10th	Night	23% 17% 37% 19% 4	960
	11th to 20th	Night	25% 16% 35% 21% 3	950
	21st to end	Night	24% 24% 32% 18% 2	1045

Page generated at 2024-11-29 09:43:08. Version ac07

Copyright © 2024 Attilla Danko.