Many Worlds Cross Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Many Worlds Cross Observatory clear sky chart from 2005-11-06 to 2025-02-21.

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	16% 10% 4 9% 5% 4 4 4 5% 7% 32%	108437
	Night	16% 11% 4 9% 5% 4 4 4 5% 6% 32%	110131
Transparency	Day	50% 4 11% 21% 12% 1	111989
	Night	50% 5% 11% 20% 12% 2	114743
Seeing	Day	26% 19% 28% 17% 7% 2	15156
	Night	24% 19% 27% 22% 7% 1	24330

By Month

Percentage Cloud Cover NE (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	10% 13% 6% 22% 9% 4 4 3 4 4 21%	3597
	11th to 20th	Day	14% 12% 5% 15% 8% 5% 4 4 4 5% 25%	3570
	21st to end	Day	15% 15% 8% 10% 5% 4 4 3 4 4 30%	4034
February	1st to 10th	Day	16% 12% 4 11% 7% 6% 6% 4 6% 5% 24%	1812
	11th to 20th	Day	12% 11% 6% 13% 8% 5% 4 4 4 6% 27%	1948
	21st to end	Day	18% 13% 4 12% 6% 4 4 3 4 4 28%	1570
March	1st to 10th	Day	22% 16% 5% 9% 4 3 3 2 4 4 27%	3116
	11th to 20th	Day	11% 13% 6% 11% 6% 5% 5% 4 5% 6% 28%	3272
	21st to end	Day	20% 8% 4 11% 6% 4 4 3 3 5% 32%	4166
April	1st to 10th	Day	18% 14% 3 9% 5% 4 4 3 5% 5% 31%	2280
	11th to 20th	Day	17% 10% 3 7% 4 5% 6% 4 5% 6% 34%	2254
	21st to end	Day	19% 9% 4 8% 6% 5% 4 4 5% 5% 31%	2389
May	1st to 10th	Day	26% 11% 3 7% 4 4 4 3 5% 6% 28%	4106
	11th to 20th	Day	19% 9% 3 8% 5% 5% 4 4 6% 7% 31%	4393
	21st to end	Day	13% 6% 2 6% 4 4 5% 5% 7% 8% 39%	4837
June	1st to 10th	Day	17% 7% 2 7% 6% 6% 5% 5% 7% 9% 30%	2660
	11th to 20th	Day	19% 6% 2 6% 5% 5% 4 5% 6% 10% 32%	2660
	21st to end	Day	17% 7% 3 8% 5% 6% 5% 4 5% 8% 30%	2660
July	1st to 10th	Day	12% 7% 3 7% 6% 5% 5% 5% 7% 9% 35%	4440
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 5% 8% 10% 35%	4440
	21st to end	Day	15% 9% 3 8% 5% 5% 5% 5% 6% 7% 32%	4814
August	1st to 10th	Day	18% 8% 3 8% 4 5% 5% 4 6% 8% 30%	4345
	11th to 20th	Day	14% 8% 3 7% 5% 5% 6% 4 8% 8% 33%	3768
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 5% 7% 8% 37%	4180
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 5% 7% 41%	2280
	11th to 20th	Day	16% 6% 2 6% 4 3 4 3 5% 7% 45%	2168
	21st to end	Day	17% 6% 3 7% 4 4 4 4 6% 7% 39%	2090
October	1st to 10th	Day	22% 9% 3 8% 4 4 4 2 5% 5% 35%	2024
	11th to 20th	Day	18% 8% 3 6% 5% 3 4 4 5% 6% 39%	1886
	21st to end	Day	22% 13% 4 8% 4 4 3 3 5% 5% 30%	1881
November	1st to 10th	Day	12% 9% 4 7% 5% 3 3 3 4 6% 44%	1761
	11th to 20th	Day	17% 11% 3 7% 6% 3 5% 3 6% 6% 35%	1800
	21st to end	Day	17% 12% 4 8% 5% 4 4 3 4 6% 31%	1690
December	1st to 10th	Day	15% 13% 5% 12% 6% 5% 5% 3 5% 5% 25%	2600
	11th to 20th	Day	18% 15% 6% 8% 5% 3 3 3 3 4 32%	2986
	21st to end	Day	17% 14% 5% 12% 4 4 3 3 5% 5% 28%	3960
January	1st to 10th	Night	11% 11% 7% 20% 8% 5% 3 3 4 5% 23%	6349
	11th to 20th	Night	11% 12% 4 18% 9% 6% 6% 4 5% 5% 20%	6315
	21st to end	Night	14% 14% 4 8% 5% 6% 6% 4 6% 6% 28%	6905
February	1st to 10th	Night	15% 11% 4 10% 7% 6% 5% 5% 6% 5% 25%	2586
	11th to 20th	Night	12% 10% 5% 11% 7% 6% 6% 5% 6% 5% 26%	2338
	21st to end	Night	16% 13% 4 10% 6% 4 5% 4 6% 5% 29%	1885
March	1st to 10th	Night	22% 12% 4 10% 5% 4 5% 3 5% 4 25%	3724
	11th to 20th	Night	11% 12% 5% 9% 7% 6% 5% 4 5% 5% 30%	3684
	21st to end	Night	17% 15% 5% 10% 5% 4 3 2 4 4 31%	3466
April	1st to 10th	Night	18% 12% 3 8% 5% 4 5% 4 5% 6% 30%	1900
	11th to 20th	Night	18% 11% 3 7% 5% 4 4 3 4 6% 35%	1875
	21st to end	Night	20% 10% 3 6% 4 3 4 4 5% 5% 36%	1791
May	1st to 10th	Night	26% 11% 3 6% 4 4 4 3 5% 6% 29%	2834
	11th to 20th	Night	17% 10% 3 7% 6% 6% 5% 4 5% 7% 30%	2527
	21st to end	Night	15% 8% 2 7% 4 4 4 3 6% 8% 38%	2738
June	1st to 10th	Night	19% 7% 2 7% 5% 4 4 3 6% 7% 37%	1520
	11th to 20th	Night	17% 7% 2 6% 4 4 5% 4 6% 8% 37%	1520
	21st to end	Night	15% 6% 2 5% 4 5% 5% 5% 6% 7% 40%	1520
July	1st to 10th	Night	13% 6% 3 7% 5% 4 5% 4 7% 9% 37%	2520
	11th to 20th	Night	16% 7% 2 6% 4 4 4 5% 6% 8% 38%	2520
	21st to end	Night	17% 8% 3 6% 4 4 5% 4 5% 6% 39%	2739
August	1st to 10th	Night	25% 8% 3 7% 3 4 4 3 5% 6% 34%	2552
	11th to 20th	Night	15% 7% 3 7% 5% 4 5% 4 5% 7% 39%	3057
	21st to end	Night	9% 8% 2 6% 3 4 4 3 5% 8% 47%	3476
September	1st to 10th	Night	14% 7% 2 7% 4 4 4 4 5% 6% 44%	1900
	11th to 20th	Night	14% 5% 2 5% 3 3 4 3 4 7% 51%	2010
	21st to end	Night	17% 7% 2 6% 4 3 3 3 4 6% 43%	2090
October	1st to 10th	Night	21% 8% 2 6% 4 4 3 3 5% 5% 37%	2153
	11th to 20th	Night	16% 8% 3 6% 5% 4 4 4 5% 5% 41%	2294
	21st to end	Night	20% 12% 3 7% 5% 3 4 3 5% 6% 32%	2717
November	1st to 10th	Night	14% 10% 2 6% 4 3 4 4 5% 6% 42%	2537
	11th to 20th	Night	17% 9% 3 9% 5% 5% 5% 3 4 5% 35%	2600
	21st to end	Night	13% 13% 3 9% 5% 5% 5% 4 6% 6% 32%	2705
December	1st to 10th	Night	17% 14% 5% 13% 6% 5% 4 4 5% 6% 22%	4580
	11th to 20th	Night	24% 13% 5% 8% 4 4 3 3 3 4 29%	5208
	21st to end	Night	18% 14% 6% 12% 5% 4 4 3 4 4 26%	6996

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	60% 6% 7% 21% 5%	3598
	11th to 20th	Day	60% 4 9% 13% 12% 3	3600
	21st to end	Day	55% 5% 6% 21% 12% 1	4034
February	1st to 10th	Day	58% 5% 11% 15% 10% 1	1812
	11th to 20th	Day	54% 6% 8% 19% 11% 1	1957
	21st to end	Day	58% 4 9% 18% 10% 1	1570
March	1st to 10th	Day	61% 3 11% 14% 10% 1	3119
	11th to 20th	Day	55% 3 13% 19% 9% 1	3272
	21st to end	Day	56% 2 5% 16% 18% 3	4166
April	1st to 10th	Day	55% 4 7% 21% 11% 2	2280
	11th to 20th	Day	50% 4 10% 21% 14% 1	2254
	21st to end	Day	54% 4 8% 19% 12% 3	2389
May	1st to 10th	Day	59% 3 10% 17% 10% 1	4120
	11th to 20th	Day	53% 3 14% 21% 8% 1	4397
	21st to end	Day	41% 5% 13% 26% 14% 1	4837
June	1st to 10th	Day	50% 6% 13% 22% 9%	2660
	11th to 20th	Day	47% 5% 15% 21% 11% 1	2660
	21st to end	Day	51% 5% 13% 21% 10%	2660
July	1st to 10th	Day	45% 6% 12% 24% 13% 1	4370
	11th to 20th	Day	42% 6% 16% 24% 11%	4365
	21st to end	Day	49% 4 14% 18% 14% 1	4661
August	1st to 10th	Day	51% 5% 14% 21% 9% 1	4331
	11th to 20th	Day	46% 5% 16% 26% 6%	3805
	21st to end	Day	41% 6% 13% 29% 11% 1	4180
September	1st to 10th	Day	42% 5% 11% 27% 14% 1	2280
	11th to 20th	Day	41% 4 8% 25% 20% 2	2168
	21st to end	Day	44% 5% 11% 23% 15% 2	2090
October	1st to 10th	Day	49% 5% 7% 19% 18% 2	3362
	11th to 20th	Day	42% 3 10% 24% 17% 4	3114
	21st to end	Day	40% 5% 12% 26% 13% 4	3081
November	1st to 10th	Day	40% 4 15% 24% 14% 2	1761
	11th to 20th	Day	48% 5% 9% 19% 17% 2	1800
	21st to end	Day	52% 4 14% 20% 8% 2	1690
December	1st to 10th	Day	54% 6% 13% 20% 6%	2600
	11th to 20th	Day	56% 3 11% 16% 13% 1	2986
	21st to end	Day	58% 3 7% 14% 14% 4	3960
January	1st to 10th	Night	58% 7% 9% 17% 7% 1	6349
	11th to 20th	Night	59% 6% 11% 13% 8% 2	6360
	21st to end	Night	52% 4 10% 16% 16% 3	6905
February	1st to 10th	Night	54% 5% 12% 19% 8% 2	2586
	11th to 20th	Night	53% 6% 10% 17% 12% 1	2340
	21st to end	Night	54% 4 10% 21% 9% 3	1885
March	1st to 10th	Night	60% 3 9% 18% 9% 1	3734
	11th to 20th	Night	52% 4 12% 23% 8% 1	3685
	21st to end	Night	55% 3 5% 14% 19% 4	3466
April	1st to 10th	Night	52% 4 10% 21% 11% 2	1900
	11th to 20th	Night	50% 4 9% 21% 15% 1	1875
	21st to end	Night	49% 4 10% 19% 15% 3	1791
May	1st to 10th	Night	58% 3 11% 16% 11% 1	2840
	11th to 20th	Night	55% 4 15% 18% 8% 1	2528
	21st to end	Night	44% 5% 15% 22% 14% 1	2739
June	1st to 10th	Night	46% 5% 12% 25% 11%	1520
	11th to 20th	Night	44% 5% 16% 23% 11%	1520
	21st to end	Night	41% 7% 15% 25% 12%	1520
July	1st to 10th	Night	41% 6% 16% 22% 14% 1	2480
	11th to 20th	Night	42% 5% 14% 27% 12%	2472
	21st to end	Night	45% 5% 14% 22% 14% 1	2651
August	1st to 10th	Night	52% 4 14% 23% 7% 1	2542
	11th to 20th	Night	43% 6% 18% 26% 7%	3086
	21st to end	Night	32% 7% 15% 34% 12% 1	3476
September	1st to 10th	Night	40% 5% 12% 26% 16% 1	1900
	11th to 20th	Night	37% 3 10% 27% 21% 1	2010
	21st to end	Night	43% 4 10% 25% 16% 2	2090
October	1st to 10th	Night	46% 5% 12% 21% 15% 1	3595
	11th to 20th	Night	37% 4 11% 23% 19% 5%	3805
	21st to end	Night	39% 4 14% 30% 12% 1	4467
November	1st to 10th	Night	41% 5% 11% 22% 18% 3	2537
	11th to 20th	Night	49% 4 9% 19% 16% 2	2600
	21st to end	Night	49% 5% 14% 23% 8% 1	2705
December	1st to 10th	Night	56% 8% 10% 22% 5%	4580
	11th to 20th	Night	58% 4 11% 11% 15% 1	5208
	21st to end	Night	59% 4 6% 13% 13% 4	6996

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	35% 30% 27% 6% 3 1	200
	11th to 20th	Day	33% 32% 28% 7% 1 1	200
	21st to end	Day	27% 31% 28% 11% 3	237
February	1st to 10th	Day	41% 32% 22% 3 2	312
	11th to 20th	Day	38% 28% 24% 9% 1	496
	21st to end	Day	34% 25% 29% 11% 1	382
March	1st to 10th	Day	32% 27% 28% 12% 2	460
	11th to 20th	Day	33% 27% 27% 9% 3	460
	21st to end	Day	35% 25% 24% 10% 4 2	506
April	1st to 10th	Day	38% 23% 22% 11% 5% 1	460
	11th to 20th	Day	33% 24% 26% 11% 5% 2	452
	21st to end	Day	28% 21% 32% 13% 4 2	460
May	1st to 10th	Day	34% 21% 26% 12% 5% 2	463
	11th to 20th	Day	23% 20% 33% 18% 4 1	487
	21st to end	Day	21% 14% 30% 24% 9% 2	529
June	1st to 10th	Day	18% 18% 33% 20% 10% 1	490
	11th to 20th	Day	22% 14% 30% 22% 12% 1	490
	21st to end	Day	20% 19% 31% 19% 9% 2	490
July	1st to 10th	Day	16% 11% 33% 26% 12% 2	485
	11th to 20th	Day	13% 9% 34% 31% 11% 2	484
	21st to end	Day	15% 11% 39% 24% 9% 2	532
August	1st to 10th	Day	14% 12% 29% 30% 11% 5%	486
	11th to 20th	Day	16% 9% 33% 23% 13% 6%	479
	21st to end	Day	14% 13% 28% 26% 12% 6%	539
September	1st to 10th	Day	19% 11% 27% 23% 13% 6%	490
	11th to 20th	Day	18% 14% 23% 19% 16% 10%	490
	21st to end	Day	21% 12% 30% 21% 10% 6%	490
October	1st to 10th	Day	29% 14% 24% 19% 11% 3	490
	11th to 20th	Day	26% 18% 27% 20% 7% 2	483
	21st to end	Day	33% 19% 25% 18% 5% 1	429
November	1st to 10th	Day	25% 23% 25% 19% 8% 1	395
	11th to 20th	Day	30% 26% 26% 13% 4 1	400
	21st to end	Day	36% 23% 24% 14% 2 1	290
December	1st to 10th	Day	34% 29% 24% 11% 3	200
	11th to 20th	Day	40% 26% 24% 10% 1	200
	21st to end	Day	35% 22% 31% 10% 2	220
January	1st to 10th	Night	26% 30% 31% 11% 2	800
	11th to 20th	Night	29% 26% 28% 15% 2	800
	21st to end	Night	24% 26% 33% 16% 2	880
February	1st to 10th	Night	28% 26% 32% 14% 1	800
	11th to 20th	Night	28% 28% 31% 12% 1	783
	21st to end	Night	30% 28% 26% 14% 2	629
March	1st to 10th	Night	30% 24% 28% 16% 3	760
	11th to 20th	Night	26% 27% 29% 15% 3	760
	21st to end	Night	30% 22% 25% 17% 6%	836
April	1st to 10th	Night	29% 21% 29% 18% 4	760
	11th to 20th	Night	27% 22% 27% 17% 6%	751
	21st to end	Night	29% 20% 27% 19% 5%	651
May	1st to 10th	Night	31% 14% 29% 19% 6% 1	570
	11th to 20th	Night	21% 15% 32% 28% 4	393
	21st to end	Night	19% 8% 29% 30% 13% 1	411
June	1st to 10th	Night	21% 9% 30% 28% 12%	380
	11th to 20th	Night	17% 11% 28% 34% 11% 1	380
	21st to end	Night	17% 9% 26% 36% 12% 1	380
July	1st to 10th	Night	16% 5% 23% 41% 13% 1	370
	11th to 20th	Night	15% 5% 23% 40% 15% 1	368
	21st to end	Night	12% 7% 24% 42% 14%	416
August	1st to 10th	Night	14% 4 24% 40% 16% 1	398
	11th to 20th	Night	17% 5% 23% 34% 20% 2	722
	21st to end	Night	15% 8% 22% 33% 20% 2	836
September	1st to 10th	Night	17% 8% 29% 28% 16% 2	760
	11th to 20th	Night	16% 10% 23% 26% 21% 5%	760
	21st to end	Night	20% 12% 24% 27% 14% 3	760
October	1st to 10th	Night	28% 11% 24% 26% 11% 2	760
	11th to 20th	Night	22% 16% 29% 24% 9%	760
	21st to end	Night	29% 18% 28% 21% 4	836
November	1st to 10th	Night	21% 22% 28% 22% 7%	780
	11th to 20th	Night	27% 23% 26% 17% 6% 2	800
	21st to end	Night	27% 22% 29% 17% 4 1	800
December	1st to 10th	Night	30% 27% 24% 14% 4	800
	11th to 20th	Night	33% 23% 26% 16% 3	800
	21st to end	Night	30% 28% 25% 14% 2	880

Page generated at 2025-02-18 03:26:32. Version ac07

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