Mayland Earth to Sky Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mayland Earth to Sky Park clear sky chart from 2005-11-06 to 2024-12-06.

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	11% 7% 3 8% 6% 6% 6% 5% 7% 8% 34%	101436
	Night	10% 8% 3 8% 6% 5% 5% 4 6% 8% 36%	98222
Transparency	Day	42% 8% 12% 20% 14% 4	105178
	Night	38% 9% 13% 20% 14% 5%	102619
Seeing	Day	20% 16% 26% 20% 12% 6%	15182
	Night	19% 14% 22% 25% 17% 3	25263

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	9% 8% 3 10% 6% 4 4 4 7% 8% 36%	2836
	11th to 20th	Day	9% 9% 3 9% 5% 5% 6% 5% 5% 6% 36%	2840
	21st to end	Day	15% 11% 5% 10% 5% 4 3 3 5% 5% 35%	3124
February	1st to 10th	Day	11% 9% 3 7% 6% 5% 6% 5% 7% 6% 35%	1752
	11th to 20th	Day	12% 11% 3 10% 6% 4 4 4 5% 7% 34%	1848
	21st to end	Day	13% 7% 4 10% 6% 5% 5% 4 6% 6% 36%	1570
March	1st to 10th	Day	17% 8% 3 8% 4 3 4 4 6% 6% 36%	3391
	11th to 20th	Day	9% 7% 3 7% 5% 4 4 3 5% 5% 48%	3480
	21st to end	Day	16% 9% 3 6% 5% 4 5% 4 6% 7% 37%	3815
April	1st to 10th	Day	9% 7% 2 8% 6% 4 6% 4 7% 8% 40%	2090
	11th to 20th	Day	12% 9% 2 6% 5% 4 5% 4 6% 7% 39%	2272
	21st to end	Day	11% 8% 4 7% 5% 5% 4 4 5% 7% 40%	2470
May	1st to 10th	Day	12% 8% 3 9% 7% 7% 7% 5% 6% 7% 29%	4082
	11th to 20th	Day	15% 8% 3 10% 6% 7% 7% 5% 7% 7% 25%	4081
	21st to end	Day	8% 5% 2 8% 6% 5% 6% 5% 8% 10% 36%	4476
June	1st to 10th	Day	10% 7% 3 7% 7% 6% 7% 5% 8% 9% 30%	2470
	11th to 20th	Day	8% 7% 3 8% 6% 7% 7% 6% 8% 10% 30%	2470
	21st to end	Day	7% 7% 3 8% 7% 8% 6% 6% 8% 9% 31%	2470
July	1st to 10th	Day	6% 5% 2 9% 8% 7% 7% 6% 8% 11% 30%	4120
	11th to 20th	Day	8% 7% 3 10% 7% 7% 7% 6% 9% 9% 27%	4120
	21st to end	Day	11% 9% 4 12% 11% 9% 8% 6% 7% 7% 15%	4466
August	1st to 10th	Day	12% 7% 3 9% 7% 7% 7% 6% 9% 9% 23%	4104
	11th to 20th	Day	7% 6% 3 9% 7% 8% 7% 7% 9% 12% 26%	4044
	21st to end	Day	6% 6% 2 6% 6% 6% 6% 5% 8% 9% 41%	4238
September	1st to 10th	Day	10% 7% 3 8% 7% 5% 6% 5% 6% 8% 34%	2090
	11th to 20th	Day	15% 7% 3 9% 6% 5% 6% 5% 6% 8% 30%	2090
	21st to end	Day	14% 8% 3 7% 5% 6% 6% 5% 6% 7% 34%	2090
October	1st to 10th	Day	13% 7% 2 7% 3 4 4 4 5% 6% 45%	2033
	11th to 20th	Day	9% 6% 3 6% 5% 4 3 4 4 6% 50%	1900
	21st to end	Day	11% 7% 3 6% 5% 3 3 3 5% 6% 49%	2090
November	1st to 10th	Day	7% 7% 2 5% 4 3 4 4 5% 8% 50%	1882
	11th to 20th	Day	9% 6% 2 5% 5% 5% 4 4 6% 8% 47%	1800
	21st to end	Day	10% 8% 2 9% 5% 4 4 3 5% 6% 45%	1800
December	1st to 10th	Day	11% 8% 4 10% 6% 5% 6% 5% 6% 6% 32%	1755
	11th to 20th	Day	11% 5% 2 7% 6% 4 6% 5% 8% 8% 39%	2153
	21st to end	Day	15% 6% 4 8% 6% 5% 5% 4 6% 7% 34%	3124
January	1st to 10th	Night	11% 6% 3 11% 6% 6% 6% 5% 8% 7% 30%	4109
	11th to 20th	Night	8% 9% 4 10% 6% 5% 5% 3 5% 8% 37%	4120
	21st to end	Night	15% 11% 4 9% 5% 4 4 3 5% 6% 33%	4532
February	1st to 10th	Night	9% 7% 3 7% 6% 5% 6% 5% 6% 8% 38%	2423
	11th to 20th	Night	13% 9% 3 7% 7% 6% 5% 3 6% 7% 35%	2218
	21st to end	Night	11% 8% 3 9% 7% 5% 5% 4 7% 7% 33%	1884
March	1st to 10th	Night	17% 12% 5% 12% 6% 4 4 3 4 5% 26%	3459
	11th to 20th	Night	7% 8% 3 8% 5% 4 5% 4 6% 8% 43%	3480
	21st to end	Night	13% 7% 3 6% 5% 4 5% 4 6% 7% 40%	3817
April	1st to 10th	Night	9% 7% 3 8% 6% 5% 3 4 7% 8% 41%	2090
	11th to 20th	Night	10% 8% 2 6% 6% 4 4 3 6% 7% 43%	1870
	21st to end	Night	10% 7% 2 7% 4 4 4 4 5% 8% 44%	1710
May	1st to 10th	Night	11% 10% 4 8% 5% 5% 5% 4 7% 9% 31%	2813
	11th to 20th	Night	14% 11% 4 10% 6% 5% 4 4 6% 8% 28%	2812
	21st to end	Night	7% 6% 3 7% 4 6% 6% 5% 7% 9% 39%	3079
June	1st to 10th	Night	8% 7% 2 6% 5% 6% 6% 6% 8% 11% 36%	1710
	11th to 20th	Night	7% 6% 2 7% 5% 4 6% 5% 8% 10% 40%	1710
	21st to end	Night	6% 5% 3 5% 5% 7% 6% 6% 8% 11% 38%	1710
July	1st to 10th	Night	4 6% 2 7% 6% 7% 8% 6% 8% 12% 34%	2840
	11th to 20th	Night	6% 5% 2 6% 5% 5% 6% 6% 8% 12% 38%	2840
	21st to end	Night	7% 8% 5% 11% 10% 8% 7% 6% 7% 9% 20%	3087
August	1st to 10th	Night	8% 8% 3 8% 6% 7% 7% 5% 8% 12% 28%	2825
	11th to 20th	Night	7% 9% 3 9% 7% 6% 6% 6% 7% 8% 33%	2785
	21st to end	Night	6% 5% 2 5% 5% 5% 5% 4 6% 10% 47%	3368
September	1st to 10th	Night	10% 8% 3 8% 6% 4 6% 4 5% 7% 39%	2090
	11th to 20th	Night	14% 9% 3 9% 5% 5% 4 4 5% 7% 34%	2090
	21st to end	Night	14% 9% 2 7% 4 4 4 3 4 6% 42%	2090
October	1st to 10th	Night	13% 7% 3 6% 5% 3 4 3 5% 7% 45%	2146
	11th to 20th	Night	10% 7% 3 7% 4 4 4 4 5% 6% 46%	2280
	21st to end	Night	10% 7% 2 6% 4 3 3 3 5% 6% 50%	2508
November	1st to 10th	Night	10% 7% 3 6% 4 4 4 5% 6% 6% 45%	2411
	11th to 20th	Night	10% 6% 3 6% 5% 4 4 4 5% 7% 46%	2600
	21st to end	Night	10% 6% 2 7% 5% 4 5% 4 6% 6% 43%	2600
December	1st to 10th	Night	12% 8% 3 10% 7% 5% 6% 4 7% 6% 32%	2542
	11th to 20th	Night	10% 8% 3 12% 6% 4 5% 4 6% 6% 36%	3042
	21st to end	Night	14% 9% 5% 9% 6% 6% 6% 5% 7% 7% 26%	4532

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	36% 3 9% 25% 22% 5%	2837
	11th to 20th	Day	41% 5% 10% 18% 21% 6%	2840
	21st to end	Day	46% 3 6% 21% 20% 4	3124
February	1st to 10th	Day	43% 5% 14% 18% 16% 4	1752
	11th to 20th	Day	47% 5% 10% 17% 16% 5%	1858
	21st to end	Day	46% 5% 10% 17% 15% 6%	1570
March	1st to 10th	Day	44% 5% 9% 18% 16% 7%	3391
	11th to 20th	Day	35% 5% 9% 20% 20% 11%	3480
	21st to end	Day	45% 5% 9% 23% 14% 4	3815
April	1st to 10th	Day	38% 6% 11% 23% 17% 4	2090
	11th to 20th	Day	41% 6% 10% 20% 18% 5%	2272
	21st to end	Day	42% 5% 14% 24% 12% 2	2470
May	1st to 10th	Day	46% 10% 13% 21% 9% 1	4120
	11th to 20th	Day	51% 11% 12% 19% 7% 1	4085
	21st to end	Day	38% 8% 16% 20% 15% 1	4489
June	1st to 10th	Day	46% 11% 16% 17% 9% 1	2470
	11th to 20th	Day	44% 11% 16% 17% 11% 2	2470
	21st to end	Day	43% 12% 14% 18% 11% 2	2470
July	1st to 10th	Day	43% 16% 17% 17% 7%	4055
	11th to 20th	Day	46% 14% 19% 15% 5% 1	4051
	21st to end	Day	62% 12% 11% 10% 4	4324
August	1st to 10th	Day	48% 14% 17% 17% 3	4091
	11th to 20th	Day	40% 16% 21% 14% 7% 2	4083
	21st to end	Day	35% 11% 16% 31% 7% 2	4238
September	1st to 10th	Day	46% 9% 12% 17% 14% 3	2090
	11th to 20th	Day	49% 9% 10% 18% 13% 2	2090
	21st to end	Day	47% 8% 12% 16% 14% 4	2090
October	1st to 10th	Day	29% 7% 9% 17% 25% 13%	3384
	11th to 20th	Day	23% 5% 7% 24% 20% 22%	3140
	21st to end	Day	24% 6% 11% 25% 19% 16%	3428
November	1st to 10th	Day	32% 5% 11% 19% 26% 7%	1882
	11th to 20th	Day	33% 5% 8% 22% 24% 8%	1800
	21st to end	Day	37% 5% 7% 24% 21% 6%	1800
December	1st to 10th	Day	49% 5% 10% 17% 16% 4	1755
	11th to 20th	Day	35% 5% 10% 21% 21% 7%	2150
	21st to end	Day	43% 4 8% 25% 17% 2	3124
January	1st to 10th	Night	38% 5% 10% 24% 15% 8%	4109
	11th to 20th	Night	39% 4 8% 18% 21% 9%	4120
	21st to end	Night	47% 4 8% 16% 19% 6%	4532
February	1st to 10th	Night	39% 6% 13% 20% 19% 3	2423
	11th to 20th	Night	45% 4 10% 21% 15% 5%	2219
	21st to end	Night	45% 7% 12% 18% 14% 6%	1884
March	1st to 10th	Night	53% 8% 8% 13% 14% 4	3459
	11th to 20th	Night	35% 5% 10% 25% 16% 10%	3480
	21st to end	Night	40% 7% 11% 24% 12% 6%	3817
April	1st to 10th	Night	37% 6% 14% 23% 16% 4	2090
	11th to 20th	Night	38% 4 12% 21% 20% 5%	1870
	21st to end	Night	37% 6% 15% 26% 14% 1	1710
May	1st to 10th	Night	42% 10% 17% 23% 7% 1	2840
	11th to 20th	Night	45% 11% 16% 21% 7%	2813
	21st to end	Night	32% 10% 22% 25% 10% 1	3087
June	1st to 10th	Night	38% 15% 19% 19% 8% 1	1710
	11th to 20th	Night	34% 12% 23% 21% 8% 1	1710
	21st to end	Night	35% 13% 18% 19% 13% 2	1710
July	1st to 10th	Night	37% 17% 20% 19% 6% 1	2795
	11th to 20th	Night	31% 18% 28% 18% 5% 1	2786
	21st to end	Night	52% 18% 15% 12% 4	2988
August	1st to 10th	Night	39% 16% 26% 14% 5%	2814
	11th to 20th	Night	39% 17% 22% 15% 7%	2812
	21st to end	Night	29% 11% 20% 31% 8% 2	3368
September	1st to 10th	Night	42% 10% 12% 19% 13% 3	2090
	11th to 20th	Night	46% 10% 11% 18% 14% 1	2090
	21st to end	Night	43% 7% 11% 20% 16% 3	2090
October	1st to 10th	Night	27% 11% 13% 17% 20% 12%	3575
	11th to 20th	Night	24% 6% 8% 21% 23% 18%	3779
	21st to end	Night	24% 7% 11% 22% 23% 12%	4120
November	1st to 10th	Night	34% 7% 10% 21% 20% 8%	2411
	11th to 20th	Night	34% 5% 8% 21% 24% 9%	2600
	21st to end	Night	36% 6% 8% 24% 21% 5%	2600
December	1st to 10th	Night	46% 7% 10% 19% 14% 4	2542
	11th to 20th	Night	40% 5% 10% 19% 20% 6%	3044
	21st to end	Night	47% 4 11% 21% 14% 2	4532

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% 29% 27% 8% 1 1	270
	11th to 20th	Day	36% 22% 31% 10% 1	270
	21st to end	Day	34% 31% 27% 6% 1	297
February	1st to 10th	Day	27% 31% 33% 9% 1	270
	11th to 20th	Day	43% 28% 25% 4	270
	21st to end	Day	41% 29% 24% 5%	225
March	1st to 10th	Day	30% 24% 26% 16% 4	427
	11th to 20th	Day	28% 28% 28% 12% 3 1	460
	21st to end	Day	27% 30% 26% 12% 5%	506
April	1st to 10th	Day	28% 21% 25% 19% 6% 2	460
	11th to 20th	Day	25% 22% 25% 19% 9% 2	452
	21st to end	Day	22% 20% 28% 16% 11% 3	460
May	1st to 10th	Day	21% 21% 29% 16% 7% 5%	463
	11th to 20th	Day	20% 14% 28% 18% 13% 7%	487
	21st to end	Day	15% 12% 26% 22% 14% 11%	529
June	1st to 10th	Day	14% 10% 29% 24% 13% 9%	490
	11th to 20th	Day	10% 9% 27% 24% 21% 9%	490
	21st to end	Day	9% 12% 33% 22% 15% 9%	490
July	1st to 10th	Day	10% 5% 20% 30% 22% 14%	485
	11th to 20th	Day	8% 7% 14% 33% 23% 14%	484
	21st to end	Day	7% 5% 19% 34% 23% 12%	532
August	1st to 10th	Day	16% 8% 22% 25% 15% 14%	486
	11th to 20th	Day	9% 7% 24% 26% 22% 12%	479
	21st to end	Day	12% 4 18% 28% 21% 17%	539
September	1st to 10th	Day	11% 6% 20% 31% 22% 10%	490
	11th to 20th	Day	18% 8% 18% 24% 24% 7%	490
	21st to end	Day	21% 10% 21% 29% 16% 3	490
October	1st to 10th	Day	21% 12% 21% 26% 13% 7%	490
	11th to 20th	Day	18% 16% 27% 23% 13% 3	490
	21st to end	Day	20% 14% 29% 25% 10% 3	539
November	1st to 10th	Day	18% 21% 29% 21% 9% 3	420
	11th to 20th	Day	25% 23% 31% 18% 3 1	300
	21st to end	Day	25% 21% 31% 16% 5% 1	300
December	1st to 10th	Day	28% 27% 34% 9% 1	285
	11th to 20th	Day	23% 23% 38% 14% 2 1	270
	21st to end	Day	25% 22% 40% 8% 5%	297
January	1st to 10th	Night	27% 20% 30% 18% 5%	760
	11th to 20th	Night	26% 19% 29% 22% 4	760
	21st to end	Night	24% 24% 29% 19% 4	836
February	1st to 10th	Night	21% 19% 30% 26% 3	760
	11th to 20th	Night	29% 26% 27% 17% 1	743
	21st to end	Night	26% 26% 29% 18% 2	628
March	1st to 10th	Night	23% 23% 27% 23% 4	760
	11th to 20th	Night	25% 19% 30% 18% 7% 1	760
	21st to end	Night	22% 21% 29% 20% 7%	836
April	1st to 10th	Night	24% 20% 24% 24% 7% 1	760
	11th to 20th	Night	22% 19% 23% 23% 11% 2	682
	21st to end	Night	16% 15% 24% 31% 12% 1	570
May	1st to 10th	Night	15% 16% 28% 24% 14% 2	570
	11th to 20th	Night	17% 11% 21% 28% 20% 3	561
	21st to end	Night	12% 8% 18% 27% 28% 7%	617
June	1st to 10th	Night	11% 6% 20% 32% 26% 6%	570
	11th to 20th	Night	9% 6% 17% 29% 31% 8%	570
	21st to end	Night	7% 5% 17% 32% 33% 5%	570
July	1st to 10th	Night	10% 4 12% 28% 40% 7%	555
	11th to 20th	Night	9% 3 11% 27% 40% 10%	552
	21st to end	Night	6% 4 10% 32% 38% 9%	624
August	1st to 10th	Night	11% 5% 11% 31% 36% 7%	567
	11th to 20th	Night	12% 5% 12% 26% 37% 7%	564
	21st to end	Night	12% 3 11% 25% 40% 9%	693
September	1st to 10th	Night	12% 6% 15% 25% 36% 7%	760
	11th to 20th	Night	20% 7% 12% 25% 30% 6%	760
	21st to end	Night	21% 9% 14% 28% 25% 3	760
October	1st to 10th	Night	18% 13% 16% 22% 25% 7%	760
	11th to 20th	Night	18% 15% 23% 26% 15% 3	760
	21st to end	Night	18% 14% 22% 32% 11% 3	836
November	1st to 10th	Night	18% 14% 23% 29% 15% 3	780
	11th to 20th	Night	22% 15% 20% 31% 9% 2	800
	21st to end	Night	23% 14% 23% 29% 10% 2	800
December	1st to 10th	Night	24% 19% 27% 24% 7%	783
	11th to 20th	Night	21% 17% 27% 27% 7% 1	760
	21st to end	Night	27% 17% 25% 26% 4	836

Page generated at 2024-12-03 06:45:13. Version ac07

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