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 2026-03-18.

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	10% 7% 3 8% 6% 6% 6% 5% 7% 8% 35%	131440
	Night	9% 7% 3 8% 6% 5% 5% 4 6% 8% 37%	130058
Transparency	Day	40% 9% 13% 19% 14% 5%	135138
	Night	37% 10% 14% 20% 15% 5%	134430
Seeing	Day	21% 17% 26% 20% 11% 6%	16848
	Night	19% 14% 22% 25% 16% 3	26996

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	8% 8% 4 9% 7% 5% 4 4 6% 7% 40%	5258
	11th to 20th	Day	6% 7% 3 7% 6% 6% 5% 4 4 5% 47%	5280
	21st to end	Day	9% 8% 5% 9% 5% 4 5% 4 5% 5% 40%	5780
February	1st to 10th	Day	10% 8% 3 7% 6% 5% 6% 4 7% 7% 36%	1937
	11th to 20th	Day	11% 11% 3 9% 6% 4 4 4 5% 7% 34%	2048
	21st to end	Day	12% 7% 4 10% 6% 5% 5% 4 6% 6% 36%	1730
March	1st to 10th	Day	14% 7% 3 9% 5% 5% 5% 4 6% 6% 37%	4985
	11th to 20th	Day	8% 7% 3 7% 5% 5% 4 3 5% 6% 48%	5057
	21st to end	Day	12% 8% 3 7% 5% 4 5% 4 6% 6% 42%	5465
April	1st to 10th	Day	9% 7% 2 8% 6% 4 6% 4 7% 8% 40%	2200
	11th to 20th	Day	12% 8% 2 6% 5% 4 5% 4 6% 7% 40%	2394
	21st to end	Day	11% 8% 3 7% 5% 5% 5% 4 5% 7% 39%	2600
May	1st to 10th	Day	10% 7% 3 10% 7% 7% 8% 6% 7% 9% 26%	5862
	11th to 20th	Day	14% 8% 3 10% 6% 7% 8% 6% 8% 9% 22%	5861
	21st to end	Day	10% 6% 3 9% 6% 6% 6% 5% 8% 9% 32%	6433
June	1st to 10th	Day	10% 7% 3 7% 7% 6% 7% 5% 8% 9% 30%	2600
	11th to 20th	Day	8% 7% 3 8% 6% 7% 7% 6% 8% 11% 30%	2600
	21st to end	Day	7% 6% 3 8% 6% 7% 6% 6% 9% 9% 31%	2600
July	1st to 10th	Day	6% 5% 2 9% 7% 7% 8% 6% 8% 10% 32%	5900
	11th to 20th	Day	7% 6% 3 11% 8% 8% 9% 7% 10% 10% 22%	5900
	21st to end	Day	10% 7% 3 11% 10% 9% 8% 6% 8% 9% 17%	6424
August	1st to 10th	Day	12% 8% 3 9% 7% 7% 7% 6% 9% 9% 23%	4234
	11th to 20th	Day	7% 6% 3 9% 7% 8% 7% 6% 9% 12% 26%	4174
	21st to end	Day	6% 6% 2 6% 6% 6% 6% 5% 8% 9% 41%	4372
September	1st to 10th	Day	10% 7% 3 9% 7% 5% 6% 5% 7% 8% 35%	2200
	11th to 20th	Day	15% 7% 3 9% 6% 5% 6% 5% 6% 9% 30%	2200
	21st to end	Day	14% 7% 3 7% 6% 6% 6% 4 6% 8% 33%	2200
October	1st to 10th	Day	12% 7% 2 7% 3 4 5% 3 5% 6% 46%	2140
	11th to 20th	Day	9% 6% 3 6% 5% 4 3 4 4 6% 51%	2000
	21st to end	Day	11% 7% 3 6% 5% 3 3 3 5% 6% 48%	2200
November	1st to 10th	Day	7% 7% 2 5% 4 3 4 4 5% 7% 51%	1978
	11th to 20th	Day	9% 5% 2 5% 5% 5% 4 4 6% 7% 47%	1890
	21st to end	Day	9% 8% 2 9% 5% 4 4 3 5% 7% 45%	1890
December	1st to 10th	Day	8% 7% 3 8% 5% 5% 6% 4 6% 6% 42%	3020
	11th to 20th	Day	10% 6% 3 8% 6% 7% 6% 5% 7% 7% 35%	3463
	21st to end	Day	11% 6% 3 9% 6% 6% 6% 4 6% 8% 35%	4565
January	1st to 10th	Night	8% 7% 3 11% 6% 6% 6% 5% 6% 6% 35%	7635
	11th to 20th	Night	7% 8% 3 9% 5% 5% 5% 3 5% 6% 44%	7680
	21st to end	Night	10% 9% 4 8% 5% 5% 6% 3 5% 6% 40%	8401
February	1st to 10th	Night	9% 8% 3 7% 6% 6% 5% 5% 6% 8% 38%	2677
	11th to 20th	Night	12% 9% 3 8% 7% 6% 5% 3 5% 7% 34%	2458
	21st to end	Night	10% 7% 3 10% 6% 5% 5% 5% 7% 7% 34%	2076
March	1st to 10th	Night	15% 9% 4 10% 6% 4 4 3 5% 6% 34%	5085
	11th to 20th	Night	7% 6% 3 7% 5% 4 4 3 6% 8% 48%	5058
	21st to end	Night	10% 7% 4 6% 5% 5% 5% 4 6% 7% 42%	5467
April	1st to 10th	Night	9% 7% 3 8% 6% 5% 4 4 7% 8% 40%	2200
	11th to 20th	Night	10% 7% 2 6% 6% 4 4 3 6% 7% 44%	1969
	21st to end	Night	10% 7% 2 7% 5% 4 4 4 5% 8% 43%	1800
May	1st to 10th	Night	11% 9% 3 8% 5% 5% 6% 5% 8% 11% 29%	4033
	11th to 20th	Night	14% 10% 4 10% 7% 6% 5% 5% 7% 9% 24%	4032
	21st to end	Night	10% 9% 3 9% 5% 6% 5% 4 6% 8% 34%	4421
June	1st to 10th	Night	8% 7% 2 7% 5% 6% 7% 6% 8% 11% 35%	1800
	11th to 20th	Night	7% 6% 2 7% 5% 4 6% 5% 8% 10% 40%	1800
	21st to end	Night	6% 5% 3 5% 5% 7% 6% 6% 8% 11% 37%	1800
July	1st to 10th	Night	4 6% 2 7% 6% 7% 8% 6% 8% 11% 35%	4058
	11th to 20th	Night	5% 5% 3 8% 6% 7% 7% 6% 8% 12% 31%	4057
	21st to end	Night	6% 7% 4 11% 10% 9% 9% 6% 7% 9% 22%	4427
August	1st to 10th	Night	8% 8% 3 8% 6% 7% 7% 5% 8% 12% 28%	2915
	11th to 20th	Night	7% 9% 3 9% 7% 6% 6% 6% 7% 8% 32%	2875
	21st to end	Night	6% 5% 2 5% 5% 5% 5% 4 6% 9% 46%	3475
September	1st to 10th	Night	10% 8% 4 8% 6% 5% 6% 4 5% 7% 38%	2200
	11th to 20th	Night	14% 8% 3 9% 5% 5% 5% 4 6% 8% 35%	2200
	21st to end	Night	14% 9% 2 7% 4 5% 4 3 5% 6% 41%	2200
October	1st to 10th	Night	13% 7% 2 6% 5% 4 5% 3 5% 7% 44%	2259
	11th to 20th	Night	9% 6% 3 7% 4 5% 4 4 5% 6% 46%	2400
	21st to end	Night	10% 7% 2 6% 4 3 3 3 5% 6% 50%	2640
November	1st to 10th	Night	10% 7% 3 6% 4 4 4 4 6% 6% 46%	2535
	11th to 20th	Night	10% 5% 3 6% 5% 4 4 4 5% 7% 46%	2730
	21st to end	Night	10% 6% 2 7% 5% 4 5% 4 6% 6% 43%	2730
December	1st to 10th	Night	8% 5% 3 9% 7% 5% 5% 4 6% 5% 41%	4380
	11th to 20th	Night	11% 8% 4 13% 7% 6% 6% 4 5% 6% 31%	4952
	21st to end	Night	11% 8% 4 10% 6% 5% 5% 4 6% 8% 33%	6633

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	34% 7% 11% 23% 21% 3	5259
	11th to 20th	Day	29% 6% 10% 16% 31% 9%	5280
	21st to end	Day	40% 4 9% 22% 18% 7%	5780
February	1st to 10th	Day	41% 6% 14% 19% 16% 4	1937
	11th to 20th	Day	46% 5% 10% 18% 16% 4	2058
	21st to end	Day	44% 6% 10% 17% 16% 6%	1730
March	1st to 10th	Day	41% 6% 10% 17% 17% 10%	4985
	11th to 20th	Day	32% 6% 8% 18% 21% 15%	5057
	21st to end	Day	41% 5% 8% 26% 16% 4	5465
April	1st to 10th	Day	38% 7% 12% 23% 17% 4	2200
	11th to 20th	Day	40% 6% 11% 21% 18% 5%	2394
	21st to end	Day	42% 5% 14% 24% 12% 2	2600
May	1st to 10th	Day	47% 11% 15% 19% 8% 1	5897
	11th to 20th	Day	51% 12% 14% 16% 6% 1	5865
	21st to end	Day	42% 10% 14% 18% 14% 2	6447
June	1st to 10th	Day	45% 11% 16% 18% 9% 1	2600
	11th to 20th	Day	43% 11% 16% 17% 11% 1	2600
	21st to end	Day	42% 12% 15% 18% 10% 2	2600
July	1st to 10th	Day	40% 15% 17% 19% 9%	5835
	11th to 20th	Day	47% 19% 19% 11% 4	5831
	21st to end	Day	54% 15% 14% 10% 5%	6240
August	1st to 10th	Day	49% 15% 17% 16% 3	4221
	11th to 20th	Day	40% 16% 21% 14% 7% 2	4213
	21st to end	Day	35% 11% 16% 31% 7% 2	4372
September	1st to 10th	Day	44% 9% 13% 17% 14% 3	2200
	11th to 20th	Day	48% 9% 11% 18% 12% 2	2200
	21st to end	Day	47% 9% 12% 15% 13% 4	2200
October	1st to 10th	Day	29% 7% 9% 17% 25% 12%	3491
	11th to 20th	Day	23% 5% 7% 24% 20% 22%	3240
	21st to end	Day	24% 6% 11% 25% 19% 15%	3538
November	1st to 10th	Day	31% 5% 12% 19% 27% 7%	1978
	11th to 20th	Day	33% 5% 9% 23% 23% 8%	1890
	21st to end	Day	37% 5% 7% 24% 21% 6%	1890
December	1st to 10th	Day	35% 7% 10% 18% 25% 5%	3020
	11th to 20th	Day	39% 7% 12% 19% 18% 5%	3460
	21st to end	Day	38% 8% 13% 24% 13% 3	4565
January	1st to 10th	Night	33% 10% 13% 26% 13% 5%	7636
	11th to 20th	Night	31% 8% 8% 19% 26% 9%	7680
	21st to end	Night	38% 6% 11% 18% 20% 7%	8401
February	1st to 10th	Night	38% 6% 13% 21% 18% 3	2677
	11th to 20th	Night	44% 5% 11% 20% 15% 5%	2459
	21st to end	Night	43% 7% 12% 18% 14% 6%	2076
March	1st to 10th	Night	43% 8% 9% 16% 18% 7%	5085
	11th to 20th	Night	30% 6% 9% 21% 20% 14%	5058
	21st to end	Night	37% 8% 12% 26% 11% 5%	5467
April	1st to 10th	Night	37% 7% 14% 22% 16% 4	2200
	11th to 20th	Night	37% 4 12% 22% 19% 5%	1969
	21st to end	Night	38% 7% 15% 25% 13% 1	1800
May	1st to 10th	Night	42% 12% 18% 20% 7% 1	4060
	11th to 20th	Night	49% 12% 16% 18% 5%	4033
	21st to end	Night	40% 10% 18% 21% 10% 1	4429
June	1st to 10th	Night	38% 15% 19% 19% 8% 1	1800
	11th to 20th	Night	35% 13% 22% 21% 8% 1	1800
	21st to end	Night	34% 14% 18% 20% 13% 2	1800
July	1st to 10th	Night	35% 17% 21% 21% 6%	4015
	11th to 20th	Night	35% 22% 26% 12% 3 1	4006
	21st to end	Night	47% 19% 17% 12% 5%	4297
August	1st to 10th	Night	40% 17% 25% 13% 4	2904
	11th to 20th	Night	39% 17% 22% 15% 7%	2902
	21st to end	Night	29% 11% 20% 31% 8% 1	3475
September	1st to 10th	Night	42% 11% 12% 18% 14% 3	2200
	11th to 20th	Night	44% 10% 12% 19% 15% 1	2200
	21st to end	Night	43% 8% 12% 19% 15% 3	2200
October	1st to 10th	Night	27% 12% 13% 17% 20% 12%	3688
	11th to 20th	Night	24% 7% 8% 21% 24% 17%	3899
	21st to end	Night	25% 7% 10% 22% 23% 12%	4252
November	1st to 10th	Night	33% 7% 10% 21% 21% 8%	2535
	11th to 20th	Night	33% 5% 8% 22% 24% 8%	2730
	21st to end	Night	36% 6% 8% 24% 21% 5%	2730
December	1st to 10th	Night	34% 11% 11% 19% 22% 3	4380
	11th to 20th	Night	43% 10% 11% 19% 14% 4	4954
	21st to end	Night	41% 7% 15% 21% 14% 2	6633

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	39% 28% 24% 7% 1 1	330
	11th to 20th	Day	40% 21% 28% 9% 1	330
	21st to end	Day	37% 31% 26% 5% 1	363
February	1st to 10th	Day	26% 34% 32% 8% 1	330
	11th to 20th	Day	45% 26% 24% 4 1	330
	21st to end	Day	40% 30% 23% 7%	273
March	1st to 10th	Day	29% 23% 27% 16% 4	504
	11th to 20th	Day	29% 28% 29% 11% 2 1	528
	21st to end	Day	28% 30% 26% 12% 5%	550
April	1st to 10th	Day	28% 22% 25% 18% 6% 1	500
	11th to 20th	Day	25% 23% 25% 18% 8% 1	492
	21st to end	Day	21% 19% 29% 16% 11% 3	500
May	1st to 10th	Day	20% 22% 29% 17% 7% 4	503
	11th to 20th	Day	21% 15% 28% 17% 12% 6%	527
	21st to end	Day	17% 13% 26% 21% 13% 10%	573
June	1st to 10th	Day	15% 12% 29% 24% 13% 8%	530
	11th to 20th	Day	9% 9% 27% 25% 21% 9%	530
	21st to end	Day	8% 12% 31% 23% 17% 8%	530
July	1st to 10th	Day	9% 5% 21% 30% 21% 14%	525
	11th to 20th	Day	8% 7% 14% 32% 25% 14%	524
	21st to end	Day	7% 5% 19% 34% 23% 12%	576
August	1st to 10th	Day	17% 9% 22% 25% 14% 13%	526
	11th to 20th	Day	9% 7% 23% 27% 22% 13%	519
	21st to end	Day	11% 6% 20% 27% 20% 16%	583
September	1st to 10th	Day	10% 6% 21% 32% 22% 10%	530
	11th to 20th	Day	17% 8% 19% 24% 24% 8%	530
	21st to end	Day	20% 11% 22% 29% 15% 3	530
October	1st to 10th	Day	19% 12% 22% 26% 14% 7%	530
	11th to 20th	Day	17% 16% 28% 23% 13% 3	530
	21st to end	Day	22% 15% 28% 23% 9% 3	583
November	1st to 10th	Day	19% 21% 30% 20% 8% 2	456
	11th to 20th	Day	24% 24% 32% 16% 3 1	330
	21st to end	Day	27% 23% 30% 15% 5% 1	330
December	1st to 10th	Day	30% 27% 33% 8% 1	330
	11th to 20th	Day	25% 21% 38% 13% 2 1	330
	21st to end	Day	26% 23% 38% 8% 4	363
January	1st to 10th	Night	28% 20% 29% 18% 5%	840
	11th to 20th	Night	28% 20% 29% 20% 4	840
	21st to end	Night	25% 23% 31% 18% 3	924
February	1st to 10th	Night	22% 20% 30% 25% 3	840
	11th to 20th	Night	29% 26% 28% 16% 1	823
	21st to end	Night	26% 25% 31% 17% 2	692
March	1st to 10th	Night	23% 22% 27% 24% 4	840
	11th to 20th	Night	25% 19% 31% 17% 7% 1	829
	21st to end	Night	23% 21% 29% 20% 6%	880
April	1st to 10th	Night	24% 20% 25% 24% 7% 1	800
	11th to 20th	Night	22% 19% 24% 23% 10% 2	718
	21st to end	Night	16% 15% 25% 32% 12% 1	600
May	1st to 10th	Night	15% 16% 29% 25% 14% 2	600
	11th to 20th	Night	18% 10% 22% 28% 19% 3	591
	21st to end	Night	14% 9% 18% 26% 26% 6%	650
June	1st to 10th	Night	11% 6% 21% 32% 25% 6%	600
	11th to 20th	Night	9% 6% 17% 30% 31% 8%	600
	21st to end	Night	6% 6% 17% 32% 34% 5%	600
July	1st to 10th	Night	10% 4 12% 28% 41% 6%	585
	11th to 20th	Night	9% 4 10% 26% 41% 10%	582
	21st to end	Night	6% 5% 11% 32% 39% 9%	657
August	1st to 10th	Night	12% 7% 11% 29% 34% 7%	597
	11th to 20th	Night	12% 6% 12% 26% 37% 7%	594
	21st to end	Night	11% 4 12% 26% 38% 8%	730
September	1st to 10th	Night	11% 6% 16% 26% 35% 7%	800
	11th to 20th	Night	19% 7% 12% 26% 31% 6%	800
	21st to end	Night	21% 9% 14% 28% 25% 3	800
October	1st to 10th	Night	17% 13% 17% 22% 25% 7%	800
	11th to 20th	Night	18% 15% 23% 27% 15% 3	800
	21st to end	Night	20% 14% 22% 31% 10% 3	880
November	1st to 10th	Night	18% 14% 23% 28% 14% 3	820
	11th to 20th	Night	23% 16% 20% 31% 9% 2	840
	21st to end	Night	23% 15% 23% 28% 10% 2	840
December	1st to 10th	Night	24% 18% 28% 23% 6%	840
	11th to 20th	Night	22% 16% 28% 27% 6% 1	840
	21st to end	Night	26% 18% 25% 26% 4	924

Page generated at 2026-03-15 02:23:55. Version ac07

Copyright © 2026 Attilla Danko.