Reidland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Reidland clear sky chart from 2005-11-06 to 2025-10-19.

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% 2 6% 4 4 4 4 5% 8% 42%	126295
	Night	14% 7% 3 6% 4 4 4 3 5% 7% 44%	123594
Transparency	Day	39% 5% 10% 24% 18% 3	129926
	Night	39% 5% 9% 24% 19% 4	128040
Seeing	Day	16% 7% 21% 25% 21% 10%	16756
	Night	17% 6% 23% 32% 19% 3	26479

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	16% 9% 4 10% 5% 3 4 4 5% 6% 35%	3617
	11th to 20th	Day	14% 8% 3 6% 4 4 4 3 5% 5% 45%	3758
	21st to end	Day	19% 9% 3 7% 4 4 3 3 3 6% 38%	4488
February	1st to 10th	Day	18% 11% 3 6% 5% 4 3 3 5% 7% 36%	1994
	11th to 20th	Day	19% 10% 3 7% 3 4 3 3 4 5% 38%	1948
	21st to end	Day	17% 9% 4 8% 6% 4 3 3 4 6% 36%	1650
March	1st to 10th	Day	16% 12% 3 7% 4 4 3 3 3 6% 39%	4480
	11th to 20th	Day	13% 8% 2 6% 3 3 3 2 4 6% 51%	4717
	21st to end	Day	12% 8% 3 7% 4 4 4 3 5% 7% 42%	5967
April	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 5% 7% 44%	2400
	11th to 20th	Day	14% 7% 2 7% 5% 4 4 4 5% 6% 41%	2374
	21st to end	Day	16% 8% 3 6% 4 4 4 4 5% 7% 39%	2400
May	1st to 10th	Day	16% 10% 3 9% 6% 5% 6% 5% 6% 8% 26%	5726
	11th to 20th	Day	16% 8% 3 8% 5% 5% 5% 5% 6% 8% 32%	5861
	21st to end	Day	14% 7% 3 7% 5% 5% 4 4 6% 7% 39%	6698
June	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 9% 45%	2800
	11th to 20th	Day	5% 4 2 5% 5% 4 5% 5% 6% 10% 48%	2800
	21st to end	Day	5% 5% 2 5% 5% 6% 6% 5% 7% 10% 45%	2800
July	1st to 10th	Day	8% 5% 2 6% 5% 4 5% 4 7% 10% 42%	6360
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 12% 42%	6360
	21st to end	Day	7% 7% 2 8% 5% 6% 6% 5% 8% 11% 34%	6750
August	1st to 10th	Day	5% 4 2 4 3 3 5% 4 5% 10% 55%	3905
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 10% 44%	3849
	21st to end	Day	5% 3 1 5% 4 3 4 4 6% 8% 57%	4312
September	1st to 10th	Day	11% 5% 2 5% 5% 4 5% 4 5% 7% 47%	2400
	11th to 20th	Day	10% 6% 2 5% 4 4 4 4 5% 8% 49%	2270
	21st to end	Day	12% 6% 2 5% 4 3 3 3 5% 6% 51%	2200
October	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 7% 59%	2183
	11th to 20th	Day	13% 5% 2 5% 3 4 3 2 4 6% 53%	1980
	21st to end	Day	19% 5% 2 4 3 3 3 3 4 5% 47%	1988
November	1st to 10th	Day	11% 6% 2 5% 3 3 4 3 5% 5% 52%	1762
	11th to 20th	Day	14% 8% 2 5% 4 3 3 2 4 5% 49%	1800
	21st to end	Day	18% 10% 2 5% 3 3 3 3 4 5% 43%	1800
December	1st to 10th	Day	14% 10% 2 6% 3 3 4 3 4 5% 45%	2908
	11th to 20th	Day	15% 9% 3 7% 5% 4 4 4 4 6% 38%	3008
	21st to end	Day	23% 13% 4 8% 4 4 4 3 4 4 28%	3982
January	1st to 10th	Night	18% 10% 4 9% 3 3 4 3 5% 7% 34%	6348
	11th to 20th	Night	15% 9% 3 7% 4 4 3 2 4 5% 43%	6204
	21st to end	Night	21% 9% 3 6% 3 3 3 3 5% 5% 39%	6490
February	1st to 10th	Night	21% 11% 3 8% 4 3 4 3 4 5% 34%	2404
	11th to 20th	Night	19% 8% 3 8% 4 4 3 3 4 5% 39%	2338
	21st to end	Night	18% 9% 3 7% 5% 4 4 3 4 4 39%	1980
March	1st to 10th	Night	19% 10% 4 7% 4 4 4 3 4 4 37%	5373
	11th to 20th	Night	12% 6% 2 5% 3 4 4 4 5% 6% 48%	5284
	21st to end	Night	15% 7% 3 7% 4 4 4 3 5% 7% 40%	4962
April	1st to 10th	Night	14% 5% 2 5% 4 4 3 4 6% 7% 48%	2000
	11th to 20th	Night	14% 6% 2 6% 3 3 3 3 5% 8% 47%	1975
	21st to end	Night	16% 8% 2 5% 4 4 4 4 6% 7% 40%	2000
May	1st to 10th	Night	17% 8% 3 7% 5% 4 4 4 6% 9% 32%	4156
	11th to 20th	Night	15% 8% 3 8% 5% 5% 4 4 5% 8% 35%	4032
	21st to end	Night	13% 6% 3 7% 4 4 5% 4 6% 8% 39%	4164
June	1st to 10th	Night	10% 6% 3 5% 3 4 5% 4 6% 8% 46%	1600
	11th to 20th	Night	5% 3 1 5% 3 4 5% 4 8% 9% 53%	1600
	21st to end	Night	3 3 1 4 4 4 5% 5% 9% 13% 49%	1600
July	1st to 10th	Night	8% 5% 2 5% 4 5% 5% 4 6% 7% 48%	3618
	11th to 20th	Night	5% 3 2 5% 5% 4 5% 4 7% 12% 49%	3617
	21st to end	Night	6% 5% 2 7% 5% 4 5% 5% 7% 13% 41%	4112
August	1st to 10th	Night	4 3 1 5% 3 4 3 4 6% 7% 60%	3244
	11th to 20th	Night	5% 4 2 5% 4 4 4 4 7% 8% 53%	3200
	21st to end	Night	4 3 1 3 3 3 3 3 6% 8% 62%	3586
September	1st to 10th	Night	8% 5% 2 6% 3 3 3 3 4 6% 56%	2000
	11th to 20th	Night	8% 5% 2 6% 3 4 4 3 4 7% 54%	2109
	21st to end	Night	11% 4 2 5% 3 3 4 3 5% 6% 55%	2200
October	1st to 10th	Night	7% 5% 2 4 3 3 3 3 4 6% 61%	2214
	11th to 20th	Night	13% 4 1 4 3 4 3 3 4 6% 56%	2377
	21st to end	Night	19% 6% 2 5% 4 3 3 3 4 6% 47%	2608
November	1st to 10th	Night	14% 5% 2 4 3 2 2 3 5% 6% 54%	2536
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 4 7% 51%	2600
	21st to end	Night	16% 7% 3 5% 4 3 3 2 4 5% 48%	2600
December	1st to 10th	Night	18% 8% 3 7% 4 3 3 3 3 4 45%	4268
	11th to 20th	Night	18% 8% 2 5% 4 4 3 3 4 6% 43%	5199
	21st to end	Night	23% 11% 4 7% 5% 4 4 3 4 5% 30%	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	49% 4 11% 23% 11% 2	3618
	11th to 20th	Day	41% 3 6% 26% 21% 2	3758
	21st to end	Day	49% 3 8% 18% 16% 6%	4488
February	1st to 10th	Day	49% 3 10% 24% 13% 2	1994
	11th to 20th	Day	50% 3 9% 21% 13% 5%	1958
	21st to end	Day	50% 3 8% 19% 14% 6%	1650
March	1st to 10th	Day	49% 3 4 21% 17% 6%	4480
	11th to 20th	Day	37% 3 7% 26% 22% 5%	4717
	21st to end	Day	41% 5% 10% 26% 18% 1	5969
April	1st to 10th	Day	39% 5% 10% 25% 19% 2	2400
	11th to 20th	Day	43% 3 9% 22% 18% 4	2374
	21st to end	Day	44% 5% 9% 26% 14% 2	2400
May	1st to 10th	Day	52% 8% 12% 17% 10%	5762
	11th to 20th	Day	48% 8% 11% 22% 10% 1	5865
	21st to end	Day	42% 6% 10% 21% 18% 3	6712
June	1st to 10th	Day	34% 7% 13% 23% 21% 2	2800
	11th to 20th	Day	30% 7% 13% 27% 21% 3	2800
	21st to end	Day	32% 8% 15% 24% 16% 5%	2800
July	1st to 10th	Day	36% 6% 11% 29% 16% 2	6291
	11th to 20th	Day	33% 8% 16% 32% 10% 1	6285
	21st to end	Day	41% 8% 19% 24% 8% 1	6557
August	1st to 10th	Day	25% 6% 15% 31% 23% 1	3893
	11th to 20th	Day	35% 7% 12% 27% 18% 1	3885
	21st to end	Day	24% 5% 12% 36% 21% 3	4311
September	1st to 10th	Day	35% 6% 9% 25% 21% 4	2400
	11th to 20th	Day	34% 5% 9% 24% 25% 2	2270
	21st to end	Day	35% 4 7% 24% 26% 5%	2200
October	1st to 10th	Day	18% 2 6% 19% 46% 9%	3560
	11th to 20th	Day	24% 2 5% 24% 31% 13%	3220
	21st to end	Day	30% 3 4 28% 29% 6%	3252
November	1st to 10th	Day	34% 4 8% 25% 24% 6%	1762
	11th to 20th	Day	39% 3 6% 23% 23% 6%	1800
	21st to end	Day	44% 3 6% 26% 17% 4	1800
December	1st to 10th	Day	42% 3 7% 29% 17% 1	2908
	11th to 20th	Day	47% 4 9% 24% 13% 3	3005
	21st to end	Day	59% 4 11% 18% 8% 1	3982
January	1st to 10th	Night	50% 4 9% 25% 12% 1	6348
	11th to 20th	Night	45% 4 6% 24% 20% 2	6204
	21st to end	Night	47% 3 7% 23% 16% 4	6490
February	1st to 10th	Night	54% 3 9% 19% 14% 1	2404
	11th to 20th	Night	49% 3 7% 21% 17% 3	2339
	21st to end	Night	48% 4 8% 18% 17% 4	1980
March	1st to 10th	Night	51% 4 5% 15% 19% 6%	5373
	11th to 20th	Night	37% 4 9% 21% 18% 11%	5284
	21st to end	Night	44% 4 9% 27% 14% 2	4962
April	1st to 10th	Night	36% 4 11% 26% 20% 4	2000
	11th to 20th	Night	36% 4 9% 23% 21% 6%	1975
	21st to end	Night	43% 5% 9% 23% 18% 2	2000
May	1st to 10th	Night	47% 7% 13% 22% 9% 1	4184
	11th to 20th	Night	48% 7% 12% 20% 12% 1	4033
	21st to end	Night	41% 7% 11% 25% 14% 2	4172
June	1st to 10th	Night	33% 6% 11% 23% 23% 3	1600
	11th to 20th	Night	25% 7% 14% 26% 23% 5%	1600
	21st to end	Night	24% 8% 16% 27% 18% 7%	1600
July	1st to 10th	Night	34% 7% 11% 26% 20% 3	3580
	11th to 20th	Night	28% 9% 18% 30% 13% 2	3572
	21st to end	Night	33% 8% 20% 29% 9%	3995
August	1st to 10th	Night	22% 5% 14% 38% 21%	3232
	11th to 20th	Night	27% 6% 16% 29% 19% 3	3230
	21st to end	Night	20% 5% 9% 36% 26% 3	3586
September	1st to 10th	Night	30% 5% 8% 28% 24% 6%	2000
	11th to 20th	Night	30% 5% 7% 27% 25% 4	2109
	21st to end	Night	31% 4 9% 25% 24% 7%	2200
October	1st to 10th	Night	18% 3 4 16% 45% 14%	3617
	11th to 20th	Night	21% 2 4 21% 40% 12%	3876
	21st to end	Night	29% 2 5% 24% 28% 11%	4294
November	1st to 10th	Night	32% 3 7% 26% 26% 6%	2536
	11th to 20th	Night	35% 3 6% 24% 24% 8%	2600
	21st to end	Night	40% 3 7% 25% 22% 3	2600
December	1st to 10th	Night	44% 3 7% 25% 19% 1	4268
	11th to 20th	Night	44% 3 10% 23% 19% 2	5201
	21st to end	Night	56% 4 9% 19% 9% 2	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	27% 12% 33% 20% 6% 1	300
	11th to 20th	Day	28% 16% 33% 20% 3 1	300
	21st to end	Day	22% 12% 44% 16% 5%	330
February	1st to 10th	Day	27% 13% 35% 19% 5% 1	300
	11th to 20th	Day	28% 18% 36% 14% 2 1	300
	21st to end	Day	27% 13% 35% 18% 5%	249
March	1st to 10th	Day	22% 12% 39% 20% 6% 1	300
	11th to 20th	Day	24% 15% 36% 20% 4 1	305
	21st to end	Day	23% 15% 33% 20% 7% 1	550
April	1st to 10th	Day	21% 12% 30% 24% 11% 1	500
	11th to 20th	Day	20% 13% 27% 26% 12% 2	492
	21st to end	Day	20% 7% 33% 26% 11% 4	500
May	1st to 10th	Day	19% 11% 26% 28% 12% 4	503
	11th to 20th	Day	22% 4 20% 27% 20% 8%	527
	21st to end	Day	13% 3 21% 28% 22% 13%	682
June	1st to 10th	Day	12% 3 15% 28% 27% 15%	730
	11th to 20th	Day	7% 1 15% 31% 34% 12%	730
	21st to end	Day	7% 2 14% 35% 27% 15%	730
July	1st to 10th	Day	11% 2 9% 26% 27% 25%	721
	11th to 20th	Day	6% 2 10% 28% 36% 18%	718
	21st to end	Day	8% 2 10% 26% 34% 20%	774
August	1st to 10th	Day	10% 2 8% 27% 34% 20%	526
	11th to 20th	Day	11% 3 9% 25% 34% 18%	519
	21st to end	Day	8% 2 8% 23% 36% 24%	583
September	1st to 10th	Day	9% 3 10% 25% 34% 19%	530
	11th to 20th	Day	11% 2 6% 25% 33% 22%	530
	21st to end	Day	15% 5% 17% 24% 25% 13%	530
October	1st to 10th	Day	9% 3 16% 33% 30% 9%	513
	11th to 20th	Day	14% 7% 30% 28% 15% 6%	324
	21st to end	Day	25% 11% 27% 24% 11% 3	330
November	1st to 10th	Day	18% 7% 27% 28% 12% 7%	300
	11th to 20th	Day	15% 10% 33% 27% 13% 2	300
	21st to end	Day	28% 7% 26% 26% 10% 2	300
December	1st to 10th	Day	22% 12% 33% 20% 11% 2	300
	11th to 20th	Day	24% 12% 29% 24% 11%	300
	21st to end	Day	29% 12% 33% 22% 3 1	330
January	1st to 10th	Night	24% 11% 30% 29% 6%	1000
	11th to 20th	Night	25% 12% 34% 23% 5%	1000
	21st to end	Night	22% 8% 38% 29% 3	1100
February	1st to 10th	Night	26% 9% 34% 28% 3	804
	11th to 20th	Night	25% 12% 35% 25% 3	783
	21st to end	Night	24% 12% 36% 27% 2	660
March	1st to 10th	Night	23% 11% 28% 32% 6%	800
	11th to 20th	Night	23% 7% 35% 28% 7%	740
	21st to end	Night	21% 10% 28% 34% 7%	660
April	1st to 10th	Night	16% 9% 33% 32% 9% 1	600
	11th to 20th	Night	17% 9% 29% 32% 12% 1	593
	21st to end	Night	19% 5% 29% 34% 12% 1	600
May	1st to 10th	Night	20% 3 27% 34% 15% 1	600
	11th to 20th	Night	15% 6% 16% 38% 23% 2	591
	21st to end	Night	8% 2 15% 41% 29% 4	650
June	1st to 10th	Night	12% 2 13% 38% 31% 4	600
	11th to 20th	Night	6% 2 8% 44% 39% 2	600
	21st to end	Night	5% 2 12% 40% 38% 5%	600
July	1st to 10th	Night	9% 1 6% 28% 46% 11%	585
	11th to 20th	Night	7% 2 7% 29% 47% 8%	582
	21st to end	Night	6% 2 9% 30% 43% 9%	657
August	1st to 10th	Night	6% 2 7% 32% 46% 8%	597
	11th to 20th	Night	9% 2 9% 33% 42% 6%	594
	21st to end	Night	9% 1 5% 30% 47% 9%	660
September	1st to 10th	Night	11% 1 8% 34% 41% 6%	600
	11th to 20th	Night	10% 1 6% 31% 44% 7%	709
	21st to end	Night	12% 4 14% 35% 30% 6%	800
October	1st to 10th	Night	9% 3 15% 36% 31% 5%	800
	11th to 20th	Night	15% 4 23% 35% 21% 2	793
	21st to end	Night	22% 6% 24% 33% 13% 1	836
November	1st to 10th	Night	16% 5% 25% 37% 16% 1	780
	11th to 20th	Night	17% 6% 31% 32% 13%	800
	21st to end	Night	21% 8% 27% 31% 12% 1	800
December	1st to 10th	Night	24% 9% 28% 30% 8% 1	805
	11th to 20th	Night	23% 6% 29% 34% 8%	1000
	21st to end	Night	29% 9% 28% 30% 5%	1100

Page generated at 2025-10-16 00:50:27. Version ac07

Copyright © 2025 Attilla Danko.