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 2024-01-13.

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	13% 6% 3 5% 5% 3 4 5% 5% 8% 42%	74801
	Night	14% 6% 3 5% 5% 3 4 4 5% 7% 45%	74939
Transparency	Day	40% 5% 11% 24% 16% 3	74508
	Night	39% 5% 10% 24% 19% 4	74754
Seeing	Day	16% 6% 20% 26% 22% 11%	14282
	Night	17% 6% 23% 32% 19% 3	24189

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	20% 7% 4 8% 6% 2 4 4 4 5% 38%	1517
	11th to 20th	Day	22% 8% 4 5% 5% 3 4 4 5% 5% 34%	1510
	21st to end	Day	14% 8% 3 8% 6% 3 4 4 3 5% 42%	1782
February	1st to 10th	Day	19% 10% 3 6% 5% 3 4 3 5% 7% 36%	1795
	11th to 20th	Day	19% 10% 3 6% 4 3 4 4 4 5% 37%	1748
	21st to end	Day	19% 9% 4 7% 6% 3 3 4 4 6% 35%	1480
March	1st to 10th	Day	16% 9% 3 5% 5% 3 3 4 4 6% 42%	1800
	11th to 20th	Day	21% 10% 3 7% 5% 3 4 3 4 5% 35%	1871
	21st to end	Day	18% 9% 3 6% 5% 3 5% 5% 5% 7% 33%	2376
April	1st to 10th	Day	11% 6% 3 5% 5% 3 4 5% 5% 8% 46%	2160
	11th to 20th	Day	15% 7% 3 6% 6% 2 4 4 5% 7% 41%	2134
	21st to end	Day	17% 7% 3 5% 5% 3 4 5% 5% 7% 39%	2160
May	1st to 10th	Day	16% 6% 3 6% 6% 3 5% 5% 6% 9% 37%	2286
	11th to 20th	Day	15% 6% 3 7% 5% 3 4 5% 5% 7% 40%	2301
	21st to end	Day	9% 5% 2 6% 7% 4 6% 7% 7% 10% 37%	2628
June	1st to 10th	Day	8% 4 2 5% 5% 3 5% 6% 7% 10% 45%	2520
	11th to 20th	Day	4 3 2 5% 5% 3 5% 7% 7% 10% 50%	2520
	21st to end	Day	6% 4 2 4 5% 4 6% 6% 7% 11% 45%	2520
July	1st to 10th	Day	8% 4 2 5% 6% 4 6% 6% 7% 11% 39%	2520
	11th to 20th	Day	5% 4 1 5% 5% 4 5% 5% 7% 11% 47%	2520
	21st to end	Day	6% 4 2 5% 5% 4 6% 6% 8% 12% 42%	2677
August	1st to 10th	Day	8% 5% 3 5% 5% 3 5% 6% 6% 10% 45%	2148
	11th to 20th	Day	8% 4 3 5% 6% 4 6% 5% 6% 9% 43%	2125
	21st to end	Day	8% 4 1 5% 5% 3 5% 5% 7% 10% 46%	2376
September	1st to 10th	Day	12% 5% 2 4 5% 3 4 6% 5% 8% 46%	2160
	11th to 20th	Day	10% 5% 2 4 5% 3 4 5% 5% 8% 49%	2044
	21st to end	Day	11% 5% 2 4 4 2 3 4 4 7% 53%	1980
October	1st to 10th	Day	9% 4 2 4 4 2 4 4 4 6% 57%	1965
	11th to 20th	Day	15% 4 2 5% 4 3 3 2 4 6% 51%	1800
	21st to end	Day	20% 5% 2 4 4 2 3 4 4 5% 46%	1884
November	1st to 10th	Day	10% 5% 2 4 3 3 4 4 5% 6% 54%	1672
	11th to 20th	Day	15% 7% 2 4 5% 2 3 3 4 5% 49%	1710
	21st to end	Day	19% 9% 2 4 3 3 3 4 4 5% 43%	1710
December	1st to 10th	Day	17% 9% 3 5% 4 2 4 5% 4 6% 40%	1701
	11th to 20th	Day	15% 9% 4 6% 6% 3 5% 5% 4 6% 36%	1918
	21st to end	Day	20% 13% 4 6% 6% 3 4 4 4 5% 31%	2783
January	1st to 10th	Night	19% 7% 3 6% 5% 2 4 4 5% 6% 39%	2648
	11th to 20th	Night	20% 9% 5% 6% 5% 2 4 4 4 6% 34%	2491
	21st to end	Night	17% 8% 3 6% 4 2 4 4 5% 6% 42%	2574
February	1st to 10th	Night	21% 10% 4 7% 5% 3 4 4 3 5% 35%	2164
	11th to 20th	Night	18% 7% 4 7% 5% 3 4 4 4 5% 40%	2098
	21st to end	Night	20% 9% 3 6% 6% 3 4 4 4 5% 37%	1776
March	1st to 10th	Night	17% 8% 3 5% 4 3 4 4 4 5% 43%	2160
	11th to 20th	Night	18% 9% 3 6% 5% 3 4 4 4 5% 40%	2102
	21st to end	Night	18% 9% 3 7% 5% 3 4 5% 5% 6% 35%	1980
April	1st to 10th	Night	12% 5% 2 4 4 3 3 4 6% 8% 50%	1800
	11th to 20th	Night	15% 6% 2 5% 4 3 3 4 5% 8% 46%	1775
	21st to end	Night	17% 7% 2 4 4 3 5% 4 5% 7% 42%	1800
May	1st to 10th	Night	15% 7% 3 5% 4 2 4 5% 4 8% 43%	1674
	11th to 20th	Night	13% 7% 2 5% 6% 3 4 4 5% 8% 42%	1592
	21st to end	Night	5% 4 3 6% 5% 3 5% 6% 7% 11% 44%	1643
June	1st to 10th	Night	10% 5% 3 3 4 3 4 6% 6% 9% 47%	1440
	11th to 20th	Night	4 3 1 4 4 3 4 6% 7% 9% 55%	1440
	21st to end	Night	4 2 1 3 4 2 5% 6% 8% 14% 50%	1440
July	1st to 10th	Night	7% 3 2 4 5% 4 7% 6% 7% 8% 47%	1440
	11th to 20th	Night	7% 3 2 4 4 2 4 4 5% 11% 53%	1440
	21st to end	Night	6% 4 2 4 4 2 4 5% 6% 11% 51%	1634
August	1st to 10th	Night	6% 4 1 5% 5% 3 4 5% 7% 9% 52%	1790
	11th to 20th	Night	7% 4 2 3 4 3 4 5% 7% 10% 52%	1776
	21st to end	Night	7% 4 2 3 4 2 4 5% 8% 10% 51%	1980
September	1st to 10th	Night	9% 5% 2 4 5% 2 4 4 4 6% 56%	1800
	11th to 20th	Night	8% 5% 2 5% 4 2 4 4 4 7% 54%	1897
	21st to end	Night	10% 4 2 4 3 2 4 3 4 7% 57%	1980
October	1st to 10th	Night	8% 5% 2 4 4 3 3 4 4 6% 59%	1992
	11th to 20th	Night	14% 4 1 3 5% 3 4 3 4 6% 53%	2160
	21st to end	Night	20% 6% 2 4 4 2 3 4 4 5% 45%	2470
November	1st to 10th	Night	13% 4 2 3 3 2 2 3 4 6% 56%	2406
	11th to 20th	Night	14% 5% 2 4 4 2 4 3 4 6% 51%	2470
	21st to end	Night	17% 6% 3 4 4 2 3 3 4 5% 49%	2470
December	1st to 10th	Night	19% 9% 4 5% 5% 2 4 4 4 5% 39%	2474
	11th to 20th	Night	18% 8% 3 5% 5% 3 4 4 4 5% 43%	3279
	21st to end	Night	18% 11% 4 7% 7% 3 5% 4 4 6% 31%	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	49% 4 7% 25% 11% 3	1518
	11th to 20th	Day	52% 4 9% 24% 11% 1	1510
	21st to end	Day	45% 4 11% 25% 13% 2	1782
February	1st to 10th	Day	49% 3 9% 24% 13% 2	1795
	11th to 20th	Day	50% 3 9% 22% 12% 4	1758
	21st to end	Day	52% 3 9% 19% 12% 5%	1480
March	1st to 10th	Day	45% 4 8% 22% 17% 4	1800
	11th to 20th	Day	52% 4 11% 20% 11% 2	1871
	21st to end	Day	51% 5% 11% 20% 12% 1	2376
April	1st to 10th	Day	38% 5% 10% 26% 19% 2	2160
	11th to 20th	Day	44% 3 9% 22% 19% 3	2134
	21st to end	Day	44% 5% 9% 26% 14% 2	2160
May	1st to 10th	Day	44% 7% 12% 25% 12% 1	2286
	11th to 20th	Day	44% 6% 12% 21% 16% 1	2305
	21st to end	Day	39% 9% 16% 21% 12% 2	2628
June	1st to 10th	Day	33% 7% 13% 23% 22% 2	2520
	11th to 20th	Day	28% 7% 14% 28% 20% 3	2520
	21st to end	Day	32% 8% 15% 24% 16% 6%	2520
July	1st to 10th	Day	37% 7% 16% 22% 13% 5%	2451
	11th to 20th	Day	31% 8% 15% 27% 16% 4	2445
	21st to end	Day	33% 8% 15% 29% 13% 2	2528
August	1st to 10th	Day	33% 8% 16% 27% 15% 1	2136
	11th to 20th	Day	36% 9% 12% 26% 16% 1	2125
	21st to end	Day	31% 6% 15% 25% 17% 5%	2376
September	1st to 10th	Day	36% 6% 9% 26% 19% 3	2160
	11th to 20th	Day	34% 5% 9% 25% 24% 3	2044
	21st to end	Day	33% 4 7% 26% 26% 5%	1980
October	1st to 10th	Day	29% 4 10% 25% 26% 6%	1965
	11th to 20th	Day	37% 3 6% 24% 22% 8%	1800
	21st to end	Day	41% 4 6% 25% 20% 4	1884
November	1st to 10th	Day	32% 4 8% 25% 24% 6%	1672
	11th to 20th	Day	39% 3 6% 23% 23% 6%	1710
	21st to end	Day	44% 3 6% 26% 17% 4	1710
December	1st to 10th	Day	46% 4 10% 23% 14% 2	1701
	11th to 20th	Day	47% 5% 8% 24% 13% 2	1915
	21st to end	Day	55% 4 11% 18% 11% 1	2783
January	1st to 10th	Night	47% 4 8% 24% 16% 2	2648
	11th to 20th	Night	52% 5% 8% 21% 13% 1	2491
	21st to end	Night	44% 4 10% 25% 16% 2	2574
February	1st to 10th	Night	54% 3 8% 20% 14% 1	2164
	11th to 20th	Night	48% 3 7% 22% 16% 3	2099
	21st to end	Night	50% 5% 9% 18% 15% 4	1776
March	1st to 10th	Night	44% 5% 7% 17% 21% 6%	2160
	11th to 20th	Night	48% 4 11% 20% 15% 3	2102
	21st to end	Night	50% 5% 10% 21% 12% 2	1980
April	1st to 10th	Night	34% 4 11% 27% 21% 4	1800
	11th to 20th	Night	37% 4 9% 22% 21% 7%	1775
	21st to end	Night	42% 5% 9% 24% 19% 2	1800
May	1st to 10th	Night	40% 6% 10% 23% 19% 2	1674
	11th to 20th	Night	40% 6% 13% 23% 16% 2	1593
	21st to end	Night	32% 8% 15% 26% 16% 3	1644
June	1st to 10th	Night	33% 6% 12% 23% 24% 3	1440
	11th to 20th	Night	23% 7% 15% 28% 21% 5%	1440
	21st to end	Night	23% 8% 16% 27% 18% 7%	1440
July	1st to 10th	Night	32% 8% 14% 25% 17% 4	1400
	11th to 20th	Night	26% 6% 17% 27% 18% 6%	1392
	21st to end	Night	27% 8% 13% 34% 17% 1	1544
August	1st to 10th	Night	28% 6% 17% 29% 19% 1	1778
	11th to 20th	Night	27% 8% 15% 27% 21% 3	1776
	21st to end	Night	28% 7% 13% 26% 20% 5%	1980
September	1st to 10th	Night	31% 6% 8% 29% 21% 5%	1800
	11th to 20th	Night	30% 6% 8% 28% 24% 5%	1897
	21st to end	Night	29% 4 8% 27% 24% 7%	1980
October	1st to 10th	Night	28% 4 7% 24% 29% 8%	1992
	11th to 20th	Night	34% 3 6% 22% 26% 8%	2160
	21st to end	Night	42% 3 5% 22% 21% 6%	2470
November	1st to 10th	Night	31% 3 7% 27% 27% 6%	2406
	11th to 20th	Night	35% 3 6% 24% 23% 8%	2470
	21st to end	Night	40% 3 7% 24% 23% 3	2470
December	1st to 10th	Night	48% 4 10% 21% 15% 2	2474
	11th to 20th	Night	44% 4 9% 22% 19% 3	3281
	21st to end	Night	54% 5% 9% 17% 12% 3	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% 11% 33% 22% 7% 1	270
	11th to 20th	Day	30% 11% 31% 23% 3 1	246
	21st to end	Day	21% 11% 45% 17% 6%	264
February	1st to 10th	Day	27% 12% 37% 19% 3 1	240
	11th to 20th	Day	28% 17% 39% 13% 3	240
	21st to end	Day	30% 12% 32% 19% 7% 1	198
March	1st to 10th	Day	21% 12% 40% 20% 6%	240
	11th to 20th	Day	26% 13% 34% 21% 5% 1	244
	21st to end	Day	23% 14% 31% 23% 8% 2	462
April	1st to 10th	Day	17% 11% 31% 27% 14% 1	420
	11th to 20th	Day	20% 10% 27% 27% 14% 2	412
	21st to end	Day	22% 6% 31% 27% 11% 4	420
May	1st to 10th	Day	18% 10% 27% 30% 12% 4	423
	11th to 20th	Day	21% 4 19% 28% 20% 9%	447
	21st to end	Day	11% 2 18% 30% 24% 15%	582
June	1st to 10th	Day	12% 3 12% 27% 29% 17%	630
	11th to 20th	Day	5% 15% 32% 34% 13%	630
	21st to end	Day	7% 2 14% 35% 26% 16%	630
July	1st to 10th	Day	10% 2 8% 24% 29% 28%	621
	11th to 20th	Day	6% 2 9% 26% 37% 20%	618
	21st to end	Day	8% 1 9% 27% 35% 21%	666
August	1st to 10th	Day	10% 1 6% 27% 36% 20%	446
	11th to 20th	Day	12% 2 7% 25% 36% 18%	439
	21st to end	Day	9% 2 6% 21% 37% 25%	495
September	1st to 10th	Day	10% 3 7% 22% 36% 22%	450
	11th to 20th	Day	11% 2 6% 25% 34% 23%	450
	21st to end	Day	13% 5% 16% 24% 28% 15%	450
October	1st to 10th	Day	9% 3 16% 34% 28% 9%	435
	11th to 20th	Day	16% 7% 31% 28% 13% 5%	270
	21st to end	Day	26% 11% 25% 23% 11% 3	297
November	1st to 10th	Day	17% 4 29% 29% 14% 7%	270
	11th to 20th	Day	14% 9% 33% 28% 14% 2	270
	21st to end	Day	28% 7% 25% 27% 11% 2	270
December	1st to 10th	Day	21% 11% 33% 20% 12% 3	270
	11th to 20th	Day	23% 12% 29% 25% 11%	270
	21st to end	Day	27% 12% 35% 22% 3 1	297
January	1st to 10th	Night	24% 11% 30% 29% 6%	950
	11th to 20th	Night	25% 12% 33% 24% 5%	911
	21st to end	Night	21% 8% 39% 29% 3	990
February	1st to 10th	Night	26% 9% 33% 29% 3	724
	11th to 20th	Night	23% 11% 36% 26% 3	703
	21st to end	Night	25% 11% 35% 26% 3	592
March	1st to 10th	Night	22% 11% 29% 33% 6%	720
	11th to 20th	Night	23% 7% 34% 28% 8%	666
	21st to end	Night	22% 9% 25% 36% 8%	594
April	1st to 10th	Night	14% 8% 34% 34% 9% 1	540
	11th to 20th	Night	18% 8% 27% 33% 13% 1	533
	21st to end	Night	19% 4 29% 34% 12% 1	540
May	1st to 10th	Night	18% 4 26% 35% 16% 1	540
	11th to 20th	Night	14% 5% 17% 38% 24% 2	531
	21st to end	Night	7% 2 14% 41% 32% 5%	584
June	1st to 10th	Night	12% 2 12% 37% 33% 4	540
	11th to 20th	Night	5% 1 8% 44% 40% 2	540
	21st to end	Night	4 1 12% 41% 36% 5%	540
July	1st to 10th	Night	8% 1 5% 29% 46% 12%	525
	11th to 20th	Night	7% 2 7% 27% 48% 9%	522
	21st to end	Night	6% 1 9% 31% 43% 9%	591
August	1st to 10th	Night	6% 2 5% 32% 47% 9%	537
	11th to 20th	Night	9% 1 7% 34% 43% 6%	534
	21st to end	Night	9% 1 4 29% 48% 10%	594
September	1st to 10th	Night	11% 1 7% 32% 42% 6%	540
	11th to 20th	Night	9% 1 7% 31% 44% 8%	637
	21st to end	Night	11% 3 14% 35% 31% 6%	720
October	1st to 10th	Night	10% 3 16% 35% 31% 6%	720
	11th to 20th	Night	16% 4 24% 35% 19% 2	720
	21st to end	Night	23% 6% 23% 33% 13% 2	792
November	1st to 10th	Night	15% 5% 25% 38% 17% 1	740
	11th to 20th	Night	17% 6% 31% 32% 13%	760
	21st to end	Night	21% 7% 27% 31% 12% 1	760
December	1st to 10th	Night	24% 8% 29% 31% 8% 1	764
	11th to 20th	Night	23% 5% 29% 34% 8%	950
	21st to end	Night	28% 9% 29% 30% 5%	1045

Page generated at 2024-01-10 00:24:59. Version ac07

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