High Plains Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Plains Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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	5% 5% 2 4 4 3 5% 5% 6% 8% 53%	74788
	Night	5% 6% 2 4 4 2 4 4 5% 8% 56%	74990
Transparency	Day	29% 3 9% 25% 24% 10%	74493
	Night	28% 3 9% 26% 25% 9%	74807
Seeing	Day	8% 6% 20% 33% 24% 10%	14456
	Night	7% 3 23% 47% 18% 2	24612

By Month

Percentage Cloud Cover SW (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	2 6% 2 4 4 2 3 3 5% 9% 60%	1518
	11th to 20th	Day	2 7% 4 5% 4 3 3 3 4 6% 59%	1484
	21st to end	Day	2 7% 4 5% 5% 3 4 5% 5% 8% 54%	1782
February	1st to 10th	Day	3 7% 4 6% 3 2 5% 5% 6% 7% 52%	1620
	11th to 20th	Day	1 5% 3 5% 5% 3 5% 4 6% 8% 57%	1727
	21st to end	Day	3 6% 3 5% 5% 2 4 4 5% 7% 55%	1480
March	1st to 10th	Day	4 5% 2 5% 5% 3 5% 3 6% 9% 53%	1800
	11th to 20th	Day	6% 6% 2 5% 4 3 5% 5% 6% 7% 51%	1940
	21st to end	Day	7% 5% 3 5% 4 4 4 5% 7% 9% 47%	2318
April	1st to 10th	Day	7% 6% 2 4 4 2 4 4 6% 8% 53%	2160
	11th to 20th	Day	10% 8% 2 5% 5% 4 4 4 5% 7% 46%	2131
	21st to end	Day	9% 7% 3 4 5% 4 4 5% 6% 8% 44%	2160
May	1st to 10th	Day	12% 6% 2 5% 5% 3 6% 5% 6% 9% 40%	2291
	11th to 20th	Day	13% 8% 2 4 5% 3 5% 5% 7% 10% 37%	2474
	21st to end	Day	7% 5% 2 4 4 4 7% 6% 8% 10% 44%	2724
June	1st to 10th	Day	5% 4 2 4 4 3 5% 6% 8% 10% 49%	2520
	11th to 20th	Day	6% 3 2 4 4 3 6% 6% 7% 9% 51%	2520
	21st to end	Day	3 3 1 4 4 3 5% 6% 9% 10% 51%	2520
July	1st to 10th	Day	6% 4 1 4 4 3 5% 6% 8% 10% 48%	2520
	11th to 20th	Day	3 3 2 3 4 3 6% 6% 8% 10% 53%	2520
	21st to end	Day	5% 3 2 5% 5% 4 5% 6% 9% 10% 46%	2725
August	1st to 10th	Day	4 4 2 5% 5% 4 7% 8% 8% 11% 43%	2328
	11th to 20th	Day	3 3 1 4 3 2 5% 7% 6% 11% 55%	2127
	21st to end	Day	3 3 1 4 5% 3 5% 6% 7% 10% 52%	2376
September	1st to 10th	Day	5% 3 2 3 4 2 3 4 5% 8% 61%	2160
	11th to 20th	Day	5% 3 1 3 4 3 4 4 5% 7% 60%	2134
	21st to end	Day	6% 5% 1 3 3 2 3 3 3 6% 64%	1980
October	1st to 10th	Day	7% 5% 2 4 4 2 3 4 5% 5% 60%	1823
	11th to 20th	Day	4 4 1 4 3 2 3 3 5% 5% 66%	1800
	21st to end	Day	5% 7% 2 4 3 2 3 3 3 6% 63%	1897
November	1st to 10th	Day	2 4 1 3 3 2 4 4 5% 9% 63%	1673
	11th to 20th	Day	2 6% 3 3 3 2 4 4 4 7% 62%	1710
	21st to end	Day	4 5% 3 4 4 2 4 3 6% 7% 59%	1606
December	1st to 10th	Day	2 5% 2 6% 4 3 3 4 6% 9% 57%	1520
	11th to 20th	Day	3 5% 2 4 4 3 4 4 5% 8% 59%	1926
	21st to end	Day	5% 8% 4 6% 5% 3 4 4 5% 6% 50%	2794
January	1st to 10th	Night	2 6% 3 5% 4 2 3 3 4 7% 61%	2647
	11th to 20th	Night	2 5% 3 6% 4 2 4 3 4 7% 60%	2571
	21st to end	Night	3 8% 4 5% 5% 2 4 3 4 7% 54%	2574
February	1st to 10th	Night	2 9% 4 6% 3 3 4 4 4 7% 55%	2340
	11th to 20th	Night	2 8% 4 6% 5% 4 4 4 5% 7% 51%	2120
	21st to end	Night	3 10% 3 6% 4 3 3 3 5% 6% 53%	1776
March	1st to 10th	Night	3 6% 3 4 5% 3 4 4 5% 8% 54%	2160
	11th to 20th	Night	6% 7% 2 4 3 2 4 4 4 7% 57%	2016
	21st to end	Night	7% 7% 3 5% 4 2 3 4 4 9% 51%	2036
April	1st to 10th	Night	6% 7% 3 4 4 3 5% 4 5% 5% 55%	1800
	11th to 20th	Night	11% 6% 3 5% 5% 2 3 5% 5% 7% 48%	1777
	21st to end	Night	13% 8% 3 4 5% 2 4 4 5% 8% 45%	1800
May	1st to 10th	Night	11% 7% 3 5% 5% 4 4 5% 5% 7% 44%	1666
	11th to 20th	Night	15% 6% 2 5% 5% 3 3 4 6% 7% 44%	1417
	21st to end	Night	8% 5% 1 4 5% 2 4 4 6% 9% 52%	1552
June	1st to 10th	Night	6% 3 3 4 3 4 4 7% 10% 56%	1440
	11th to 20th	Night	5% 3 2 4 4 3 4 4 5% 7% 59%	1440
	21st to end	Night	5% 3 1 4 4 3 3 4 6% 9% 58%	1440
July	1st to 10th	Night	6% 4 1 4 4 3 4 5% 6% 11% 51%	1440
	11th to 20th	Night	2 2 1 4 3 3 5% 6% 7% 9% 58%	1440
	21st to end	Night	5% 4 2 4 4 2 6% 6% 7% 11% 50%	1589
August	1st to 10th	Night	4 4 2 5% 5% 3 5% 6% 7% 11% 48%	1611
	11th to 20th	Night	5% 3 2 3 4 3 5% 5% 6% 9% 57%	1773
	21st to end	Night	3 4 2 4 3 3 4 5% 6% 9% 56%	1980
September	1st to 10th	Night	6% 3 1 3 4 3 4 5% 6% 8% 57%	1800
	11th to 20th	Night	7% 2 1 3 3 2 3 5% 5% 7% 62%	1825
	21st to end	Night	6% 3 2 3 3 2 3 3 4 7% 63%	1980
October	1st to 10th	Night	9% 5% 2 3 4 2 2 3 5% 6% 61%	2132
	11th to 20th	Night	4 4 2 4 3 2 3 3 4 6% 65%	2160
	21st to end	Night	7% 7% 3 4 3 2 3 3 3 5% 60%	2439
November	1st to 10th	Night	4 4 2 3 3 2 3 4 5% 6% 65%	2405
	11th to 20th	Night	4 4 2 5% 3 2 3 4 4 6% 62%	2470
	21st to end	Night	4 7% 2 4 4 2 3 3 5% 7% 59%	2570
December	1st to 10th	Night	3 6% 3 5% 3 3 3 4 5% 8% 59%	2660
	11th to 20th	Night	2 6% 2 4 4 2 3 3 6% 10% 57%	3271
	21st to end	Night	6% 10% 3 5% 5% 2 3 4 5% 6% 49%	4873

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	23% 2 11% 34% 24% 6%	1519
	11th to 20th	Day	28% 2 7% 32% 25% 7%	1484
	21st to end	Day	30% 3 6% 34% 21% 7%	1782
February	1st to 10th	Day	31% 3 11% 29% 19% 6%	1620
	11th to 20th	Day	26% 4 7% 31% 27% 6%	1737
	21st to end	Day	30% 2 6% 28% 25% 9%	1480
March	1st to 10th	Day	29% 2 9% 27% 26% 8%	1800
	11th to 20th	Day	32% 4 8% 25% 24% 7%	1940
	21st to end	Day	33% 3 11% 27% 20% 6%	2318
April	1st to 10th	Day	29% 3 10% 25% 23% 10%	2160
	11th to 20th	Day	38% 3 7% 23% 21% 9%	2134
	21st to end	Day	37% 4 7% 27% 22% 3	2160
May	1st to 10th	Day	41% 5% 10% 25% 15% 4	2291
	11th to 20th	Day	41% 4 12% 26% 14% 2	2478
	21st to end	Day	33% 5% 16% 25% 16% 6%	2724
June	1st to 10th	Day	28% 4 15% 25% 19% 9%	2520
	11th to 20th	Day	28% 4 10% 18% 25% 15%	2520
	21st to end	Day	25% 4 8% 25% 26% 12%	2520
July	1st to 10th	Day	29% 5% 9% 23% 22% 12%	2451
	11th to 20th	Day	24% 5% 8% 25% 24% 14%	2445
	21st to end	Day	31% 4 11% 26% 19% 8%	2573
August	1st to 10th	Day	32% 5% 14% 24% 16% 9%	2313
	11th to 20th	Day	23% 4 9% 25% 25% 15%	2127
	21st to end	Day	26% 4 7% 22% 27% 14%	2376
September	1st to 10th	Day	23% 2 6% 23% 25% 21%	2160
	11th to 20th	Day	23% 3 6% 20% 29% 19%	2134
	21st to end	Day	23% 2 4 22% 37% 12%	1980
October	1st to 10th	Day	27% 3 7% 22% 29% 13%	1823
	11th to 20th	Day	22% 2 6% 24% 32% 15%	1800
	21st to end	Day	25% 2 6% 28% 25% 14%	1897
November	1st to 10th	Day	20% 3 8% 27% 28% 14%	1673
	11th to 20th	Day	24% 2 5% 27% 35% 8%	1710
	21st to end	Day	25% 3 6% 23% 32% 11%	1606
December	1st to 10th	Day	26% 3 10% 31% 22% 8%	1520
	11th to 20th	Day	25% 3 7% 28% 33% 5%	1924
	21st to end	Day	37% 1 7% 24% 24% 7%	2794
January	1st to 10th	Night	26% 2 10% 30% 27% 6%	2647
	11th to 20th	Night	26% 3 7% 26% 30% 7%	2571
	21st to end	Night	31% 2 6% 31% 23% 7%	2574
February	1st to 10th	Night	31% 3 10% 29% 23% 6%	2340
	11th to 20th	Night	33% 2 6% 30% 22% 6%	2120
	21st to end	Night	32% 2 4 26% 26% 10%	1776
March	1st to 10th	Night	28% 3 7% 26% 28% 8%	2160
	11th to 20th	Night	28% 2 8% 26% 30% 6%	2016
	21st to end	Night	33% 3 11% 27% 21% 5%	2036
April	1st to 10th	Night	32% 4 9% 24% 22% 10%	1800
	11th to 20th	Night	36% 3 9% 25% 19% 7%	1777
	21st to end	Night	39% 3 7% 27% 20% 5%	1800
May	1st to 10th	Night	39% 6% 13% 24% 15% 4	1666
	11th to 20th	Night	39% 5% 18% 22% 14% 2	1418
	21st to end	Night	30% 4 21% 26% 11% 8%	1552
June	1st to 10th	Night	23% 4 21% 30% 14% 7%	1440
	11th to 20th	Night	26% 3 13% 20% 23% 15%	1440
	21st to end	Night	23% 4 10% 27% 28% 8%	1440
July	1st to 10th	Night	31% 5% 12% 24% 22% 7%	1400
	11th to 20th	Night	22% 4 10% 27% 24% 13%	1392
	21st to end	Night	28% 4 16% 30% 17% 5%	1501
August	1st to 10th	Night	30% 5% 19% 25% 15% 6%	1602
	11th to 20th	Night	25% 4 9% 28% 23% 12%	1773
	21st to end	Night	24% 4 9% 26% 25% 11%	1980
September	1st to 10th	Night	25% 4 9% 21% 22% 19%	1800
	11th to 20th	Night	21% 3 7% 26% 25% 18%	1825
	21st to end	Night	23% 3 6% 22% 34% 12%	1980
October	1st to 10th	Night	26% 2 10% 21% 28% 12%	2132
	11th to 20th	Night	22% 2 8% 23% 29% 16%	2160
	21st to end	Night	28% 2 7% 23% 26% 13%	2439
November	1st to 10th	Night	21% 2 8% 27% 28% 14%	2405
	11th to 20th	Night	25% 2 4 29% 31% 8%	2470
	21st to end	Night	26% 2 8% 24% 32% 9%	2570
December	1st to 10th	Night	26% 2 11% 29% 22% 9%	2660
	11th to 20th	Night	25% 3 7% 30% 32% 4	3272
	21st to end	Night	37% 2 6% 25% 25% 5%	4873

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	6% 7% 17% 42% 19% 9%	270
	11th to 20th	Day	8% 6% 22% 44% 18% 2	249
	21st to end	Day	5% 2 32% 45% 13% 3	264
February	1st to 10th	Day	5% 9% 33% 41% 10% 2	240
	11th to 20th	Day	3 5% 35% 44% 10% 4	240
	21st to end	Day	6% 7% 31% 43% 11% 2	198
March	1st to 10th	Day	6% 6% 28% 36% 20% 4	240
	11th to 20th	Day	11% 11% 27% 32% 15% 4	380
	21st to end	Day	13% 12% 29% 32% 13% 2	462
April	1st to 10th	Day	14% 10% 25% 30% 17% 3	420
	11th to 20th	Day	15% 16% 29% 27% 10% 4	412
	21st to end	Day	14% 12% 27% 26% 16% 5%	420
May	1st to 10th	Day	15% 8% 21% 35% 18% 3	554
	11th to 20th	Day	20% 6% 13% 29% 24% 8%	625
	21st to end	Day	12% 6% 20% 30% 23% 9%	679
June	1st to 10th	Day	7% 5% 14% 29% 28% 17%	630
	11th to 20th	Day	8% 3 21% 35% 25% 8%	630
	21st to end	Day	5% 5% 17% 32% 31% 11%	630
July	1st to 10th	Day	8% 3 10% 24% 37% 17%	621
	11th to 20th	Day	6% 1 12% 28% 36% 18%	618
	21st to end	Day	6% 3 10% 20% 43% 18%	667
August	1st to 10th	Day	6% 3 16% 30% 30% 16%	447
	11th to 20th	Day	3 5% 14% 31% 30% 16%	437
	21st to end	Day	5% 4 15% 26% 32% 18%	495
September	1st to 10th	Day	8% 3 12% 33% 30% 15%	450
	11th to 20th	Day	5% 3 15% 32% 29% 16%	424
	21st to end	Day	6% 3 14% 30% 29% 19%	270
October	1st to 10th	Day	11% 3 16% 26% 22% 21%	270
	11th to 20th	Day	4 7% 17% 36% 29% 7%	270
	21st to end	Day	10% 3 23% 35% 21% 8%	297
November	1st to 10th	Day	6% 3 18% 43% 19% 11%	270
	11th to 20th	Day	7% 6% 22% 40% 19% 6%	270
	21st to end	Day	8% 2 23% 44% 19% 4	270
December	1st to 10th	Day	5% 7% 23% 41% 18% 5%	270
	11th to 20th	Day	5% 4 27% 43% 19% 2	270
	21st to end	Day	7% 5% 29% 42% 13% 4	297
January	1st to 10th	Night	5% 3 28% 47% 14% 3	950
	11th to 20th	Night	4 5% 30% 48% 12% 1	916
	21st to end	Night	6% 1 29% 52% 11% 1	792
February	1st to 10th	Night	7% 2 35% 48% 7%	720
	11th to 20th	Night	5% 4 31% 49% 11%	704
	21st to end	Night	8% 4 33% 49% 6%	592
March	1st to 10th	Night	5% 2 33% 49% 10%	720
	11th to 20th	Night	10% 4 25% 48% 13% 1	720
	21st to end	Night	10% 6% 26% 48% 9%	650
April	1st to 10th	Night	9% 7% 32% 45% 7%	540
	11th to 20th	Night	15% 7% 26% 42% 9%	533
	21st to end	Night	16% 5% 24% 40% 15%	540
May	1st to 10th	Night	14% 5% 21% 42% 17% 1	540
	11th to 20th	Night	18% 3 13% 44% 20% 2	531
	21st to end	Night	9% 5% 19% 42% 24% 1	584
June	1st to 10th	Night	7% 2 14% 45% 28% 4	540
	11th to 20th	Night	6% 3 17% 52% 21% 1	540
	21st to end	Night	4 3 15% 47% 30% 1	540
July	1st to 10th	Night	7% 2 11% 37% 38% 3	525
	11th to 20th	Night	4 2 8% 44% 39% 3	522
	21st to end	Night	6% 2 7% 36% 46% 4	591
August	1st to 10th	Night	8% 2 7% 37% 43% 2	537
	11th to 20th	Night	5% 2 6% 50% 35% 2	534
	21st to end	Night	5% 2 8% 44% 37% 3	594
September	1st to 10th	Night	6% 3 11% 44% 31% 5%	540
	11th to 20th	Night	7% 1 12% 47% 29% 3	540
	21st to end	Night	7% 3 15% 50% 24% 2	540
October	1st to 10th	Night	11% 4 16% 44% 21% 3	692
	11th to 20th	Night	5% 2 21% 52% 19% 2	720
	21st to end	Night	10% 2 21% 49% 14% 2	855
November	1st to 10th	Night	5% 3 24% 51% 15% 2	925
	11th to 20th	Night	6% 5% 27% 51% 10% 1	950
	21st to end	Night	7% 3 26% 47% 16% 1	950
December	1st to 10th	Night	5% 3 32% 49% 11%	950
	11th to 20th	Night	6% 4 31% 47% 11% 1	950
	21st to end	Night	7% 4 31% 48% 9% 1	1045

Page generated at 2024-01-11 11:31:57. Version ac07

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