Prairie Skies Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prairie Skies Star Party 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	14% 8% 4 6% 6% 3 5% 5% 5% 7% 37%	74815
	Night	15% 9% 4 6% 5% 3 4 4 5% 7% 39%	74966
Transparency	Day	46% 7% 13% 21% 12% 2	74516
	Night	45% 6% 12% 21% 14% 2	74786
Seeing	Day	17% 9% 28% 25% 15% 6%	14589
	Night	18% 9% 30% 30% 12% 1	24566

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	15% 13% 6% 8% 8% 3 5% 5% 4 6% 28%	1517
	11th to 20th	Day	14% 19% 6% 12% 6% 4 5% 3 4 6% 22%	1464
	21st to end	Day	15% 15% 8% 10% 7% 3 3 4 4 6% 23%	1645
February	1st to 10th	Day	20% 12% 5% 8% 7% 4 5% 5% 5% 5% 25%	1683
	11th to 20th	Day	16% 10% 5% 8% 8% 4 4 3 5% 6% 32%	1748
	21st to end	Day	18% 13% 6% 8% 5% 3 4 4 4 6% 29%	1480
March	1st to 10th	Day	17% 14% 5% 7% 5% 3 5% 4 5% 6% 29%	1800
	11th to 20th	Day	14% 10% 3 7% 6% 3 6% 5% 6% 8% 32%	1850
	21st to end	Day	21% 12% 5% 8% 6% 3 5% 4 5% 6% 25%	2376
April	1st to 10th	Day	17% 11% 3 7% 6% 3 4 4 4 8% 33%	2160
	11th to 20th	Day	17% 9% 3 6% 6% 3 4 5% 4 7% 37%	2134
	21st to end	Day	20% 7% 3 7% 6% 3 5% 5% 5% 7% 33%	2248
May	1st to 10th	Day	19% 9% 3 7% 6% 4 5% 5% 7% 8% 30%	2340
	11th to 20th	Day	19% 7% 3 6% 6% 3 5% 5% 5% 7% 35%	2381
	21st to end	Day	13% 5% 3 7% 5% 4 5% 5% 6% 8% 38%	2725
June	1st to 10th	Day	10% 4 2 5% 5% 3 5% 5% 6% 8% 45%	2520
	11th to 20th	Day	10% 4 2 4 6% 4 5% 5% 7% 8% 45%	2520
	21st to end	Day	11% 5% 3 6% 5% 4 6% 6% 7% 8% 39%	2520
July	1st to 10th	Day	8% 4 2 5% 5% 3 5% 6% 6% 10% 45%	2520
	11th to 20th	Day	10% 4 1 4 4 3 5% 6% 7% 10% 46%	2520
	21st to end	Day	7% 4 2 5% 6% 3 6% 7% 7% 10% 44%	2743
August	1st to 10th	Day	8% 4 2 5% 5% 3 6% 6% 7% 10% 45%	2427
	11th to 20th	Day	9% 5% 2 5% 5% 3 5% 6% 6% 9% 46%	2125
	21st to end	Day	8% 4 2 5% 4 3 5% 5% 7% 9% 49%	2376
September	1st to 10th	Day	11% 6% 2 5% 4 3 5% 5% 6% 8% 45%	2160
	11th to 20th	Day	13% 4 2 3 3 3 4 5% 5% 7% 51%	2039
	21st to end	Day	9% 6% 3 5% 4 4 5% 5% 6% 9% 46%	1980
October	1st to 10th	Day	12% 7% 2 6% 5% 2 4 5% 5% 6% 45%	1948
	11th to 20th	Day	20% 6% 3 5% 6% 4 4 5% 5% 7% 37%	1794
	21st to end	Day	21% 8% 3 6% 5% 3 4 4 5% 6% 34%	1782
November	1st to 10th	Day	13% 8% 2 4 4 2 4 4 5% 7% 47%	1672
	11th to 20th	Day	17% 9% 5% 6% 6% 3 4 4 5% 6% 35%	1710
	21st to end	Day	18% 10% 4 7% 5% 3 4 4 4 5% 36%	1687
December	1st to 10th	Day	15% 14% 5% 9% 6% 5% 5% 4 3 5% 30%	1520
	11th to 20th	Day	14% 13% 4 8% 7% 4 5% 4 5% 6% 28%	1918
	21st to end	Day	23% 19% 9% 13% 7% 3 4 3 3 4 14%	2783
January	1st to 10th	Night	15% 14% 4 8% 7% 3 4 4 5% 5% 32%	2648
	11th to 20th	Night	16% 14% 6% 10% 5% 3 4 4 4 5% 27%	2575
	21st to end	Night	15% 14% 7% 9% 7% 3 4 4 4 6% 26%	2709
February	1st to 10th	Night	18% 14% 5% 7% 7% 3 4 4 4 6% 29%	2275
	11th to 20th	Night	15% 10% 4 8% 5% 3 5% 4 5% 7% 34%	2098
	21st to end	Night	20% 11% 5% 7% 5% 3 4 4 4 5% 33%	1776
March	1st to 10th	Night	16% 11% 4 6% 6% 4 5% 4 4 5% 34%	2160
	11th to 20th	Night	14% 7% 3 6% 5% 2 4 4 5% 8% 40%	2125
	21st to end	Night	21% 11% 4 6% 6% 3 4 4 4 6% 31%	1980
April	1st to 10th	Night	14% 7% 3 6% 6% 3 4 4 5% 6% 40%	1800
	11th to 20th	Night	19% 8% 3 5% 5% 3 4 4 4 5% 40%	1775
	21st to end	Night	19% 7% 3 6% 5% 4 5% 5% 6% 6% 36%	1710
May	1st to 10th	Night	17% 7% 3 6% 5% 3 5% 4 6% 9% 36%	1620
	11th to 20th	Night	16% 5% 2 5% 4 3 4 5% 5% 9% 41%	1510
	21st to end	Night	11% 5% 2 5% 6% 4 5% 6% 7% 9% 41%	1551
June	1st to 10th	Night	11% 4 2 4 5% 3 4 4 5% 7% 51%	1440
	11th to 20th	Night	9% 4 3 5% 5% 3 4 4 6% 10% 48%	1440
	21st to end	Night	10% 4 3 5% 5% 3 5% 5% 6% 9% 43%	1440
July	1st to 10th	Night	8% 4 2 4 4 3 4 6% 6% 10% 49%	1440
	11th to 20th	Night	6% 3 1 5% 4 2 5% 5% 5% 8% 56%	1440
	21st to end	Night	4 3 2 4 5% 3 5% 5% 6% 10% 54%	1575
August	1st to 10th	Night	6% 3 2 4 6% 3 5% 5% 6% 10% 51%	1505
	11th to 20th	Night	7% 4 2 4 3 4 4 5% 7% 9% 52%	1776
	21st to end	Night	8% 3 1 4 5% 3 3 4 5% 8% 55%	1980
September	1st to 10th	Night	10% 5% 2 4 4 3 3 4 5% 7% 53%	1800
	11th to 20th	Night	10% 4 2 4 4 2 3 4 6% 8% 55%	1903
	21st to end	Night	9% 5% 2 5% 6% 4 5% 5% 6% 8% 46%	1980
October	1st to 10th	Night	11% 5% 2 5% 5% 2 4 4 4 6% 51%	2009
	11th to 20th	Night	16% 8% 3 5% 4 3 3 3 5% 7% 45%	2164
	21st to end	Night	21% 8% 3 6% 5% 3 3 3 4 6% 39%	2574
November	1st to 10th	Night	12% 7% 3 4 4 3 3 4 5% 6% 48%	2406
	11th to 20th	Night	14% 9% 4 7% 5% 3 4 4 4 6% 38%	2470
	21st to end	Night	19% 9% 4 5% 6% 3 4 3 4 6% 38%	2489
December	1st to 10th	Night	16% 11% 5% 9% 5% 3 4 4 4 7% 32%	2660
	11th to 20th	Night	16% 14% 5% 8% 6% 3 4 3 4 4 33%	3279
	21st to end	Night	24% 17% 7% 11% 7% 4 4 3 4 4 15%	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	58% 5% 12% 15% 10% 1	1518
	11th to 20th	Day	66% 5% 11% 12% 5% 1	1464
	21st to end	Day	62% 6% 11% 14% 7% 1	1645
February	1st to 10th	Day	60% 6% 11% 14% 6% 2	1683
	11th to 20th	Day	54% 5% 11% 21% 8% 2	1758
	21st to end	Day	57% 6% 10% 19% 6% 2	1480
March	1st to 10th	Day	55% 5% 12% 19% 7% 1	1800
	11th to 20th	Day	48% 6% 14% 20% 10% 1	1850
	21st to end	Day	60% 6% 12% 17% 5% 1	2376
April	1st to 10th	Day	50% 6% 12% 19% 13%	2160
	11th to 20th	Day	47% 6% 11% 20% 11% 4	2134
	21st to end	Day	50% 7% 13% 16% 11% 2	2248
May	1st to 10th	Day	51% 7% 13% 21% 8%	2340
	11th to 20th	Day	47% 8% 12% 20% 12% 1	2385
	21st to end	Day	42% 8% 12% 19% 16% 2	2725
June	1st to 10th	Day	35% 8% 14% 24% 17% 2	2520
	11th to 20th	Day	35% 8% 12% 22% 21% 3	2520
	21st to end	Day	40% 10% 14% 21% 14% 2	2520
July	1st to 10th	Day	33% 9% 14% 26% 14% 3	2451
	11th to 20th	Day	32% 8% 18% 25% 15% 2	2445
	21st to end	Day	34% 8% 17% 24% 15% 3	2591
August	1st to 10th	Day	32% 9% 18% 28% 13% 2	2412
	11th to 20th	Day	32% 8% 16% 26% 16% 1	2125
	21st to end	Day	29% 9% 14% 25% 19% 4	2376
September	1st to 10th	Day	36% 7% 14% 23% 16% 4	2160
	11th to 20th	Day	32% 6% 13% 26% 20% 4	2039
	21st to end	Day	34% 6% 11% 27% 20% 2	1980
October	1st to 10th	Day	38% 7% 12% 24% 17% 3	1948
	11th to 20th	Day	46% 6% 11% 22% 14% 1	1794
	21st to end	Day	49% 6% 12% 21% 10% 2	1782
November	1st to 10th	Day	37% 5% 16% 24% 16% 3	1672
	11th to 20th	Day	49% 5% 13% 21% 12% 1	1710
	21st to end	Day	52% 5% 11% 22% 10% 1	1687
December	1st to 10th	Day	57% 6% 12% 18% 7%	1520
	11th to 20th	Day	56% 6% 11% 20% 6% 1	1915
	21st to end	Day	76% 5% 8% 8% 4	2783
January	1st to 10th	Night	54% 6% 10% 18% 11% 1	2648
	11th to 20th	Night	60% 5% 14% 13% 8%	2575
	21st to end	Night	59% 5% 12% 16% 8% 1	2709
February	1st to 10th	Night	57% 5% 12% 16% 8% 2	2275
	11th to 20th	Night	49% 6% 12% 21% 11% 1	2099
	21st to end	Night	53% 6% 9% 19% 10% 3	1776
March	1st to 10th	Night	51% 6% 11% 21% 10% 1	2160
	11th to 20th	Night	42% 6% 13% 20% 15% 3	2125
	21st to end	Night	54% 7% 12% 18% 9% 1	1980
April	1st to 10th	Night	44% 6% 13% 21% 13% 2	1800
	11th to 20th	Night	45% 5% 10% 19% 16% 4	1775
	21st to end	Night	47% 8% 12% 18% 12% 3	1710
May	1st to 10th	Night	46% 7% 13% 23% 12%	1620
	11th to 20th	Night	41% 8% 14% 21% 15% 1	1511
	21st to end	Night	38% 10% 13% 19% 16% 4	1552
June	1st to 10th	Night	32% 7% 12% 25% 20% 4	1440
	11th to 20th	Night	31% 6% 14% 23% 22% 3	1440
	21st to end	Night	36% 10% 15% 22% 14% 4	1440
July	1st to 10th	Night	30% 9% 15% 25% 16% 5%	1400
	11th to 20th	Night	27% 6% 15% 27% 22% 3	1392
	21st to end	Night	25% 7% 18% 27% 18% 5%	1487
August	1st to 10th	Night	28% 7% 19% 28% 17% 1	1496
	11th to 20th	Night	28% 7% 17% 24% 21% 3	1776
	21st to end	Night	28% 6% 13% 26% 22% 5%	1980
September	1st to 10th	Night	30% 7% 12% 25% 21% 5%	1800
	11th to 20th	Night	28% 6% 10% 28% 25% 4	1903
	21st to end	Night	35% 8% 11% 25% 19% 3	1980
October	1st to 10th	Night	33% 7% 10% 25% 22% 3	2009
	11th to 20th	Night	39% 5% 10% 25% 20% 2	2164
	21st to end	Night	49% 3 10% 22% 14% 2	2574
November	1st to 10th	Night	37% 5% 10% 27% 18% 4	2406
	11th to 20th	Night	46% 5% 13% 21% 13% 2	2470
	21st to end	Night	49% 5% 11% 23% 12%	2489
December	1st to 10th	Night	53% 5% 13% 19% 9% 1	2660
	11th to 20th	Night	54% 5% 11% 19% 10% 1	3281
	21st to end	Night	72% 6% 8% 10% 4	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	23% 11% 35% 23% 7% 1	270
	11th to 20th	Day	30% 12% 35% 17% 6%	249
	21st to end	Day	21% 18% 30% 25% 6%	264
February	1st to 10th	Day	27% 17% 40% 13% 3	240
	11th to 20th	Day	26% 13% 37% 20% 5%	240
	21st to end	Day	29% 14% 42% 13% 3	198
March	1st to 10th	Day	22% 23% 35% 19% 2	240
	11th to 20th	Day	24% 17% 33% 19% 6%	266
	21st to end	Day	31% 14% 30% 17% 7% 2	462
April	1st to 10th	Day	21% 14% 32% 23% 8% 1	420
	11th to 20th	Day	20% 16% 31% 18% 12% 3	412
	21st to end	Day	22% 15% 33% 20% 8% 3	420
May	1st to 10th	Day	22% 11% 30% 26% 8% 3	423
	11th to 20th	Day	22% 8% 29% 23% 13% 4	527
	21st to end	Day	14% 8% 30% 23% 16% 9%	679
June	1st to 10th	Day	10% 6% 27% 30% 21% 6%	630
	11th to 20th	Day	11% 4 29% 31% 20% 5%	630
	21st to end	Day	13% 8% 30% 29% 15% 5%	630
July	1st to 10th	Day	9% 3 18% 29% 25% 16%	621
	11th to 20th	Day	9% 4 21% 32% 22% 12%	618
	21st to end	Day	8% 3 22% 34% 25% 8%	684
August	1st to 10th	Day	7% 3 14% 33% 29% 14%	550
	11th to 20th	Day	10% 5% 17% 28% 26% 15%	439
	21st to end	Day	10% 3 17% 32% 27% 12%	495
September	1st to 10th	Day	14% 4 19% 27% 28% 8%	450
	11th to 20th	Day	12% 4 15% 28% 29% 12%	450
	21st to end	Day	12% 7% 26% 25% 21% 8%	450
October	1st to 10th	Day	15% 6% 30% 27% 17% 5%	418
	11th to 20th	Day	19% 21% 31% 22% 7%	270
	21st to end	Day	31% 12% 34% 19% 4	297
November	1st to 10th	Day	14% 12% 35% 23% 11% 4	270
	11th to 20th	Day	24% 14% 35% 16% 10% 1	270
	21st to end	Day	26% 10% 35% 21% 7%	270
December	1st to 10th	Day	17% 18% 38% 19% 8% 1	270
	11th to 20th	Day	20% 15% 35% 24% 6% 1	270
	21st to end	Day	25% 23% 36% 13% 3	297
January	1st to 10th	Night	20% 15% 37% 22% 5%	950
	11th to 20th	Night	23% 15% 35% 22% 4 1	920
	21st to end	Night	22% 13% 35% 27% 4	990
February	1st to 10th	Night	27% 10% 38% 22% 3	835
	11th to 20th	Night	20% 14% 35% 26% 5%	703
	21st to end	Night	24% 14% 39% 20% 4	592
March	1st to 10th	Night	21% 14% 37% 22% 5%	720
	11th to 20th	Night	18% 10% 38% 28% 6% 1	712
	21st to end	Night	27% 10% 33% 23% 6% 1	594
April	1st to 10th	Night	17% 12% 39% 25% 6%	540
	11th to 20th	Night	21% 11% 33% 27% 7% 1	533
	21st to end	Night	22% 9% 34% 28% 7%	540
May	1st to 10th	Night	19% 7% 34% 32% 8%	540
	11th to 20th	Night	18% 5% 31% 34% 11% 1	531
	21st to end	Night	12% 4 28% 36% 19% 1	584
June	1st to 10th	Night	11% 4 24% 46% 14%	540
	11th to 20th	Night	12% 4 26% 44% 14% 1	540
	21st to end	Night	11% 4 26% 41% 17% 1	540
July	1st to 10th	Night	9% 1 14% 43% 28% 5%	525
	11th to 20th	Night	7% 2 17% 43% 28% 2	522
	21st to end	Night	5% 2 17% 47% 29% 1	591
August	1st to 10th	Night	7% 1 10% 47% 32% 3	537
	11th to 20th	Night	7% 3 11% 44% 31% 4	534
	21st to end	Night	9% 1 16% 36% 34% 4	594
September	1st to 10th	Night	11% 4 16% 39% 26% 3	540
	11th to 20th	Night	9% 5% 16% 36% 31% 3	643
	21st to end	Night	10% 6% 24% 34% 23% 3	720
October	1st to 10th	Night	13% 6% 25% 36% 19% 1	720
	11th to 20th	Night	20% 12% 31% 27% 10%	720
	21st to end	Night	25% 12% 32% 24% 7%	792
November	1st to 10th	Night	15% 11% 39% 25% 10% 1	740
	11th to 20th	Night	19% 15% 34% 26% 6%	760
	21st to end	Night	22% 11% 36% 25% 7%	779
December	1st to 10th	Night	22% 14% 36% 24% 5%	950
	11th to 20th	Night	24% 11% 34% 26% 5%	950
	21st to end	Night	28% 14% 34% 22% 2	1045

Page generated at 2024-01-11 12:32:01. Version ac07

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