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Northern Prairie Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Northern Prairie Star Party clear sky chart from 2005-11-06 to 2024-11-06.

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	9% 9% 3 9% 6% 5% 5% 4 6% 8% 36%	105707
	Night	8% 9% 4 9% 6% 5% 5% 4 6% 8% 34%	101922
Transparency	Day	44% 8% 17% 23% 8%	105449
	Night	45% 8% 16% 21% 8% 1	101826
Seeing	Day	12% 7% 25% 31% 18% 6%	15510
	Night	12% 6% 28% 36% 16% 2	24492

By Month

Percentage Cloud Cover NW (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	4 12% 5% 13% 8% 8% 6% 4 5% 7% 27%	2219
	11th to 20th	Day	4 9% 3 9% 8% 6% 7% 6% 11% 9% 28%	2199
	21st to end	Day	7% 11% 4 11% 7% 5% 4 3 6% 7% 35%	2574
February	1st to 10th	Day	8% 15% 5% 12% 7% 5% 6% 4 7% 6% 25%	1520
	11th to 20th	Day	6% 13% 5% 11% 6% 6% 6% 5% 7% 7% 26%	1654
	21st to end	Day	5% 13% 5% 10% 9% 6% 7% 5% 7% 8% 26%	1431
March	1st to 10th	Day	4 11% 5% 13% 8% 6% 6% 5% 6% 10% 26%	3160
	11th to 20th	Day	5% 13% 4 9% 5% 4 4 3 5% 11% 36%	3489
	21st to end	Day	7% 14% 6% 18% 7% 5% 4 3 5% 6% 25%	3825
April	1st to 10th	Day	9% 12% 5% 8% 6% 6% 7% 4 6% 8% 30%	2390
	11th to 20th	Day	13% 12% 4 9% 5% 4 5% 4 6% 7% 31%	2440
	21st to end	Day	14% 11% 3 7% 5% 5% 5% 3 6% 8% 33%	2470
May	1st to 10th	Day	16% 10% 4 10% 6% 5% 5% 4 4 6% 30%	4594
	11th to 20th	Day	12% 11% 3 8% 6% 6% 6% 5% 6% 7% 30%	4694
	21st to end	Day	12% 8% 3 9% 5% 6% 6% 5% 7% 8% 31%	5161
June	1st to 10th	Day	14% 9% 3 8% 5% 5% 6% 5% 6% 7% 31%	2850
	11th to 20th	Day	19% 10% 3 7% 6% 7% 5% 4 7% 7% 24%	2850
	21st to end	Day	11% 6% 2 7% 5% 6% 6% 5% 7% 10% 35%	2850
July	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 4 6% 8% 47%	4740
	11th to 20th	Day	8% 5% 2 5% 4 5% 4 4 7% 8% 47%	4740
	21st to end	Day	10% 6% 2 5% 4 4 5% 4 6% 9% 46%	5138
August	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	4571
	11th to 20th	Day	7% 5% 2 6% 5% 4 5% 5% 7% 10% 44%	4086
	21st to end	Day	10% 5% 2 5% 4 3 5% 5% 7% 10% 45%	4521
September	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 6% 8% 44%	2422
	11th to 20th	Day	14% 8% 3 7% 3 4 4 3 5% 8% 42%	2090
	21st to end	Day	8% 7% 2 6% 4 4 4 4 6% 9% 46%	2090
October	1st to 10th	Day	9% 9% 3 8% 6% 5% 4 4 5% 7% 40%	3244
	11th to 20th	Day	10% 8% 4 7% 5% 5% 5% 4 6% 10% 38%	2951
	21st to end	Day	7% 11% 3 8% 5% 5% 5% 3 6% 8% 40%	3013
November	1st to 10th	Day	9% 15% 5% 10% 6% 6% 5% 4 6% 7% 26%	1528
	11th to 20th	Day	6% 11% 6% 15% 6% 5% 6% 4 4 7% 30%	1419
	21st to end	Day	5% 10% 5% 13% 6% 5% 4 4 6% 8% 32%	1330
December	1st to 10th	Day	5% 13% 4 12% 9% 7% 7% 5% 7% 7% 24%	1330
	11th to 20th	Day	7% 9% 3 14% 7% 6% 6% 5% 8% 10% 25%	1682
	21st to end	Day	4 9% 3 8% 6% 6% 5% 4 5% 7% 43%	2442
January	1st to 10th	Night	4 10% 5% 14% 9% 7% 7% 6% 7% 7% 25%	4726
	11th to 20th	Night	3 8% 3 10% 9% 7% 7% 6% 6% 7% 33%	4699
	21st to end	Night	6% 12% 4 11% 6% 5% 5% 3 6% 8% 33%	5110
February	1st to 10th	Night	6% 11% 4 13% 9% 7% 6% 5% 6% 7% 27%	2660
	11th to 20th	Night	7% 12% 4 10% 7% 7% 6% 4 7% 7% 30%	2412
	21st to end	Night	4 11% 4 10% 8% 6% 6% 5% 7% 9% 30%	2022
March	1st to 10th	Night	4 10% 5% 13% 7% 6% 6% 5% 6% 10% 27%	3714
	11th to 20th	Night	4 9% 3 10% 7% 5% 5% 4 6% 8% 39%	3490
	21st to end	Night	6% 11% 6% 15% 8% 6% 7% 4 7% 8% 22%	3828
April	1st to 10th	Night	6% 11% 3 8% 6% 5% 6% 5% 8% 8% 34%	1787
	11th to 20th	Night	11% 11% 5% 9% 6% 6% 6% 4 6% 6% 28%	1691
	21st to end	Night	13% 10% 3 8% 5% 5% 5% 5% 7% 6% 34%	1710
May	1st to 10th	Night	23% 9% 3 8% 5% 4 5% 3 5% 5% 31%	2366
	11th to 20th	Night	10% 10% 3 9% 6% 6% 6% 5% 7% 8% 28%	2199
	21st to end	Night	12% 10% 2 10% 8% 6% 6% 5% 6% 8% 27%	2414
June	1st to 10th	Night	15% 7% 3 8% 6% 6% 5% 5% 6% 7% 31%	1330
	11th to 20th	Night	17% 9% 3 8% 7% 6% 5% 6% 7% 8% 24%	1330
	21st to end	Night	9% 5% 3 6% 5% 5% 7% 6% 7% 10% 37%	1330
July	1st to 10th	Night	8% 6% 2 7% 5% 5% 5% 5% 8% 8% 41%	2220
	11th to 20th	Night	7% 4 2 6% 5% 5% 6% 5% 7% 11% 42%	2220
	21st to end	Night	11% 5% 2 5% 4 3 4 3 7% 10% 45%	2414
August	1st to 10th	Night	16% 4 2 6% 4 5% 4 4 6% 7% 42%	2358
	11th to 20th	Night	9% 6% 3 6% 5% 5% 6% 4 7% 9% 41%	2751
	21st to end	Night	9% 5% 1 7% 4 5% 5% 5% 6% 9% 44%	3146
September	1st to 10th	Night	11% 5% 2 6% 4 3 4 4 6% 9% 46%	1755
	11th to 20th	Night	13% 7% 2 5% 3 4 4 3 5% 6% 48%	2090
	21st to end	Night	8% 7% 2 6% 4 5% 5% 4 5% 7% 47%	2090
October	1st to 10th	Night	9% 7% 3 8% 4 5% 5% 4 6% 8% 42%	3728
	11th to 20th	Night	9% 7% 3 6% 4 4 5% 4 7% 9% 41%	3962
	21st to end	Night	6% 10% 3 8% 5% 5% 6% 4 6% 9% 38%	4514
November	1st to 10th	Night	12% 16% 6% 8% 6% 5% 4 4 6% 6% 28%	2673
	11th to 20th	Night	7% 12% 4 11% 8% 6% 6% 5% 6% 7% 29%	2759
	21st to end	Night	5% 12% 4 12% 9% 6% 5% 4 6% 8% 30%	2850
December	1st to 10th	Night	7% 13% 4 12% 8% 6% 6% 4 6% 7% 27%	2850
	11th to 20th	Night	6% 11% 5% 14% 7% 6% 6% 6% 7% 8% 25%	3510
	21st to end	Night	3 8% 3 8% 6% 6% 6% 4 6% 8% 44%	5214

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	55% 8% 11% 20% 5%	2219
	11th to 20th	Day	46% 8% 13% 17% 15% 1	2220
	21st to end	Day	48% 8% 18% 21% 6%	2574
February	1st to 10th	Day	58% 5% 14% 15% 8%	1520
	11th to 20th	Day	53% 7% 16% 15% 8%	1663
	21st to end	Day	52% 7% 13% 20% 7%	1431
March	1st to 10th	Day	51% 8% 15% 18% 8%	3160
	11th to 20th	Day	42% 8% 21% 19% 10%	3490
	21st to end	Day	57% 9% 11% 19% 4	3825
April	1st to 10th	Day	50% 9% 14% 18% 8% 1	2390
	11th to 20th	Day	49% 7% 15% 20% 8%	2440
	21st to end	Day	48% 7% 15% 21% 7% 1	2470
May	1st to 10th	Day	53% 7% 11% 23% 5%	4594
	11th to 20th	Day	47% 10% 12% 22% 8% 1	4698
	21st to end	Day	44% 12% 17% 17% 9%	5162
June	1st to 10th	Day	48% 9% 13% 19% 9% 1	2850
	11th to 20th	Day	56% 8% 15% 17% 4 1	2850
	21st to end	Day	40% 12% 20% 20% 7% 1	2850
July	1st to 10th	Day	32% 8% 18% 30% 12% 1	4666
	11th to 20th	Day	32% 8% 18% 29% 12%	4659
	21st to end	Day	34% 8% 21% 26% 10%	4976
August	1st to 10th	Day	38% 8% 18% 33% 3	4553
	11th to 20th	Day	33% 8% 25% 28% 7%	4126
	21st to end	Day	33% 8% 27% 28% 4 1	4520
September	1st to 10th	Day	37% 8% 20% 25% 8% 2	2422
	11th to 20th	Day	40% 7% 17% 29% 7%	2090
	21st to end	Day	34% 9% 19% 27% 8% 2	2090
October	1st to 10th	Day	44% 5% 21% 24% 5%	3244
	11th to 20th	Day	42% 6% 16% 26% 10%	2951
	21st to end	Day	43% 6% 19% 28% 4	3013
November	1st to 10th	Day	56% 7% 15% 15% 6% 1	1528
	11th to 20th	Day	53% 7% 16% 19% 4	1419
	21st to end	Day	50% 9% 18% 18% 6% 1	1330
December	1st to 10th	Day	56% 8% 13% 14% 8% 1	1330
	11th to 20th	Day	49% 10% 18% 17% 6%	1684
	21st to end	Day	40% 5% 10% 29% 14% 2	2442
January	1st to 10th	Night	55% 9% 13% 16% 6% 1	4726
	11th to 20th	Night	48% 7% 14% 18% 12% 1	4740
	21st to end	Night	48% 7% 17% 21% 6%	5110
February	1st to 10th	Night	55% 6% 14% 17% 8% 1	2660
	11th to 20th	Night	50% 7% 14% 17% 11% 1	2413
	21st to end	Night	47% 8% 12% 23% 9% 1	2022
March	1st to 10th	Night	50% 8% 15% 20% 7%	3714
	11th to 20th	Night	40% 8% 20% 20% 11% 1	3490
	21st to end	Night	52% 13% 14% 17% 5%	3828
April	1st to 10th	Night	43% 8% 16% 20% 13% 1	1787
	11th to 20th	Night	52% 8% 12% 18% 8% 3	1691
	21st to end	Night	45% 8% 14% 20% 11% 2	1710
May	1st to 10th	Night	53% 7% 9% 23% 7% 1	2366
	11th to 20th	Night	45% 12% 13% 19% 10% 1	2199
	21st to end	Night	48% 13% 13% 17% 8% 1	2414
June	1st to 10th	Night	47% 9% 12% 21% 8% 1	1330
	11th to 20th	Night	55% 12% 12% 15% 6%	1330
	21st to end	Night	38% 12% 21% 22% 6% 1	1330
July	1st to 10th	Night	37% 8% 19% 19% 17% 1	2185
	11th to 20th	Night	34% 9% 16% 29% 11% 1	2178
	21st to end	Night	33% 8% 23% 28% 8%	2337
August	1st to 10th	Night	38% 8% 20% 32% 2	2351
	11th to 20th	Night	37% 7% 23% 25% 8%	2777
	21st to end	Night	35% 7% 22% 31% 6%	3146
September	1st to 10th	Night	33% 9% 20% 24% 11% 3	1755
	11th to 20th	Night	36% 7% 18% 28% 9% 2	2090
	21st to end	Night	34% 9% 15% 26% 13% 3	2090
October	1st to 10th	Night	39% 5% 21% 27% 7%	3728
	11th to 20th	Night	37% 6% 15% 34% 8%	3962
	21st to end	Night	43% 6% 22% 25% 5%	4514
November	1st to 10th	Night	55% 7% 12% 19% 7% 1	2673
	11th to 20th	Night	54% 8% 14% 17% 6% 1	2759
	21st to end	Night	52% 8% 16% 18% 6% 1	2850
December	1st to 10th	Night	55% 7% 13% 16% 8% 1	2850
	11th to 20th	Night	55% 9% 16% 13% 7%	3507
	21st to end	Night	37% 7% 16% 20% 17% 3	5214

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	9% 5% 27% 37% 17% 4	180
	11th to 20th	Day	11% 9% 23% 36% 18% 3	180
	21st to end	Day	9% 8% 31% 32% 16% 5%	198
February	1st to 10th	Day	11% 9% 29% 37% 12% 2	180
	11th to 20th	Day	10% 7% 30% 34% 15% 4	265
	21st to end	Day	7% 7% 28% 33% 17% 7%	243
March	1st to 10th	Day	9% 9% 28% 34% 17% 2	460
	11th to 20th	Day	8% 6% 32% 32% 16% 6%	460
	21st to end	Day	12% 6% 28% 30% 20% 4	506
April	1st to 10th	Day	10% 12% 30% 33% 12% 4	460
	11th to 20th	Day	16% 9% 22% 32% 18% 4	452
	21st to end	Day	18% 10% 26% 30% 13% 3	460
May	1st to 10th	Day	15% 9% 22% 33% 17% 5%	639
	11th to 20th	Day	10% 6% 25% 33% 19% 7%	675
	21st to end	Day	16% 6% 23% 26% 20% 9%	734
June	1st to 10th	Day	16% 10% 25% 31% 14% 3	680
	11th to 20th	Day	20% 7% 26% 23% 17% 7%	680
	21st to end	Day	11% 5% 21% 31% 23% 10%	680
July	1st to 10th	Day	11% 3 16% 35% 27% 9%	671
	11th to 20th	Day	12% 3 19% 32% 25% 9%	668
	21st to end	Day	10% 5% 18% 31% 26% 10%	739
August	1st to 10th	Day	11% 5% 17% 30% 24% 12%	592
	11th to 20th	Day	9% 5% 22% 32% 24% 8%	477
	21st to end	Day	12% 7% 19% 30% 23% 9%	539
September	1st to 10th	Day	12% 9% 26% 29% 17% 6%	490
	11th to 20th	Day	18% 6% 25% 31% 16% 4	490
	21st to end	Day	14% 13% 28% 28% 14% 3	490
October	1st to 10th	Day	16% 9% 28% 28% 16% 5%	348
	11th to 20th	Day	12% 9% 32% 30% 15% 2	300
	21st to end	Day	12% 11% 37% 24% 12% 4	330
November	1st to 10th	Day	20% 6% 29% 30% 12% 2	285
	11th to 20th	Day	11% 10% 35% 33% 9% 1	221
	21st to end	Day	7% 9% 36% 33% 11% 4	180
December	1st to 10th	Day	8% 10% 31% 31% 15% 6%	180
	11th to 20th	Day	8% 8% 31% 35% 17% 1	180
	21st to end	Day	8% 6% 24% 41% 17% 5%	198
January	1st to 10th	Night	11% 7% 32% 36% 13% 2	950
	11th to 20th	Night	9% 8% 33% 36% 12% 2	950
	21st to end	Night	13% 9% 32% 33% 10% 2	980
February	1st to 10th	Night	8% 9% 26% 36% 18% 2	760
	11th to 20th	Night	10% 6% 32% 35% 16% 1	744
	21st to end	Night	7% 5% 26% 37% 20% 5%	628
March	1st to 10th	Night	9% 5% 28% 40% 16% 2	760
	11th to 20th	Night	10% 4 32% 36% 15% 3	760
	21st to end	Night	13% 6% 26% 37% 16% 3	836
April	1st to 10th	Night	8% 8% 28% 33% 19% 3	637
	11th to 20th	Night	14% 6% 30% 36% 13% 1	563
	21st to end	Night	16% 6% 24% 38% 15% 1	570
May	1st to 10th	Night	16% 7% 23% 35% 18% 2	461
	11th to 20th	Night	11% 5% 23% 39% 20% 2	374
	21st to end	Night	18% 5% 22% 34% 19% 2	411
June	1st to 10th	Night	16% 8% 23% 36% 15% 2	380
	11th to 20th	Night	18% 6% 24% 31% 19% 2	380
	21st to end	Night	12% 4 18% 37% 24% 4	380
July	1st to 10th	Night	11% 3 17% 42% 26% 1	370
	11th to 20th	Night	11% 4 18% 47% 19% 2	368
	21st to end	Night	10% 4 18% 38% 27% 3	416
August	1st to 10th	Night	12% 2 17% 35% 29% 4	378
	11th to 20th	Night	13% 5% 16% 38% 27% 2	528
	21st to end	Night	11% 3 24% 37% 25% 1	627
September	1st to 10th	Night	13% 3 20% 38% 24% 2	572
	11th to 20th	Night	16% 4 21% 40% 18% 1	760
	21st to end	Night	11% 5% 31% 38% 14% 1	760
October	1st to 10th	Night	16% 4 27% 37% 16% 1	760
	11th to 20th	Night	13% 5% 31% 36% 14% 1	760
	21st to end	Night	14% 6% 36% 33% 12%	869
November	1st to 10th	Night	19% 7% 31% 33% 9% 1	955
	11th to 20th	Night	14% 7% 35% 30% 11% 3	950
	21st to end	Night	9% 5% 39% 34% 11% 1	950
December	1st to 10th	Night	13% 8% 33% 29% 14% 3	950
	11th to 20th	Night	11% 7% 34% 35% 12% 1	950
	21st to end	Night	9% 4 31% 38% 15% 3	1045

Page generated at 2024-11-03 11:18:59. Version ac07

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