Northwest Nebraska Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Northwest Nebraska Star Party clear sky chart from 2005-11-06 to 2026-01-02.

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	7% 5% 2 5% 3 3 4 4 6% 8% 53%	136102
	Night	6% 6% 2 6% 4 4 4 4 6% 7% 51%	132720
Transparency	Day	29% 5% 12% 28% 21% 6%	130925
	Night	31% 5% 13% 27% 19% 5%	128904
Seeing	Day	12% 12% 30% 29% 14% 3	17398
	Night	10% 11% 36% 33% 9% 1	27445

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 7% 4 9% 6% 5% 5% 4 6% 7% 46%	3646
	11th to 20th	Day	3 9% 4 8% 6% 5% 6% 5% 7% 8% 41%	3640
	21st to end	Day	2 4 2 7% 3 3 4 4 5% 6% 61%	4117
February	1st to 10th	Day	5% 11% 4 8% 5% 5% 5% 5% 5% 7% 41%	1800
	11th to 20th	Day	4 9% 4 8% 6% 4 4 4 5% 8% 45%	1934
	21st to end	Day	3 9% 4 6% 3 3 3 3 5% 7% 53%	1650
March	1st to 10th	Day	6% 11% 3 5% 3 3 3 3 4 7% 53%	4500
	11th to 20th	Day	7% 6% 2 3 2 2 3 3 5% 7% 60%	4684
	21st to end	Day	11% 10% 3 7% 4 3 4 3 6% 8% 41%	5969
April	1st to 10th	Day	9% 9% 2 6% 4 5% 3 4 6% 8% 46%	2400
	11th to 20th	Day	12% 8% 2 6% 4 3 4 4 7% 8% 43%	2371
	21st to end	Day	14% 8% 2 5% 3 3 4 4 5% 8% 44%	2505
May	1st to 10th	Day	12% 7% 2 5% 3 4 4 3 5% 7% 49%	5940
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 8% 46%	6298
	21st to end	Day	16% 6% 2 5% 3 3 3 3 5% 7% 48%	6925
June	1st to 10th	Day	7% 4 1 4 3 3 4 4 7% 9% 53%	2800
	11th to 20th	Day	9% 3 1 4 3 4 4 4 6% 9% 53%	2800
	21st to end	Day	6% 3 1 3 3 2 4 4 6% 8% 60%	2800
July	1st to 10th	Day	4 3 1 4 3 3 4 4 6% 9% 58%	6339
	11th to 20th	Day	6% 2 1 3 3 3 4 4 7% 9% 57%	6340
	21st to end	Day	9% 3 1 3 2 3 4 3 6% 9% 56%	6903
August	1st to 10th	Day	7% 4 1 4 3 4 4 3 7% 10% 54%	6232
	11th to 20th	Day	3 3 1 3 3 3 4 4 6% 8% 62%	5380
	21st to end	Day	5% 5% 2 5% 4 4 4 4 6% 8% 52%	5984
September	1st to 10th	Day	6% 4 1 3 3 3 3 3 5% 6% 64%	2400
	11th to 20th	Day	8% 3 1 3 3 3 4 2 4 6% 64%	2318
	21st to end	Day	7% 4 1 3 2 2 2 2 4 6% 65%	2200
October	1st to 10th	Day	6% 3 1 2 1 2 2 2 2 4 73%	3430
	11th to 20th	Day	9% 4 2 4 3 3 3 2 4 5% 61%	3233
	21st to end	Day	8% 7% 2 5% 3 3 3 3 5% 7% 55%	3190
November	1st to 10th	Day	4 6% 2 4 3 3 4 4 6% 9% 54%	1853
	11th to 20th	Day	4 4 2 6% 3 4 4 3 6% 6% 58%	1890
	21st to end	Day	3 8% 3 5% 3 4 4 3 5% 7% 55%	1733
December	1st to 10th	Day	3 4 1 5% 4 4 4 4 4 6% 60%	2700
	11th to 20th	Day	3 4 2 5% 3 4 4 4 7% 9% 57%	3106
	21st to end	Day	3 9% 3 8% 5% 4 4 4 5% 6% 49%	4092
January	1st to 10th	Night	3 9% 4 10% 5% 5% 3 3 5% 7% 47%	6342
	11th to 20th	Night	2 6% 3 8% 5% 5% 4 4 7% 8% 48%	6340
	21st to end	Night	2 3 2 6% 5% 5% 5% 4 4 7% 58%	6905
February	1st to 10th	Night	5% 10% 4 8% 5% 5% 5% 5% 6% 7% 40%	2600
	11th to 20th	Night	4 10% 3 8% 5% 6% 5% 4 6% 6% 42%	2353
	21st to end	Night	4 8% 3 7% 4 4 5% 4 5% 7% 49%	1980
March	1st to 10th	Night	6% 9% 3 6% 4 3 3 3 4 5% 55%	5374
	11th to 20th	Night	5% 7% 2 5% 3 3 4 3 4 7% 56%	5297
	21st to end	Night	10% 10% 3 8% 5% 5% 4 3 6% 8% 37%	4984
April	1st to 10th	Night	11% 8% 2 4 4 3 4 4 5% 7% 47%	2000
	11th to 20th	Night	11% 8% 2 5% 4 3 4 3 5% 7% 46%	1977
	21st to end	Night	15% 8% 2 5% 4 4 4 4 5% 7% 41%	1895
May	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 6% 48%	4036
	11th to 20th	Night	12% 5% 1 4 3 4 5% 4 6% 8% 48%	3617
	21st to end	Night	17% 5% 2 4 3 4 4 4 6% 8% 43%	3972
June	1st to 10th	Night	7% 4 2 4 3 5% 4 4 6% 10% 50%	1600
	11th to 20th	Night	9% 3 1 4 3 4 3 4 8% 9% 51%	1600
	21st to end	Night	6% 3 1 4 4 3 4 5% 6% 9% 55%	1600
July	1st to 10th	Night	4 3 1 5% 5% 5% 5% 4 6% 7% 53%	3640
	11th to 20th	Night	8% 3 1 4 4 5% 5% 5% 7% 11% 48%	3640
	21st to end	Night	5% 4 2 5% 5% 5% 5% 5% 7% 9% 49%	3970
August	1st to 10th	Night	8% 3 1 5% 4 5% 6% 5% 7% 10% 47%	3580
	11th to 20th	Night	3 4 2 6% 4 4 5% 4 7% 9% 52%	4464
	21st to end	Night	6% 7% 2 6% 5% 5% 5% 4 7% 8% 46%	4993
September	1st to 10th	Night	7% 4 2 4 3 3 3 3 4 7% 61%	2000
	11th to 20th	Night	7% 4 2 4 3 4 3 3 6% 6% 59%	2081
	21st to end	Night	10% 4 1 4 2 3 2 2 5% 5% 62%	2200
October	1st to 10th	Night	7% 3 1 3 2 2 2 1 3 4 73%	3752
	11th to 20th	Night	7% 5% 2 4 3 2 3 3 4 8% 58%	3898
	21st to end	Night	8% 5% 2 5% 2 3 4 4 6% 8% 54%	4594
November	1st to 10th	Night	7% 5% 2 5% 3 4 4 3 6% 7% 54%	2665
	11th to 20th	Night	4 5% 2 6% 5% 5% 4 4 6% 7% 53%	2730
	21st to end	Night	4 7% 3 5% 3 4 4 3 5% 8% 54%	2882
December	1st to 10th	Night	2 4 1 5% 3 3 5% 4 5% 8% 59%	4710
	11th to 20th	Night	3 5% 2 5% 5% 5% 6% 4 6% 8% 52%	5321
	21st to end	Night	4 9% 3 9% 5% 4 4 4 6% 7% 45%	7128

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	37% 4 13% 30% 15% 1	3647
	11th to 20th	Day	39% 4 16% 24% 15% 2	3640
	21st to end	Day	25% 4 15% 31% 19% 7%	4117
February	1st to 10th	Day	41% 7% 14% 21% 14% 3	1800
	11th to 20th	Day	38% 5% 15% 23% 14% 5%	1944
	21st to end	Day	31% 5% 16% 27% 17% 4	1650
March	1st to 10th	Day	31% 3 7% 30% 25% 4	4500
	11th to 20th	Day	25% 4 13% 30% 26% 2	4684
	21st to end	Day	40% 6% 15% 28% 10% 1	5969
April	1st to 10th	Day	36% 6% 15% 26% 13% 4	2400
	11th to 20th	Day	38% 7% 12% 21% 19% 3	2374
	21st to end	Day	37% 6% 14% 29% 14% 1	2505
May	1st to 10th	Day	35% 5% 11% 30% 16% 2	5940
	11th to 20th	Day	33% 6% 13% 27% 18% 3	6302
	21st to end	Day	35% 5% 14% 29% 16% 1	6926
June	1st to 10th	Day	25% 7% 18% 31% 15% 3	2800
	11th to 20th	Day	27% 6% 15% 27% 19% 7%	2800
	21st to end	Day	20% 6% 10% 29% 26% 9%	2800
July	1st to 10th	Day	22% 5% 9% 28% 29% 9%	6271
	11th to 20th	Day	22% 5% 10% 29% 24% 11%	6265
	21st to end	Day	24% 5% 9% 20% 22% 19%	6705
August	1st to 10th	Day	26% 5% 14% 26% 22% 6%	4536
	11th to 20th	Day	22% 7% 12% 25% 26% 8%	3896
	21st to end	Day	22% 4 9% 21% 28% 16%	4311
September	1st to 10th	Day	22% 4 8% 24% 28% 14%	2400
	11th to 20th	Day	22% 4 7% 28% 27% 12%	2318
	21st to end	Day	22% 3 8% 30% 31% 7%	2200
October	1st to 10th	Day	18% 3 8% 16% 36% 18%	3430
	11th to 20th	Day	26% 3 10% 32% 23% 5%	3233
	21st to end	Day	30% 3 12% 33% 18% 5%	3190
November	1st to 10th	Day	26% 6% 15% 27% 20% 6%	1853
	11th to 20th	Day	25% 6% 12% 31% 23% 4	1890
	21st to end	Day	28% 5% 14% 30% 21% 3	1733
December	1st to 10th	Day	25% 4 18% 31% 20% 2	2700
	11th to 20th	Day	24% 4 16% 37% 17% 1	3104
	21st to end	Day	34% 4 10% 35% 16% 1	4092
January	1st to 10th	Night	38% 4 11% 31% 13% 2	6342
	11th to 20th	Night	32% 4 19% 24% 17% 3	6340
	21st to end	Night	26% 4 17% 32% 18% 3	6905
February	1st to 10th	Night	40% 7% 15% 23% 12% 3	2600
	11th to 20th	Night	41% 6% 14% 22% 13% 4	2353
	21st to end	Night	34% 4 12% 27% 17% 5%	1980
March	1st to 10th	Night	33% 3 8% 25% 24% 7%	5374
	11th to 20th	Night	29% 3 14% 24% 28% 2	5297
	21st to end	Night	45% 6% 15% 22% 11% 1	4984
April	1st to 10th	Night	36% 5% 14% 25% 17% 3	2000
	11th to 20th	Night	37% 6% 12% 24% 17% 4	1977
	21st to end	Night	41% 6% 12% 27% 14% 1	1895
May	1st to 10th	Night	36% 5% 12% 29% 17% 1	4036
	11th to 20th	Night	31% 7% 13% 32% 14% 3	3618
	21st to end	Night	38% 7% 15% 25% 13% 2	3972
June	1st to 10th	Night	28% 8% 23% 25% 13% 3	1600
	11th to 20th	Night	26% 8% 19% 27% 14% 7%	1600
	21st to end	Night	23% 7% 12% 30% 21% 6%	1600
July	1st to 10th	Night	28% 5% 10% 25% 24% 8%	3600
	11th to 20th	Night	29% 5% 14% 30% 17% 6%	3592
	21st to end	Night	30% 5% 13% 22% 21% 9%	3856
August	1st to 10th	Night	32% 6% 16% 22% 19% 5%	2600
	11th to 20th	Night	30% 7% 14% 22% 21% 6%	3224
	21st to end	Night	24% 5% 12% 22% 25% 12%	3597
September	1st to 10th	Night	24% 4 7% 26% 28% 11%	2000
	11th to 20th	Night	25% 5% 9% 27% 23% 11%	2081
	21st to end	Night	25% 4 6% 29% 25% 12%	2200
October	1st to 10th	Night	18% 2 7% 19% 31% 22%	3752
	11th to 20th	Night	26% 4 11% 32% 22% 5%	3898
	21st to end	Night	28% 4 11% 30% 19% 8%	4594
November	1st to 10th	Night	28% 4 13% 27% 22% 6%	2665
	11th to 20th	Night	29% 5% 11% 29% 21% 5%	2730
	21st to end	Night	28% 5% 12% 29% 22% 4	2882
December	1st to 10th	Night	23% 5% 17% 31% 20% 3	4710
	11th to 20th	Night	29% 4 15% 37% 13% 2	5322
	21st to end	Night	37% 4 10% 35% 12% 2	7128

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	8% 14% 35% 29% 12% 2	303
	11th to 20th	Day	16% 20% 31% 26% 7% 1	300
	21st to end	Day	10% 24% 40% 18% 6% 1	330
February	1st to 10th	Day	14% 21% 42% 20% 3	300
	11th to 20th	Day	7% 22% 47% 19% 5% 1	300
	21st to end	Day	13% 26% 37% 20% 4	249
March	1st to 10th	Day	11% 21% 35% 24% 8% 1	300
	11th to 20th	Day	14% 17% 39% 20% 9% 1	350
	21st to end	Day	21% 18% 33% 21% 6% 1	550
April	1st to 10th	Day	17% 21% 35% 21% 5% 1	500
	11th to 20th	Day	20% 23% 33% 17% 6% 1	492
	21st to end	Day	22% 13% 30% 26% 7% 2	605
May	1st to 10th	Day	18% 14% 28% 24% 13% 3	703
	11th to 20th	Day	21% 9% 25% 27% 15% 3	725
	21st to end	Day	18% 13% 28% 25% 14% 2	789
June	1st to 10th	Day	7% 8% 24% 35% 19% 6%	730
	11th to 20th	Day	10% 10% 35% 32% 11% 2	730
	21st to end	Day	8% 7% 28% 35% 19% 3	730
July	1st to 10th	Day	6% 5% 25% 38% 22% 4	721
	11th to 20th	Day	7% 4 24% 43% 20% 3	718
	21st to end	Day	8% 3 21% 40% 24% 3	794
August	1st to 10th	Day	7% 4 25% 38% 23% 4	726
	11th to 20th	Day	5% 5% 22% 38% 25% 5%	526
	21st to end	Day	5% 7% 27% 33% 21% 7%	583
September	1st to 10th	Day	8% 6% 23% 36% 21% 5%	530
	11th to 20th	Day	10% 6% 23% 31% 23% 6%	448
	21st to end	Day	10% 10% 28% 31% 13% 7%	330
October	1st to 10th	Day	12% 11% 28% 24% 19% 6%	330
	11th to 20th	Day	18% 15% 30% 21% 11% 4	330
	21st to end	Day	13% 16% 34% 23% 12% 3	363
November	1st to 10th	Day	11% 16% 40% 19% 11% 3	330
	11th to 20th	Day	13% 17% 37% 23% 8% 2	330
	21st to end	Day	11% 13% 44% 22% 9% 2	330
December	1st to 10th	Day	14% 19% 40% 22% 5%	330
	11th to 20th	Day	12% 22% 41% 20% 5%	330
	21st to end	Day	12% 22% 37% 22% 6% 1	363
January	1st to 10th	Night	7% 16% 37% 30% 9% 1	1006
	11th to 20th	Night	10% 20% 37% 26% 6% 1	1000
	21st to end	Night	8% 17% 41% 28% 5%	1070
February	1st to 10th	Night	9% 16% 44% 26% 5%	800
	11th to 20th	Night	10% 16% 40% 29% 5%	784
	21st to end	Night	9% 14% 47% 25% 4	660
March	1st to 10th	Night	11% 13% 39% 31% 6%	800
	11th to 20th	Night	11% 10% 38% 32% 6% 1	795
	21st to end	Night	16% 12% 33% 33% 5%	660
April	1st to 10th	Night	18% 12% 36% 30% 4	600
	11th to 20th	Night	16% 16% 35% 30% 4	593
	21st to end	Night	19% 13% 28% 31% 10%	600
May	1st to 10th	Night	18% 11% 29% 30% 12% 1	600
	11th to 20th	Night	18% 7% 31% 31% 12% 1	591
	21st to end	Night	18% 8% 34% 31% 8% 1	650
June	1st to 10th	Night	9% 6% 34% 37% 13% 2	600
	11th to 20th	Night	10% 8% 41% 34% 7%	600
	21st to end	Night	7% 7% 32% 43% 11%	600
July	1st to 10th	Night	6% 5% 26% 43% 17% 1	585
	11th to 20th	Night	5% 4 30% 49% 12% 1	582
	21st to end	Night	5% 4 28% 46% 17%	657
August	1st to 10th	Night	5% 5% 27% 47% 16% 1	597
	11th to 20th	Night	5% 3 27% 51% 13%	594
	21st to end	Night	5% 5% 27% 46% 16%	660
September	1st to 10th	Night	9% 4 26% 44% 16% 1	600
	11th to 20th	Night	8% 7% 34% 36% 14% 1	600
	21st to end	Night	12% 6% 31% 37% 13%	600
October	1st to 10th	Night	15% 9% 29% 33% 14% 1	697
	11th to 20th	Night	12% 9% 30% 39% 9%	800
	21st to end	Night	11% 11% 36% 31% 9% 1	1084
November	1st to 10th	Night	10% 11% 39% 31% 8% 1	1025
	11th to 20th	Night	9% 15% 42% 28% 6% 1	1050
	21st to end	Night	8% 13% 40% 33% 6%	1050
December	1st to 10th	Night	8% 15% 46% 26% 5%	1050
	11th to 20th	Night	9% 12% 41% 33% 4	1050
	21st to end	Night	12% 17% 41% 26% 4	1155

Page generated at 2025-12-29 23:14:07. Version ac07

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