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 2024-11-12.

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% 54%	105280
	Night	6% 6% 2 6% 4 4 4 4 6% 8% 52%	102622
Transparency	Day	28% 5% 13% 27% 20% 6%	105021
	Night	30% 5% 14% 27% 18% 5%	102471
Seeing	Day	12% 12% 30% 29% 15% 3	15860
	Night	10% 11% 36% 34% 9% 1	25829

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% 3 7% 5% 5% 5% 4 6% 7% 51%	2538
	11th to 20th	Day	3 7% 3 8% 5% 5% 5% 5% 7% 8% 42%	2540
	21st to end	Day	3 5% 2 6% 3 2 3 3 5% 6% 62%	2865
February	1st to 10th	Day	5% 12% 5% 8% 4 5% 6% 4 5% 7% 40%	1710
	11th to 20th	Day	4 9% 3 8% 6% 4 4 4 5% 8% 45%	1834
	21st to end	Day	3 10% 4 6% 4 3 3 3 6% 7% 51%	1570
March	1st to 10th	Day	5% 9% 2 5% 4 3 3 3 5% 8% 53%	3130
	11th to 20th	Day	7% 7% 2 3 3 2 3 3 5% 7% 59%	3272
	21st to end	Day	12% 10% 3 8% 4 3 4 3 6% 8% 40%	4165
April	1st to 10th	Day	9% 9% 2 6% 4 5% 3 4 6% 8% 45%	2280
	11th to 20th	Day	12% 8% 2 6% 5% 3 4 4 6% 8% 42%	2251
	21st to end	Day	13% 8% 2 5% 4 3 4 4 5% 8% 44%	2380
May	1st to 10th	Day	16% 9% 2 6% 4 5% 4 3 4 7% 39%	4147
	11th to 20th	Day	10% 5% 2 4 3 4 4 4 7% 8% 48%	4388
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 8% 46%	4825
June	1st to 10th	Day	6% 4 1 4 3 3 4 4 7% 10% 53%	2660
	11th to 20th	Day	9% 3 2 4 3 3 4 4 7% 8% 52%	2660
	21st to end	Day	5% 2 1 3 3 2 4 5% 6% 8% 61%	2660
July	1st to 10th	Day	4 3 1 3 3 3 3 4 6% 8% 61%	4430
	11th to 20th	Day	4 2 1 3 3 3 4 5% 7% 10% 60%	4430
	21st to end	Day	4 2 1 3 3 3 4 3 7% 10% 62%	4802
August	1st to 10th	Day	9% 4 1 4 3 3 4 3 7% 9% 52%	4411
	11th to 20th	Day	4 3 1 4 3 3 4 5% 7% 8% 56%	3740
	21st to end	Day	3 3 1 4 3 3 4 3 6% 7% 61%	4180
September	1st to 10th	Day	6% 4 1 3 3 3 3 3 5% 6% 63%	2280
	11th to 20th	Day	7% 2 1 3 2 3 3 2 4 6% 66%	2202
	21st to end	Day	8% 4 1 3 3 2 2 2 4 6% 65%	2090
October	1st to 10th	Day	6% 3 1 2 1 2 2 2 2 4 74%	3325
	11th to 20th	Day	9% 4 2 4 3 3 3 2 3 5% 62%	3133
	21st to end	Day	9% 7% 2 5% 3 3 3 3 5% 7% 54%	3091
November	1st to 10th	Day	5% 6% 2 4 3 3 4 4 6% 9% 54%	1763
	11th to 20th	Day	4 5% 2 6% 3 4 4 3 6% 6% 58%	1719
	21st to end	Day	3 8% 3 5% 3 4 3 3 5% 7% 57%	1569
December	1st to 10th	Day	5% 6% 2 6% 4 4 4 4 5% 8% 52%	1520
	11th to 20th	Day	4 5% 2 5% 3 3 3 3 6% 9% 57%	1926
	21st to end	Day	4 11% 4 8% 4 4 4 3 4 5% 49%	2794
January	1st to 10th	Night	2 6% 3 8% 5% 5% 4 3 5% 7% 52%	4417
	11th to 20th	Night	2 6% 3 8% 5% 4 4 4 7% 8% 49%	4430
	21st to end	Night	2 4 2 5% 4 4 5% 4 5% 8% 57%	4832
February	1st to 10th	Night	5% 10% 4 8% 4 5% 4 5% 6% 7% 41%	2470
	11th to 20th	Night	5% 10% 3 8% 5% 6% 5% 4 6% 6% 43%	2233
	21st to end	Night	4 8% 3 8% 4 4 5% 4 5% 7% 48%	1884
March	1st to 10th	Night	5% 8% 3 7% 4 3 4 3 4 6% 52%	3734
	11th to 20th	Night	6% 7% 2 5% 4 4 4 3 4 7% 53%	3696
	21st to end	Night	9% 10% 3 8% 6% 5% 4 3 7% 7% 37%	3477
April	1st to 10th	Night	11% 8% 2 4 4 3 4 4 5% 6% 48%	1900
	11th to 20th	Night	11% 8% 2 5% 4 3 4 4 5% 8% 45%	1877
	21st to end	Night	15% 7% 2 5% 4 4 4 4 5% 8% 41%	1800
May	1st to 10th	Night	14% 9% 2 6% 5% 5% 4 3 6% 6% 41%	2819
	11th to 20th	Night	9% 4 1 4 3 4 4 4 6% 9% 51%	2517
	21st to end	Night	14% 5% 2 4 3 4 5% 4 6% 9% 43%	2762
June	1st to 10th	Night	6% 4 2 4 3 4 4 4 6% 11% 51%	1520
	11th to 20th	Night	9% 3 1 4 3 4 3 4 8% 9% 51%	1520
	21st to end	Night	6% 3 1 3 4 3 4 5% 6% 9% 56%	1520
July	1st to 10th	Night	6% 3 1 5% 5% 5% 5% 3 6% 6% 54%	2540
	11th to 20th	Night	3 3 1 4 4 4 5% 5% 8% 12% 51%	2540
	21st to end	Night	2 2 1 5% 4 5% 5% 4 8% 9% 54%	2761
August	1st to 10th	Night	9% 3 1 5% 5% 5% 5% 5% 7% 9% 46%	2528
	11th to 20th	Night	4 5% 2 6% 4 5% 6% 5% 7% 8% 49%	3094
	21st to end	Night	3 3 1 4 4 4 5% 4 7% 9% 56%	3487
September	1st to 10th	Night	7% 4 2 4 3 3 3 3 4 7% 60%	1900
	11th to 20th	Night	6% 4 2 4 3 3 3 3 6% 6% 61%	1977
	21st to end	Night	10% 4 1 4 2 3 2 2 4 5% 62%	2090
October	1st to 10th	Night	7% 3 1 3 2 2 2 1 3 4 73%	3637
	11th to 20th	Night	7% 5% 1 4 3 2 3 3 4 8% 58%	3778
	21st to end	Night	8% 5% 2 5% 2 3 4 4 6% 8% 54%	4452
November	1st to 10th	Night	7% 5% 2 5% 3 4 4 3 6% 7% 54%	2535
	11th to 20th	Night	5% 5% 2 6% 5% 5% 4 4 6% 7% 52%	2484
	21st to end	Night	5% 7% 3 5% 3 4 4 3 6% 8% 54%	2607
December	1st to 10th	Night	4 7% 2 6% 3 4 5% 4 5% 8% 52%	2660
	11th to 20th	Night	3 6% 2 5% 3 4 4 4 5% 8% 56%	3271
	21st to end	Night	5% 10% 3 8% 4 4 3 3 5% 7% 48%	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	31% 5% 16% 30% 18% 1	2539
	11th to 20th	Day	37% 5% 17% 26% 13% 2	2540
	21st to end	Day	24% 4 20% 35% 13% 5%	2865
February	1st to 10th	Day	42% 7% 14% 21% 13% 3	1710
	11th to 20th	Day	38% 6% 14% 23% 14% 5%	1844
	21st to end	Day	33% 5% 16% 26% 17% 4	1570
March	1st to 10th	Day	28% 4 9% 28% 26% 5%	3130
	11th to 20th	Day	25% 5% 18% 35% 16% 2	3272
	21st to end	Day	42% 6% 16% 28% 7% 1	4165
April	1st to 10th	Day	36% 6% 16% 26% 13% 4	2280
	11th to 20th	Day	39% 7% 13% 21% 17% 3	2254
	21st to end	Day	37% 6% 14% 29% 14% 1	2380
May	1st to 10th	Day	43% 6% 13% 23% 12% 3	4147
	11th to 20th	Day	31% 7% 14% 32% 14% 2	4392
	21st to end	Day	34% 6% 17% 30% 12% 2	4825
June	1st to 10th	Day	24% 8% 19% 31% 14% 4	2660
	11th to 20th	Day	27% 6% 14% 27% 19% 6%	2660
	21st to end	Day	19% 6% 10% 30% 26% 9%	2660
July	1st to 10th	Day	20% 5% 10% 26% 32% 8%	4361
	11th to 20th	Day	18% 5% 10% 28% 25% 13%	4355
	21st to end	Day	17% 4 9% 23% 26% 20%	4651
August	1st to 10th	Day	27% 5% 14% 25% 22% 7%	4396
	11th to 20th	Day	23% 7% 12% 24% 26% 7%	3776
	21st to end	Day	21% 4 9% 20% 28% 17%	4179
September	1st to 10th	Day	22% 4 8% 22% 29% 14%	2280
	11th to 20th	Day	20% 4 8% 28% 28% 13%	2202
	21st to end	Day	22% 3 8% 31% 30% 7%	2090
October	1st to 10th	Day	18% 3 8% 16% 36% 18%	3325
	11th to 20th	Day	26% 4 10% 32% 23% 5%	3133
	21st to end	Day	30% 3 12% 32% 18% 5%	3091
November	1st to 10th	Day	26% 6% 15% 27% 20% 6%	1763
	11th to 20th	Day	26% 6% 12% 31% 22% 4	1719
	21st to end	Day	27% 5% 14% 29% 21% 4	1569
December	1st to 10th	Day	31% 5% 17% 26% 19% 3	1520
	11th to 20th	Day	25% 5% 16% 36% 16% 1	1924
	21st to end	Day	38% 4 10% 30% 17% 2	2794
January	1st to 10th	Night	32% 5% 12% 36% 15% 1	4417
	11th to 20th	Night	31% 5% 22% 25% 14% 3	4430
	21st to end	Night	25% 5% 21% 34% 14% 2	4832
February	1st to 10th	Night	39% 7% 15% 24% 12% 3	2470
	11th to 20th	Night	40% 6% 14% 22% 13% 5%	2233
	21st to end	Night	36% 4 12% 26% 16% 5%	1884
March	1st to 10th	Night	32% 5% 10% 26% 22% 4	3734
	11th to 20th	Night	31% 4 17% 28% 18% 2	3696
	21st to end	Night	44% 8% 16% 24% 8% 1	3477
April	1st to 10th	Night	36% 5% 15% 24% 16% 3	1900
	11th to 20th	Night	38% 6% 12% 24% 15% 3	1877
	21st to end	Night	40% 6% 12% 26% 14% 1	1800
May	1st to 10th	Night	42% 6% 14% 23% 14% 2	2819
	11th to 20th	Night	27% 8% 15% 36% 11% 3	2518
	21st to end	Night	35% 8% 19% 24% 11% 2	2762
June	1st to 10th	Night	28% 8% 24% 25% 12% 3	1520
	11th to 20th	Night	26% 8% 18% 27% 14% 6%	1520
	21st to end	Night	22% 7% 12% 31% 21% 6%	1520
July	1st to 10th	Night	30% 5% 9% 26% 22% 9%	2500
	11th to 20th	Night	23% 5% 16% 27% 21% 8%	2492
	21st to end	Night	24% 6% 12% 25% 22% 11%	2674
August	1st to 10th	Night	32% 6% 16% 22% 19% 5%	2520
	11th to 20th	Night	30% 7% 14% 22% 21% 5%	3124
	21st to end	Night	23% 5% 12% 22% 25% 13%	3487
September	1st to 10th	Night	25% 4 7% 24% 29% 11%	1900
	11th to 20th	Night	23% 5% 9% 28% 24% 11%	1977
	21st to end	Night	26% 4 7% 29% 24% 11%	2090
October	1st to 10th	Night	18% 3 7% 19% 31% 22%	3637
	11th to 20th	Night	26% 4 11% 32% 22% 5%	3778
	21st to end	Night	28% 4 11% 30% 19% 8%	4452
November	1st to 10th	Night	29% 4 13% 27% 22% 5%	2535
	11th to 20th	Night	29% 5% 11% 29% 20% 5%	2484
	21st to end	Night	28% 5% 12% 28% 22% 5%	2607
December	1st to 10th	Night	30% 6% 15% 27% 18% 4	2660
	11th to 20th	Night	26% 5% 17% 35% 14% 2	3272
	21st to end	Night	36% 5% 11% 33% 12% 2	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	9% 14% 34% 29% 12% 2	270
	11th to 20th	Day	15% 19% 31% 27% 7% 1	270
	21st to end	Day	9% 24% 41% 19% 7% 1	297
February	1st to 10th	Day	14% 20% 41% 21% 3	270
	11th to 20th	Day	7% 23% 46% 17% 5% 1	270
	21st to end	Day	12% 26% 36% 21% 4	225
March	1st to 10th	Day	10% 21% 36% 25% 8%	270
	11th to 20th	Day	13% 15% 41% 20% 10% 1	317
	21st to end	Day	20% 16% 34% 22% 6% 1	506
April	1st to 10th	Day	17% 19% 36% 22% 5% 1	460
	11th to 20th	Day	20% 23% 33% 17% 6% 1	452
	21st to end	Day	21% 13% 31% 26% 8% 2	560
May	1st to 10th	Day	18% 15% 28% 24% 13% 2	653
	11th to 20th	Day	21% 8% 25% 27% 16% 4	675
	21st to end	Day	17% 13% 28% 26% 14% 2	734
June	1st to 10th	Day	6% 8% 25% 35% 20% 6%	680
	11th to 20th	Day	10% 10% 35% 32% 11% 3	680
	21st to end	Day	8% 7% 28% 35% 19% 3	680
July	1st to 10th	Day	6% 5% 24% 38% 22% 4	671
	11th to 20th	Day	6% 4 24% 43% 20% 3	668
	21st to end	Day	7% 3 20% 41% 26% 3	739
August	1st to 10th	Day	7% 4 25% 38% 23% 4	676
	11th to 20th	Day	5% 5% 23% 37% 24% 5%	486
	21st to end	Day	5% 7% 27% 33% 22% 7%	539
September	1st to 10th	Day	9% 5% 23% 36% 22% 5%	490
	11th to 20th	Day	9% 7% 23% 31% 24% 6%	412
	21st to end	Day	11% 11% 29% 31% 13% 6%	300
October	1st to 10th	Day	12% 10% 26% 25% 20% 6%	300
	11th to 20th	Day	15% 16% 30% 23% 12% 4	300
	21st to end	Day	13% 15% 35% 23% 12% 2	330
November	1st to 10th	Day	10% 16% 40% 19% 11% 3	300
	11th to 20th	Day	11% 16% 37% 25% 9% 1	273
	21st to end	Day	10% 14% 45% 20% 9% 2	270
December	1st to 10th	Day	12% 17% 41% 24% 5%	270
	11th to 20th	Day	10% 20% 42% 22% 6%	270
	21st to end	Day	13% 21% 36% 25% 5% 1	297
January	1st to 10th	Night	6% 16% 37% 30% 9% 1	950
	11th to 20th	Night	9% 19% 37% 27% 7% 1	950
	21st to end	Night	7% 17% 41% 29% 6%	1017
February	1st to 10th	Night	9% 15% 44% 28% 5%	760
	11th to 20th	Night	10% 15% 40% 30% 6%	744
	21st to end	Night	10% 14% 46% 26% 4	628
March	1st to 10th	Night	11% 13% 39% 31% 5%	760
	11th to 20th	Night	12% 10% 38% 33% 7% 1	755
	21st to end	Night	15% 12% 34% 33% 5%	627
April	1st to 10th	Night	18% 12% 36% 29% 4	570
	11th to 20th	Night	15% 15% 34% 31% 4	563
	21st to end	Night	18% 13% 28% 31% 10%	570
May	1st to 10th	Night	18% 10% 29% 30% 12% 1	570
	11th to 20th	Night	18% 6% 31% 32% 13% 1	561
	21st to end	Night	17% 8% 34% 32% 8% 1	617
June	1st to 10th	Night	8% 6% 34% 37% 13% 2	570
	11th to 20th	Night	10% 8% 42% 33% 6%	570
	21st to end	Night	7% 5% 32% 44% 11%	570
July	1st to 10th	Night	7% 6% 26% 43% 18% 1	555
	11th to 20th	Night	4 4 30% 50% 12% 1	552
	21st to end	Night	4 4 27% 47% 18%	624
August	1st to 10th	Night	5% 4 26% 47% 16% 1	567
	11th to 20th	Night	5% 3 28% 50% 13%	564
	21st to end	Night	4 4 27% 47% 17%	627
September	1st to 10th	Night	9% 4 27% 43% 16% 1	570
	11th to 20th	Night	7% 6% 34% 36% 14% 1	570
	21st to end	Night	12% 6% 32% 36% 13%	570
October	1st to 10th	Night	15% 9% 29% 32% 14% 1	662
	11th to 20th	Night	11% 9% 30% 40% 9%	760
	21st to end	Night	12% 11% 36% 32% 9% 1	1030
November	1st to 10th	Night	10% 10% 39% 31% 8% 1	975
	11th to 20th	Night	8% 14% 43% 28% 6% 1	956
	21st to end	Night	8% 13% 39% 33% 6% 1	950
December	1st to 10th	Night	8% 15% 47% 25% 5%	950
	11th to 20th	Night	8% 12% 40% 35% 5%	950
	21st to end	Night	12% 16% 40% 27% 5%	1045

Page generated at 2024-11-08 20:45:38. Version ac07

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