Nebraska Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nebraska Star Party clear sky chart from 2005-11-06 to 2024-03-28.

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	8% 6% 3 5% 4 3 4 4 5% 7% 51%	78743
	Night	8% 6% 3 5% 5% 3 4 4 5% 7% 50%	81305
Transparency	Day	32% 7% 14% 27% 17% 4	78447
	Night	33% 7% 14% 26% 17% 3	81123
Seeing	Day	11% 9% 31% 32% 15% 3	14904
	Night	11% 8% 38% 35% 8%	25058

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	3 7% 4 10% 7% 3 4 4 4 5% 48%	2538
	11th to 20th	Day	5% 8% 3 6% 6% 5% 5% 8% 6% 9% 40%	2540
	21st to end	Day	4 6% 2 5% 4 3 4 4 5% 7% 55%	2794
February	1st to 10th	Day	7% 11% 5% 7% 7% 4 5% 4 6% 6% 38%	1765
	11th to 20th	Day	6% 9% 4 6% 5% 3 4 4 4 7% 47%	1849
	21st to end	Day	7% 8% 3 5% 5% 3 3 3 4 6% 52%	1570
March	1st to 10th	Day	7% 8% 3 5% 4 2 3 4 5% 6% 53%	1900
	11th to 20th	Day	8% 7% 3 6% 4 3 4 4 5% 7% 48%	2022
	21st to end	Day	12% 10% 4 6% 6% 3 4 5% 6% 7% 37%	2329
April	1st to 10th	Day	13% 8% 3 4 4 3 3 4 6% 7% 46%	2160
	11th to 20th	Day	15% 9% 3 6% 5% 3 4 4 5% 7% 40%	2168
	21st to end	Day	14% 7% 3 4 4 3 4 4 4 7% 46%	2340
May	1st to 10th	Day	13% 6% 3 4 4 3 4 5% 5% 8% 44%	2340
	11th to 20th	Day	16% 6% 2 5% 5% 3 4 4 5% 7% 43%	2302
	21st to end	Day	14% 6% 3 5% 5% 3 4 4 6% 9% 41%	2723
June	1st to 10th	Day	8% 4 2 3 4 2 4 4 5% 10% 53%	2520
	11th to 20th	Day	9% 3 2 4 5% 3 5% 4 5% 9% 52%	2520
	21st to end	Day	5% 3 1 3 3 2 4 5% 6% 9% 60%	2520
July	1st to 10th	Day	5% 3 2 3 5% 3 5% 6% 6% 9% 52%	2520
	11th to 20th	Day	4 2 1 3 3 2 4 5% 6% 8% 62%	2520
	21st to end	Day	6% 3 2 4 4 3 4 5% 6% 8% 54%	2742
August	1st to 10th	Day	7% 5% 2 5% 6% 4 5% 6% 7% 9% 45%	2354
	11th to 20th	Day	5% 4 2 4 3 2 4 4 6% 8% 57%	2301
	21st to end	Day	5% 3 1 4 5% 3 3 4 5% 7% 60%	2384
September	1st to 10th	Day	8% 3 2 4 3 2 3 4 4 6% 62%	2156
	11th to 20th	Day	7% 3 1 3 3 2 3 4 4 7% 63%	1980
	21st to end	Day	9% 4 1 3 3 2 3 3 5% 5% 60%	1980
October	1st to 10th	Day	13% 5% 2 4 3 2 3 4 3 5% 55%	1980
	11th to 20th	Day	9% 6% 2 3 3 2 3 3 4 6% 59%	1758
	21st to end	Day	11% 6% 2 4 4 2 4 3 4 7% 54%	1782
November	1st to 10th	Day	5% 6% 2 5% 3 3 4 5% 5% 7% 55%	1673
	11th to 20th	Day	6% 6% 3 5% 5% 2 4 4 5% 7% 54%	1710
	21st to end	Day	6% 8% 2 5% 4 2 4 3 4 9% 54%	1710
December	1st to 10th	Day	5% 9% 3 5% 4 3 4 4 6% 7% 50%	1573
	11th to 20th	Day	5% 5% 3 6% 4 3 4 4 5% 7% 54%	1926
	21st to end	Day	10% 13% 6% 5% 5% 3 4 4 4 5% 40%	2794
January	1st to 10th	Night	3 10% 4 10% 9% 3 4 4 5% 7% 41%	4417
	11th to 20th	Night	3 8% 5% 9% 5% 3 5% 5% 5% 7% 44%	4430
	21st to end	Night	3 5% 2 6% 6% 3 4 4 6% 9% 52%	4873
February	1st to 10th	Night	10% 10% 4 7% 5% 3 4 4 5% 8% 40%	2428
	11th to 20th	Night	7% 7% 4 7% 6% 3 5% 4 5% 7% 45%	2218
	21st to end	Night	6% 7% 3 6% 4 3 4 4 6% 7% 49%	1884
March	1st to 10th	Night	8% 8% 3 6% 4 2 4 4 5% 7% 50%	2280
	11th to 20th	Night	8% 6% 3 5% 4 3 5% 5% 5% 8% 48%	2157
	21st to end	Night	11% 9% 4 7% 5% 2 5% 5% 5% 9% 37%	2178
April	1st to 10th	Night	12% 7% 3 6% 5% 3 6% 4 6% 9% 40%	1800
	11th to 20th	Night	15% 8% 3 5% 4 3 4 4 6% 5% 45%	1738
	21st to end	Night	14% 7% 1 5% 5% 3 4 4 5% 7% 43%	1620
May	1st to 10th	Night	12% 7% 2 6% 5% 3 4 4 5% 7% 44%	1620
	11th to 20th	Night	15% 7% 2 5% 3 3 5% 4 5% 7% 42%	1593
	21st to end	Night	15% 5% 2 5% 5% 3 5% 5% 8% 9% 40%	1552
June	1st to 10th	Night	10% 5% 1 3 3 2 4 5% 5% 10% 53%	1440
	11th to 20th	Night	12% 3 1 4 4 3 5% 5% 7% 9% 47%	1440
	21st to end	Night	4 3 2 4 5% 3 5% 5% 8% 11% 52%	1440
July	1st to 10th	Night	6% 3 2 4 4 3 4 6% 7% 10% 52%	1440
	11th to 20th	Night	4 2 1 4 4 2 4 4 6% 8% 60%	1440
	21st to end	Night	5% 4 2 5% 5% 4 4 5% 7% 8% 52%	1576
August	1st to 10th	Night	4 3 2 5% 5% 4 5% 6% 8% 8% 50%	1583
	11th to 20th	Night	6% 4 1 3 4 2 4 4 6% 8% 58%	1600
	21st to end	Night	4 4 1 4 4 2 4 5% 4 8% 60%	1969
September	1st to 10th	Night	9% 2 1 4 4 2 4 4 5% 6% 59%	1804
	11th to 20th	Night	8% 3 1 3 3 2 4 3 5% 7% 61%	1980
	21st to end	Night	10% 3 1 4 3 3 3 3 3 6% 60%	1980
October	1st to 10th	Night	13% 5% 2 5% 4 2 4 3 4 6% 52%	1980
	11th to 20th	Night	10% 5% 1 3 3 2 2 3 4 6% 61%	2179
	21st to end	Night	9% 6% 2 5% 4 2 2 4 5% 6% 55%	2574
November	1st to 10th	Night	8% 5% 2 4 4 2 3 4 6% 7% 54%	2405
	11th to 20th	Night	6% 6% 2 5% 5% 3 5% 4 5% 7% 54%	2470
	21st to end	Night	5% 5% 3 5% 4 2 4 4 6% 8% 53%	2470
December	1st to 10th	Night	5% 6% 3 7% 5% 3 4 4 4 7% 51%	2603
	11th to 20th	Night	4 6% 4 5% 4 2 4 4 6% 7% 53%	3271
	21st to end	Night	12% 13% 3 5% 5% 3 3 3 4 6% 43%	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	37% 6% 11% 29% 15% 1	2539
	11th to 20th	Day	38% 10% 17% 21% 11% 2	2540
	21st to end	Day	28% 7% 22% 27% 13% 3	2794
February	1st to 10th	Day	45% 6% 13% 21% 12% 2	1765
	11th to 20th	Day	38% 5% 14% 23% 15% 5%	1859
	21st to end	Day	34% 5% 15% 26% 16% 5%	1570
March	1st to 10th	Day	32% 6% 13% 27% 20% 3	1900
	11th to 20th	Day	34% 6% 14% 26% 17% 2	2022
	21st to end	Day	44% 8% 17% 20% 8% 2	2329
April	1st to 10th	Day	37% 7% 17% 23% 13% 3	2160
	11th to 20th	Day	43% 7% 12% 22% 13% 2	2171
	21st to end	Day	38% 7% 15% 28% 12% 1	2340
May	1st to 10th	Day	37% 7% 16% 27% 12% 1	2340
	11th to 20th	Day	40% 8% 18% 25% 9% 1	2306
	21st to end	Day	39% 9% 16% 22% 12% 2	2723
June	1st to 10th	Day	27% 9% 19% 31% 12% 2	2520
	11th to 20th	Day	29% 8% 16% 27% 16% 4	2520
	21st to end	Day	18% 9% 17% 31% 20% 4	2520
July	1st to 10th	Day	25% 10% 13% 30% 19% 3	2451
	11th to 20th	Day	19% 7% 15% 26% 23% 10%	2445
	21st to end	Day	24% 9% 14% 27% 20% 7%	2590
August	1st to 10th	Day	31% 11% 17% 24% 14% 4	2338
	11th to 20th	Day	25% 7% 13% 33% 19% 4	2301
	21st to end	Day	23% 6% 11% 28% 24% 8%	2384
September	1st to 10th	Day	24% 5% 11% 26% 23% 11%	2156
	11th to 20th	Day	21% 6% 12% 29% 25% 7%	1980
	21st to end	Day	25% 5% 9% 31% 26% 3	1980
October	1st to 10th	Day	32% 5% 10% 22% 27% 4	1980
	11th to 20th	Day	26% 4 12% 31% 20% 6%	1758
	21st to end	Day	32% 5% 13% 27% 18% 6%	1782
November	1st to 10th	Day	28% 5% 17% 24% 21% 5%	1673
	11th to 20th	Day	30% 5% 11% 28% 21% 6%	1710
	21st to end	Day	30% 4 15% 28% 18% 4	1710
December	1st to 10th	Day	33% 6% 14% 27% 17% 3	1573
	11th to 20th	Day	29% 7% 16% 32% 15% 2	1924
	21st to end	Day	45% 7% 9% 27% 10% 2	2794
January	1st to 10th	Night	42% 6% 12% 25% 14% 1	4417
	11th to 20th	Night	38% 7% 16% 25% 13% 1	4430
	21st to end	Night	29% 8% 20% 28% 15% 1	4873
February	1st to 10th	Night	42% 6% 14% 23% 12% 2	2428
	11th to 20th	Night	38% 7% 13% 26% 13% 4	2218
	21st to end	Night	32% 7% 15% 25% 15% 5%	1884
March	1st to 10th	Night	35% 5% 13% 26% 19% 3	2280
	11th to 20th	Night	34% 6% 13% 26% 20% 2	2157
	21st to end	Night	43% 9% 14% 21% 12% 1	2178
April	1st to 10th	Night	39% 8% 15% 20% 15% 3	1800
	11th to 20th	Night	40% 7% 11% 24% 15% 3	1738
	21st to end	Night	39% 8% 13% 26% 13% 1	1620
May	1st to 10th	Night	39% 7% 17% 22% 14% 1	1620
	11th to 20th	Night	40% 9% 14% 27% 9% 1	1594
	21st to end	Night	38% 11% 19% 20% 10% 2	1552
June	1st to 10th	Night	27% 9% 20% 27% 15% 2	1440
	11th to 20th	Night	32% 8% 18% 24% 14% 4	1440
	21st to end	Night	23% 9% 19% 30% 17% 3	1440
July	1st to 10th	Night	25% 8% 18% 30% 17% 3	1400
	11th to 20th	Night	22% 7% 12% 28% 24% 8%	1392
	21st to end	Night	26% 10% 14% 24% 20% 5%	1488
August	1st to 10th	Night	28% 11% 18% 24% 16% 3	1575
	11th to 20th	Night	23% 7% 14% 31% 20% 5%	1600
	21st to end	Night	21% 7% 11% 27% 25% 9%	1969
September	1st to 10th	Night	25% 6% 10% 25% 25% 8%	1804
	11th to 20th	Night	23% 7% 12% 29% 25% 5%	1980
	21st to end	Night	27% 4 8% 28% 27% 5%	1980
October	1st to 10th	Night	34% 6% 10% 24% 23% 3	1980
	11th to 20th	Night	26% 4 12% 28% 22% 7%	2179
	21st to end	Night	31% 5% 12% 24% 21% 7%	2574
November	1st to 10th	Night	28% 6% 14% 24% 22% 6%	2405
	11th to 20th	Night	29% 6% 13% 24% 23% 5%	2470
	21st to end	Night	29% 6% 14% 28% 20% 4	2470
December	1st to 10th	Night	32% 5% 16% 25% 18% 4	2603
	11th to 20th	Night	29% 6% 14% 35% 15% 1	3272
	21st to end	Night	43% 6% 11% 27% 11% 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	6% 14% 34% 31% 12% 3	270
	11th to 20th	Day	11% 18% 33% 29% 9% 1	270
	21st to end	Day	12% 10% 43% 24% 8% 3	297
February	1st to 10th	Day	13% 11% 48% 24% 4	270
	11th to 20th	Day	11% 14% 43% 23% 9%	270
	21st to end	Day	11% 13% 48% 25% 4	225
March	1st to 10th	Day	10% 12% 41% 23% 13% 1	270
	11th to 20th	Day	10% 10% 37% 30% 12% 1	270
	21st to end	Day	18% 12% 37% 21% 10% 2	359
April	1st to 10th	Day	18% 15% 38% 22% 7%	420
	11th to 20th	Day	19% 21% 31% 23% 5% 1	449
	21st to end	Day	19% 11% 29% 30% 10% 1	600
May	1st to 10th	Day	15% 11% 32% 28% 11% 2	603
	11th to 20th	Day	19% 9% 30% 25% 13% 4	625
	21st to end	Day	16% 9% 31% 28% 13% 3	679
June	1st to 10th	Day	7% 5% 28% 32% 20% 8%	630
	11th to 20th	Day	10% 6% 32% 33% 16% 3	630
	21st to end	Day	6% 5% 28% 41% 18% 2	630
July	1st to 10th	Day	5% 3 25% 38% 23% 6%	621
	11th to 20th	Day	5% 4 23% 44% 21% 3	618
	21st to end	Day	7% 2 24% 44% 22% 2	684
August	1st to 10th	Day	7% 4 22% 44% 19% 5%	626
	11th to 20th	Day	8% 3 24% 41% 21% 3	615
	21st to end	Day	4 4 23% 41% 23% 6%	503
September	1st to 10th	Day	7% 3 27% 40% 19% 4	446
	11th to 20th	Day	6% 5% 21% 30% 29% 9%	270
	21st to end	Day	13% 11% 29% 29% 16% 2	270
October	1st to 10th	Day	17% 7% 22% 31% 16% 6%	270
	11th to 20th	Day	10% 14% 37% 26% 10% 3	270
	21st to end	Day	13% 14% 30% 30% 10% 2	297
November	1st to 10th	Day	10% 9% 36% 26% 16% 3	270
	11th to 20th	Day	12% 10% 36% 30% 11% 1	270
	21st to end	Day	14% 8% 39% 26% 10% 2	270
December	1st to 10th	Day	10% 11% 46% 25% 7% 1	270
	11th to 20th	Day	11% 11% 44% 22% 10% 1	270
	21st to end	Day	15% 16% 39% 24% 4 1	297
January	1st to 10th	Night	8% 14% 42% 29% 7% 1	950
	11th to 20th	Night	7% 14% 42% 32% 5%	950
	21st to end	Night	10% 9% 45% 28% 7%	1045
February	1st to 10th	Night	13% 11% 45% 25% 5%	879
	11th to 20th	Night	10% 10% 50% 23% 6%	744
	21st to end	Night	10% 10% 47% 29% 4	628
March	1st to 10th	Night	12% 11% 40% 33% 5%	760
	11th to 20th	Night	10% 9% 43% 30% 7% 1	637
	21st to end	Night	16% 11% 35% 31% 8%	615
April	1st to 10th	Night	17% 10% 41% 27% 4	540
	11th to 20th	Night	17% 13% 38% 29% 3	533
	21st to end	Night	17% 10% 31% 33% 7% 1	540
May	1st to 10th	Night	14% 8% 34% 34% 9%	540
	11th to 20th	Night	19% 7% 31% 33% 10%	531
	21st to end	Night	16% 9% 34% 33% 7% 1	584
June	1st to 10th	Night	10% 5% 29% 41% 14% 1	540
	11th to 20th	Night	11% 5% 37% 39% 9%	540
	21st to end	Night	4 3 30% 50% 14%	540
July	1st to 10th	Night	6% 2 31% 46% 15%	525
	11th to 20th	Night	5% 2 30% 53% 10%	522
	21st to end	Night	4 3 29% 53% 12%	591
August	1st to 10th	Night	4 1 28% 51% 15% 1	537
	11th to 20th	Night	8% 2 30% 48% 13%	534
	21st to end	Night	4 4 34% 43% 15%	594
September	1st to 10th	Night	9% 4 31% 45% 11% 1	540
	11th to 20th	Night	9% 3 33% 40% 15%	540
	21st to end	Night	12% 7% 31% 39% 10% 1	540
October	1st to 10th	Night	15% 8% 34% 33% 10%	540
	11th to 20th	Night	12% 9% 35% 35% 10%	739
	21st to end	Night	13% 10% 34% 32% 9% 1	990
November	1st to 10th	Night	10% 7% 41% 34% 7% 1	925
	11th to 20th	Night	9% 10% 41% 32% 8%	950
	21st to end	Night	8% 8% 42% 34% 8%	950
December	1st to 10th	Night	10% 11% 45% 28% 6%	950
	11th to 20th	Night	10% 8% 44% 31% 6%	950
	21st to end	Night	16% 13% 37% 29% 5%	1045

Page generated at 2024-03-24 22:36:58. Version ac07

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