Norfolk(NE)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Norfolk(NE) clear sky chart from 2005-11-06 to 2024-07-02.

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	11% 7% 3 7% 4 4 4 3 5% 7% 44%	89516
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 47%	89685
Transparency	Day	39% 5% 13% 26% 15% 2	89278
	Night	37% 5% 13% 26% 17% 3	89528
Seeing	Day	14% 10% 31% 29% 13% 2	15350
	Night	13% 10% 35% 32% 9% 1	25301

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	9% 13% 5% 13% 8% 6% 5% 4 4 5% 29%	2538
	11th to 20th	Day	6% 12% 6% 11% 5% 5% 8% 4 5% 6% 32%	2792
	21st to end	Day	6% 11% 4 14% 5% 4 3 3 5% 5% 40%	3135
February	1st to 10th	Day	10% 12% 4 9% 6% 6% 5% 5% 5% 6% 33%	1710
	11th to 20th	Day	7% 10% 4 7% 5% 5% 4 4 6% 7% 42%	1753
	21st to end	Day	9% 11% 3 8% 5% 4 5% 3 4 7% 41%	1570
March	1st to 10th	Day	10% 8% 3 6% 4 3 3 3 5% 6% 49%	3280
	11th to 20th	Day	11% 10% 3 6% 4 3 3 3 4 6% 49%	3480
	21st to end	Day	21% 11% 3 11% 5% 5% 5% 4 5% 6% 23%	3814
April	1st to 10th	Day	13% 8% 3 7% 4 4 4 3 5% 7% 42%	2121
	11th to 20th	Day	17% 8% 2 6% 4 4 3 4 6% 7% 40%	2442
	21st to end	Day	19% 9% 3 6% 4 3 3 3 5% 6% 39%	2470
May	1st to 10th	Day	15% 8% 3 7% 5% 4 5% 4 5% 8% 36%	4082
	11th to 20th	Day	11% 7% 3 6% 4 3 4 3 5% 6% 48%	4082
	21st to end	Day	16% 6% 2 6% 4 5% 4 4 5% 7% 41%	4477
June	1st to 10th	Day	8% 4 2 5% 4 3 4 4 6% 10% 49%	2670
	11th to 20th	Day	11% 5% 2 6% 3 4 4 4 7% 8% 45%	2850
	21st to end	Day	6% 5% 1 4 4 4 4 4 6% 9% 52%	2795
July	1st to 10th	Day	7% 4 2 5% 3 4 4 3 8% 9% 51%	2536
	11th to 20th	Day	6% 3 1 5% 3 4 4 4 6% 7% 57%	2434
	21st to end	Day	5% 4 2 4 4 4 4 4 7% 10% 52%	2546
August	1st to 10th	Day	8% 6% 2 8% 5% 6% 5% 5% 6% 9% 39%	2328
	11th to 20th	Day	10% 5% 2 4 4 4 4 3 6% 7% 51%	2301
	21st to end	Day	9% 4 1 5% 4 3 4 3 5% 8% 54%	2574
September	1st to 10th	Day	13% 6% 2 5% 3 3 4 4 4 7% 49%	2041
	11th to 20th	Day	9% 5% 1 5% 3 3 3 3 5% 7% 56%	1980
	21st to end	Day	11% 4 1 4 3 3 3 2 5% 6% 57%	1980
October	1st to 10th	Day	16% 5% 2 5% 4 3 3 3 4 6% 49%	1891
	11th to 20th	Day	11% 5% 2 4 3 3 3 2 4 7% 57%	1800
	21st to end	Day	15% 7% 2 6% 3 3 3 2 4 6% 50%	1904
November	1st to 10th	Day	8% 6% 2 5% 4 4 3 3 6% 7% 52%	1673
	11th to 20th	Day	9% 7% 1 7% 5% 4 4 3 5% 7% 47%	1710
	21st to end	Day	10% 10% 3 7% 3 3 3 3 5% 8% 45%	1534
December	1st to 10th	Day	7% 9% 3 8% 4 4 3 4 5% 6% 47%	1520
	11th to 20th	Day	6% 9% 3 8% 7% 5% 6% 4 6% 7% 39%	1918
	21st to end	Day	15% 10% 3 14% 5% 4 3 3 6% 6% 30%	2785
January	1st to 10th	Night	7% 13% 3 12% 7% 7% 6% 4 6% 6% 28%	4417
	11th to 20th	Night	4 10% 3 9% 5% 4 9% 4 8% 7% 35%	4171
	21st to end	Night	7% 10% 6% 14% 5% 4 4 3 5% 6% 37%	4532
February	1st to 10th	Night	11% 10% 4 9% 6% 4 4 3 4 5% 40%	2470
	11th to 20th	Night	8% 9% 3 7% 4 5% 5% 4 6% 6% 43%	2331
	21st to end	Night	9% 6% 3 6% 5% 4 5% 3 5% 6% 48%	1884
March	1st to 10th	Night	10% 7% 2 6% 3 3 3 3 5% 6% 52%	3578
	11th to 20th	Night	10% 8% 3 5% 3 3 3 3 4 6% 52%	3480
	21st to end	Night	17% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	3817
April	1st to 10th	Night	13% 8% 3 6% 4 4 4 4 5% 6% 44%	2055
	11th to 20th	Night	13% 8% 2 7% 4 4 4 3 4 7% 44%	1689
	21st to end	Night	15% 8% 2 6% 3 4 3 4 6% 7% 42%	1710
May	1st to 10th	Night	17% 6% 1 4 4 3 3 3 4 7% 47%	2823
	11th to 20th	Night	10% 5% 2 6% 3 4 3 3 6% 8% 50%	2823
	21st to end	Night	15% 6% 2 5% 4 4 3 3 6% 8% 44%	3090
June	1st to 10th	Night	6% 3 2 3 3 3 5% 4 7% 8% 56%	1501
	11th to 20th	Night	8% 4 2 6% 3 4 3 3 5% 7% 56%	1330
	21st to end	Night	3 4 2 4 3 4 4 4 6% 8% 60%	1377
July	1st to 10th	Night	6% 4 1 5% 3 4 4 3 5% 10% 55%	1452
	11th to 20th	Night	3 2 1 4 3 4 3 5% 6% 8% 61%	1523
	21st to end	Night	2 4 2 4 4 3 4 4 6% 9% 57%	1772
August	1st to 10th	Night	5% 5% 2 6% 5% 4 6% 4 6% 10% 48%	1611
	11th to 20th	Night	6% 4 1 4 3 3 4 3 6% 8% 58%	1600
	21st to end	Night	7% 3 1 5% 3 3 3 2 5% 9% 58%	1782
September	1st to 10th	Night	8% 3 1 5% 3 3 3 3 5% 6% 59%	1915
	11th to 20th	Night	8% 4 2 4 3 3 4 3 4 6% 60%	1980
	21st to end	Night	9% 4 2 4 3 3 3 2 4 6% 60%	1980
October	1st to 10th	Night	16% 5% 2 4 3 3 3 3 4 6% 50%	2050
	11th to 20th	Night	12% 6% 2 4 3 2 3 3 4 5% 56%	2160
	21st to end	Night	14% 5% 1 5% 3 3 3 2 5% 6% 53%	2450
November	1st to 10th	Night	7% 5% 2 4 3 3 3 3 4 6% 59%	2405
	11th to 20th	Night	8% 7% 2 7% 5% 4 3 3 5% 6% 51%	2470
	21st to end	Night	9% 8% 3 5% 3 3 3 3 5% 7% 52%	2644
December	1st to 10th	Night	7% 8% 3 8% 5% 4 3 3 5% 7% 47%	2660
	11th to 20th	Night	8% 8% 3 6% 4 4 4 4 6% 8% 46%	3279
	21st to end	Night	15% 11% 5% 13% 4 4 4 3 4 5% 33%	4874

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	57% 5% 12% 18% 8% 1	2539
	11th to 20th	Day	52% 4 15% 20% 9% 1	2792
	21st to end	Day	46% 5% 17% 18% 14% 1	3135
February	1st to 10th	Day	50% 5% 15% 18% 10% 1	1710
	11th to 20th	Day	42% 6% 11% 23% 15% 3	1762
	21st to end	Day	43% 5% 12% 24% 13% 4	1570
March	1st to 10th	Day	36% 5% 10% 30% 18% 2	3280
	11th to 20th	Day	37% 5% 10% 29% 16% 4	3480
	21st to end	Day	60% 6% 17% 12% 4 1	3814
April	1st to 10th	Day	43% 4 12% 26% 13% 1	2121
	11th to 20th	Day	44% 4 13% 22% 14% 3	2442
	21st to end	Day	45% 5% 12% 26% 12%	2470
May	1st to 10th	Day	44% 6% 12% 21% 15% 2	4120
	11th to 20th	Day	36% 5% 13% 26% 17% 2	4086
	21st to end	Day	42% 5% 12% 26% 13% 1	4489
June	1st to 10th	Day	30% 7% 17% 32% 12% 2	2670
	11th to 20th	Day	34% 7% 15% 26% 16% 3	2850
	21st to end	Day	28% 6% 17% 32% 13% 4	2795
July	1st to 10th	Day	28% 6% 17% 29% 16% 2	2467
	11th to 20th	Day	26% 5% 14% 31% 18% 6%	2359
	21st to end	Day	24% 8% 15% 33% 18% 2	2405
August	1st to 10th	Day	39% 7% 16% 25% 11% 2	2314
	11th to 20th	Day	32% 6% 14% 32% 14% 2	2301
	21st to end	Day	29% 6% 12% 27% 21% 5%	2574
September	1st to 10th	Day	35% 5% 12% 25% 18% 5%	2041
	11th to 20th	Day	29% 5% 12% 36% 17% 2	1980
	21st to end	Day	28% 4 9% 33% 25% 1	1980
October	1st to 10th	Day	37% 4 8% 26% 23% 2	1891
	11th to 20th	Day	29% 3 12% 31% 19% 6%	1800
	21st to end	Day	38% 3 12% 25% 19% 3	1904
November	1st to 10th	Day	32% 4 15% 26% 21% 2	1673
	11th to 20th	Day	37% 5% 12% 27% 18% 2	1710
	21st to end	Day	39% 4 12% 27% 14% 3	1534
December	1st to 10th	Day	38% 4 17% 26% 11% 3	1520
	11th to 20th	Day	42% 5% 16% 29% 8%	1915
	21st to end	Day	53% 6% 10% 21% 9% 1	2785
January	1st to 10th	Night	52% 7% 11% 20% 9% 1	4417
	11th to 20th	Night	46% 4 14% 26% 10% 1	4171
	21st to end	Night	48% 5% 13% 20% 14% 1	4532
February	1st to 10th	Night	47% 5% 12% 22% 12% 2	2470
	11th to 20th	Night	40% 5% 14% 23% 14% 4	2332
	21st to end	Night	36% 5% 12% 26% 17% 4	1884
March	1st to 10th	Night	33% 4 10% 26% 23% 3	3578
	11th to 20th	Night	34% 4 8% 29% 21% 4	3480
	21st to end	Night	48% 6% 20% 19% 5% 1	3817
April	1st to 10th	Night	39% 6% 11% 27% 16% 1	2055
	11th to 20th	Night	40% 5% 10% 27% 17% 2	1689
	21st to end	Night	38% 6% 13% 26% 15% 2	1710
May	1st to 10th	Night	37% 5% 11% 25% 20% 2	2850
	11th to 20th	Night	32% 6% 14% 25% 20% 2	2824
	21st to end	Night	38% 5% 14% 24% 16% 2	3099
June	1st to 10th	Night	23% 8% 17% 34% 15% 4	1501
	11th to 20th	Night	29% 4 15% 28% 19% 5%	1330
	21st to end	Night	21% 6% 16% 36% 18% 3	1377
July	1st to 10th	Night	27% 5% 15% 31% 19% 4	1412
	11th to 20th	Night	20% 7% 15% 30% 21% 7%	1475
	21st to end	Night	22% 6% 18% 30% 21% 3	1673
August	1st to 10th	Night	31% 7% 17% 28% 15% 2	1601
	11th to 20th	Night	24% 6% 14% 33% 19% 3	1600
	21st to end	Night	25% 5% 13% 25% 24% 7%	1782
September	1st to 10th	Night	26% 5% 11% 30% 22% 7%	1915
	11th to 20th	Night	26% 4 11% 34% 22% 3	1980
	21st to end	Night	27% 4 9% 31% 25% 4	1980
October	1st to 10th	Night	37% 4 9% 24% 24% 1	2050
	11th to 20th	Night	30% 4 8% 27% 26% 5%	2160
	21st to end	Night	33% 3 14% 24% 23% 3	2450
November	1st to 10th	Night	26% 4 15% 27% 24% 4	2405
	11th to 20th	Night	33% 4 13% 27% 19% 4	2470
	21st to end	Night	33% 4 13% 29% 19% 3	2644
December	1st to 10th	Night	37% 4 15% 29% 14% 1	2660
	11th to 20th	Night	35% 4 16% 34% 10% 1	3281
	21st to end	Night	54% 4 10% 22% 8% 1	4874

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	18% 13% 35% 21% 11% 1	270
	11th to 20th	Day	18% 16% 32% 26% 7% 1	270
	21st to end	Day	13% 9% 44% 26% 8% 1	297
February	1st to 10th	Day	15% 17% 40% 26% 2	270
	11th to 20th	Day	13% 15% 39% 26% 6% 1	270
	21st to end	Day	16% 19% 42% 19% 5%	225
March	1st to 10th	Day	14% 19% 43% 18% 6% 1	270
	11th to 20th	Day	19% 12% 40% 20% 8% 1	270
	21st to end	Day	28% 14% 33% 17% 6% 1	297
April	1st to 10th	Day	20% 18% 40% 18% 3	301
	11th to 20th	Day	21% 17% 33% 22% 7%	640
	21st to end	Day	24% 15% 30% 21% 8% 2	650
May	1st to 10th	Day	20% 12% 35% 23% 9% 1	653
	11th to 20th	Day	19% 12% 30% 24% 14% 3	675
	21st to end	Day	19% 8% 31% 28% 11% 2	734
June	1st to 10th	Day	7% 8% 27% 34% 21% 4	680
	11th to 20th	Day	12% 6% 33% 33% 14% 3	680
	21st to end	Day	8% 8% 32% 34% 17% 2	680
July	1st to 10th	Day	9% 4 20% 34% 28% 5%	627
	11th to 20th	Day	5% 2 27% 42% 19% 5%	618
	21st to end	Day	6% 2 24% 44% 21% 3	684
August	1st to 10th	Day	10% 4 20% 41% 23% 2	626
	11th to 20th	Day	12% 4 22% 37% 21% 4	615
	21st to end	Day	11% 3 26% 36% 21% 4	693
September	1st to 10th	Day	14% 4 27% 39% 12% 4	331
	11th to 20th	Day	8% 6% 38% 29% 14% 4	270
	21st to end	Day	14% 12% 31% 29% 11% 3	270
October	1st to 10th	Day	23% 8% 26% 27% 13% 3	270
	11th to 20th	Day	16% 14% 36% 23% 9% 3	270
	21st to end	Day	19% 15% 36% 21% 7% 1	297
November	1st to 10th	Day	16% 14% 34% 26% 7% 4	270
	11th to 20th	Day	13% 16% 44% 22% 6%	270
	21st to end	Day	18% 17% 32% 25% 8%	270
December	1st to 10th	Day	11% 13% 43% 26% 6% 1	270
	11th to 20th	Day	15% 14% 38% 27% 7%	270
	21st to end	Day	18% 17% 41% 19% 4 1	297
January	1st to 10th	Night	13% 14% 38% 28% 6% 1	950
	11th to 20th	Night	11% 15% 39% 28% 6% 1	950
	21st to end	Night	15% 9% 43% 26% 6%	1045
February	1st to 10th	Night	15% 13% 40% 27% 4	950
	11th to 20th	Night	12% 11% 42% 28% 5%	857
	21st to end	Night	13% 11% 42% 28% 6%	628
March	1st to 10th	Night	14% 14% 40% 28% 4	669
	11th to 20th	Night	16% 11% 39% 28% 5%	570
	21st to end	Night	20% 8% 40% 25% 6%	627
April	1st to 10th	Night	19% 14% 38% 25% 4	570
	11th to 20th	Night	16% 14% 38% 27% 5%	563
	21st to end	Night	17% 13% 35% 26% 8%	570
May	1st to 10th	Night	17% 9% 35% 29% 9%	570
	11th to 20th	Night	14% 9% 32% 34% 10% 1	561
	21st to end	Night	18% 6% 32% 33% 10% 1	617
June	1st to 10th	Night	8% 4 26% 48% 14% 1	570
	11th to 20th	Night	9% 6% 34% 39% 11% 1	570
	21st to end	Night	5% 6% 29% 47% 13%	570
July	1st to 10th	Night	7% 4 18% 45% 25% 1	530
	11th to 20th	Night	4 1 24% 51% 20% 1	522
	21st to end	Night	3 3 21% 57% 17% 1	591
August	1st to 10th	Night	5% 3 21% 48% 22% 1	537
	11th to 20th	Night	8% 4 22% 46% 21%	534
	21st to end	Night	7% 3 29% 42% 18% 1	594
September	1st to 10th	Night	9% 4 27% 41% 16% 2	540
	11th to 20th	Night	9% 6% 32% 37% 14% 2	540
	21st to end	Night	12% 9% 34% 32% 14%	540
October	1st to 10th	Night	19% 7% 34% 29% 10%	610
	11th to 20th	Night	14% 14% 37% 27% 7%	720
	21st to end	Night	17% 11% 32% 30% 10%	866
November	1st to 10th	Night	10% 11% 38% 32% 7% 1	925
	11th to 20th	Night	13% 12% 40% 30% 6%	950
	21st to end	Night	14% 12% 37% 29% 9%	950
December	1st to 10th	Night	12% 12% 45% 26% 5% 1	950
	11th to 20th	Night	15% 11% 37% 29% 7%	950
	21st to end	Night	18% 14% 39% 24% 6%	1045

Page generated at 2024-06-29 06:12:29. Version ac07

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