Sussex
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sussex clear sky chart from 2005-11-06 to 2024-02-05.

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	19% 11% 4 7% 6% 3 4 4 5% 6% 32%	77963
	Night	18% 11% 4 7% 6% 3 4 4 5% 6% 32%	80903
Transparency	Day	53% 6% 11% 19% 10% 1	77664
	Night	54% 6% 10% 20% 10% 1	80737
Seeing	Day	29% 21% 29% 15% 5% 1	15517
	Night	27% 18% 29% 20% 5%	23427

By Month

Percentage Cloud Cover NE (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	10% 14% 5% 10% 8% 4 4 3 4 5% 32%	2207
	11th to 20th	Day	15% 13% 6% 12% 8% 3 3 3 3 3 30%	2407
	21st to end	Day	13% 10% 6% 10% 6% 3 5% 5% 6% 8% 30%	3124
February	1st to 10th	Day	16% 13% 4 8% 6% 3 5% 5% 5% 7% 29%	1656
	11th to 20th	Day	17% 16% 3 8% 5% 5% 4 3 5% 6% 27%	1573
	21st to end	Day	11% 13% 5% 8% 6% 4 4 5% 5% 5% 35%	1390
March	1st to 10th	Day	16% 20% 6% 7% 5% 3 3 4 4 4 28%	1928
	11th to 20th	Day	15% 12% 6% 9% 6% 4 3 3 3 6% 32%	1980
	21st to end	Day	18% 15% 7% 7% 4 3 4 3 3 5% 31%	2178
April	1st to 10th	Day	22% 17% 5% 7% 6% 3 4 4 4 5% 25%	2098
	11th to 20th	Day	19% 14% 3 6% 4 3 4 3 5% 6% 32%	2301
	21st to end	Day	23% 13% 4 5% 4 3 4 4 4 7% 29%	2340
May	1st to 10th	Day	25% 12% 3 7% 5% 3 5% 4 5% 6% 25%	2340
	11th to 20th	Day	24% 9% 3 5% 5% 3 4 4 4 5% 34%	2478
	21st to end	Day	20% 8% 4 7% 6% 3 4 4 5% 7% 32%	2724
June	1st to 10th	Day	28% 9% 3 6% 5% 4 5% 5% 5% 6% 25%	2695
	11th to 20th	Day	21% 8% 3 7% 5% 3 4 5% 4 7% 32%	2700
	21st to end	Day	27% 9% 3 6% 5% 3 4 4 4 6% 28%	2700
July	1st to 10th	Day	18% 7% 2 5% 5% 3 5% 5% 6% 8% 35%	2700
	11th to 20th	Day	16% 6% 3 6% 6% 4 5% 6% 7% 9% 33%	2696
	21st to end	Day	18% 7% 3 7% 7% 3 6% 6% 7% 7% 29%	2609
August	1st to 10th	Day	17% 6% 3 6% 6% 3 5% 6% 6% 8% 34%	2327
	11th to 20th	Day	18% 6% 2 6% 7% 3 6% 6% 7% 7% 31%	2304
	21st to end	Day	16% 6% 3 5% 5% 3 4 4 6% 7% 41%	2548
September	1st to 10th	Day	15% 6% 2 4 5% 2 4 5% 5% 8% 43%	2160
	11th to 20th	Day	19% 7% 3 5% 3 2 4 3 5% 5% 44%	2008
	21st to end	Day	20% 6% 3 4 4 2 3 3 3 6% 45%	1976
October	1st to 10th	Day	19% 8% 3 6% 4 2 3 4 4 7% 39%	1800
	11th to 20th	Day	20% 10% 2 6% 5% 3 5% 4 4 7% 35%	1800
	21st to end	Day	20% 11% 4 7% 5% 3 5% 3 4 6% 31%	1918
November	1st to 10th	Day	21% 12% 3 6% 5% 3 4 3 4 6% 33%	1557
	11th to 20th	Day	17% 12% 5% 7% 6% 3 2 4 4 6% 33%	1520
	21st to end	Day	18% 14% 6% 8% 7% 4 4 3 4 4 28%	1520
December	1st to 10th	Day	24% 14% 6% 7% 6% 2 4 4 3 5% 26%	1520
	11th to 20th	Day	17% 17% 5% 9% 7% 3 4 3 4 5% 25%	1750
	21st to end	Day	19% 13% 6% 9% 6% 3 4 4 4 4 28%	2431
January	1st to 10th	Night	14% 11% 5% 7% 6% 3 5% 4 4 5% 36%	4748
	11th to 20th	Night	14% 14% 5% 9% 8% 3 4 4 4 6% 29%	4550
	21st to end	Night	13% 13% 5% 9% 8% 3 5% 4 4 6% 30%	4532
February	1st to 10th	Night	16% 12% 4 8% 7% 3 5% 4 5% 6% 30%	2399
	11th to 20th	Night	17% 15% 4 8% 7% 4 5% 4 5% 6% 26%	2273
	21st to end	Night	12% 13% 7% 9% 5% 3 5% 4 6% 6% 31%	1862
March	1st to 10th	Night	14% 17% 4 9% 5% 3 4 4 4 6% 30%	2018
	11th to 20th	Night	16% 12% 5% 8% 7% 4 5% 5% 4 6% 28%	1979
	21st to end	Night	17% 14% 6% 10% 6% 3 3 3 3 3 32%	2178
April	1st to 10th	Night	22% 14% 4 7% 6% 3 5% 3 4 5% 26%	1861
	11th to 20th	Night	22% 12% 2 5% 5% 2 4 3 5% 7% 32%	1607
	21st to end	Night	21% 14% 3 7% 5% 3 6% 4 4 5% 29%	1620
May	1st to 10th	Night	22% 11% 3 7% 5% 3 4 4 5% 7% 28%	1619
	11th to 20th	Night	25% 8% 4 5% 4 2 4 3 5% 7% 32%	1416
	21st to end	Night	16% 8% 3 7% 6% 4 6% 6% 6% 7% 31%	1550
June	1st to 10th	Night	24% 8% 4 6% 5% 3 5% 5% 6% 7% 27%	1278
	11th to 20th	Night	22% 7% 3 5% 5% 3 3 5% 4 7% 34%	1260
	21st to end	Night	24% 9% 4 6% 4 4 5% 4 4 5% 31%	1260
July	1st to 10th	Night	16% 8% 3 7% 6% 3 5% 5% 6% 9% 33%	1260
	11th to 20th	Night	17% 8% 3 5% 5% 4 5% 5% 6% 9% 33%	1260
	21st to end	Night	16% 7% 4 8% 6% 4 6% 7% 7% 7% 29%	1691
August	1st to 10th	Night	15% 7% 3 5% 5% 3 6% 5% 5% 8% 39%	1612
	11th to 20th	Night	16% 7% 3 5% 5% 3 5% 6% 7% 10% 33%	1596
	21st to end	Night	14% 7% 2 6% 5% 3 3 4 6% 8% 42%	1806
September	1st to 10th	Night	18% 5% 3 4 4 3 4 5% 6% 8% 41%	1800
	11th to 20th	Night	19% 6% 3 4 4 2 3 4 5% 7% 44%	1950
	21st to end	Night	19% 6% 2 5% 4 2 3 4 4 7% 42%	1982
October	1st to 10th	Night	20% 6% 3 5% 5% 3 3 4 4 7% 39%	2160
	11th to 20th	Night	16% 10% 3 7% 6% 3 3 5% 3 7% 37%	2160
	21st to end	Night	24% 11% 3 7% 6% 3 4 3 4 5% 32%	2435
November	1st to 10th	Night	22% 10% 4 5% 5% 2 4 4 4 6% 34%	2521
	11th to 20th	Night	18% 12% 5% 8% 5% 3 4 4 5% 6% 31%	2660
	21st to end	Night	19% 13% 5% 7% 6% 3 4 4 4 6% 30%	2660
December	1st to 10th	Night	23% 13% 5% 9% 6% 4 4 3 4 4 25%	2660
	11th to 20th	Night	20% 16% 6% 9% 6% 3 4 3 3 4 26%	3444
	21st to end	Night	22% 16% 5% 8% 6% 2 3 3 3 3 28%	5236

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% 4 14% 17% 9%	2208
	11th to 20th	Day	57% 4 6% 20% 10% 1	2407
	21st to end	Day	51% 6% 13% 15% 15% 1	3124
February	1st to 10th	Day	55% 5% 11% 17% 10% 2	1656
	11th to 20th	Day	60% 4 10% 16% 9% 1	1581
	21st to end	Day	51% 5% 10% 21% 10% 3	1390
March	1st to 10th	Day	61% 3 7% 18% 10% 1	1932
	11th to 20th	Day	56% 3 11% 16% 12% 2	1980
	21st to end	Day	58% 4 7% 16% 12% 4	2178
April	1st to 10th	Day	63% 5% 7% 13% 10% 2	2098
	11th to 20th	Day	53% 5% 9% 20% 12% 1	2301
	21st to end	Day	57% 5% 9% 16% 11% 3	2340
May	1st to 10th	Day	60% 5% 8% 15% 10% 1	2340
	11th to 20th	Day	53% 6% 7% 21% 12% 1	2482
	21st to end	Day	53% 7% 10% 22% 8% 1	2724
June	1st to 10th	Day	59% 6% 9% 16% 9%	2695
	11th to 20th	Day	52% 7% 11% 20% 10% 1	2700
	21st to end	Day	58% 6% 11% 15% 9% 1	2700
July	1st to 10th	Day	46% 9% 15% 21% 9% 1	2625
	11th to 20th	Day	45% 9% 16% 21% 8% 1	2615
	21st to end	Day	51% 9% 14% 19% 7%	2463
August	1st to 10th	Day	47% 8% 14% 23% 7%	2314
	11th to 20th	Day	50% 10% 13% 21% 6%	2304
	21st to end	Day	42% 7% 13% 26% 11%	2548
September	1st to 10th	Day	39% 8% 13% 25% 13% 1	2160
	11th to 20th	Day	43% 5% 10% 24% 15% 2	2008
	21st to end	Day	42% 4 9% 27% 16% 1	1976
October	1st to 10th	Day	46% 5% 9% 26% 13%	1800
	11th to 20th	Day	50% 6% 11% 25% 7% 1	1800
	21st to end	Day	55% 6% 10% 17% 13%	1918
November	1st to 10th	Day	56% 4 9% 20% 11% 1	1557
	11th to 20th	Day	53% 4 13% 18% 12% 1	1520
	21st to end	Day	61% 5% 11% 17% 6%	1520
December	1st to 10th	Day	62% 5% 10% 16% 6% 1	1520
	11th to 20th	Day	64% 5% 7% 15% 8% 1	1749
	21st to end	Day	60% 4 13% 13% 7% 2	2431
January	1st to 10th	Night	51% 5% 11% 26% 6% 1	4748
	11th to 20th	Night	55% 7% 9% 20% 8% 1	4550
	21st to end	Night	54% 6% 8% 20% 10% 1	4532
February	1st to 10th	Night	56% 4 11% 16% 12% 1	2399
	11th to 20th	Night	59% 5% 9% 15% 10% 2	2276
	21st to end	Night	54% 5% 9% 18% 11% 2	1862
March	1st to 10th	Night	57% 3 9% 17% 12% 2	2027
	11th to 20th	Night	57% 5% 9% 15% 12% 2	1980
	21st to end	Night	58% 5% 5% 17% 12% 3	2178
April	1st to 10th	Night	61% 4 7% 13% 10% 4	1861
	11th to 20th	Night	53% 4 10% 20% 12% 1	1607
	21st to end	Night	58% 5% 10% 15% 12% 1	1620
May	1st to 10th	Night	57% 6% 9% 17% 10% 2	1619
	11th to 20th	Night	52% 6% 9% 21% 10%	1417
	21st to end	Night	53% 8% 11% 18% 9% 1	1551
June	1st to 10th	Night	55% 8% 10% 19% 7% 1	1278
	11th to 20th	Night	50% 8% 9% 22% 9% 2	1260
	21st to end	Night	56% 6% 11% 16% 9% 1	1260
July	1st to 10th	Night	48% 9% 15% 20% 9%	1225
	11th to 20th	Night	47% 8% 13% 22% 9%	1218
	21st to end	Night	52% 11% 12% 17% 8% 1	1597
August	1st to 10th	Night	43% 9% 15% 24% 9%	1600
	11th to 20th	Night	44% 12% 17% 21% 6%	1596
	21st to end	Night	40% 7% 16% 26% 10% 1	1806
September	1st to 10th	Night	42% 6% 11% 29% 12% 1	1800
	11th to 20th	Night	41% 6% 13% 26% 14% 1	1950
	21st to end	Night	44% 6% 9% 25% 14% 2	1982
October	1st to 10th	Night	46% 5% 10% 25% 14%	2160
	11th to 20th	Night	49% 6% 11% 27% 7%	2160
	21st to end	Night	56% 5% 10% 17% 11% 1	2435
November	1st to 10th	Night	53% 5% 11% 19% 11% 1	2521
	11th to 20th	Night	55% 6% 12% 18% 9% 1	2660
	21st to end	Night	57% 6% 13% 16% 7%	2660
December	1st to 10th	Night	62% 5% 10% 17% 6%	2660
	11th to 20th	Night	64% 4 7% 15% 9%	3446
	21st to end	Night	63% 4 10% 16% 6% 1	5236

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	33% 26% 31% 9%	180
	11th to 20th	Day	44% 25% 23% 6% 3	200
	21st to end	Day	23% 25% 32% 16% 4	407
February	1st to 10th	Day	30% 26% 26% 14% 2	352
	11th to 20th	Day	39% 28% 20% 10% 2	336
	21st to end	Day	26% 30% 28% 12% 4	306
March	1st to 10th	Day	28% 33% 28% 9% 2	420
	11th to 20th	Day	29% 25% 32% 10% 3 1	420
	21st to end	Day	35% 26% 25% 11% 3 1	462
April	1st to 10th	Day	41% 25% 23% 8% 2	420
	11th to 20th	Day	33% 29% 25% 9% 4	412
	21st to end	Day	34% 23% 26% 11% 5%	420
May	1st to 10th	Day	39% 23% 25% 9% 4	423
	11th to 20th	Day	31% 20% 30% 14% 4 1	624
	21st to end	Day	29% 21% 30% 16% 4	680
June	1st to 10th	Day	34% 21% 27% 13% 5%	630
	11th to 20th	Day	28% 19% 29% 19% 5% 1	630
	21st to end	Day	29% 16% 28% 21% 6%	630
July	1st to 10th	Day	23% 17% 35% 18% 6% 1	620
	11th to 20th	Day	20% 12% 35% 22% 9% 1	618
	21st to end	Day	21% 16% 36% 21% 6% 1	549
August	1st to 10th	Day	18% 15% 42% 20% 5%	446
	11th to 20th	Day	24% 13% 33% 23% 5% 1	439
	21st to end	Day	20% 17% 31% 23% 7% 2	495
September	1st to 10th	Day	16% 16% 40% 20% 6% 2	450
	11th to 20th	Day	28% 18% 23% 22% 6% 3	450
	21st to end	Day	22% 25% 28% 15% 8% 2	448
October	1st to 10th	Day	25% 17% 24% 20% 11% 3	360
	11th to 20th	Day	29% 19% 26% 20% 5% 1	360
	21st to end	Day	31% 24% 26% 13% 5% 1	396
November	1st to 10th	Day	32% 19% 28% 13% 5% 2	365
	11th to 20th	Day	33% 22% 26% 14% 5%	370
	21st to end	Day	30% 27% 30% 10% 3	370
December	1st to 10th	Day	36% 22% 25% 15% 2 1	370
	11th to 20th	Day	39% 29% 21% 11% 1	261
	21st to end	Day	33% 29% 28% 8% 1	198
January	1st to 10th	Night	30% 23% 27% 18% 3	850
	11th to 20th	Night	29% 24% 26% 17% 5%	799
	21st to end	Night	23% 23% 32% 18% 5%	836
February	1st to 10th	Night	27% 24% 29% 17% 2	739
	11th to 20th	Night	29% 27% 25% 16% 2	703
	21st to end	Night	22% 23% 31% 20% 4	592
March	1st to 10th	Night	26% 23% 32% 16% 2	720
	11th to 20th	Night	26% 21% 31% 18% 4 1	720
	21st to end	Night	26% 21% 31% 15% 5%	792
April	1st to 10th	Night	34% 20% 26% 17% 2	601
	11th to 20th	Night	28% 20% 32% 16% 4	534
	21st to end	Night	31% 18% 29% 17% 5%	540
May	1st to 10th	Night	29% 16% 30% 21% 4	540
	11th to 20th	Night	29% 18% 32% 17% 3	532
	21st to end	Night	22% 17% 40% 18% 2 1	583
June	1st to 10th	Night	28% 11% 33% 23% 5%	378
	11th to 20th	Night	26% 13% 29% 26% 6%	360
	21st to end	Night	24% 13% 28% 29% 6%	360
July	1st to 10th	Night	19% 11% 36% 27% 7%	350
	11th to 20th	Night	19% 11% 32% 30% 8%	348
	21st to end	Night	19% 11% 34% 30% 5%	575
August	1st to 10th	Night	18% 9% 35% 30% 7%	538
	11th to 20th	Night	21% 11% 28% 32% 9%	532
	21st to end	Night	17% 12% 30% 29% 12%	594
September	1st to 10th	Night	22% 10% 35% 26% 6% 1	540
	11th to 20th	Night	23% 12% 25% 28% 11% 1	690
	21st to end	Night	23% 16% 27% 25% 9%	720
October	1st to 10th	Night	23% 13% 28% 25% 10% 1	720
	11th to 20th	Night	23% 18% 32% 18% 8% 1	720
	21st to end	Night	32% 21% 26% 19% 3	792
November	1st to 10th	Night	32% 16% 25% 20% 6% 1	794
	11th to 20th	Night	29% 21% 27% 17% 6% 1	850
	21st to end	Night	30% 22% 26% 19% 4	850
December	1st to 10th	Night	32% 18% 29% 16% 4	850
	11th to 20th	Night	33% 25% 24% 14% 3	850
	21st to end	Night	33% 23% 25% 15% 4 1	935

Page generated at 2024-02-02 06:20:29. Version ac07

Copyright 2024 Attilla Danko