Keppel Henge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keppel Henge clear sky chart from 2005-11-06 to 2024-04-10.

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	14% 11% 5% 9% 7% 3 5% 4 5% 6% 30%	82962
	Night	15% 13% 6% 10% 7% 4 5% 4 5% 6% 26%	85835
Transparency	Day	55% 4 11% 20% 10% 1	82668
	Night	62% 3 10% 17% 8% 1	85663
Seeing	Day	18% 7% 24% 29% 17% 5%	14287
	Night	21% 10% 27% 27% 13% 3	23693

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	14% 22% 13% 16% 12% 4 5% 3 3 3 5%	2208
	11th to 20th	Day	11% 19% 10% 25% 16% 4 5% 3 2 2 3	2598
	21st to end	Day	18% 19% 11% 14% 10% 5% 5% 4 4 3 7%	3124
February	1st to 10th	Day	11% 18% 8% 17% 12% 5% 6% 4 4 4 11%	1710
	11th to 20th	Day	11% 14% 8% 15% 12% 6% 5% 4 5% 6% 15%	1663
	21st to end	Day	13% 15% 8% 11% 8% 6% 6% 4 4 6% 18%	1517
March	1st to 10th	Day	16% 15% 5% 8% 6% 4 5% 3 5% 5% 29%	3340
	11th to 20th	Day	10% 15% 8% 12% 8% 4 5% 4 5% 4 25%	3480
	21st to end	Day	14% 10% 6% 8% 7% 3 5% 5% 5% 6% 31%	3815
April	1st to 10th	Day	18% 11% 5% 7% 7% 3 5% 4 5% 7% 29%	2180
	11th to 20th	Day	18% 10% 3 6% 5% 3 4 3 5% 6% 38%	2310
	21st to end	Day	19% 8% 4 6% 5% 2 4 4 6% 7% 35%	2340
May	1st to 10th	Day	16% 7% 2 5% 5% 3 4 5% 5% 9% 38%	2340
	11th to 20th	Day	15% 6% 3 5% 5% 3 4 4 4 7% 43%	2413
	21st to end	Day	10% 5% 2 6% 5% 2 5% 4 5% 9% 46%	2725
June	1st to 10th	Day	13% 6% 3 5% 4 3 5% 6% 6% 8% 41%	2641
	11th to 20th	Day	10% 6% 3 5% 5% 3 5% 5% 6% 9% 44%	2700
	21st to end	Day	12% 6% 3 5% 5% 3 4 5% 6% 8% 44%	2700
July	1st to 10th	Day	10% 4 2 3 4 3 4 5% 6% 9% 51%	2700
	11th to 20th	Day	10% 6% 3 5% 5% 3 5% 4 6% 8% 47%	2663
	21st to end	Day	10% 5% 2 5% 5% 3 5% 5% 6% 10% 45%	2547
August	1st to 10th	Day	11% 5% 2 4 4 2 5% 5% 6% 9% 48%	2327
	11th to 20th	Day	10% 5% 2 5% 6% 3 5% 5% 7% 8% 45%	2303
	21st to end	Day	12% 6% 2 5% 5% 4 5% 5% 7% 9% 40%	2553
September	1st to 10th	Day	13% 7% 3 5% 6% 3 4 5% 6% 8% 40%	2152
	11th to 20th	Day	12% 6% 2 6% 6% 3 4 5% 6% 9% 41%	1980
	21st to end	Day	17% 7% 3 6% 6% 4 5% 5% 6% 6% 35%	1980
October	1st to 10th	Day	18% 9% 3 6% 6% 4 5% 4 5% 6% 33%	1818
	11th to 20th	Day	23% 12% 5% 9% 8% 4 5% 4 5% 6% 20%	1800
	21st to end	Day	28% 15% 5% 8% 6% 3 5% 4 3 5% 17%	1918
November	1st to 10th	Day	14% 17% 4 9% 7% 4 6% 5% 6% 6% 21%	1615
	11th to 20th	Day	15% 16% 6% 9% 9% 4 7% 6% 6% 6% 17%	1520
	21st to end	Day	19% 19% 8% 11% 8% 4 7% 5% 4 4 10%	1520
December	1st to 10th	Day	14% 24% 11% 16% 9% 3 5% 4 4 4 6%	1520
	11th to 20th	Day	19% 20% 9% 15% 8% 4 5% 5% 4 5% 7%	1811
	21st to end	Day	26% 23% 7% 16% 7% 3 3 3 3 4 5%	2431
January	1st to 10th	Night	15% 22% 10% 17% 9% 4 5% 4 3 4 7%	4748
	11th to 20th	Night	13% 17% 10% 21% 14% 5% 5% 4 3 3 5%	4361
	21st to end	Night	16% 18% 10% 15% 10% 5% 7% 4 3 4 7%	4532
February	1st to 10th	Night	12% 16% 7% 17% 10% 6% 5% 4 5% 4 14%	2470
	11th to 20th	Night	11% 13% 8% 14% 11% 5% 5% 4 5% 5% 18%	2403
	21st to end	Night	15% 12% 6% 11% 8% 5% 6% 5% 4 6% 23%	1937
March	1st to 10th	Night	12% 11% 4 8% 6% 3 5% 4 5% 7% 34%	3499
	11th to 20th	Night	10% 13% 5% 8% 7% 3 4 4 4 7% 34%	3479
	21st to end	Night	12% 10% 5% 7% 6% 4 4 5% 5% 5% 35%	3817
April	1st to 10th	Night	21% 9% 4 6% 7% 3 5% 4 4 6% 32%	1990
	11th to 20th	Night	17% 7% 4 6% 5% 3 4 5% 5% 7% 38%	1615
	21st to end	Night	20% 9% 4 7% 7% 3 4 4 5% 7% 32%	1620
May	1st to 10th	Night	14% 8% 3 6% 5% 3 5% 4 6% 8% 38%	1620
	11th to 20th	Night	14% 5% 3 5% 6% 4 5% 4 6% 6% 42%	1479
	21st to end	Night	9% 5% 2 6% 5% 3 5% 5% 7% 7% 46%	1550
June	1st to 10th	Night	14% 6% 2 6% 6% 3 6% 4 5% 8% 40%	1314
	11th to 20th	Night	11% 5% 2 5% 5% 3 5% 5% 6% 9% 43%	1260
	21st to end	Night	12% 6% 2 6% 5% 3 5% 5% 5% 9% 42%	1260
July	1st to 10th	Night	9% 3 2 4 3 1 3 5% 6% 9% 54%	1260
	11th to 20th	Night	8% 5% 3 4 5% 4 5% 5% 5% 9% 47%	1293
	21st to end	Night	8% 4 2 5% 5% 4 6% 5% 6% 6% 49%	1771
August	1st to 10th	Night	10% 4 2 5% 4 3 4 4 7% 9% 48%	1611
	11th to 20th	Night	8% 5% 3 5% 4 3 6% 5% 6% 8% 46%	1598
	21st to end	Night	11% 7% 3 6% 5% 3 4 4 7% 9% 43%	1784
September	1st to 10th	Night	10% 5% 3 5% 4 2 4 5% 6% 9% 46%	1806
	11th to 20th	Night	11% 6% 2 5% 5% 2 5% 5% 5% 7% 46%	1980
	21st to end	Night	16% 8% 4 7% 7% 3 4 4 5% 7% 36%	1980
October	1st to 10th	Night	18% 8% 3 7% 7% 3 4 5% 5% 7% 32%	2142
	11th to 20th	Night	22% 13% 4 8% 7% 4 4 5% 5% 6% 21%	2160
	21st to end	Night	25% 15% 5% 8% 6% 3 6% 4 4 5% 18%	2435
November	1st to 10th	Night	16% 13% 5% 9% 7% 4 6% 5% 5% 5% 25%	2463
	11th to 20th	Night	16% 16% 6% 9% 7% 5% 6% 6% 5% 7% 17%	2660
	21st to end	Night	20% 19% 7% 10% 7% 4 5% 6% 4 5% 13%	2660
December	1st to 10th	Night	18% 21% 10% 12% 9% 5% 6% 4 4 4 8%	2660
	11th to 20th	Night	13% 21% 10% 17% 9% 4 5% 4 4 4 10%	3382
	21st to end	Night	23% 21% 9% 15% 9% 3 3 3 3 3 7%	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	88% 2 6% 4	2209
	11th to 20th	Day	91% 3 3 3 1	2598
	21st to end	Day	84% 1 9% 5% 1	3124
February	1st to 10th	Day	76% 3 8% 11% 2	1710
	11th to 20th	Day	72% 4 8% 10% 6%	1672
	21st to end	Day	66% 4 9% 15% 5%	1517
March	1st to 10th	Day	59% 2 13% 16% 9% 1	3343
	11th to 20th	Day	61% 2 9% 20% 6% 1	3480
	21st to end	Day	54% 2 12% 20% 11% 2	3815
April	1st to 10th	Day	53% 5% 10% 19% 11% 1	2180
	11th to 20th	Day	47% 4 7% 23% 17% 2	2310
	21st to end	Day	48% 4 12% 21% 12% 3	2340
May	1st to 10th	Day	43% 3 10% 26% 14% 4	2340
	11th to 20th	Day	42% 5% 8% 24% 19% 2	2417
	21st to end	Day	36% 4 16% 25% 16% 3	2725
June	1st to 10th	Day	38% 5% 11% 27% 17% 1	2641
	11th to 20th	Day	36% 5% 11% 28% 18% 2	2700
	21st to end	Day	37% 5% 14% 29% 14% 2	2700
July	1st to 10th	Day	30% 4 16% 29% 20% 2	2626
	11th to 20th	Day	34% 4 15% 34% 12% 2	2582
	21st to end	Day	34% 5% 14% 29% 16% 1	2405
August	1st to 10th	Day	32% 4 19% 28% 15% 2	2314
	11th to 20th	Day	35% 6% 16% 30% 13% 1	2303
	21st to end	Day	39% 6% 15% 27% 13% 1	2553
September	1st to 10th	Day	42% 4 13% 28% 13% 1	2152
	11th to 20th	Day	38% 4 15% 32% 10%	1980
	21st to end	Day	48% 4 14% 25% 8% 1	1980
October	1st to 10th	Day	50% 5% 12% 22% 11% 1	1818
	11th to 20th	Day	65% 4 12% 14% 5% 1	1800
	21st to end	Day	70% 3 10% 13% 3	1918
November	1st to 10th	Day	62% 5% 12% 16% 6%	1615
	11th to 20th	Day	69% 4 12% 10% 5%	1520
	21st to end	Day	78% 3 10% 7% 1	1520
December	1st to 10th	Day	85% 3 7% 4 1	1520
	11th to 20th	Day	84% 3 6% 7%	1810
	21st to end	Day	86% 2 8% 4	2431
January	1st to 10th	Night	85% 1 7% 6%	4748
	11th to 20th	Night	88% 2 6% 4 1	4361
	21st to end	Night	86% 2 6% 4 1	4532
February	1st to 10th	Night	74% 3 8% 12% 3	2470
	11th to 20th	Night	71% 3 8% 14% 4	2405
	21st to end	Night	63% 3 12% 16% 7%	1937
March	1st to 10th	Night	52% 2 15% 21% 10% 1	3509
	11th to 20th	Night	51% 1 13% 23% 10% 2	3480
	21st to end	Night	54% 2 8% 25% 10% 1	3817
April	1st to 10th	Night	55% 3 8% 21% 12% 1	1990
	11th to 20th	Night	45% 4 7% 23% 19% 2	1615
	21st to end	Night	53% 3 9% 18% 16% 2	1620
May	1st to 10th	Night	44% 4 9% 22% 17% 3	1620
	11th to 20th	Night	42% 3 7% 24% 21% 3	1480
	21st to end	Night	36% 3 14% 26% 17% 4	1551
June	1st to 10th	Night	43% 4 9% 22% 20% 3	1314
	11th to 20th	Night	37% 3 11% 28% 19% 1	1260
	21st to end	Night	40% 3 12% 28% 15% 2	1260
July	1st to 10th	Night	28% 3 12% 29% 24% 4	1225
	11th to 20th	Night	34% 3 12% 33% 16% 2	1251
	21st to end	Night	34% 4 14% 29% 18% 1	1672
August	1st to 10th	Night	32% 4 18% 28% 16% 2	1600
	11th to 20th	Night	34% 5% 16% 27% 16% 2	1598
	21st to end	Night	39% 4 15% 28% 12% 2	1784
September	1st to 10th	Night	35% 5% 14% 31% 15% 1	1806
	11th to 20th	Night	38% 4 16% 31% 12%	1980
	21st to end	Night	49% 3 14% 26% 8%	1980
October	1st to 10th	Night	51% 4 10% 24% 10% 1	2142
	11th to 20th	Night	64% 3 11% 17% 5%	2160
	21st to end	Night	70% 3 9% 12% 5%	2435
November	1st to 10th	Night	61% 3 11% 19% 5%	2463
	11th to 20th	Night	70% 4 12% 10% 3 1	2660
	21st to end	Night	76% 3 11% 8% 1	2660
December	1st to 10th	Night	84% 3 7% 6% 1	2660
	11th to 20th	Night	82% 3 9% 6% 1	3382
	21st to end	Night	86% 2 8% 4	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	17% 19% 34% 19% 8% 2	180
	11th to 20th	Day	20% 14% 35% 23% 8% 1	265
	21st to end	Day	26% 9% 33% 25% 7% 1	297
February	1st to 10th	Day	18% 17% 40% 19% 6%	270
	11th to 20th	Day	16% 13% 41% 26% 3 1	270
	21st to end	Day	19% 20% 40% 20% 1	225
March	1st to 10th	Day	20% 9% 35% 25% 9% 1	402
	11th to 20th	Day	18% 13% 32% 28% 9% 1	460
	21st to end	Day	23% 8% 28% 30% 10% 1	506
April	1st to 10th	Day	19% 8% 31% 30% 10% 1	457
	11th to 20th	Day	24% 7% 27% 22% 14% 5%	412
	21st to end	Day	24% 5% 26% 29% 13% 2	420
May	1st to 10th	Day	21% 3 24% 33% 17% 3	423
	11th to 20th	Day	15% 5% 20% 33% 21% 6%	447
	21st to end	Day	12% 4 17% 35% 23% 9%	485
June	1st to 10th	Day	12% 2 20% 38% 23% 4	571
	11th to 20th	Day	12% 3 20% 38% 23% 4	630
	21st to end	Day	14% 4 18% 35% 23% 6%	630
July	1st to 10th	Day	10% 2 14% 35% 30% 8%	621
	11th to 20th	Day	11% 3 18% 31% 25% 11%	604
	21st to end	Day	10% 3 13% 40% 27% 7%	488
August	1st to 10th	Day	12% 3 14% 31% 29% 10%	446
	11th to 20th	Day	11% 2 10% 33% 33% 10%	439
	21st to end	Day	15% 5% 17% 33% 22% 8%	495
September	1st to 10th	Day	16% 5% 18% 30% 25% 7%	450
	11th to 20th	Day	13% 4 20% 22% 28% 12%	450
	21st to end	Day	17% 7% 20% 27% 21% 7%	450
October	1st to 10th	Day	23% 6% 25% 22% 16% 7%	450
	11th to 20th	Day	25% 11% 29% 27% 8% 1	450
	21st to end	Day	35% 13% 25% 20% 7%	433
November	1st to 10th	Day	17% 19% 30% 20% 11% 2	243
	11th to 20th	Day	24% 12% 34% 22% 6% 2	180
	21st to end	Day	26% 11% 36% 24% 3	180
December	1st to 10th	Day	25% 17% 31% 22% 6%	180
	11th to 20th	Day	27% 21% 32% 14% 6%	180
	21st to end	Day	33% 18% 34% 11% 3	198
January	1st to 10th	Night	24% 15% 33% 21% 6% 1	950
	11th to 20th	Night	25% 17% 32% 20% 6% 1	892
	21st to end	Night	20% 10% 35% 25% 9% 1	836
February	1st to 10th	Night	20% 16% 38% 22% 4	760
	11th to 20th	Night	17% 14% 35% 26% 8% 1	743
	21st to end	Night	21% 11% 37% 24% 6%	628
March	1st to 10th	Night	16% 12% 36% 28% 7%	760
	11th to 20th	Night	16% 10% 36% 28% 8% 1	760
	21st to end	Night	19% 8% 29% 30% 14% 2	836
April	1st to 10th	Night	22% 9% 28% 32% 9% 1	760
	11th to 20th	Night	20% 7% 27% 30% 13% 3	551
	21st to end	Night	23% 5% 24% 30% 15% 3	540
May	1st to 10th	Night	18% 4 18% 38% 19% 4	540
	11th to 20th	Night	18% 4 16% 37% 23% 3	418
	21st to end	Night	12% 2 19% 40% 22% 6%	389
June	1st to 10th	Night	14% 3 18% 43% 18% 4	360
	11th to 20th	Night	13% 4 17% 37% 26% 3	360
	21st to end	Night	13% 3 18% 35% 29% 3	360
July	1st to 10th	Night	9% 2 11% 45% 27% 6%	350
	11th to 20th	Night	10% 3 17% 30% 33% 6%	368
	21st to end	Night	7% 4 15% 45% 25% 4	591
August	1st to 10th	Night	13% 1 15% 34% 30% 7%	537
	11th to 20th	Night	10% 3 14% 34% 31% 8%	534
	21st to end	Night	14% 4 20% 30% 27% 5%	596
September	1st to 10th	Night	12% 6% 18% 30% 25% 9%	720
	11th to 20th	Night	16% 5% 18% 29% 24% 8%	720
	21st to end	Night	20% 7% 18% 26% 20% 8%	720
October	1st to 10th	Night	25% 6% 24% 25% 16% 3	720
	11th to 20th	Night	30% 12% 24% 23% 9% 2	720
	21st to end	Night	38% 10% 24% 21% 6% 1	792
November	1st to 10th	Night	26% 12% 27% 25% 8% 2	740
	11th to 20th	Night	25% 16% 33% 17% 8%	760
	21st to end	Night	32% 15% 29% 18% 5%	760
December	1st to 10th	Night	30% 19% 30% 17% 5%	760
	11th to 20th	Night	25% 18% 36% 16% 4 1	817
	21st to end	Night	33% 15% 33% 16% 4	1045

Page generated at 2024-04-07 09:28:15. Version ac07

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