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 2024-11-05.

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	14% 11% 4 9% 5% 5% 4 4 5% 7% 32%	101563
	Night	14% 13% 5% 11% 6% 5% 5% 3 5% 6% 28%	97525
Transparency	Day	28% 46% 6% 13% 6% 1	105109
	Night	32% 45% 6% 11% 6%	102054
Seeing	Day	18% 7% 23% 29% 18% 5%	15160
	Night	21% 10% 26% 27% 14% 3	24321

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% 23% 12% 18% 10% 6% 4 3 3 3 5%	2208
	11th to 20th	Day	10% 21% 9% 31% 10% 5% 4 2 2 2 3	2598
	21st to end	Day	18% 21% 10% 16% 8% 6% 4 3 4 3 7%	3124
February	1st to 10th	Day	11% 20% 7% 19% 11% 6% 5% 3 4 4 11%	1710
	11th to 20th	Day	10% 15% 8% 16% 11% 7% 5% 3 5% 6% 15%	1663
	21st to end	Day	12% 17% 6% 12% 8% 8% 5% 3 5% 6% 18%	1517
March	1st to 10th	Day	16% 16% 5% 9% 6% 5% 3 3 5% 5% 29%	3340
	11th to 20th	Day	10% 15% 8% 13% 7% 5% 5% 3 5% 4 25%	3480
	21st to end	Day	14% 11% 6% 9% 6% 5% 5% 3 5% 6% 31%	3815
April	1st to 10th	Day	16% 13% 4 8% 5% 5% 4 3 5% 7% 29%	2190
	11th to 20th	Day	19% 10% 2 7% 4 3 4 2 5% 6% 38%	2440
	21st to end	Day	19% 9% 3 7% 4 3 4 3 6% 6% 35%	2470
May	1st to 10th	Day	15% 8% 3 6% 4 4 4 4 5% 7% 40%	4108
	11th to 20th	Day	14% 7% 2 5% 4 4 4 4 6% 9% 41%	4291
	21st to end	Day	13% 5% 2 6% 4 3 4 4 5% 8% 46%	4837
June	1st to 10th	Day	13% 7% 3 5% 4 5% 5% 5% 6% 7% 40%	2788
	11th to 20th	Day	9% 6% 3 5% 4 4 4 5% 6% 8% 44%	2850
	21st to end	Day	13% 7% 3 6% 4 4 4 4 6% 7% 43%	2850
July	1st to 10th	Day	12% 6% 3 7% 5% 5% 5% 4 6% 9% 39%	4760
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 7% 51%	4681
	21st to end	Day	9% 5% 2 6% 4 3 3 3 6% 9% 51%	4466
August	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 7% 8% 44%	4104
	11th to 20th	Day	14% 6% 2 5% 4 4 5% 4 6% 9% 40%	4044
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 46%	4483
September	1st to 10th	Day	13% 7% 3 6% 5% 4 4 4 6% 8% 41%	2271
	11th to 20th	Day	11% 6% 2 7% 4 4 4 4 6% 9% 43%	2090
	21st to end	Day	17% 7% 3 8% 5% 5% 4 4 6% 6% 35%	2090
October	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 3 5% 6% 34%	1918
	11th to 20th	Day	21% 12% 4 11% 6% 6% 5% 3 5% 6% 21%	1900
	21st to end	Day	27% 15% 4 10% 5% 4 5% 3 4 6% 17%	2024
November	1st to 10th	Day	14% 18% 3 11% 6% 5% 6% 4 6% 6% 21%	1651
	11th to 20th	Day	15% 18% 5% 11% 7% 6% 6% 5% 5% 6% 17%	1520
	21st to end	Day	19% 21% 7% 13% 7% 5% 6% 4 4 4 10%	1520
December	1st to 10th	Day	13% 27% 9% 17% 8% 4 5% 4 4 3 6%	1520
	11th to 20th	Day	19% 22% 8% 16% 7% 5% 5% 3 4 5% 7%	1811
	21st to end	Day	25% 24% 6% 17% 6% 4 3 2 3 4 5%	2431
January	1st to 10th	Night	14% 23% 10% 19% 7% 5% 5% 3 3 3 7%	4748
	11th to 20th	Night	13% 18% 9% 25% 10% 6% 5% 3 3 3 5%	4361
	21st to end	Night	16% 19% 10% 18% 8% 6% 6% 3 3 4 7%	4532
February	1st to 10th	Night	12% 18% 6% 18% 8% 6% 5% 3 5% 4 14%	2470
	11th to 20th	Night	11% 14% 8% 16% 10% 6% 4 3 5% 5% 18%	2403
	21st to end	Night	15% 13% 6% 12% 7% 6% 5% 4 5% 5% 22%	1937
March	1st to 10th	Night	12% 12% 4 9% 5% 5% 4 3 5% 6% 34%	3499
	11th to 20th	Night	9% 13% 5% 9% 6% 4 4 3 5% 7% 34%	3479
	21st to end	Night	12% 11% 5% 8% 6% 5% 5% 4 5% 5% 35%	3817
April	1st to 10th	Night	20% 10% 3 7% 6% 5% 4 3 4 6% 33%	1990
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 4 5% 7% 37%	1705
	21st to end	Night	19% 9% 4 8% 5% 4 4 3 5% 7% 32%	1710
May	1st to 10th	Night	15% 7% 3 8% 4 4 4 3 5% 7% 40%	2833
	11th to 20th	Night	13% 7% 2 7% 6% 4 4 4 6% 8% 39%	2601
	21st to end	Night	9% 6% 3 7% 4 4 4 4 6% 7% 46%	2738
June	1st to 10th	Night	14% 6% 2 7% 5% 5% 6% 3 6% 7% 38%	1387
	11th to 20th	Night	10% 6% 2 5% 5% 4 5% 4 7% 9% 43%	1330
	21st to end	Night	12% 6% 2 7% 5% 4 5% 5% 5% 9% 41%	1330
July	1st to 10th	Night	9% 7% 2 8% 3 4 4 4 5% 7% 46%	2210
	11th to 20th	Night	11% 5% 2 4 3 4 4 3 5% 7% 52%	2284
	21st to end	Night	7% 6% 2 6% 5% 4 4 4 6% 7% 50%	3087
August	1st to 10th	Night	11% 7% 2 6% 4 4 5% 3 7% 8% 43%	2825
	11th to 20th	Night	14% 6% 3 7% 3 5% 5% 4 6% 8% 40%	2785
	21st to end	Night	11% 6% 3 6% 3 4 3 4 5% 9% 46%	3140
September	1st to 10th	Night	10% 5% 2 5% 3 3 4 4 7% 8% 47%	1907
	11th to 20th	Night	11% 6% 2 6% 4 3 4 4 5% 7% 48%	2090
	21st to end	Night	16% 8% 3 8% 6% 3 5% 4 5% 7% 36%	2090
October	1st to 10th	Night	18% 8% 2 8% 5% 4 5% 3 6% 7% 33%	2261
	11th to 20th	Night	21% 14% 4 10% 6% 5% 5% 3 5% 6% 23%	2280
	21st to end	Night	24% 15% 4 9% 5% 5% 6% 3 5% 5% 19%	2571
November	1st to 10th	Night	16% 14% 4 10% 6% 5% 5% 4 5% 5% 25%	2527
	11th to 20th	Night	16% 17% 5% 11% 6% 7% 6% 4 5% 7% 17%	2660
	21st to end	Night	20% 20% 6% 11% 6% 5% 5% 4 4 5% 13%	2660
December	1st to 10th	Night	17% 24% 8% 13% 8% 6% 5% 3 4 4 7%	2660
	11th to 20th	Night	12% 22% 8% 19% 7% 5% 4 3 4 4 10%	3382
	21st to end	Night	23% 22% 9% 16% 7% 4 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	58% 36% 4 2	2209
	11th to 20th	Day	60% 36% 2 1	2598
	21st to end	Day	51% 38% 6% 3 1	3124
February	1st to 10th	Day	26% 65% 1 6% 1	1710
	11th to 20th	Day	23% 64% 3 6% 3	1672
	21st to end	Day	21% 64% 4 8% 3	1517
March	1st to 10th	Day	37% 39% 8% 9% 6%	3343
	11th to 20th	Day	40% 39% 5% 13% 3 1	3480
	21st to end	Day	34% 39% 7% 13% 6% 1	3815
April	1st to 10th	Day	21% 64% 3 8% 4	2190
	11th to 20th	Day	19% 64% 2 9% 5% 1	2440
	21st to end	Day	17% 64% 5% 8% 5% 1	2470
May	1st to 10th	Day	28% 39% 7% 14% 12% 1	4120
	11th to 20th	Day	27% 38% 10% 18% 7%	4295
	21st to end	Day	25% 38% 6% 13% 13% 3	4837
June	1st to 10th	Day	15% 65% 3 10% 7% 1	2788
	11th to 20th	Day	14% 65% 4 9% 7% 1	2850
	21st to end	Day	15% 63% 3 11% 7% 1	2850
July	1st to 10th	Day	29% 37% 11% 13% 10% 1	4686
	11th to 20th	Day	20% 36% 9% 27% 9%	4600
	21st to end	Day	18% 36% 7% 24% 15% 1	4324
August	1st to 10th	Day	22% 37% 10% 20% 10% 1	4091
	11th to 20th	Day	29% 38% 11% 16% 6%	4083
	21st to end	Day	20% 38% 9% 26% 7%	4483
September	1st to 10th	Day	18% 59% 6% 11% 5%	2271
	11th to 20th	Day	13% 60% 4 15% 8%	2090
	21st to end	Day	18% 59% 6% 12% 5%	2090
October	1st to 10th	Day	25% 37% 8% 19% 10%	3178
	11th to 20th	Day	32% 37% 6% 17% 7%	3140
	21st to end	Day	37% 38% 10% 12% 3	3313
November	1st to 10th	Day	31% 57% 5% 5% 2	1651
	11th to 20th	Day	29% 59% 5% 5% 2	1520
	21st to end	Day	32% 60% 4 4	1520
December	1st to 10th	Day	34% 59% 3 3 1	1520
	11th to 20th	Day	44% 49% 2 4	1810
	21st to end	Day	56% 36% 5% 2	2431
January	1st to 10th	Night	55% 36% 4 4	4748
	11th to 20th	Night	57% 36% 4 3 1	4361
	21st to end	Night	54% 38% 4 3 1	4532
February	1st to 10th	Night	26% 64% 2 6% 2	2470
	11th to 20th	Night	22% 64% 3 8% 3	2405
	21st to end	Night	20% 64% 4 7% 4	1937
March	1st to 10th	Night	30% 39% 10% 14% 7%	3509
	11th to 20th	Night	30% 38% 8% 16% 6% 1	3480
	21st to end	Night	35% 39% 4 17% 5%	3817
April	1st to 10th	Night	23% 64% 3 6% 4	1990
	11th to 20th	Night	18% 65% 2 9% 6% 1	1705
	21st to end	Night	20% 64% 4 6% 5% 1	1710
May	1st to 10th	Night	28% 39% 7% 14% 12% 1	2840
	11th to 20th	Night	30% 38% 6% 16% 9% 2	2602
	21st to end	Night	27% 38% 5% 16% 13% 2	2739
June	1st to 10th	Night	13% 64% 2 10% 9% 1	1387
	11th to 20th	Night	12% 65% 4 12% 7% 1	1330
	21st to end	Night	13% 63% 4 12% 7% 1	1330
July	1st to 10th	Night	27% 35% 9% 14% 11% 4	2175
	11th to 20th	Night	22% 35% 5% 28% 10%	2242
	21st to end	Night	22% 36% 7% 18% 16% 1	2988
August	1st to 10th	Night	25% 36% 9% 18% 11% 1	2814
	11th to 20th	Night	30% 39% 11% 13% 7%	2812
	21st to end	Night	22% 38% 8% 23% 9%	3140
September	1st to 10th	Night	13% 60% 7% 14% 7%	1907
	11th to 20th	Night	13% 59% 4 14% 10%	2090
	21st to end	Night	18% 59% 6% 12% 5%	2090
October	1st to 10th	Night	24% 37% 6% 20% 13%	3768
	11th to 20th	Night	30% 36% 10% 16% 9%	3779
	21st to end	Night	33% 38% 10% 17% 3	4232
November	1st to 10th	Night	30% 56% 5% 7% 2	2527
	11th to 20th	Night	28% 60% 6% 5% 2	2660
	21st to end	Night	32% 60% 3 4 1	2660
December	1st to 10th	Night	32% 59% 3 4 1	2660
	11th to 20th	Night	43% 48% 5% 4 1	3382
	21st to end	Night	55% 36% 6% 3 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	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% 9% 32% 30% 10% 1	460
	11th to 20th	Day	25% 8% 28% 21% 13% 5%	452
	21st to end	Day	24% 7% 26% 29% 12% 2	460
May	1st to 10th	Day	20% 3 23% 34% 17% 3	463
	11th to 20th	Day	15% 5% 20% 33% 21% 6%	487
	21st to end	Day	12% 4 18% 35% 22% 8%	529
June	1st to 10th	Day	14% 2 19% 38% 23% 4	618
	11th to 20th	Day	11% 3 19% 38% 24% 4	680
	21st to end	Day	15% 4 18% 35% 23% 5%	680
July	1st to 10th	Day	10% 2 13% 36% 31% 8%	671
	11th to 20th	Day	11% 3 18% 32% 25% 11%	653
	21st to end	Day	10% 3 12% 39% 28% 9%	532
August	1st to 10th	Day	12% 3 14% 32% 29% 10%	486
	11th to 20th	Day	12% 2 10% 32% 32% 11%	479
	21st to end	Day	14% 4 16% 33% 24% 9%	539
September	1st to 10th	Day	17% 5% 17% 29% 25% 7%	490
	11th to 20th	Day	12% 4 19% 21% 28% 16%	490
	21st to end	Day	18% 7% 19% 26% 23% 7%	490
October	1st to 10th	Day	22% 7% 26% 22% 17% 7%	490
	11th to 20th	Day	23% 11% 28% 26% 9% 2	490
	21st to end	Day	33% 12% 26% 21% 8%	473
November	1st to 10th	Day	18% 18% 30% 21% 11% 2	255
	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	581
	21st to end	Night	23% 6% 24% 29% 15% 2	570
May	1st to 10th	Night	18% 4 17% 38% 19% 4	570
	11th to 20th	Night	17% 4 15% 38% 23% 3	441
	21st to end	Night	12% 3 18% 39% 22% 5%	411
June	1st to 10th	Night	14% 3 18% 42% 18% 4	380
	11th to 20th	Night	12% 4 17% 37% 27% 3	380
	21st to end	Night	13% 2 18% 35% 28% 3	380
July	1st to 10th	Night	9% 2 10% 46% 27% 6%	370
	11th to 20th	Night	10% 3 16% 31% 34% 6%	390
	21st to end	Night	7% 4 14% 43% 27% 4	624
August	1st to 10th	Night	13% 2 14% 34% 29% 7%	567
	11th to 20th	Night	10% 3 14% 33% 31% 9%	564
	21st to end	Night	14% 4 19% 30% 28% 5%	630
September	1st to 10th	Night	13% 6% 18% 30% 25% 9%	760
	11th to 20th	Night	15% 4 17% 28% 25% 10%	760
	21st to end	Night	20% 6% 18% 26% 21% 8%	760
October	1st to 10th	Night	24% 6% 25% 26% 16% 3	760
	11th to 20th	Night	29% 12% 24% 23% 10% 2	760
	21st to end	Night	36% 10% 25% 22% 6%	836
November	1st to 10th	Night	26% 12% 27% 25% 8% 2	760
	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 2024-11-03 02:11:12. Version ac07

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