White Bluff
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White Bluff clear sky chart from 2005-11-06 to 2024-11-08.

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	13% 7% 3 6% 4 4 5% 4 6% 7% 41%	101080
	Night	13% 8% 3 6% 4 4 4 3 5% 7% 44%	98007
Transparency	Day	41% 4 10% 24% 18% 3	104799
	Night	40% 3 9% 24% 20% 4	102415
Seeing	Day	17% 12% 24% 24% 17% 7%	15239
	Night	17% 10% 24% 28% 17% 3	24968

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	12% 13% 6% 11% 5% 5% 5% 3 4 5% 31%	2527
	11th to 20th	Day	20% 9% 3 10% 4 4 3 3 3 5% 36%	2531
	21st to end	Day	24% 11% 6% 5% 4 3 3 3 4 5% 34%	3457
February	1st to 10th	Day	17% 12% 4 8% 4 4 4 2 4 6% 37%	1900
	11th to 20th	Day	19% 11% 4 8% 5% 4 3 2 4 5% 35%	1848
	21st to end	Day	19% 10% 4 7% 4 4 4 3 5% 5% 36%	1570
March	1st to 10th	Day	21% 13% 3 8% 4 4 3 3 3 5% 32%	3120
	11th to 20th	Day	13% 6% 3 6% 3 3 4 3 5% 6% 47%	3283
	21st to end	Day	12% 8% 3 7% 5% 4 4 3 5% 7% 42%	4096
April	1st to 10th	Day	12% 6% 2 6% 4 5% 4 3 6% 7% 45%	2280
	11th to 20th	Day	14% 8% 2 6% 5% 4 4 3 5% 6% 43%	2254
	21st to end	Day	13% 7% 3 7% 5% 5% 4 3 6% 7% 41%	2285
May	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 4 6% 8% 35%	4082
	11th to 20th	Day	15% 9% 3 7% 4 4 4 3 5% 8% 37%	4081
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 4 6% 8% 40%	4476
June	1st to 10th	Day	9% 6% 2 6% 5% 5% 6% 5% 6% 9% 41%	2540
	11th to 20th	Day	5% 3 1 5% 5% 5% 6% 5% 8% 10% 45%	2660
	21st to end	Day	5% 4 2 5% 5% 6% 6% 5% 8% 11% 42%	2660
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 7% 6% 8% 10% 38%	4440
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 6% 8% 11% 37%	4440
	21st to end	Day	15% 10% 4 9% 6% 6% 5% 4 7% 8% 26%	4471
August	1st to 10th	Day	4 3 1 4 3 4 4 5% 7% 10% 54%	3827
	11th to 20th	Day	7% 5% 3 6% 5% 5% 6% 5% 8% 10% 40%	3729
	21st to end	Day	5% 4 2 4 4 4 5% 4 7% 8% 53%	4180
September	1st to 10th	Day	11% 6% 2 5% 4 5% 6% 4 6% 8% 42%	2275
	11th to 20th	Day	14% 5% 2 6% 4 4 5% 3 4 8% 45%	2090
	21st to end	Day	11% 6% 2 6% 4 4 4 3 5% 6% 48%	2090
October	1st to 10th	Day	10% 4 1 4 4 3 3 3 4 7% 56%	2090
	11th to 20th	Day	12% 5% 2 5% 3 3 4 3 5% 6% 53%	2011
	21st to end	Day	17% 6% 2 5% 3 3 4 3 4 5% 48%	1924
November	1st to 10th	Day	13% 5% 2 4 3 3 3 2 5% 6% 55%	1735
	11th to 20th	Day	14% 7% 2 5% 4 2 4 3 5% 6% 49%	1710
	21st to end	Day	15% 8% 3 5% 3 4 4 4 4 5% 46%	1710
December	1st to 10th	Day	21% 11% 3 5% 4 4 4 3 4 5% 37%	1710
	11th to 20th	Day	16% 10% 3 7% 4 4 5% 4 5% 5% 38%	2153
	21st to end	Day	14% 12% 4 8% 6% 4 5% 4 5% 8% 31%	2845
January	1st to 10th	Night	17% 12% 3 6% 4 3 4 3 5% 6% 38%	4428
	11th to 20th	Night	17% 12% 3 10% 5% 4 3 2 4 4 36%	4436
	21st to end	Night	23% 12% 5% 6% 3 3 3 2 4 4 35%	4182
February	1st to 10th	Night	19% 11% 4 8% 4 4 4 3 5% 5% 33%	2280
	11th to 20th	Night	21% 9% 3 7% 3 4 4 2 4 5% 36%	2218
	21st to end	Night	22% 10% 3 8% 4 4 4 4 4 5% 33%	1884
March	1st to 10th	Night	23% 11% 3 7% 4 3 3 3 4 6% 33%	3733
	11th to 20th	Night	13% 8% 2 5% 4 4 4 3 4 5% 48%	3675
	21st to end	Night	14% 9% 3 7% 5% 4 4 3 5% 7% 40%	3562
April	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 47%	1900
	11th to 20th	Night	15% 7% 2 5% 3 4 4 3 4 7% 47%	1875
	21st to end	Night	12% 7% 3 5% 4 4 4 4 6% 8% 44%	1892
May	1st to 10th	Night	13% 8% 3 7% 5% 4 4 3 5% 6% 41%	2813
	11th to 20th	Night	12% 8% 2 6% 5% 4 3 3 6% 7% 44%	2812
	21st to end	Night	7% 5% 2 6% 6% 4 5% 4 7% 10% 43%	3079
June	1st to 10th	Night	9% 7% 2 5% 5% 4 4 4 6% 10% 45%	1634
	11th to 20th	Night	3 4 1 4 3 3 4 5% 8% 10% 55%	1520
	21st to end	Night	3 3 2 4 3 4 5% 6% 9% 13% 48%	1520
July	1st to 10th	Night	6% 4 2 6% 5% 5% 6% 5% 9% 13% 40%	2530
	11th to 20th	Night	5% 4 2 5% 4 4 4 5% 7% 11% 50%	2530
	21st to end	Night	10% 8% 4 10% 6% 5% 6% 5% 7% 10% 29%	3077
August	1st to 10th	Night	4 3 1 4 3 3 4 3 5% 9% 61%	3098
	11th to 20th	Night	4 3 2 5% 4 4 6% 5% 8% 12% 49%	3100
	21st to end	Night	5% 3 1 4 3 4 5% 3 7% 9% 57%	3476
September	1st to 10th	Night	11% 5% 1 6% 4 4 5% 4 5% 6% 49%	1900
	11th to 20th	Night	11% 5% 2 4 5% 4 4 3 5% 8% 50%	2076
	21st to end	Night	11% 4 2 5% 3 3 4 3 5% 5% 54%	2090
October	1st to 10th	Night	8% 5% 1 3 3 3 3 2 3 5% 62%	2090
	11th to 20th	Night	15% 5% 2 5% 3 4 3 2 4 5% 53%	2166
	21st to end	Night	15% 7% 2 5% 3 3 3 3 5% 5% 49%	2673
November	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 4 5% 53%	2504
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 5% 8% 50%	2470
	21st to end	Night	16% 8% 2 5% 4 3 4 2 4 6% 46%	2470
December	1st to 10th	Night	19% 12% 3 7% 4 3 3 3 5% 5% 35%	2470
	11th to 20th	Night	16% 10% 2 6% 4 3 2 4 4 5% 45%	3042
	21st to end	Night	16% 12% 4 10% 5% 5% 5% 4 5% 6% 29%	4802

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% 2 5% 21% 13% 2	2528
	11th to 20th	Day	53% 2 6% 19% 19% 1	2531
	21st to end	Day	54% 2 7% 24% 13% 1	3457
February	1st to 10th	Day	51% 3 8% 21% 15% 3	1900
	11th to 20th	Day	53% 3 7% 20% 14% 4	1858
	21st to end	Day	51% 2 8% 17% 16% 6%	1570
March	1st to 10th	Day	57% 2 5% 15% 13% 8%	3120
	11th to 20th	Day	39% 3 9% 25% 19% 6%	3283
	21st to end	Day	44% 2 9% 26% 17% 1	4096
April	1st to 10th	Day	39% 3 10% 23% 21% 4	2280
	11th to 20th	Day	43% 3 7% 22% 21% 5%	2254
	21st to end	Day	43% 3 10% 26% 16% 2	2285
May	1st to 10th	Day	47% 3 12% 24% 13% 1	4120
	11th to 20th	Day	47% 3 12% 25% 13%	4085
	21st to end	Day	42% 5% 10% 23% 19% 1	4489
June	1st to 10th	Day	38% 6% 13% 24% 17% 2	2540
	11th to 20th	Day	31% 6% 15% 27% 19% 3	2660
	21st to end	Day	32% 8% 15% 25% 17% 4	2660
July	1st to 10th	Day	38% 5% 19% 28% 8% 2	4371
	11th to 20th	Day	38% 5% 16% 31% 9% 2	4365
	21st to end	Day	56% 4 12% 19% 7% 1	4329
August	1st to 10th	Day	24% 5% 13% 34% 22% 2	3814
	11th to 20th	Day	37% 4 13% 27% 17% 2	3765
	21st to end	Day	28% 5% 9% 32% 25% 2	4179
September	1st to 10th	Day	39% 6% 10% 23% 19% 4	2275
	11th to 20th	Day	40% 5% 8% 23% 22% 2	2090
	21st to end	Day	36% 4 9% 25% 21% 5%	2090
October	1st to 10th	Day	21% 3 5% 17% 45% 9%	3480
	11th to 20th	Day	24% 2 6% 25% 29% 14%	3316
	21st to end	Day	32% 2 5% 24% 31% 7%	3149
November	1st to 10th	Day	32% 3 8% 24% 28% 5%	1735
	11th to 20th	Day	37% 2 7% 23% 24% 6%	1710
	21st to end	Day	40% 3 7% 25% 19% 5%	1710
December	1st to 10th	Day	51% 2 6% 22% 16% 3	1710
	11th to 20th	Day	48% 3 7% 21% 19% 2	2150
	21st to end	Day	53% 2 9% 22% 12% 2	2845
January	1st to 10th	Night	50% 2 5% 27% 16% 1	4428
	11th to 20th	Night	54% 2 5% 19% 16% 4	4436
	21st to end	Night	55% 2 6% 22% 14% 1	4182
February	1st to 10th	Night	55% 2 8% 18% 16% 1	2280
	11th to 20th	Night	52% 2 5% 20% 16% 4	2219
	21st to end	Night	54% 3 7% 16% 16% 5%	1884
March	1st to 10th	Night	54% 3 7% 13% 16% 7%	3733
	11th to 20th	Night	40% 2 8% 23% 16% 11%	3675
	21st to end	Night	46% 3 8% 23% 19% 1	3562
April	1st to 10th	Night	37% 3 10% 25% 21% 3	1900
	11th to 20th	Night	39% 3 7% 21% 23% 8%	1875
	21st to end	Night	39% 3 10% 27% 18% 2	1892
May	1st to 10th	Night	46% 2 13% 23% 14% 2	2840
	11th to 20th	Night	40% 4 16% 22% 17% 1	2813
	21st to end	Night	36% 5% 16% 25% 17% 1	3087
June	1st to 10th	Night	35% 5% 14% 24% 18% 3	1634
	11th to 20th	Night	22% 6% 17% 32% 20% 4	1520
	21st to end	Night	24% 8% 18% 29% 16% 4	1520
July	1st to 10th	Night	34% 5% 19% 31% 9% 2	2490
	11th to 20th	Night	28% 5% 16% 39% 9% 3	2482
	21st to end	Night	51% 6% 13% 20% 9% 1	2979
August	1st to 10th	Night	21% 3 11% 40% 24% 1	3087
	11th to 20th	Night	27% 5% 21% 30% 16% 1	3130
	21st to end	Night	24% 4 11% 33% 25% 3	3476
September	1st to 10th	Night	35% 5% 10% 25% 19% 5%	1900
	11th to 20th	Night	34% 5% 9% 23% 27% 3	2076
	21st to end	Night	31% 4 8% 25% 25% 6%	2090
October	1st to 10th	Night	20% 2 5% 18% 43% 11%	3480
	11th to 20th	Night	22% 1 4 23% 33% 17%	3587
	21st to end	Night	27% 2 6% 26% 29% 11%	4398
November	1st to 10th	Night	35% 3 6% 23% 26% 7%	2504
	11th to 20th	Night	34% 3 6% 22% 27% 8%	2470
	21st to end	Night	41% 2 7% 23% 22% 5%	2470
December	1st to 10th	Night	52% 2 8% 19% 16% 3	2470
	11th to 20th	Night	43% 2 6% 23% 22% 4	3044
	21st to end	Night	58% 2 7% 18% 12% 3	4802

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	24% 24% 36% 11% 6%	270
	11th to 20th	Day	32% 29% 25% 12% 1 1	270
	21st to end	Day	24% 27% 37% 9% 3	297
February	1st to 10th	Day	30% 24% 30% 13% 1 1	270
	11th to 20th	Day	36% 26% 29% 7% 2	270
	21st to end	Day	37% 27% 26% 8% 1	225
March	1st to 10th	Day	30% 20% 35% 12% 3	270
	11th to 20th	Day	26% 26% 32% 13% 4 1	341
	21st to end	Day	26% 19% 34% 17% 5%	506
April	1st to 10th	Day	24% 17% 30% 21% 7% 1	460
	11th to 20th	Day	23% 17% 28% 23% 7% 1	452
	21st to end	Day	19% 20% 30% 20% 10% 2	460
May	1st to 10th	Day	19% 19% 27% 22% 10% 3	463
	11th to 20th	Day	16% 10% 27% 24% 17% 5%	487
	21st to end	Day	12% 7% 23% 28% 19% 11%	529
June	1st to 10th	Day	11% 6% 23% 26% 20% 13%	560
	11th to 20th	Day	5% 4 19% 33% 27% 12%	680
	21st to end	Day	6% 5% 23% 32% 23% 12%	680
July	1st to 10th	Day	8% 3 15% 31% 28% 15%	671
	11th to 20th	Day	8% 4 14% 29% 30% 15%	668
	21st to end	Day	11% 3 15% 29% 25% 17%	537
August	1st to 10th	Day	9% 3 14% 30% 29% 14%	486
	11th to 20th	Day	11% 4 15% 35% 28% 6%	479
	21st to end	Day	12% 2 10% 23% 34% 18%	539
September	1st to 10th	Day	11% 3 14% 30% 29% 12%	490
	11th to 20th	Day	14% 3 13% 26% 31% 13%	490
	21st to end	Day	17% 6% 18% 28% 23% 8%	490
October	1st to 10th	Day	12% 4 25% 28% 24% 7%	490
	11th to 20th	Day	14% 16% 33% 22% 13% 2	411
	21st to end	Day	25% 15% 28% 24% 7% 1	330
November	1st to 10th	Day	19% 14% 29% 28% 8% 2	291
	11th to 20th	Day	16% 22% 38% 19% 4	270
	21st to end	Day	22% 18% 30% 19% 9% 2	270
December	1st to 10th	Day	33% 18% 27% 18% 4	270
	11th to 20th	Day	24% 23% 30% 16% 6% 1	270
	21st to end	Day	27% 22% 34% 15% 1	297
January	1st to 10th	Night	23% 21% 30% 23% 4	950
	11th to 20th	Night	28% 21% 28% 19% 4	950
	21st to end	Night	22% 18% 36% 22% 2	838
February	1st to 10th	Night	27% 15% 32% 23% 3	760
	11th to 20th	Night	28% 20% 30% 21% 2	743
	21st to end	Night	32% 20% 31% 16% 1	628
March	1st to 10th	Night	23% 17% 29% 25% 5%	760
	11th to 20th	Night	21% 17% 34% 21% 6% 1	760
	21st to end	Night	21% 15% 31% 25% 8%	684
April	1st to 10th	Night	16% 14% 34% 28% 8% 1	570
	11th to 20th	Night	20% 12% 33% 25% 9% 1	563
	21st to end	Night	17% 12% 32% 28% 11% 1	570
May	1st to 10th	Night	14% 9% 32% 27% 16% 2	570
	11th to 20th	Night	11% 7% 27% 32% 20% 4	561
	21st to end	Night	9% 3 20% 38% 25% 5%	617
June	1st to 10th	Night	11% 4 16% 36% 28% 4	570
	11th to 20th	Night	5% 2 12% 39% 36% 6%	570
	21st to end	Night	4 2 16% 37% 34% 7%	570
July	1st to 10th	Night	8% 2 9% 32% 36% 13%	555
	11th to 20th	Night	7% 2 11% 30% 40% 10%	552
	21st to end	Night	8% 2 10% 32% 40% 9%	624
August	1st to 10th	Night	7% 2 8% 32% 44% 8%	567
	11th to 20th	Night	8% 2 11% 39% 35% 6%	564
	21st to end	Night	9% 1 9% 30% 41% 9%	627
September	1st to 10th	Night	12% 2 11% 33% 37% 5%	570
	11th to 20th	Night	14% 3 12% 27% 36% 7%	746
	21st to end	Night	13% 4 17% 30% 33% 5%	760
October	1st to 10th	Night	11% 6% 18% 33% 27% 6%	760
	11th to 20th	Night	19% 8% 24% 30% 18% 1	760
	21st to end	Night	19% 10% 26% 28% 15% 2	836
November	1st to 10th	Night	16% 9% 22% 35% 16% 2	771
	11th to 20th	Night	15% 13% 33% 26% 12% 1	760
	21st to end	Night	21% 13% 27% 28% 11%	760
December	1st to 10th	Night	27% 14% 28% 25% 6%	760
	11th to 20th	Night	22% 12% 31% 26% 7% 1	760
	21st to end	Night	28% 17% 28% 23% 4	1002

Page generated at 2024-11-05 07:15:52. Version ac07

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