Wally's Corner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wally's Corner clear sky chart from 2005-11-06 to 2024-11-12.

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	12% 7% 3 7% 5% 4 5% 4 6% 7% 40%	101548
	Night	10% 7% 3 7% 5% 4 4 4 5% 7% 43%	97694
Transparency	Day	40% 7% 14% 24% 13% 1	105162
	Night	38% 7% 14% 24% 15% 2	102211
Seeing	Day	15% 10% 32% 28% 13% 2	15975
	Night	13% 9% 34% 33% 10% 1	25853

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	11% 13% 4 14% 10% 7% 8% 3 4 5% 20%	2382
	11th to 20th	Day	5% 14% 6% 12% 5% 5% 9% 3 9% 9% 22%	2670
	21st to end	Day	6% 12% 8% 15% 7% 8% 7% 4 5% 6% 21%	3135
February	1st to 10th	Day	9% 10% 4 12% 8% 7% 6% 5% 5% 7% 26%	1710
	11th to 20th	Day	8% 11% 4 9% 7% 6% 5% 4 6% 6% 34%	1667
	21st to end	Day	10% 11% 4 8% 4 5% 4 4 7% 6% 36%	1570
March	1st to 10th	Day	12% 9% 4 8% 4 4 4 3 4 8% 41%	3316
	11th to 20th	Day	10% 9% 3 8% 4 3 3 4 4 6% 45%	3480
	21st to end	Day	25% 12% 4 11% 4 4 3 3 5% 5% 24%	3814
April	1st to 10th	Day	17% 8% 3 6% 4 3 5% 4 7% 7% 37%	2153
	11th to 20th	Day	19% 10% 3 6% 4 4 4 3 5% 5% 38%	2442
	21st to end	Day	21% 9% 2 6% 4 3 4 3 5% 6% 36%	2470
May	1st to 10th	Day	16% 6% 2 7% 4 5% 4 4 7% 8% 36%	4082
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 5% 6% 47%	4112
	21st to end	Day	18% 6% 2 6% 4 4 4 3 6% 8% 39%	4824
June	1st to 10th	Day	12% 5% 2 5% 3 4 4 4 6% 9% 47%	2755
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 6% 7% 43%	2850
	21st to end	Day	9% 4 1 5% 4 4 5% 5% 7% 9% 47%	2850
July	1st to 10th	Day	10% 5% 2 6% 5% 6% 5% 5% 7% 9% 40%	4750
	11th to 20th	Day	6% 3 1 4 4 4 4 3 5% 8% 58%	4400
	21st to end	Day	4 3 1 6% 4 4 5% 4 7% 10% 51%	4465
August	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 8% 43%	4104
	11th to 20th	Day	16% 8% 2 7% 4 4 5% 4 7% 9% 35%	4041
	21st to end	Day	8% 5% 2 6% 4 4 4 3 5% 8% 51%	4532
September	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 6% 52%	2224
	11th to 20th	Day	11% 5% 2 4 3 3 3 3 5% 7% 54%	2090
	21st to end	Day	11% 4 2 5% 3 4 4 3 4 8% 53%	2090
October	1st to 10th	Day	14% 7% 2 5% 4 3 3 3 4 6% 48%	1948
	11th to 20th	Day	13% 7% 2 4 2 4 4 3 5% 6% 51%	1900
	21st to end	Day	15% 8% 2 7% 3 3 3 3 4 6% 45%	2015
November	1st to 10th	Day	12% 7% 3 7% 4 3 3 4 6% 8% 44%	1763
	11th to 20th	Day	8% 9% 4 12% 5% 5% 4 4 5% 7% 38%	1558
	21st to end	Day	11% 9% 3 6% 4 5% 5% 3 6% 8% 40%	1520
December	1st to 10th	Day	7% 9% 3 12% 7% 6% 4 4 5% 8% 33%	1520
	11th to 20th	Day	8% 11% 5% 11% 7% 7% 5% 4 6% 7% 28%	1904
	21st to end	Day	17% 9% 5% 15% 5% 5% 4 4 6% 7% 24%	2442
January	1st to 10th	Night	10% 11% 4 14% 11% 6% 5% 4 5% 6% 24%	4569
	11th to 20th	Night	4 9% 4 11% 8% 6% 9% 6% 10% 8% 26%	4296
	21st to end	Night	6% 11% 7% 15% 5% 6% 6% 5% 5% 6% 28%	4532
February	1st to 10th	Night	7% 11% 4 10% 7% 5% 4 4 5% 7% 36%	2470
	11th to 20th	Night	8% 9% 4 9% 5% 4 5% 4 6% 7% 40%	2403
	21st to end	Night	9% 9% 3 7% 6% 5% 5% 4 6% 8% 39%	1899
March	1st to 10th	Night	8% 7% 2 6% 4 4 4 3 5% 6% 51%	3527
	11th to 20th	Night	9% 7% 2 6% 4 3 4 4 5% 7% 49%	3480
	21st to end	Night	25% 12% 4 8% 6% 3 3 3 5% 5% 26%	3817
April	1st to 10th	Night	15% 9% 2 5% 5% 4 4 4 5% 7% 39%	2023
	11th to 20th	Night	17% 8% 3 6% 4 3 3 2 4 5% 44%	1689
	21st to end	Night	17% 8% 3 6% 4 3 4 3 6% 6% 40%	1710
May	1st to 10th	Night	18% 5% 2 5% 3 4 3 3 5% 7% 46%	2823
	11th to 20th	Night	9% 6% 2 6% 3 4 4 3 5% 7% 51%	2792
	21st to end	Night	17% 5% 2 5% 4 3 4 3 5% 7% 45%	2743
June	1st to 10th	Night	8% 4 2 5% 3 4 5% 3 5% 8% 53%	1420
	11th to 20th	Night	8% 5% 2 4 4 4 4 4 6% 9% 52%	1330
	21st to end	Night	8% 4 1 4 3 2 3 4 6% 8% 58%	1330
July	1st to 10th	Night	9% 6% 2 5% 4 3 3 4 6% 8% 50%	2220
	11th to 20th	Night	4 2 1 3 2 3 3 3 5% 7% 66%	2538
	21st to end	Night	3 3 1 4 3 3 4 4 7% 11% 58%	3098
August	1st to 10th	Night	6% 5% 3 7% 4 4 5% 4 6% 8% 48%	2836
	11th to 20th	Night	12% 4 2 5% 3 4 4 3 6% 8% 50%	2798
	21st to end	Night	8% 4 1 5% 3 3 4 3 6% 8% 55%	3135
September	1st to 10th	Night	8% 4 1 5% 2 3 3 3 4 6% 60%	1953
	11th to 20th	Night	9% 4 2 4 3 3 3 3 5% 7% 56%	2090
	21st to end	Night	9% 5% 2 3 3 3 3 3 5% 7% 57%	2090
October	1st to 10th	Night	14% 5% 2 4 3 2 3 3 4 6% 54%	2212
	11th to 20th	Night	12% 7% 3 4 4 3 3 3 4 6% 52%	2280
	21st to end	Night	14% 8% 2 6% 3 4 3 3 4 6% 47%	2579
November	1st to 10th	Night	10% 6% 2 6% 3 4 4 3 4 6% 51%	2535
	11th to 20th	Night	9% 8% 3 9% 4 4 4 4 5% 6% 44%	2644
	21st to end	Night	10% 8% 2 6% 4 5% 4 4 5% 7% 46%	2660
December	1st to 10th	Night	7% 9% 3 11% 6% 5% 4 4 6% 7% 37%	2660
	11th to 20th	Night	10% 9% 4 9% 5% 4 5% 4 6% 8% 36%	3288
	21st to end	Night	17% 10% 4 15% 6% 4 4 3 5% 5% 27%	5225

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	64% 6% 12% 12% 5%	2383
	11th to 20th	Day	56% 5% 9% 24% 7%	2670
	21st to end	Day	59% 9% 14% 13% 5%	3135
February	1st to 10th	Day	55% 8% 12% 15% 9%	1710
	11th to 20th	Day	49% 7% 13% 21% 8% 2	1676
	21st to end	Day	46% 9% 14% 19% 11% 1	1570
March	1st to 10th	Day	41% 8% 13% 29% 9% 1	3316
	11th to 20th	Day	38% 6% 10% 28% 14% 3	3480
	21st to end	Day	61% 8% 12% 14% 4 1	3814
April	1st to 10th	Day	44% 7% 14% 24% 10% 1	2153
	11th to 20th	Day	47% 6% 11% 23% 12% 2	2442
	21st to end	Day	48% 6% 12% 24% 9%	2470
May	1st to 10th	Day	40% 10% 13% 23% 14%	4120
	11th to 20th	Day	35% 8% 12% 26% 15% 3	4116
	21st to end	Day	41% 8% 12% 23% 15% 1	4837
June	1st to 10th	Day	33% 9% 16% 28% 12% 2	2755
	11th to 20th	Day	38% 8% 14% 23% 14% 3	2850
	21st to end	Day	31% 9% 16% 28% 14% 3	2850
July	1st to 10th	Day	36% 9% 19% 23% 11% 1	4676
	11th to 20th	Day	25% 6% 14% 33% 20% 3	4323
	21st to end	Day	25% 8% 19% 27% 20% 1	4325
August	1st to 10th	Day	36% 8% 15% 27% 14% 2	4090
	11th to 20th	Day	44% 8% 15% 25% 8% 1	4080
	21st to end	Day	31% 6% 19% 26% 15% 2	4531
September	1st to 10th	Day	32% 6% 11% 30% 18% 1	2224
	11th to 20th	Day	31% 6% 16% 31% 15% 1	2090
	21st to end	Day	30% 6% 11% 31% 20% 2	2090
October	1st to 10th	Day	26% 4 8% 29% 30% 3	3234
	11th to 20th	Day	31% 5% 14% 25% 22% 3	3140
	21st to end	Day	41% 4 13% 24% 17% 1	3308
November	1st to 10th	Day	38% 6% 15% 24% 14% 3	1763
	11th to 20th	Day	45% 7% 14% 21% 12%	1558
	21st to end	Day	42% 6% 15% 23% 12% 1	1520
December	1st to 10th	Day	48% 6% 18% 18% 9% 2	1520
	11th to 20th	Day	53% 6% 17% 19% 5%	1901
	21st to end	Day	57% 6% 13% 15% 7% 1	2442
January	1st to 10th	Night	58% 7% 11% 16% 7%	4569
	11th to 20th	Night	49% 8% 14% 20% 9% 1	4296
	21st to end	Night	52% 10% 15% 14% 9% 1	4532
February	1st to 10th	Night	47% 6% 12% 22% 11% 1	2470
	11th to 20th	Night	43% 7% 12% 23% 12% 3	2404
	21st to end	Night	41% 8% 13% 21% 13% 4	1899
March	1st to 10th	Night	32% 7% 14% 27% 18% 2	3527
	11th to 20th	Night	33% 7% 12% 30% 16% 2	3480
	21st to end	Night	58% 8% 13% 15% 5% 1	3817
April	1st to 10th	Night	42% 8% 14% 23% 12% 1	2023
	11th to 20th	Night	42% 6% 10% 22% 17% 2	1689
	21st to end	Night	42% 7% 11% 25% 13% 2	1710
May	1st to 10th	Night	37% 7% 14% 21% 18% 2	2850
	11th to 20th	Night	30% 9% 12% 27% 19% 3	2793
	21st to end	Night	37% 8% 13% 26% 15% 1	2751
June	1st to 10th	Night	28% 8% 16% 28% 17% 3	1420
	11th to 20th	Night	28% 7% 17% 25% 20% 4	1330
	21st to end	Night	23% 7% 17% 29% 22% 2	1330
July	1st to 10th	Night	32% 6% 21% 25% 13% 2	2185
	11th to 20th	Night	18% 6% 14% 37% 23% 3	2492
	21st to end	Night	18% 9% 19% 31% 19% 3	2999
August	1st to 10th	Night	33% 7% 14% 27% 16% 2	2826
	11th to 20th	Night	33% 7% 17% 29% 13% 1	2825
	21st to end	Night	26% 7% 19% 25% 19% 3	3135
September	1st to 10th	Night	26% 6% 15% 28% 23% 3	1953
	11th to 20th	Night	26% 7% 14% 33% 18% 2	2090
	21st to end	Night	26% 6% 12% 31% 23% 2	2090
October	1st to 10th	Night	20% 3 7% 25% 40% 3	3693
	11th to 20th	Night	26% 3 14% 30% 24% 2	3779
	21st to end	Night	39% 4 12% 29% 15% 1	4240
November	1st to 10th	Night	35% 5% 15% 23% 19% 4	2535
	11th to 20th	Night	38% 7% 14% 25% 14% 2	2644
	21st to end	Night	37% 5% 16% 27% 14% 1	2660
December	1st to 10th	Night	44% 8% 17% 23% 8%	2660
	11th to 20th	Night	43% 7% 23% 20% 6%	3290
	21st to end	Night	57% 7% 10% 18% 7% 1	5225

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% 10% 35% 26% 11% 2	270
	11th to 20th	Day	18% 11% 39% 24% 7%	270
	21st to end	Day	14% 11% 38% 25% 11% 1	297
February	1st to 10th	Day	13% 19% 39% 26% 3	270
	11th to 20th	Day	11% 18% 41% 23% 7% 1	270
	21st to end	Day	16% 15% 45% 21% 2	225
March	1st to 10th	Day	20% 15% 40% 21% 3 1	270
	11th to 20th	Day	20% 13% 36% 23% 7% 1	270
	21st to end	Day	25% 13% 34% 20% 7% 1	297
April	1st to 10th	Day	25% 17% 36% 18% 4	333
	11th to 20th	Day	25% 17% 31% 22% 5% 1	640
	21st to end	Day	27% 14% 28% 20% 10% 2	650
May	1st to 10th	Day	21% 12% 31% 26% 8% 1	653
	11th to 20th	Day	21% 11% 29% 25% 11% 3	675
	21st to end	Day	20% 8% 29% 29% 12% 1	734
June	1st to 10th	Day	9% 10% 24% 33% 21% 3	680
	11th to 20th	Day	14% 8% 36% 27% 12% 3	680
	21st to end	Day	10% 7% 33% 33% 15% 2	680
July	1st to 10th	Day	7% 4 23% 38% 24% 5%	671
	11th to 20th	Day	6% 6% 29% 36% 18% 4	668
	21st to end	Day	5% 3 27% 40% 20% 5%	739
August	1st to 10th	Day	9% 4 23% 40% 20% 4	676
	11th to 20th	Day	11% 5% 25% 33% 24% 3	665
	21st to end	Day	7% 6% 29% 36% 19% 4	748
September	1st to 10th	Day	14% 8% 27% 31% 16% 4	434
	11th to 20th	Day	10% 6% 34% 33% 14% 3	300
	21st to end	Day	14% 14% 33% 25% 11% 3	300
October	1st to 10th	Day	19% 11% 30% 24% 12% 4	300
	11th to 20th	Day	14% 18% 36% 24% 8%	300
	21st to end	Day	21% 18% 35% 20% 6% 1	330
November	1st to 10th	Day	22% 9% 37% 24% 7% 2	300
	11th to 20th	Day	13% 20% 42% 18% 7%	273
	21st to end	Day	20% 17% 31% 23% 9%	270
December	1st to 10th	Day	11% 11% 44% 22% 11% 1	270
	11th to 20th	Day	15% 12% 44% 26% 3	270
	21st to end	Day	23% 14% 38% 22% 2	297
January	1st to 10th	Night	12% 10% 39% 29% 9% 1	950
	11th to 20th	Night	11% 12% 38% 32% 6% 1	950
	21st to end	Night	15% 11% 38% 29% 7%	1045
February	1st to 10th	Night	13% 11% 41% 29% 6% 1	950
	11th to 20th	Night	12% 11% 39% 31% 6% 1	929
	21st to end	Night	13% 9% 39% 29% 8% 1	643
March	1st to 10th	Night	13% 10% 42% 28% 7% 1	644
	11th to 20th	Night	16% 12% 37% 32% 3	570
	21st to end	Night	19% 11% 35% 26% 9% 1	627
April	1st to 10th	Night	19% 12% 38% 26% 4	570
	11th to 20th	Night	21% 15% 31% 27% 5% 1	563
	21st to end	Night	20% 12% 34% 25% 9% 1	570
May	1st to 10th	Night	18% 7% 36% 30% 8%	570
	11th to 20th	Night	17% 8% 32% 32% 11% 1	561
	21st to end	Night	18% 6% 31% 33% 11%	617
June	1st to 10th	Night	9% 6% 28% 38% 19%	570
	11th to 20th	Night	9% 6% 35% 41% 10%	570
	21st to end	Night	9% 4 25% 49% 13%	570
July	1st to 10th	Night	7% 2 22% 42% 26% 1	555
	11th to 20th	Night	4 1 27% 50% 18%	552
	21st to end	Night	4 2 24% 51% 18% 1	624
August	1st to 10th	Night	6% 3 23% 46% 21% 1	567
	11th to 20th	Night	9% 3 23% 40% 24% 1	564
	21st to end	Night	6% 4 28% 42% 18% 2	627
September	1st to 10th	Night	8% 3 28% 42% 15% 3	570
	11th to 20th	Night	10% 6% 32% 35% 15% 2	570
	21st to end	Night	12% 7% 34% 35% 11% 1	570
October	1st to 10th	Night	15% 9% 35% 29% 11% 1	692
	11th to 20th	Night	15% 12% 37% 30% 6%	760
	21st to end	Night	18% 11% 35% 27% 8%	907
November	1st to 10th	Night	13% 9% 37% 32% 8% 1	975
	11th to 20th	Night	13% 11% 39% 28% 8%	956
	21st to end	Night	13% 11% 37% 31% 8%	950
December	1st to 10th	Night	12% 11% 38% 32% 6% 1	950
	11th to 20th	Night	16% 9% 39% 29% 7% 1	950
	21st to end	Night	21% 11% 35% 26% 6%	1045

Page generated at 2024-11-08 21:45:35. Version ac07

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