Whiteside
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiteside clear sky chart from 2005-11-06 to 2025-03-27.

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% 8% 3 7% 4 4 4 4 5% 7% 42%	109087
	Night	13% 8% 3 7% 4 4 4 3 5% 6% 43%	110463
Transparency	Day	39% 7% 12% 23% 16% 2	112719
	Night	40% 6% 11% 23% 17% 3	114971
Seeing	Day	15% 12% 28% 26% 15% 4	16102
	Night	16% 11% 30% 29% 12% 1	26112

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	13% 12% 6% 14% 5% 4 3 3 4 6% 29%	3617
	11th to 20th	Day	9% 10% 4 8% 6% 6% 4 4 5% 6% 38%	3960
	21st to end	Day	17% 15% 6% 8% 4 4 3 2 3 4 34%	4488
February	1st to 10th	Day	16% 11% 5% 8% 4 4 4 3 5% 7% 34%	1800
	11th to 20th	Day	14% 11% 3 7% 5% 5% 4 4 5% 6% 36%	1879
	21st to end	Day	15% 12% 3 7% 4 3 3 3 5% 5% 40%	1650
March	1st to 10th	Day	17% 12% 3 6% 3 3 3 2 3 5% 43%	3338
	11th to 20th	Day	11% 8% 2 5% 3 4 4 3 5% 7% 48%	3590
	21st to end	Day	17% 10% 3 9% 4 5% 4 3 5% 7% 33%	4039
April	1st to 10th	Day	13% 7% 3 7% 6% 4 4 4 5% 6% 42%	2280
	11th to 20th	Day	17% 9% 2 6% 4 3 4 3 5% 5% 41%	2254
	21st to end	Day	18% 8% 2 6% 5% 4 4 4 6% 7% 37%	2280
May	1st to 10th	Day	12% 9% 3 8% 5% 5% 5% 4 7% 10% 33%	3902
	11th to 20th	Day	16% 9% 2 7% 5% 5% 4 3 5% 6% 37%	4399
	21st to end	Day	10% 6% 2 5% 4 4 5% 4 6% 7% 46%	4824
June	1st to 10th	Day	8% 4 2 6% 4 4 4 4 7% 9% 48%	2660
	11th to 20th	Day	8% 4 2 5% 5% 4 4 4 6% 8% 51%	2660
	21st to end	Day	6% 4 2 6% 4 5% 6% 4 7% 9% 47%	2660
July	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 7% 10% 40%	4440
	11th to 20th	Day	5% 4 2 5% 5% 4 4 5% 6% 10% 49%	4440
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 5% 8% 11% 40%	4538
August	1st to 10th	Day	5% 4 2 6% 4 4 5% 4 7% 10% 50%	4104
	11th to 20th	Day	13% 5% 2 6% 4 5% 5% 4 6% 9% 41%	3794
	21st to end	Day	5% 4 2 6% 4 4 5% 4 7% 10% 50%	4180
September	1st to 10th	Day	12% 5% 2 4 3 3 3 3 5% 6% 53%	2280
	11th to 20th	Day	10% 4 2 5% 3 4 4 3 6% 8% 51%	2280
	21st to end	Day	7% 5% 2 5% 4 4 3 4 5% 8% 51%	2039
October	1st to 10th	Day	11% 4 2 6% 3 3 3 3 5% 6% 55%	1900
	11th to 20th	Day	15% 8% 2 5% 3 3 3 3 4 5% 51%	1900
	21st to end	Day	17% 8% 3 5% 4 3 3 2 4 5% 46%	2090
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 6% 53%	1764
	11th to 20th	Day	15% 7% 3 6% 4 3 3 3 4 6% 46%	1800
	21st to end	Day	15% 11% 3 7% 4 3 3 3 4 7% 40%	1658
December	1st to 10th	Day	8% 9% 3 7% 4 3 3 3 4 5% 51%	2610
	11th to 20th	Day	12% 9% 6% 9% 5% 4 4 3 5% 7% 37%	3008
	21st to end	Day	22% 18% 5% 10% 5% 4 4 3 4 4 21%	3982
January	1st to 10th	Night	15% 11% 7% 12% 4 4 4 3 4 5% 31%	6348
	11th to 20th	Night	11% 11% 5% 13% 5% 5% 6% 4 4 4 34%	6018
	21st to end	Night	17% 14% 5% 8% 4 3 4 2 4 5% 33%	6490
February	1st to 10th	Night	16% 11% 5% 9% 5% 5% 4 4 4 5% 34%	2600
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 3 4 5% 39%	2407
	21st to end	Night	15% 9% 2 7% 4 4 3 2 5% 5% 43%	1980
March	1st to 10th	Night	20% 11% 3 5% 3 3 3 2 3 4 43%	3764
	11th to 20th	Night	13% 7% 2 5% 3 3 3 2 5% 6% 50%	3590
	21st to end	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 32%	3730
April	1st to 10th	Night	11% 7% 3 7% 4 4 4 4 5% 5% 46%	1900
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 7% 45%	1875
	21st to end	Night	18% 8% 2 6% 4 4 4 2 4 6% 42%	1900
May	1st to 10th	Night	16% 8% 2 6% 4 4 4 4 5% 10% 38%	2992
	11th to 20th	Night	14% 9% 2 6% 4 4 4 3 5% 7% 42%	2506
	21st to end	Night	9% 5% 1 5% 4 4 5% 4 6% 9% 47%	2743
June	1st to 10th	Night	7% 4 2 5% 5% 4 3 4 6% 9% 52%	1520
	11th to 20th	Night	6% 5% 2 5% 3 4 5% 4 5% 8% 53%	1520
	21st to end	Night	5% 3 2 5% 4 4 5% 4 8% 10% 51%	1520
July	1st to 10th	Night	12% 6% 3 6% 4 4 3 3 6% 10% 43%	2530
	11th to 20th	Night	4 2 1 4 3 3 4 4 5% 10% 59%	2530
	21st to end	Night	8% 5% 2 7% 5% 4 5% 4 7% 10% 43%	3021
August	1st to 10th	Night	5% 2 1 4 3 3 3 4 5% 8% 62%	2836
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 51%	3037
	21st to end	Night	5% 3 1 4 3 4 4 3 7% 9% 56%	3476
September	1st to 10th	Night	12% 5% 1 4 3 3 3 3 4 7% 56%	1900
	11th to 20th	Night	9% 4 2 5% 4 4 3 3 7% 6% 53%	1900
	21st to end	Night	7% 5% 2 5% 4 4 3 2 5% 6% 55%	2116
October	1st to 10th	Night	8% 4 2 5% 3 3 3 2 4 6% 59%	2280
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 5% 6% 54%	2280
	21st to end	Night	17% 8% 2 4 4 3 4 3 4 5% 46%	2508
November	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 4 6% 54%	2531
	11th to 20th	Night	13% 6% 2 6% 4 3 3 3 5% 6% 49%	2600
	21st to end	Night	16% 9% 3 6% 4 3 3 4 4 6% 42%	2740
December	1st to 10th	Night	11% 9% 3 7% 4 4 3 3 4 5% 47%	4580
	11th to 20th	Night	15% 9% 3 6% 4 3 4 3 6% 7% 40%	5199
	21st to end	Night	23% 19% 5% 9% 5% 4 3 3 3 4 20%	6996

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	54% 7% 11% 17% 10% 2	3618
	11th to 20th	Day	45% 6% 12% 18% 14% 5%	3960
	21st to end	Day	55% 4 8% 14% 16% 3	4488
February	1st to 10th	Day	50% 6% 12% 20% 10% 1	1800
	11th to 20th	Day	48% 6% 11% 18% 14% 3	1888
	21st to end	Day	46% 4 10% 22% 15% 3	1650
March	1st to 10th	Day	44% 5% 8% 22% 18% 3	3338
	11th to 20th	Day	34% 6% 14% 25% 17% 4	3590
	21st to end	Day	48% 10% 16% 19% 7%	4039
April	1st to 10th	Day	41% 6% 11% 24% 16% 1	2280
	11th to 20th	Day	43% 5% 10% 25% 14% 3	2254
	21st to end	Day	45% 7% 13% 21% 13% 1	2280
May	1st to 10th	Day	41% 12% 15% 22% 9% 1	3937
	11th to 20th	Day	46% 8% 10% 24% 11% 1	4403
	21st to end	Day	33% 9% 11% 25% 21% 1	4837
June	1st to 10th	Day	29% 9% 15% 29% 15% 2	2660
	11th to 20th	Day	29% 8% 13% 25% 21% 3	2660
	21st to end	Day	30% 9% 17% 24% 16% 4	2660
July	1st to 10th	Day	37% 8% 13% 27% 13% 2	4371
	11th to 20th	Day	28% 8% 14% 29% 19% 1	4365
	21st to end	Day	33% 11% 19% 24% 11% 1	4395
August	1st to 10th	Day	27% 8% 16% 36% 13% 1	4090
	11th to 20th	Day	37% 7% 14% 25% 16% 1	3831
	21st to end	Day	27% 7% 16% 33% 13% 3	4179
September	1st to 10th	Day	32% 5% 11% 25% 22% 5%	2280
	11th to 20th	Day	30% 6% 10% 28% 21% 4	2280
	21st to end	Day	30% 6% 11% 27% 23% 3	2039
October	1st to 10th	Day	19% 3 6% 18% 47% 7%	3160
	11th to 20th	Day	24% 3 7% 20% 39% 7%	3140
	21st to end	Day	35% 4 7% 26% 26% 2	3428
November	1st to 10th	Day	33% 5% 11% 25% 21% 5%	1764
	11th to 20th	Day	39% 4 10% 23% 19% 5%	1800
	21st to end	Day	45% 6% 10% 25% 14%	1658
December	1st to 10th	Day	34% 5% 16% 28% 16%	2610
	11th to 20th	Day	46% 6% 13% 21% 12% 1	3005
	21st to end	Day	66% 6% 12% 11% 5%	3982
January	1st to 10th	Night	55% 5% 10% 21% 8% 1	6348
	11th to 20th	Night	54% 5% 9% 20% 11% 2	6018
	21st to end	Night	54% 4 9% 18% 14% 2	6490
February	1st to 10th	Night	52% 5% 11% 19% 11% 2	2600
	11th to 20th	Night	46% 5% 10% 20% 16% 2	2408
	21st to end	Night	43% 4 11% 25% 14% 3	1980
March	1st to 10th	Night	45% 5% 9% 23% 16% 2	3764
	11th to 20th	Night	35% 6% 10% 24% 21% 5%	3590
	21st to end	Night	51% 8% 12% 23% 6%	3730
April	1st to 10th	Night	38% 7% 11% 24% 17% 4	1900
	11th to 20th	Night	38% 6% 11% 22% 19% 4	1875
	21st to end	Night	44% 6% 10% 21% 17% 2	1900
May	1st to 10th	Night	41% 10% 17% 18% 13% 1	3022
	11th to 20th	Night	41% 9% 12% 26% 12% 1	2507
	21st to end	Night	29% 10% 15% 22% 21% 2	2751
June	1st to 10th	Night	27% 8% 16% 27% 19% 3	1520
	11th to 20th	Night	28% 9% 10% 25% 25% 3	1520
	21st to end	Night	27% 7% 16% 26% 18% 6%	1520
July	1st to 10th	Night	37% 7% 9% 32% 12% 2	2490
	11th to 20th	Night	20% 7% 13% 36% 22% 2	2482
	21st to end	Night	33% 9% 18% 26% 14% 1	2925
August	1st to 10th	Night	20% 7% 17% 36% 18% 1	2826
	11th to 20th	Night	33% 6% 12% 27% 21% 2	3066
	21st to end	Night	23% 6% 19% 33% 16% 3	3476
September	1st to 10th	Night	29% 6% 10% 23% 25% 7%	1900
	11th to 20th	Night	29% 7% 10% 23% 26% 5%	1900
	21st to end	Night	29% 6% 9% 25% 27% 4	2116
October	1st to 10th	Night	18% 4 7% 20% 46% 6%	3800
	11th to 20th	Night	22% 3 8% 23% 36% 8%	3779
	21st to end	Night	32% 5% 8% 25% 25% 5%	4120
November	1st to 10th	Night	31% 6% 12% 25% 20% 6%	2531
	11th to 20th	Night	36% 4 9% 27% 20% 4	2600
	21st to end	Night	44% 4 11% 24% 15% 2	2740
December	1st to 10th	Night	39% 5% 10% 32% 13% 1	4580
	11th to 20th	Night	43% 5% 13% 21% 17%	5201
	21st to end	Night	67% 6% 12% 10% 5% 1	6996

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	22% 24% 34% 15% 5%	300
	11th to 20th	Day	28% 22% 34% 15% 1	300
	21st to end	Day	17% 24% 43% 14% 2	330
February	1st to 10th	Day	26% 20% 39% 13% 2	300
	11th to 20th	Day	27% 24% 30% 14% 3 1	300
	21st to end	Day	27% 20% 39% 12% 2	249
March	1st to 10th	Day	18% 25% 44% 12% 1	300
	11th to 20th	Day	28% 22% 30% 18% 2 1	300
	21st to end	Day	32% 19% 33% 14% 3	410
April	1st to 10th	Day	20% 13% 41% 19% 6% 1	460
	11th to 20th	Day	22% 19% 30% 20% 8% 1	452
	21st to end	Day	21% 18% 37% 18% 5% 1	460
May	1st to 10th	Day	16% 17% 35% 23% 7% 2	502
	11th to 20th	Day	18% 12% 28% 26% 14% 2	675
	21st to end	Day	13% 11% 29% 28% 13% 6%	734
June	1st to 10th	Day	8% 5% 25% 31% 23% 7%	680
	11th to 20th	Day	9% 5% 23% 38% 22% 4	680
	21st to end	Day	6% 7% 31% 36% 16% 3	680
July	1st to 10th	Day	11% 4 15% 29% 29% 11%	671
	11th to 20th	Day	6% 4 21% 36% 28% 5%	668
	21st to end	Day	9% 3 18% 35% 29% 7%	739
August	1st to 10th	Day	7% 4 18% 36% 26% 8%	676
	11th to 20th	Day	10% 4 17% 35% 26% 7%	520
	21st to end	Day	7% 4 16% 32% 32% 9%	539
September	1st to 10th	Day	12% 4 16% 31% 28% 8%	490
	11th to 20th	Day	8% 3 18% 35% 27% 10%	490
	21st to end	Day	9% 10% 25% 29% 20% 8%	437
October	1st to 10th	Day	12% 9% 29% 30% 16% 4	300
	11th to 20th	Day	19% 21% 27% 25% 6% 1	300
	21st to end	Day	27% 20% 30% 18% 5%	330
November	1st to 10th	Day	15% 15% 37% 21% 9% 3	300
	11th to 20th	Day	20% 18% 36% 18% 7% 1	300
	21st to end	Day	28% 16% 31% 22% 3 1	300
December	1st to 10th	Day	14% 20% 41% 15% 7% 3	300
	11th to 20th	Day	22% 19% 38% 18% 4	300
	21st to end	Day	26% 23% 33% 15% 2	330
January	1st to 10th	Night	18% 18% 38% 21% 5%	1000
	11th to 20th	Night	20% 19% 36% 20% 4	1000
	21st to end	Night	19% 17% 40% 22% 2	1100
February	1st to 10th	Night	22% 17% 37% 22% 2	1000
	11th to 20th	Night	22% 16% 38% 21% 2	852
	21st to end	Night	22% 19% 38% 20% 2	660
March	1st to 10th	Night	22% 17% 38% 21% 3	750
	11th to 20th	Night	22% 12% 35% 27% 6%	600
	21st to end	Night	26% 13% 34% 24% 3	647
April	1st to 10th	Night	16% 18% 36% 25% 5%	570
	11th to 20th	Night	15% 15% 34% 27% 9% 1	563
	21st to end	Night	21% 10% 40% 24% 6%	570
May	1st to 10th	Night	18% 9% 31% 33% 9% 1	570
	11th to 20th	Night	17% 8% 29% 32% 14% 1	561
	21st to end	Night	12% 5% 24% 38% 19% 2	617
June	1st to 10th	Night	8% 2 24% 40% 24% 1	570
	11th to 20th	Night	7% 3 23% 45% 20% 1	570
	21st to end	Night	5% 2 25% 46% 21% 1	570
July	1st to 10th	Night	10% 2 12% 37% 33% 6%	555
	11th to 20th	Night	6% 1 16% 45% 30% 3	552
	21st to end	Night	7% 1 14% 43% 32% 2	624
August	1st to 10th	Night	8% 2 10% 42% 34% 3	567
	11th to 20th	Night	8% 1 15% 40% 32% 4	564
	21st to end	Night	5% 2 14% 39% 38% 3	627
September	1st to 10th	Night	11% 3 18% 35% 27% 5%	570
	11th to 20th	Night	10% 2 17% 35% 31% 5%	570
	21st to end	Night	9% 6% 24% 34% 23% 4	737
October	1st to 10th	Night	9% 5% 28% 32% 22% 3	760
	11th to 20th	Night	16% 11% 32% 28% 11% 1	760
	21st to end	Night	22% 13% 34% 24% 7%	836
November	1st to 10th	Night	13% 11% 38% 28% 9%	780
	11th to 20th	Night	17% 15% 36% 26% 6%	800
	21st to end	Night	21% 15% 36% 23% 5%	940
December	1st to 10th	Night	20% 16% 36% 23% 5% 1	1000
	11th to 20th	Night	23% 13% 33% 27% 5%	1000
	21st to end	Night	26% 19% 33% 20% 2	1100

Page generated at 2025-03-24 08:04:29. Version ac07

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