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 2026-07-31.

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%	138394
	Night	13% 8% 3 7% 4 4 4 3 5% 7% 43%	134934
Transparency	Day	39% 7% 12% 24% 16% 2	141987
	Night	40% 6% 11% 23% 17% 3	139420
Seeing	Day	15% 12% 28% 26% 15% 4	18066
	Night	16% 11% 30% 29% 12% 1	27833

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% 11% 5% 13% 5% 5% 3 3 4 7% 33%	4691
	11th to 20th	Day	7% 10% 3 8% 7% 5% 4 4 5% 7% 40%	5148
	21st to end	Day	15% 15% 6% 8% 4 4 3 2 3 4 36%	5812
February	1st to 10th	Day	15% 11% 5% 8% 4 4 4 3 5% 6% 35%	1890
	11th to 20th	Day	14% 11% 3 7% 5% 5% 4 4 5% 6% 37%	1976
	21st to end	Day	14% 12% 3 8% 4 3 3 3 5% 5% 41%	1730
March	1st to 10th	Day	16% 10% 2 5% 2 3 3 2 3 4 49%	4753
	11th to 20th	Day	8% 7% 2 5% 3 4 5% 4 5% 7% 50%	5090
	21st to end	Day	15% 9% 3 8% 5% 5% 5% 3 6% 7% 35%	5817
April	1st to 10th	Day	15% 7% 3 7% 5% 4 4 4 5% 6% 41%	2520
	11th to 20th	Day	17% 9% 2 6% 4 3 4 4 5% 5% 41%	2494
	21st to end	Day	18% 8% 2 6% 4 4 4 4 6% 7% 37%	2520
May	1st to 10th	Day	14% 8% 3 8% 5% 5% 5% 4 6% 9% 34%	7267
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 3 5% 7% 40%	8222
	21st to end	Day	15% 8% 3 7% 5% 5% 5% 4 6% 7% 35%	9047
June	1st to 10th	Day	8% 4 2 6% 4 4 4 4 7% 9% 47%	2940
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 7% 8% 49%	2940
	21st to end	Day	7% 5% 2 6% 4 5% 5% 4 7% 9% 46%	2940
July	1st to 10th	Day	10% 5% 2 6% 3 4 4 4 6% 10% 46%	6500
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 5% 7% 11% 40%	6500
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 6% 8% 11% 38%	6656
August	1st to 10th	Day	5% 4 2 6% 4 4 5% 4 8% 9% 50%	4234
	11th to 20th	Day	12% 4 2 6% 4 5% 5% 4 6% 9% 42%	3916
	21st to end	Day	5% 4 2 6% 4 4 5% 4 7% 10% 50%	4312
September	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 5% 6% 54%	2400
	11th to 20th	Day	10% 4 2 5% 3 4 5% 3 6% 8% 51%	2400
	21st to end	Day	8% 5% 2 5% 4 4 3 4 5% 7% 52%	2146
October	1st to 10th	Day	11% 4 2 6% 3 3 3 3 5% 6% 55%	2000
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 3 5% 52%	2000
	21st to end	Day	17% 8% 3 5% 4 3 3 2 4 5% 46%	2200
November	1st to 10th	Day	11% 6% 2 5% 3 3 3 3 4 6% 54%	1854
	11th to 20th	Day	15% 7% 3 6% 4 3 3 3 4 6% 46%	1890
	21st to end	Day	16% 11% 3 7% 3 3 3 3 4 6% 40%	1741
December	1st to 10th	Day	8% 9% 3 7% 4 3 3 3 4 5% 51%	2690
	11th to 20th	Day	12% 9% 6% 9% 5% 4 4 3 5% 7% 37%	3088
	21st to end	Day	22% 18% 5% 10% 5% 4 4 3 4 4 21%	4070
January	1st to 10th	Night	12% 11% 6% 11% 4 5% 4 3 4 5% 36%	8232
	11th to 20th	Night	9% 9% 4 11% 6% 5% 5% 4 4 4 40%	7826
	21st to end	Night	15% 14% 5% 8% 5% 4 4 3 4 5% 34%	8402
February	1st to 10th	Night	15% 11% 5% 8% 5% 4 4 4 4 5% 35%	2730
	11th to 20th	Night	15% 8% 3 7% 5% 4 4 3 4 6% 40%	2530
	21st to end	Night	15% 8% 2 7% 4 4 3 2 4 6% 43%	2076
March	1st to 10th	Night	20% 12% 3 5% 3 3 2 2 3 4 43%	5363
	11th to 20th	Night	12% 8% 2 5% 3 3 3 2 5% 7% 50%	5090
	21st to end	Night	16% 10% 3 8% 5% 4 4 3 5% 7% 34%	5354
April	1st to 10th	Night	12% 7% 3 7% 4 4 4 4 5% 5% 45%	2100
	11th to 20th	Night	13% 7% 2 6% 4 4 4 4 6% 7% 45%	2075
	21st to end	Night	17% 8% 2 6% 4 4 4 2 4 6% 41%	2100
May	1st to 10th	Night	17% 8% 3 7% 5% 4 4 3 5% 8% 36%	5589
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 8% 44%	4670
	21st to end	Night	15% 7% 2 6% 5% 4 5% 4 6% 8% 36%	5139
June	1st to 10th	Night	8% 4 2 5% 4 4 3 4 6% 9% 51%	1680
	11th to 20th	Night	6% 5% 2 5% 4 4 5% 4 5% 8% 52%	1680
	21st to end	Night	6% 4 2 4 4 4 5% 4 8% 10% 50%	1680
July	1st to 10th	Night	9% 6% 3 7% 4 4 4 4 6% 9% 46%	3698
	11th to 20th	Night	5% 4 2 5% 5% 4 5% 4 6% 10% 49%	3697
	21st to end	Night	7% 5% 2 6% 4 4 5% 5% 8% 11% 43%	4431
August	1st to 10th	Night	5% 2 1 4 3 3 3 4 5% 8% 62%	2926
	11th to 20th	Night	11% 5% 2 6% 3 3 4 3 5% 7% 51%	3135
	21st to end	Night	5% 3 1 4 3 4 4 3 6% 9% 56%	3586
September	1st to 10th	Night	11% 5% 2 4 3 3 4 3 4 7% 55%	2000
	11th to 20th	Night	9% 4 2 5% 4 4 4 4 7% 6% 52%	2000
	21st to end	Night	7% 6% 2 6% 4 3 3 2 5% 6% 56%	2228
October	1st to 10th	Night	8% 4 2 5% 3 3 3 3 4 6% 60%	2400
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 5% 6% 54%	2400
	21st to end	Night	18% 8% 2 4 4 3 4 3 4 5% 46%	2640
November	1st to 10th	Night	9% 6% 2 5% 3 3 4 3 4 5% 54%	2661
	11th to 20th	Night	12% 6% 2 6% 4 3 3 3 5% 6% 50%	2730
	21st to end	Night	17% 10% 3 6% 4 3 3 4 4 6% 42%	2877
December	1st to 10th	Night	11% 9% 3 7% 4 4 3 3 4 5% 46%	4720
	11th to 20th	Night	15% 9% 4 6% 4 3 4 3 6% 7% 40%	5339
	21st to end	Night	23% 19% 5% 9% 5% 4 3 3 3 4 21%	7150

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	51% 6% 11% 20% 10% 2	4692
	11th to 20th	Day	42% 6% 12% 20% 16% 4	5148
	21st to end	Day	54% 4 9% 17% 14% 3	5812
February	1st to 10th	Day	50% 6% 12% 21% 11% 1	1890
	11th to 20th	Day	48% 6% 11% 19% 14% 3	1985
	21st to end	Day	46% 4 10% 23% 15% 3	1730
March	1st to 10th	Day	40% 4 7% 23% 24% 2	4753
	11th to 20th	Day	31% 6% 11% 26% 22% 4	5090
	21st to end	Day	45% 8% 15% 24% 7%	5819
April	1st to 10th	Day	43% 6% 11% 24% 15% 1	2520
	11th to 20th	Day	43% 6% 10% 24% 13% 3	2494
	21st to end	Day	45% 7% 13% 22% 13% 1	2520
May	1st to 10th	Day	43% 9% 13% 21% 13% 1	7302
	11th to 20th	Day	43% 7% 9% 23% 16% 2	8226
	21st to end	Day	46% 8% 10% 21% 15%	9061
June	1st to 10th	Day	31% 9% 15% 28% 15% 2	2940
	11th to 20th	Day	30% 8% 13% 25% 21% 3	2940
	21st to end	Day	31% 9% 17% 23% 16% 4	2940
July	1st to 10th	Day	33% 7% 13% 28% 18% 2	6431
	11th to 20th	Day	35% 9% 16% 24% 15% 1	6425
	21st to end	Day	35% 11% 19% 26% 9% 1	6471
August	1st to 10th	Day	27% 8% 16% 36% 13% 1	4220
	11th to 20th	Day	36% 7% 15% 26% 15% 1	3953
	21st to end	Day	27% 7% 16% 33% 14% 3	4311
September	1st to 10th	Day	32% 5% 11% 25% 22% 5%	2400
	11th to 20th	Day	30% 6% 11% 29% 21% 4	2400
	21st to end	Day	30% 6% 10% 26% 24% 3	2146
October	1st to 10th	Day	19% 3 6% 18% 47% 7%	3260
	11th to 20th	Day	24% 3 8% 20% 38% 7%	3240
	21st to end	Day	35% 4 8% 25% 26% 2	3538
November	1st to 10th	Day	33% 5% 11% 26% 21% 4	1854
	11th to 20th	Day	39% 4 10% 24% 19% 4	1890
	21st to end	Day	46% 5% 10% 24% 14%	1741
December	1st to 10th	Day	35% 5% 16% 28% 16%	2690
	11th to 20th	Day	46% 6% 13% 22% 12% 1	3085
	21st to end	Day	66% 6% 12% 12% 5%	4070
January	1st to 10th	Night	51% 6% 13% 22% 8%	8233
	11th to 20th	Night	47% 4 7% 23% 15% 3	7826
	21st to end	Night	53% 4 11% 18% 12% 2	8402
February	1st to 10th	Night	51% 5% 11% 20% 11% 2	2730
	11th to 20th	Night	45% 5% 10% 22% 15% 2	2531
	21st to end	Night	43% 4 11% 25% 14% 3	2076
March	1st to 10th	Night	46% 4 7% 21% 21% 2	5363
	11th to 20th	Night	34% 5% 8% 24% 22% 6%	5090
	21st to end	Night	48% 8% 11% 23% 10% 1	5354
April	1st to 10th	Night	39% 6% 11% 23% 17% 3	2100
	11th to 20th	Night	37% 7% 11% 22% 18% 4	2075
	21st to end	Night	43% 6% 11% 22% 17% 2	2100
May	1st to 10th	Night	44% 8% 13% 22% 11% 1	5619
	11th to 20th	Night	37% 7% 12% 24% 16% 3	4671
	21st to end	Night	42% 8% 12% 19% 17% 1	5149
June	1st to 10th	Night	28% 8% 16% 26% 18% 3	1680
	11th to 20th	Night	29% 9% 10% 25% 24% 3	1680
	21st to end	Night	26% 7% 16% 26% 17% 6%	1680
July	1st to 10th	Night	34% 7% 10% 31% 16% 2	3660
	11th to 20th	Night	28% 8% 16% 30% 16% 2	3652
	21st to end	Night	32% 9% 20% 28% 11% 1	4305
August	1st to 10th	Night	20% 7% 18% 36% 18% 1	2916
	11th to 20th	Night	32% 6% 13% 27% 20% 2	3164
	21st to end	Night	23% 6% 19% 32% 17% 3	3586
September	1st to 10th	Night	29% 6% 10% 23% 25% 6%	2000
	11th to 20th	Night	29% 7% 10% 24% 25% 5%	2000
	21st to end	Night	29% 6% 10% 24% 28% 4	2228
October	1st to 10th	Night	18% 4 7% 20% 46% 6%	3920
	11th to 20th	Night	22% 3 9% 23% 35% 8%	3899
	21st to end	Night	33% 5% 7% 25% 25% 5%	4252
November	1st to 10th	Night	31% 6% 12% 25% 20% 6%	2661
	11th to 20th	Night	36% 4 9% 27% 20% 4	2730
	21st to end	Night	45% 4 11% 24% 15% 2	2877
December	1st to 10th	Night	40% 5% 11% 31% 13% 1	4720
	11th to 20th	Night	43% 5% 13% 21% 17%	5341
	21st to end	Night	66% 6% 12% 11% 5% 1	7150

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% 23% 35% 15% 5%	330
	11th to 20th	Day	28% 23% 35% 13% 1	330
	21st to end	Day	17% 25% 43% 13% 2	363
February	1st to 10th	Day	25% 20% 39% 14% 2	330
	11th to 20th	Day	27% 25% 31% 14% 3 1	330
	21st to end	Day	27% 20% 39% 12% 2	273
March	1st to 10th	Day	20% 25% 42% 12% 1	330
	11th to 20th	Day	28% 22% 31% 17% 2 1	330
	21st to end	Day	31% 19% 35% 13% 2	468
April	1st to 10th	Day	24% 13% 40% 17% 6% 1	540
	11th to 20th	Day	23% 20% 30% 19% 7% 1	532
	21st to end	Day	20% 18% 37% 19% 5% 1	540
May	1st to 10th	Day	15% 17% 36% 24% 6% 1	586
	11th to 20th	Day	17% 14% 29% 25% 14% 2	775
	21st to end	Day	14% 11% 29% 28% 12% 6%	844
June	1st to 10th	Day	9% 7% 25% 31% 22% 7%	780
	11th to 20th	Day	9% 6% 23% 37% 21% 4	780
	21st to end	Day	7% 7% 29% 37% 17% 3	780
July	1st to 10th	Day	10% 4 15% 31% 30% 11%	771
	11th to 20th	Day	6% 4 21% 36% 27% 5%	768
	21st to end	Day	9% 3 18% 35% 29% 7%	845
August	1st to 10th	Day	7% 4 19% 37% 25% 8%	726
	11th to 20th	Day	10% 4 16% 35% 28% 7%	562
	21st to end	Day	7% 4 16% 33% 31% 9%	583
September	1st to 10th	Day	12% 4 17% 32% 27% 8%	530
	11th to 20th	Day	7% 3 16% 35% 28% 11%	530
	21st to end	Day	10% 9% 23% 28% 21% 9%	474
October	1st to 10th	Day	12% 8% 28% 32% 17% 3	330
	11th to 20th	Day	19% 21% 27% 25% 8% 1	330
	21st to end	Day	28% 20% 30% 17% 4	363
November	1st to 10th	Day	14% 17% 37% 21% 8% 2	330
	11th to 20th	Day	20% 19% 36% 18% 6% 1	330
	21st to end	Day	29% 16% 29% 22% 3 1	330
December	1st to 10th	Day	15% 19% 41% 15% 6% 3	330
	11th to 20th	Day	22% 19% 39% 18% 3	330
	21st to end	Day	26% 23% 35% 15% 1	363
January	1st to 10th	Night	17% 18% 38% 22% 5%	1050
	11th to 20th	Night	20% 20% 36% 19% 4	1050
	21st to end	Night	19% 17% 40% 22% 2	1155
February	1st to 10th	Night	21% 16% 38% 23% 2	1050
	11th to 20th	Night	22% 16% 38% 22% 2	895
	21st to end	Night	21% 19% 39% 20% 2	692
March	1st to 10th	Night	23% 17% 37% 21% 2	788
	11th to 20th	Night	22% 12% 34% 26% 5%	630
	21st to end	Night	25% 14% 34% 24% 3	693
April	1st to 10th	Night	17% 18% 37% 24% 4	630
	11th to 20th	Night	17% 15% 35% 26% 8%	623
	21st to end	Night	20% 11% 40% 24% 6%	630
May	1st to 10th	Night	17% 9% 32% 32% 9% 1	630
	11th to 20th	Night	16% 10% 29% 31% 14% 1	621
	21st to end	Night	13% 5% 24% 39% 18% 1	683
June	1st to 10th	Night	9% 3 25% 39% 23% 1	630
	11th to 20th	Night	8% 4 23% 44% 19% 1	630
	21st to end	Night	6% 2 25% 46% 20% 1	630
July	1st to 10th	Night	9% 2 11% 38% 34% 5%	615
	11th to 20th	Night	6% 1 15% 44% 31% 3	612
	21st to end	Night	7% 2 15% 43% 32% 2	687
August	1st to 10th	Night	8% 2 11% 43% 33% 3	597
	11th to 20th	Night	8% 2 14% 40% 32% 4	594
	21st to end	Night	5% 2 14% 39% 38% 3	660
September	1st to 10th	Night	11% 4 17% 35% 27% 5%	600
	11th to 20th	Night	10% 2 16% 35% 32% 5%	600
	21st to end	Night	9% 6% 23% 34% 23% 4	776
October	1st to 10th	Night	9% 5% 28% 34% 21% 3	800
	11th to 20th	Night	16% 11% 32% 28% 12% 1	800
	21st to end	Night	22% 13% 34% 24% 6%	880
November	1st to 10th	Night	13% 11% 38% 28% 9%	820
	11th to 20th	Night	16% 15% 36% 27% 6%	840
	21st to end	Night	22% 15% 35% 22% 5%	987
December	1st to 10th	Night	20% 16% 37% 22% 4 1	1050
	11th to 20th	Night	22% 14% 34% 26% 5%	1050
	21st to end	Night	25% 18% 34% 20% 2	1155

Page generated at 2026-07-28 02:25:19. Version ac07

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