Waffelow Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waffelow Creek Observatory clear sky chart from 2005-11-06 to 2026-02-16.

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% 6% 2 6% 4 4 4 4 5% 7% 44%	131056
	Night	14% 6% 2 5% 3 3 3 3 5% 7% 48%	130069
Transparency	Day	38% 6% 10% 20% 19% 7%	134666
	Night	36% 5% 10% 19% 21% 9%	134523
Seeing	Day	15% 9% 23% 26% 20% 6%	16705
	Night	16% 8% 25% 31% 17% 2	26653

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	17% 10% 3 5% 3 3 3 3 4 5% 46%	5289
	11th to 20th	Day	13% 5% 1 4 3 2 3 3 6% 7% 54%	5310
	21st to end	Day	27% 10% 2 6% 2 2 2 1 3 4 40%	5812
February	1st to 10th	Day	21% 9% 2 6% 4 4 3 2 3 6% 39%	1890
	11th to 20th	Day	21% 9% 3 6% 4 4 4 3 3 4 39%	2001
	21st to end	Day	22% 7% 3 7% 4 3 4 2 4 4 41%	1815
March	1st to 10th	Day	20% 12% 3 7% 4 3 3 2 3 4 38%	4936
	11th to 20th	Day	15% 6% 2 4 3 3 3 3 4 6% 49%	4980
	21st to end	Day	16% 9% 3 6% 4 4 4 3 5% 6% 40%	5462
April	1st to 10th	Day	14% 6% 3 8% 5% 4 4 3 4 6% 42%	2240
	11th to 20th	Day	15% 7% 2 7% 5% 4 5% 3 6% 7% 40%	2374
	21st to end	Day	11% 6% 3 7% 5% 5% 4 4 5% 7% 44%	2400
May	1st to 10th	Day	18% 8% 2 7% 5% 4 5% 4 6% 7% 34%	5487
	11th to 20th	Day	14% 6% 2 7% 5% 5% 5% 4 5% 7% 40%	5862
	21st to end	Day	11% 6% 3 7% 5% 5% 6% 5% 8% 10% 35%	6434
June	1st to 10th	Day	8% 5% 2 6% 6% 5% 6% 5% 7% 11% 38%	2600
	11th to 20th	Day	5% 4 2 5% 5% 5% 6% 5% 8% 11% 42%	2600
	21st to end	Day	6% 6% 2 6% 6% 5% 7% 6% 8% 10% 39%	2600
July	1st to 10th	Day	8% 6% 2 7% 5% 6% 7% 5% 8% 12% 34%	5900
	11th to 20th	Day	6% 4 2 6% 5% 4 5% 4 7% 10% 46%	5900
	21st to end	Day	12% 6% 3 7% 5% 4 5% 4 7% 9% 39%	6422
August	1st to 10th	Day	2 2 1 3 3 3 4 3 5% 8% 67%	4234
	11th to 20th	Day	3 3 1 4 3 4 4 3 7% 12% 56%	3974
	21st to end	Day	9% 4 2 6% 5% 6% 6% 5% 8% 10% 40%	4312
September	1st to 10th	Day	7% 6% 2 6% 6% 5% 4 6% 6% 8% 44%	2325
	11th to 20th	Day	12% 5% 2 7% 5% 5% 5% 4 6% 8% 42%	2200
	21st to end	Day	8% 4 2 5% 4 4 4 4 5% 6% 53%	2200
October	1st to 10th	Day	7% 3 1 3 2 3 3 4 6% 6% 62%	2010
	11th to 20th	Day	12% 6% 1 4 3 3 3 3 4 6% 56%	2000
	21st to end	Day	15% 5% 2 5% 3 2 3 3 4 5% 54%	2200
November	1st to 10th	Day	12% 7% 3 5% 3 4 4 4 4 6% 49%	2058
	11th to 20th	Day	12% 5% 2 5% 4 3 3 3 4 5% 53%	2100
	21st to end	Day	17% 6% 2 6% 4 4 4 3 4 5% 45%	2031
December	1st to 10th	Day	21% 6% 2 4 4 3 3 2 4 5% 46%	3030
	11th to 20th	Day	17% 9% 3 6% 4 4 4 3 4 5% 41%	3481
	21st to end	Day	16% 9% 3 7% 3 4 3 3 3 4 44%	4587
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 2 4 4 50%	7634
	11th to 20th	Night	12% 5% 2 4 2 3 3 3 5% 5% 57%	7680
	21st to end	Night	28% 10% 2 6% 3 3 2 2 3 4 36%	8402
February	1st to 10th	Night	16% 8% 2 5% 3 3 3 3 5% 5% 44%	2730
	11th to 20th	Night	22% 9% 3 5% 4 3 2 2 3 4 43%	2410
	21st to end	Night	21% 8% 2 5% 3 3 4 2 4 5% 44%	1815
March	1st to 10th	Night	22% 9% 2 5% 3 3 3 2 5% 5% 41%	4919
	11th to 20th	Night	14% 6% 2 5% 3 4 4 3 5% 7% 49%	4980
	21st to end	Night	19% 7% 3 7% 4 3 3 3 4 4 43%	5467
April	1st to 10th	Night	14% 6% 2 6% 5% 3 4 4 5% 7% 45%	2158
	11th to 20th	Night	14% 6% 1 6% 4 4 5% 3 5% 6% 45%	1975
	21st to end	Night	14% 7% 2 5% 4 4 3 2 4 7% 49%	2000
May	1st to 10th	Night	15% 9% 3 8% 5% 4 4 4 5% 8% 35%	4406
	11th to 20th	Night	14% 7% 3 7% 5% 5% 4 4 6% 7% 40%	4053
	21st to end	Night	11% 6% 2 6% 4 4 5% 4 7% 10% 41%	4443
June	1st to 10th	Night	5% 4 2 5% 3 3 4 5% 7% 11% 51%	1800
	11th to 20th	Night	3 3 1 4 3 3 4 4 6% 10% 59%	1800
	21st to end	Night	6% 4 1 5% 4 4 4 4 8% 11% 49%	1800
July	1st to 10th	Night	7% 5% 2 6% 5% 6% 6% 5% 8% 12% 38%	4078
	11th to 20th	Night	4 3 1 5% 4 4 4 4 8% 12% 50%	4077
	21st to end	Night	10% 6% 2 5% 4 4 4 4 6% 11% 45%	4449
August	1st to 10th	Night	2 1 1 2 2 2 3 2 4 8% 73%	2926
	11th to 20th	Night	2 2 1 3 2 3 4 4 7% 12% 60%	3078
	21st to end	Night	6% 4 2 6% 4 4 6% 6% 8% 9% 46%	3586
September	1st to 10th	Night	6% 6% 2 6% 4 4 4 3 6% 10% 50%	2070
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 4 8% 51%	2200
	21st to end	Night	7% 3 2 4 3 4 3 3 5% 8% 59%	2200
October	1st to 10th	Night	5% 3 2 3 3 3 3 3 5% 6% 64%	2369
	11th to 20th	Night	11% 4 1 4 2 3 3 3 4 5% 60%	2400
	21st to end	Night	13% 5% 2 4 2 2 3 2 4 4 59%	2640
November	1st to 10th	Night	13% 5% 2 4 2 3 3 3 5% 6% 55%	2460
	11th to 20th	Night	10% 6% 2 5% 4 3 3 3 4 7% 54%	2520
	21st to end	Night	16% 8% 3 5% 3 3 3 3 5% 5% 47%	2585
December	1st to 10th	Night	20% 8% 2 5% 3 4 3 2 3 5% 44%	4380
	11th to 20th	Night	17% 10% 3 6% 4 4 3 2 4 4 44%	4946
	21st to end	Night	15% 8% 2 5% 3 3 3 3 4 4 50%	6633

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	42% 3 6% 24% 22% 3	5290
	11th to 20th	Day	30% 3 5% 23% 28% 11%	5310
	21st to end	Day	51% 2 3 13% 19% 12%	5812
February	1st to 10th	Day	49% 4 4 15% 18% 10%	1890
	11th to 20th	Day	50% 4 5% 16% 18% 8%	2011
	21st to end	Day	49% 3 6% 12% 18% 11%	1815
March	1st to 10th	Day	51% 4 5% 11% 19% 11%	4936
	11th to 20th	Day	36% 5% 5% 15% 22% 18%	4980
	21st to end	Day	44% 5% 9% 20% 18% 5%	5464
April	1st to 10th	Day	45% 5% 7% 19% 17% 7%	2240
	11th to 20th	Day	42% 6% 9% 16% 19% 8%	2374
	21st to end	Day	40% 6% 9% 18% 23% 4	2400
May	1st to 10th	Day	47% 8% 11% 21% 10% 2	5522
	11th to 20th	Day	43% 6% 12% 17% 20% 2	5866
	21st to end	Day	41% 9% 12% 21% 16% 2	6447
June	1st to 10th	Day	37% 9% 14% 24% 15% 1	2600
	11th to 20th	Day	33% 9% 14% 26% 16% 3	2600
	21st to end	Day	36% 9% 14% 26% 12% 2	2600
July	1st to 10th	Day	38% 11% 24% 21% 6%	5836
	11th to 20th	Day	31% 7% 20% 32% 10%	5831
	21st to end	Day	40% 8% 15% 27% 11%	6240
August	1st to 10th	Day	16% 6% 14% 32% 30% 2	4220
	11th to 20th	Day	20% 6% 22% 40% 10% 1	4013
	21st to end	Day	37% 10% 17% 20% 15% 1	4311
September	1st to 10th	Day	36% 8% 13% 19% 16% 9%	2325
	11th to 20th	Day	39% 7% 12% 19% 17% 7%	2200
	21st to end	Day	30% 6% 10% 21% 22% 12%	2200
October	1st to 10th	Day	15% 3 6% 13% 24% 39%	3270
	11th to 20th	Day	19% 3 4 20% 30% 23%	3240
	21st to end	Day	27% 4 4 16% 37% 13%	3538
November	1st to 10th	Day	36% 5% 7% 18% 25% 9%	2058
	11th to 20th	Day	34% 4 6% 19% 25% 12%	2100
	21st to end	Day	41% 4 6% 18% 23% 7%	2031
December	1st to 10th	Day	43% 3 7% 18% 24% 6%	3030
	11th to 20th	Day	46% 4 6% 12% 22% 11%	3479
	21st to end	Day	44% 4 4 14% 28% 6%	4587
January	1st to 10th	Night	38% 3 6% 23% 25% 5%	7635
	11th to 20th	Night	31% 3 5% 18% 31% 13%	7680
	21st to end	Night	54% 2 3 13% 17% 10%	8402
February	1st to 10th	Night	42% 4 6% 15% 20% 13%	2730
	11th to 20th	Night	47% 3 6% 16% 19% 9%	2410
	21st to end	Night	45% 3 7% 13% 17% 15%	1815
March	1st to 10th	Night	46% 3 5% 12% 22% 12%	4919
	11th to 20th	Night	37% 5% 6% 15% 18% 20%	4980
	21st to end	Night	45% 5% 8% 15% 20% 7%	5467
April	1st to 10th	Night	39% 6% 9% 19% 17% 11%	2158
	11th to 20th	Night	39% 5% 9% 18% 17% 11%	1975
	21st to end	Night	37% 4 10% 19% 24% 6%	2000
May	1st to 10th	Night	46% 7% 11% 21% 13% 3	4436
	11th to 20th	Night	43% 7% 12% 17% 20% 2	4054
	21st to end	Night	36% 8% 17% 24% 12% 3	4452
June	1st to 10th	Night	27% 8% 16% 29% 18% 1	1800
	11th to 20th	Night	20% 7% 17% 33% 18% 4	1800
	21st to end	Night	27% 7% 17% 28% 18% 2	1800
July	1st to 10th	Night	35% 10% 27% 22% 4	4035
	11th to 20th	Night	24% 10% 28% 28% 10%	4026
	21st to end	Night	34% 8% 19% 30% 9% 1	4320
August	1st to 10th	Night	11% 5% 16% 33% 32% 3	2916
	11th to 20th	Night	16% 6% 23% 44% 9% 2	3105
	21st to end	Night	32% 10% 16% 23% 17% 2	3586
September	1st to 10th	Night	30% 7% 16% 20% 18% 9%	2070
	11th to 20th	Night	33% 8% 12% 22% 18% 8%	2200
	21st to end	Night	25% 5% 10% 23% 24% 12%	2200
October	1st to 10th	Night	14% 3 6% 15% 21% 41%	3876
	11th to 20th	Night	17% 2 4 19% 33% 26%	3899
	21st to end	Night	25% 3 5% 14% 38% 15%	4252
November	1st to 10th	Night	31% 4 8% 19% 25% 12%	2460
	11th to 20th	Night	32% 3 9% 18% 24% 14%	2520
	21st to end	Night	40% 3 7% 17% 23% 10%	2585
December	1st to 10th	Night	45% 3 6% 14% 27% 5%	4380
	11th to 20th	Night	44% 4 6% 12% 23% 11%	4947
	21st to end	Night	38% 4 6% 15% 31% 7%	6633

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	27% 18% 38% 13% 4	330
	11th to 20th	Day	29% 15% 35% 16% 3 1	330
	21st to end	Day	31% 22% 31% 13% 2	363
February	1st to 10th	Day	26% 20% 35% 16% 3	330
	11th to 20th	Day	40% 17% 30% 11% 1	315
	21st to end	Day	29% 27% 34% 7% 2	249
March	1st to 10th	Day	32% 18% 30% 17% 2	300
	11th to 20th	Day	25% 27% 34% 12% 2	300
	21st to end	Day	22% 19% 38% 16% 4	330
April	1st to 10th	Day	24% 18% 38% 17% 3 1	340
	11th to 20th	Day	25% 19% 27% 21% 8% 1	492
	21st to end	Day	16% 16% 35% 24% 7% 2	500
May	1st to 10th	Day	16% 13% 39% 25% 7% 1	533
	11th to 20th	Day	17% 8% 29% 28% 16% 1	725
	21st to end	Day	12% 10% 29% 30% 16% 4	789
June	1st to 10th	Day	9% 3 20% 35% 25% 8%	730
	11th to 20th	Day	7% 2 21% 42% 24% 5%	730
	21st to end	Day	8% 2 13% 36% 30% 11%	730
July	1st to 10th	Day	9% 2 10% 32% 36% 10%	721
	11th to 20th	Day	5% 2 8% 32% 42% 12%	718
	21st to end	Day	7% 1 9% 34% 38% 11%	794
August	1st to 10th	Day	3 1 7% 28% 47% 13%	726
	11th to 20th	Day	5% 4 29% 46% 16%	596
	21st to end	Day	13% 2 9% 21% 36% 19%	583
September	1st to 10th	Day	9% 11% 28% 37% 14%	455
	11th to 20th	Day	8% 1 14% 31% 33% 14%	330
	21st to end	Day	9% 3 14% 36% 28% 9%	330
October	1st to 10th	Day	6% 3 24% 39% 21% 6%	330
	11th to 20th	Day	10% 7% 33% 30% 15% 5%	330
	21st to end	Day	23% 10% 29% 20% 14% 3	363
November	1st to 10th	Day	16% 8% 30% 29% 15% 1	330
	11th to 20th	Day	15% 13% 32% 32% 7% 1	330
	21st to end	Day	22% 16% 36% 18% 6% 2	330
December	1st to 10th	Day	22% 13% 39% 17% 6% 3	330
	11th to 20th	Day	26% 14% 34% 19% 7% 1	330
	21st to end	Day	23% 20% 35% 17% 5% 1	363
January	1st to 10th	Night	23% 13% 32% 27% 5%	1050
	11th to 20th	Night	24% 15% 30% 24% 6%	1050
	21st to end	Night	25% 14% 32% 25% 4	1155
February	1st to 10th	Night	23% 14% 35% 26% 3	1050
	11th to 20th	Night	28% 16% 31% 22% 3	815
	21st to end	Night	26% 17% 34% 20% 3	495
March	1st to 10th	Night	24% 13% 35% 23% 5%	600
	11th to 20th	Night	19% 16% 33% 27% 5%	600
	21st to end	Night	18% 12% 40% 23% 6%	660
April	1st to 10th	Night	18% 14% 38% 23% 7%	600
	11th to 20th	Night	19% 13% 34% 23% 11%	593
	21st to end	Night	16% 10% 37% 26% 10%	600
May	1st to 10th	Night	12% 11% 40% 28% 9%	600
	11th to 20th	Night	16% 7% 32% 30% 14% 1	591
	21st to end	Night	9% 5% 29% 35% 19% 3	650
June	1st to 10th	Night	7% 2 15% 41% 31% 5%	600
	11th to 20th	Night	3 2 18% 51% 24% 3	600
	21st to end	Night	7% 1 12% 43% 31% 6%	600
July	1st to 10th	Night	7% 11% 38% 36% 7%	585
	11th to 20th	Night	3 1 10% 38% 42% 6%	582
	21st to end	Night	6% 1 7% 41% 39% 7%	657
August	1st to 10th	Night	3 6% 43% 41% 7%	597
	11th to 20th	Night	5% 1 7% 41% 39% 7%	594
	21st to end	Night	9% 2 7% 31% 43% 8%	660
September	1st to 10th	Night	9% 1 7% 35% 42% 6%	600
	11th to 20th	Night	12% 2 10% 27% 43% 6%	600
	21st to end	Night	7% 2 12% 36% 37% 7%	600
October	1st to 10th	Night	6% 2 15% 40% 32% 5%	769
	11th to 20th	Night	13% 5% 22% 37% 20% 3	800
	21st to end	Night	16% 6% 26% 32% 18% 2	880
November	1st to 10th	Night	14% 7% 23% 35% 19% 1	820
	11th to 20th	Night	14% 10% 27% 39% 11%	840
	21st to end	Night	20% 12% 28% 28% 12% 1	905
December	1st to 10th	Night	25% 12% 27% 28% 8%	1050
	11th to 20th	Night	25% 10% 31% 27% 6%	1050
	21st to end	Night	23% 12% 30% 28% 7%	1155

Page generated at 2026-02-13 00:42:10. Version ac07

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