UW-Whitewater Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UW-Whitewater Observatory 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	12% 9% 3 8% 5% 4 5% 4 5% 7% 37%	101428
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 38%	97737
Transparency	Day	44% 5% 11% 24% 13% 1	104968
	Night	45% 5% 11% 23% 14% 2	102338
Seeing	Day	16% 10% 29% 26% 14% 5%	15895
	Night	18% 9% 31% 30% 11% 1	25738

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	10% 15% 9% 13% 6% 5% 4 3 3 5% 26%	2527
	11th to 20th	Day	11% 14% 5% 15% 6% 4 5% 8% 7% 6% 19%	2530
	21st to end	Day	16% 18% 10% 13% 5% 4 3 2 4 6% 20%	2861
February	1st to 10th	Day	11% 14% 5% 11% 6% 5% 5% 4 5% 6% 30%	1710
	11th to 20th	Day	13% 11% 4 7% 6% 5% 5% 3 5% 5% 36%	1822
	21st to end	Day	11% 14% 4 11% 7% 5% 4 3 4 6% 31%	1570
March	1st to 10th	Day	12% 8% 3 7% 5% 4 5% 4 5% 6% 42%	3120
	11th to 20th	Day	11% 7% 3 8% 5% 5% 5% 4 5% 6% 42%	3288
	21st to end	Day	20% 12% 4 11% 6% 4 4 3 4 6% 27%	4160
April	1st to 10th	Day	17% 13% 4 8% 5% 4 5% 3 5% 5% 30%	2280
	11th to 20th	Day	16% 10% 3 7% 6% 4 5% 4 5% 8% 33%	2254
	21st to end	Day	18% 9% 3 7% 5% 4 4 4 5% 6% 34%	2371
May	1st to 10th	Day	15% 8% 2 7% 5% 4 4 4 6% 7% 38%	4136
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 3 5% 7% 44%	4399
	21st to end	Day	12% 7% 3 7% 4 5% 5% 5% 6% 8% 38%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 6% 4 6% 9% 43%	2660
	11th to 20th	Day	11% 5% 2 5% 5% 4 5% 4 7% 9% 43%	2660
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 39%	2660
July	1st to 10th	Day	12% 8% 3 7% 5% 5% 6% 5% 7% 9% 34%	4440
	11th to 20th	Day	5% 3 2 5% 4 5% 6% 4 7% 9% 50%	4440
	21st to end	Day	7% 7% 3 7% 4 5% 5% 4 7% 9% 42%	4813
August	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	4423
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 9% 46%	3745
	21st to end	Day	8% 7% 3 6% 4 4 5% 4 6% 9% 45%	4180
September	1st to 10th	Day	12% 6% 2 6% 4 5% 4 3 7% 8% 44%	2280
	11th to 20th	Day	12% 5% 2 5% 3 3 3 4 5% 8% 51%	2190
	21st to end	Day	12% 7% 2 6% 5% 5% 4 3 5% 7% 44%	2090
October	1st to 10th	Day	14% 7% 2 5% 4 4 3 3 5% 7% 47%	1986
	11th to 20th	Day	17% 11% 3 7% 4 5% 5% 3 4 7% 35%	1900
	21st to end	Day	18% 10% 3 7% 4 4 4 3 5% 5% 37%	1885
November	1st to 10th	Day	12% 9% 3 8% 4 4 3 4 3 6% 45%	1735
	11th to 20th	Day	13% 12% 5% 8% 6% 5% 4 4 6% 6% 32%	1710
	21st to end	Day	16% 12% 3 8% 5% 4 3 3 4 6% 36%	1558
December	1st to 10th	Day	14% 13% 4 10% 7% 5% 4 4 4 6% 30%	1520
	11th to 20th	Day	12% 15% 5% 10% 6% 5% 5% 4 5% 7% 26%	1918
	21st to end	Day	18% 21% 9% 14% 6% 5% 4 2 3 4 15%	2783
January	1st to 10th	Night	12% 15% 7% 11% 6% 4 4 3 4 4 30%	4428
	11th to 20th	Night	13% 15% 7% 15% 6% 4 4 5% 7% 5% 19%	4440
	21st to end	Night	16% 18% 9% 12% 5% 4 4 2 4 5% 21%	4792
February	1st to 10th	Night	12% 14% 5% 9% 5% 5% 4 3 4 6% 32%	2470
	11th to 20th	Night	12% 10% 4 7% 5% 5% 5% 4 5% 5% 38%	2242
	21st to end	Night	17% 12% 4 7% 5% 3 3 3 5% 5% 36%	1884
March	1st to 10th	Night	17% 10% 3 5% 4 4 3 3 4 5% 41%	3733
	11th to 20th	Night	9% 7% 2 6% 4 4 4 4 6% 7% 46%	3689
	21st to end	Night	22% 13% 4 9% 5% 4 4 3 3 4 29%	3470
April	1st to 10th	Night	16% 11% 4 5% 4 5% 4 3 5% 7% 36%	1900
	11th to 20th	Night	17% 10% 3 7% 4 4 4 3 5% 5% 38%	1875
	21st to end	Night	19% 8% 3 6% 4 3 4 4 5% 6% 38%	1807
May	1st to 10th	Night	16% 8% 2 7% 4 5% 4 4 6% 8% 37%	2759
	11th to 20th	Night	13% 7% 3 6% 5% 4 5% 3 6% 6% 41%	2506
	21st to end	Night	11% 9% 3 6% 4 4 4 4 6% 7% 41%	2743
June	1st to 10th	Night	8% 4 2 5% 5% 4 6% 4 7% 9% 47%	1520
	11th to 20th	Night	11% 5% 1 6% 4 3 5% 4 6% 10% 45%	1520
	21st to end	Night	9% 6% 2 7% 5% 3 4 3 5% 9% 48%	1520
July	1st to 10th	Night	14% 7% 2 6% 4 4 5% 4 5% 9% 39%	2530
	11th to 20th	Night	5% 3 1 5% 4 4 4 4 5% 10% 54%	2530
	21st to end	Night	6% 4 2 7% 4 5% 6% 6% 7% 7% 46%	2750
August	1st to 10th	Night	10% 4 2 5% 3 4 4 4 7% 8% 49%	2517
	11th to 20th	Night	9% 7% 2 6% 4 4 4 4 5% 8% 48%	3078
	21st to end	Night	8% 5% 2 5% 3 4 4 4 6% 9% 49%	3476
September	1st to 10th	Night	8% 5% 2 6% 4 3 4 2 6% 7% 54%	1900
	11th to 20th	Night	11% 4 2 4 4 4 4 3 5% 7% 52%	1970
	21st to end	Night	12% 6% 2 6% 4 3 3 2 4 7% 49%	2090
October	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 4 5% 50%	2191
	11th to 20th	Night	16% 9% 2 6% 3 4 3 3 5% 5% 43%	2280
	21st to end	Night	20% 9% 2 6% 4 4 4 3 5% 7% 36%	2712
November	1st to 10th	Night	12% 9% 2 6% 4 3 4 4 5% 6% 46%	2504
	11th to 20th	Night	13% 12% 4 9% 5% 5% 4 3 5% 6% 34%	2470
	21st to end	Night	16% 11% 4 7% 5% 4 4 3 5% 7% 36%	2618
December	1st to 10th	Night	15% 13% 4 9% 5% 5% 5% 3 5% 6% 30%	2660
	11th to 20th	Night	15% 14% 5% 10% 5% 5% 4 3 4 6% 29%	3279
	21st to end	Night	21% 18% 6% 11% 6% 4 4 3 4 5% 19%	4884

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	62% 5% 13% 16% 6%	2528
	11th to 20th	Day	62% 5% 12% 14% 6%	2530
	21st to end	Day	67% 4 8% 16% 5%	2861
February	1st to 10th	Day	55% 4 12% 18% 9% 1	1710
	11th to 20th	Day	50% 4 10% 24% 10% 2	1832
	21st to end	Day	56% 4 9% 19% 10% 2	1570
March	1st to 10th	Day	42% 6% 11% 28% 12% 2	3120
	11th to 20th	Day	42% 5% 10% 30% 13% 1	3288
	21st to end	Day	60% 5% 11% 17% 6% 2	4160
April	1st to 10th	Day	55% 5% 10% 19% 11%	2280
	11th to 20th	Day	50% 4 9% 22% 13% 2	2254
	21st to end	Day	50% 6% 12% 19% 12% 1	2371
May	1st to 10th	Day	44% 6% 10% 23% 15% 1	4174
	11th to 20th	Day	40% 6% 9% 30% 14%	4403
	21st to end	Day	40% 8% 11% 22% 16% 3	4837
June	1st to 10th	Day	37% 6% 13% 26% 17% 2	2660
	11th to 20th	Day	37% 6% 12% 25% 18% 2	2660
	21st to end	Day	40% 6% 14% 22% 15% 2	2660
July	1st to 10th	Day	45% 6% 12% 26% 9% 2	4371
	11th to 20th	Day	28% 6% 15% 31% 18% 1	4365
	21st to end	Day	37% 6% 16% 19% 20% 2	4662
August	1st to 10th	Day	38% 7% 13% 30% 12% 1	4408
	11th to 20th	Day	35% 6% 12% 34% 12% 1	3781
	21st to end	Day	35% 6% 13% 27% 18% 1	4179
September	1st to 10th	Day	37% 6% 10% 27% 18% 2	2280
	11th to 20th	Day	31% 5% 11% 33% 18% 2	2190
	21st to end	Day	40% 5% 10% 29% 15% 1	2090
October	1st to 10th	Day	25% 3 6% 40% 25% 2	3298
	11th to 20th	Day	37% 3 9% 28% 22% 1	3140
	21st to end	Day	43% 3 9% 28% 14% 2	3085
November	1st to 10th	Day	42% 5% 14% 24% 14% 2	1735
	11th to 20th	Day	52% 5% 13% 20% 9% 1	1710
	21st to end	Day	51% 4 14% 24% 7% 1	1558
December	1st to 10th	Day	56% 5% 15% 16% 7% 1	1520
	11th to 20th	Day	56% 5% 14% 17% 6% 2	1915
	21st to end	Day	75% 4 7% 9% 5%	2783
January	1st to 10th	Night	57% 5% 9% 20% 8%	4428
	11th to 20th	Night	65% 4 9% 13% 8%	4440
	21st to end	Night	67% 4 9% 14% 6%	4792
February	1st to 10th	Night	53% 5% 10% 19% 12% 2	2470
	11th to 20th	Night	47% 5% 11% 22% 14% 1	2243
	21st to end	Night	50% 4 10% 21% 11% 4	1884
March	1st to 10th	Night	45% 5% 11% 24% 9% 5%	3733
	11th to 20th	Night	36% 5% 11% 28% 17% 3	3689
	21st to end	Night	59% 5% 7% 17% 11% 1	3470
April	1st to 10th	Night	48% 5% 10% 21% 15% 1	1900
	11th to 20th	Night	49% 4 6% 21% 18% 3	1875
	21st to end	Night	46% 6% 10% 22% 14% 2	1807
May	1st to 10th	Night	43% 7% 12% 18% 17% 2	2786
	11th to 20th	Night	40% 8% 10% 28% 12% 1	2507
	21st to end	Night	39% 8% 11% 18% 19% 5%	2751
June	1st to 10th	Night	32% 6% 13% 28% 19% 2	1520
	11th to 20th	Night	33% 7% 10% 25% 23% 3	1520
	21st to end	Night	35% 6% 15% 23% 19% 3	1520
July	1st to 10th	Night	43% 6% 14% 21% 13% 4	2490
	11th to 20th	Night	26% 5% 14% 35% 18% 2	2482
	21st to end	Night	33% 7% 14% 21% 21% 3	2662
August	1st to 10th	Night	31% 6% 14% 29% 18% 2	2508
	11th to 20th	Night	34% 5% 12% 33% 16% 1	3108
	21st to end	Night	31% 6% 12% 29% 19% 3	3476
September	1st to 10th	Night	30% 5% 12% 26% 24% 3	1900
	11th to 20th	Night	31% 5% 10% 33% 19% 2	1970
	21st to end	Night	36% 4 9% 31% 18% 1	2090
October	1st to 10th	Night	25% 4 6% 38% 26% 2	3659
	11th to 20th	Night	36% 3 10% 26% 22% 2	3779
	21st to end	Night	43% 4 8% 27% 16% 2	4462
November	1st to 10th	Night	40% 4 10% 27% 17% 2	2504
	11th to 20th	Night	51% 4 12% 20% 11% 1	2470
	21st to end	Night	49% 4 14% 22% 10% 1	2618
December	1st to 10th	Night	55% 5% 11% 19% 8% 1	2660
	11th to 20th	Night	57% 5% 12% 17% 8% 1	3281
	21st to end	Night	68% 5% 9% 14% 5%	4884

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	18% 15% 33% 26% 7% 1	270
	11th to 20th	Day	19% 16% 35% 24% 4 1	270
	21st to end	Day	23% 11% 39% 21% 4 2	297
February	1st to 10th	Day	13% 19% 46% 16% 5% 1	270
	11th to 20th	Day	19% 21% 38% 17% 5%	270
	21st to end	Day	20% 17% 45% 15% 2	225
March	1st to 10th	Day	17% 17% 46% 14% 6%	270
	11th to 20th	Day	21% 20% 34% 16% 8% 1	270
	21st to end	Day	28% 13% 29% 22% 6% 2	501
April	1st to 10th	Day	23% 16% 33% 22% 5%	460
	11th to 20th	Day	23% 19% 24% 22% 8% 2	452
	21st to end	Day	25% 12% 27% 24% 11% 2	460
May	1st to 10th	Day	20% 12% 31% 28% 8% 2	491
	11th to 20th	Day	22% 10% 27% 26% 12% 3	675
	21st to end	Day	16% 10% 28% 26% 15% 5%	734
June	1st to 10th	Day	10% 8% 30% 30% 16% 5%	680
	11th to 20th	Day	13% 8% 30% 30% 14% 5%	680
	21st to end	Day	15% 8% 28% 28% 17% 4	680
July	1st to 10th	Day	8% 3 19% 31% 26% 12%	671
	11th to 20th	Day	8% 5% 27% 30% 21% 9%	668
	21st to end	Day	7% 3 24% 36% 20% 9%	739
August	1st to 10th	Day	8% 4 20% 35% 22% 11%	676
	11th to 20th	Day	11% 5% 18% 27% 25% 14%	493
	21st to end	Day	11% 3 19% 32% 24% 10%	539
September	1st to 10th	Day	14% 7% 23% 28% 21% 7%	490
	11th to 20th	Day	11% 3 21% 30% 23% 12%	490
	21st to end	Day	16% 11% 26% 23% 16% 9%	490
October	1st to 10th	Day	18% 9% 26% 25% 16% 5%	386
	11th to 20th	Day	22% 19% 30% 21% 7%	300
	21st to end	Day	28% 13% 35% 18% 5% 2	330
November	1st to 10th	Day	17% 15% 36% 20% 11% 1	291
	11th to 20th	Day	20% 16% 37% 17% 9%	270
	21st to end	Day	23% 12% 40% 21% 4	270
December	1st to 10th	Day	19% 16% 40% 18% 6% 1	270
	11th to 20th	Day	17% 18% 37% 19% 8% 1	270
	21st to end	Day	25% 16% 40% 16% 2	297
January	1st to 10th	Night	17% 14% 38% 24% 7% 1	950
	11th to 20th	Night	21% 12% 35% 25% 6% 1	950
	21st to end	Night	21% 10% 36% 28% 6%	1045
February	1st to 10th	Night	20% 11% 38% 26% 6%	950
	11th to 20th	Night	19% 14% 36% 27% 4	767
	21st to end	Night	24% 12% 37% 22% 3	628
March	1st to 10th	Night	22% 10% 36% 25% 6% 1	760
	11th to 20th	Night	16% 12% 35% 30% 7%	701
	21st to end	Night	25% 8% 29% 29% 8% 1	627
April	1st to 10th	Night	21% 11% 39% 24% 5% 1	570
	11th to 20th	Night	22% 12% 31% 28% 6% 1	563
	21st to end	Night	23% 9% 32% 27% 9% 1	570
May	1st to 10th	Night	20% 7% 35% 30% 6% 1	570
	11th to 20th	Night	19% 5% 32% 32% 11%	561
	21st to end	Night	15% 5% 26% 35% 18%	617
June	1st to 10th	Night	10% 4 26% 44% 15% 1	570
	11th to 20th	Night	13% 3 32% 39% 12% 1	570
	21st to end	Night	12% 4 28% 40% 16% 1	570
July	1st to 10th	Night	10% 2 14% 40% 31% 3	555
	11th to 20th	Night	9% 1 21% 43% 24% 3	552
	21st to end	Night	8% 2 16% 50% 23% 2	624
August	1st to 10th	Night	8% 2 14% 46% 28% 3	567
	11th to 20th	Night	9% 3 13% 42% 28% 4	564
	21st to end	Night	11% 1 16% 43% 26% 3	627
September	1st to 10th	Night	8% 4 23% 36% 24% 5%	570
	11th to 20th	Night	12% 3 22% 35% 24% 4	640
	21st to end	Night	16% 6% 26% 31% 19% 2	760
October	1st to 10th	Night	14% 7% 31% 31% 16% 2	760
	11th to 20th	Night	21% 11% 31% 28% 9%	760
	21st to end	Night	25% 10% 31% 27% 7%	836
November	1st to 10th	Night	16% 12% 37% 25% 10% 1	771
	11th to 20th	Night	21% 14% 36% 23% 6%	760
	21st to end	Night	22% 11% 38% 21% 7%	908
December	1st to 10th	Night	23% 12% 38% 20% 5%	950
	11th to 20th	Night	24% 11% 36% 23% 5% 1	950
	21st to end	Night	30% 12% 34% 22% 3	1045

Page generated at 2024-11-05 07:15:54. Version ac07

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