Middleton
Clear Sky Chart
History

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

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	7% 6% 2 6% 4 4 4 3 5% 6% 54%	105425
	Night	10% 7% 3 6% 4 4 4 3 5% 6% 47%	102953
Transparency	Day	30% 5% 11% 19% 20% 15%	105169
	Night	36% 5% 11% 18% 17% 12%	102798
Seeing	Day	9% 6% 18% 28% 25% 14%	14561
	Night	12% 5% 19% 38% 23% 3	23878

By Month

Percentage Cloud Cover SW (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% 14% 5% 10% 7% 6% 5% 5% 7% 6% 22%	2539
	11th to 20th	Day	15% 17% 4 12% 6% 4 5% 4 6% 6% 20%	2540
	21st to end	Day	19% 15% 6% 11% 6% 5% 5% 4 5% 5% 18%	2794
February	1st to 10th	Day	13% 11% 5% 10% 5% 4 5% 4 4 6% 33%	1671
	11th to 20th	Day	11% 12% 3 7% 5% 5% 4 5% 5% 6% 37%	1850
	21st to end	Day	9% 12% 3 6% 6% 5% 6% 4 6% 8% 35%	1570
March	1st to 10th	Day	9% 11% 4 9% 6% 6% 6% 5% 7% 7% 29%	3138
	11th to 20th	Day	7% 7% 2 5% 3 3 3 3 4 4 57%	3327
	21st to end	Day	9% 8% 3 8% 6% 7% 6% 5% 8% 9% 32%	4040
April	1st to 10th	Day	10% 9% 3 6% 5% 4 5% 4 6% 7% 42%	2280
	11th to 20th	Day	6% 7% 2 6% 4 5% 5% 4 5% 8% 47%	2276
	21st to end	Day	8% 6% 2 5% 4 3 5% 4 6% 7% 50%	2470
May	1st to 10th	Day	9% 5% 2 6% 4 4 4 4 6% 6% 51%	4110
	11th to 20th	Day	5% 3 1 3 2 3 3 3 4 5% 68%	4249
	21st to end	Day	6% 4 2 5% 4 4 4 3 6% 8% 55%	4813
June	1st to 10th	Day	8% 5% 2 6% 4 5% 4 5% 7% 9% 46%	2660
	11th to 20th	Day	6% 4 1 4 3 3 3 3 6% 8% 60%	2660
	21st to end	Day	3 2 1 3 2 2 3 3 4 5% 72%	2660
July	1st to 10th	Day	1 1 2 1 2 2 2 3 3 82%	4420
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 4 80%	4420
	21st to end	Day	2 2 1 3 2 2 3 2 3 4 76%	4790
August	1st to 10th	Day	4 4 1 5% 3 3 3 3 5% 6% 63%	4264
	11th to 20th	Day	2 1 2 2 2 2 2 3 5% 80%	4004
	21st to end	Day	2 2 1 3 2 2 3 2 2 3 77%	4180
September	1st to 10th	Day	3 1 1 2 2 2 3 2 3 5% 75%	2280
	11th to 20th	Day	4 3 1 3 3 3 3 2 4 7% 66%	2123
	21st to end	Day	5% 2 2 3 4 3 3 2 4 6% 66%	2090
October	1st to 10th	Day	5% 3 1 4 2 3 3 2 3 5% 69%	3490
	11th to 20th	Day	8% 3 2 5% 3 4 4 3 5% 7% 56%	3035
	21st to end	Day	7% 7% 3 6% 4 4 4 4 6% 8% 48%	3101
November	1st to 10th	Day	13% 8% 2 7% 4 4 4 4 6% 8% 39%	1764
	11th to 20th	Day	14% 9% 3 8% 6% 5% 5% 3 6% 8% 34%	1800
	21st to end	Day	10% 10% 4 9% 7% 6% 5% 5% 6% 9% 30%	1735
December	1st to 10th	Day	16% 10% 4 10% 5% 5% 5% 4 6% 7% 28%	1560
	11th to 20th	Day	14% 13% 5% 15% 7% 5% 4 5% 5% 7% 20%	1928
	21st to end	Day	12% 11% 5% 11% 6% 6% 6% 4 6% 7% 25%	2794
January	1st to 10th	Night	14% 17% 5% 12% 7% 6% 5% 5% 5% 7% 18%	4406
	11th to 20th	Night	19% 18% 5% 11% 7% 6% 5% 3 4 5% 18%	4420
	21st to end	Night	19% 14% 6% 13% 5% 4 5% 3 5% 5% 21%	4862
February	1st to 10th	Night	15% 10% 4 8% 6% 5% 5% 4 5% 7% 31%	2505
	11th to 20th	Night	12% 9% 3 6% 6% 5% 5% 5% 6% 7% 36%	2218
	21st to end	Night	12% 12% 3 8% 5% 4 5% 5% 7% 7% 32%	1884
March	1st to 10th	Night	10% 11% 3 8% 6% 6% 5% 4 6% 7% 33%	3736
	11th to 20th	Night	10% 7% 3 5% 4 3 3 3 4 5% 53%	3652
	21st to end	Night	11% 8% 3 7% 6% 5% 6% 5% 7% 9% 32%	3599
April	1st to 10th	Night	11% 8% 3 6% 4 3 4 4 6% 7% 44%	1900
	11th to 20th	Night	10% 7% 2 6% 5% 6% 5% 3 6% 6% 45%	1851
	21st to end	Night	8% 5% 2 5% 4 3 4 4 5% 7% 53%	1710
May	1st to 10th	Night	10% 5% 3 5% 4 4 4 4 6% 8% 48%	2860
	11th to 20th	Night	4 4 1 3 3 3 4 3 4 6% 65%	2644
	21st to end	Night	7% 5% 2 6% 4 4 4 4 5% 6% 53%	2762
June	1st to 10th	Night	9% 6% 2 6% 5% 4 4 4 7% 8% 46%	1520
	11th to 20th	Night	7% 5% 1 5% 4 3 4 3 3 6% 60%	1520
	21st to end	Night	2 2 1 3 3 3 4 3 4 6% 69%	1520
July	1st to 10th	Night	1 1 1 2 2 2 2 2 3 4 81%	2540
	11th to 20th	Night	1 1 1 2 1 2 3 2 4 5% 79%	2540
	21st to end	Night	1 2 1 4 3 4 4 3 4 6% 68%	2761
August	1st to 10th	Night	3 4 1 5% 4 3 4 4 6% 6% 61%	2656
	11th to 20th	Night	1 1 1 2 1 2 3 2 4 5% 78%	2833
	21st to end	Night	3 3 1 2 1 2 3 2 2 3 77%	3498
September	1st to 10th	Night	3 1 1 3 2 2 2 2 3 5% 76%	1900
	11th to 20th	Night	5% 4 1 4 3 3 3 3 4 6% 65%	2057
	21st to end	Night	7% 3 1 3 2 3 3 2 4 4 67%	2090
October	1st to 10th	Night	4 2 1 3 3 3 3 3 3 4 70%	3490
	11th to 20th	Night	6% 4 1 4 3 3 3 3 4 6% 61%	3893
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 6% 8% 47%	4457
November	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 4 6% 44%	2535
	11th to 20th	Night	17% 7% 2 7% 5% 5% 5% 4 5% 7% 38%	2600
	21st to end	Night	13% 8% 3 7% 5% 5% 5% 3 5% 8% 38%	2660
December	1st to 10th	Night	16% 12% 5% 8% 4 5% 4 3 5% 7% 31%	2736
	11th to 20th	Night	15% 13% 5% 11% 6% 6% 5% 4 5% 6% 23%	3276
	21st to end	Night	14% 11% 4 10% 6% 6% 5% 4 6% 6% 25%	4862

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	58% 9% 17% 13% 2	2539
	11th to 20th	Day	64% 9% 16% 11% 1	2540
	21st to end	Day	64% 10% 14% 10% 1	2794
February	1st to 10th	Day	51% 9% 19% 16% 4 1	1671
	11th to 20th	Day	47% 9% 15% 21% 8%	1860
	21st to end	Day	46% 6% 17% 19% 10% 1	1570
March	1st to 10th	Day	48% 7% 15% 21% 9% 1	3138
	11th to 20th	Day	29% 5% 11% 37% 16% 2	3327
	21st to end	Day	42% 9% 18% 21% 8% 2	4040
April	1st to 10th	Day	39% 5% 16% 22% 14% 3	2280
	11th to 20th	Day	35% 5% 13% 24% 18% 5%	2279
	21st to end	Day	32% 5% 12% 29% 19% 4	2470
May	1st to 10th	Day	31% 4 10% 23% 27% 6%	4110
	11th to 20th	Day	18% 3 8% 23% 33% 15%	4252
	21st to end	Day	25% 5% 13% 30% 23% 4	4814
June	1st to 10th	Day	32% 6% 12% 25% 22% 3	2660
	11th to 20th	Day	22% 4 9% 23% 30% 12%	2660
	21st to end	Day	14% 3 7% 19% 33% 25%	2660
July	1st to 10th	Day	8% 2 4 8% 20% 58%	4351
	11th to 20th	Day	10% 2 3 5% 21% 60%	4345
	21st to end	Day	12% 2 3 7% 30% 46%	4639
August	1st to 10th	Day	21% 3 5% 10% 26% 36%	4248
	11th to 20th	Day	9% 2 3 16% 35% 34%	4043
	21st to end	Day	14% 2 3 18% 36% 27%	4179
September	1st to 10th	Day	13% 3 4 17% 32% 31%	2280
	11th to 20th	Day	20% 4 8% 24% 30% 15%	2123
	21st to end	Day	22% 3 7% 25% 34% 10%	2090
October	1st to 10th	Day	21% 2 7% 20% 41% 9%	3490
	11th to 20th	Day	28% 4 12% 29% 23% 4	3035
	21st to end	Day	34% 4 12% 32% 17% 1	3101
November	1st to 10th	Day	43% 6% 15% 26% 10%	1764
	11th to 20th	Day	49% 6% 18% 22% 5% 1	1800
	21st to end	Day	48% 9% 18% 20% 5%	1735
December	1st to 10th	Day	53% 9% 20% 13% 5%	1560
	11th to 20th	Day	62% 9% 15% 11% 3	1928
	21st to end	Day	56% 7% 19% 14% 3	2794
January	1st to 10th	Night	63% 9% 17% 9% 2	4406
	11th to 20th	Night	67% 8% 12% 10% 2	4420
	21st to end	Night	63% 8% 15% 12% 2	4862
February	1st to 10th	Night	51% 7% 18% 19% 3 1	2505
	11th to 20th	Night	45% 8% 17% 21% 9%	2219
	21st to end	Night	47% 7% 16% 20% 9% 1	1884
March	1st to 10th	Night	44% 7% 16% 21% 12% 1	3736
	11th to 20th	Night	33% 4 8% 32% 22% 1	3652
	21st to end	Night	43% 9% 14% 25% 9% 1	3599
April	1st to 10th	Night	37% 4 13% 25% 18% 3	1900
	11th to 20th	Night	36% 5% 11% 25% 21% 3	1851
	21st to end	Night	30% 5% 10% 27% 24% 4	1710
May	1st to 10th	Night	31% 5% 11% 23% 25% 6%	2860
	11th to 20th	Night	20% 3 7% 19% 39% 11%	2644
	21st to end	Night	30% 5% 11% 26% 24% 3	2762
June	1st to 10th	Night	35% 6% 12% 23% 22% 2	1520
	11th to 20th	Night	26% 4 8% 20% 32% 11%	1520
	21st to end	Night	16% 3 7% 17% 31% 26%	1520
July	1st to 10th	Night	9% 1 4 8% 18% 60%	2500
	11th to 20th	Night	9% 2 3 6% 18% 62%	2492
	21st to end	Night	18% 2 4 6% 28% 43%	2674
August	1st to 10th	Night	22% 3 6% 9% 22% 37%	2648
	11th to 20th	Night	10% 2 5% 9% 28% 46%	2860
	21st to end	Night	14% 2 2 12% 33% 36%	3498
September	1st to 10th	Night	13% 3 4 12% 30% 38%	1900
	11th to 20th	Night	21% 3 7% 19% 25% 25%	2057
	21st to end	Night	21% 2 4 20% 33% 19%	2090
October	1st to 10th	Night	19% 3 5% 17% 33% 23%	3490
	11th to 20th	Night	24% 4 9% 29% 29% 5%	3893
	21st to end	Night	34% 5% 11% 29% 20% 2	4457
November	1st to 10th	Night	40% 5% 12% 25% 17% 1	2535
	11th to 20th	Night	45% 6% 14% 26% 9%	2600
	21st to end	Night	43% 7% 18% 24% 8%	2660
December	1st to 10th	Night	53% 7% 17% 16% 6%	2736
	11th to 20th	Night	59% 8% 17% 14% 3	3276
	21st to end	Night	54% 8% 20% 13% 5%	4862

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% 9% 16% 28% 17% 8%	180
	11th to 20th	Day	14% 12% 18% 28% 19% 8%	180
	21st to end	Day	17% 6% 13% 32% 24% 9%	198
February	1st to 10th	Day	16% 8% 26% 25% 16% 9%	292
	11th to 20th	Day	17% 9% 22% 32% 15% 5%	455
	21st to end	Day	16% 10% 26% 26% 15% 6%	382
March	1st to 10th	Day	14% 14% 26% 30% 13% 3	460
	11th to 20th	Day	13% 8% 23% 30% 19% 7%	460
	21st to end	Day	12% 12% 26% 27% 18% 5%	506
April	1st to 10th	Day	16% 12% 22% 21% 18% 12%	460
	11th to 20th	Day	8% 12% 28% 27% 16% 9%	452
	21st to end	Day	7% 11% 28% 27% 19% 8%	460
May	1st to 10th	Day	5% 12% 25% 29% 18% 11%	463
	11th to 20th	Day	14% 6% 17% 28% 22% 13%	488
	21st to end	Day	9% 4 15% 25% 26% 21%	529
June	1st to 10th	Day	8% 6% 16% 29% 25% 18%	490
	11th to 20th	Day	7% 6% 21% 32% 25% 9%	490
	21st to end	Day	3 3 19% 31% 27% 18%	490
July	1st to 10th	Day	2 3 14% 31% 32% 18%	486
	11th to 20th	Day	1 1 14% 35% 33% 14%	484
	21st to end	Day	3 1 10% 30% 37% 19%	531
August	1st to 10th	Day	5% 2 10% 31% 36% 16%	487
	11th to 20th	Day	2 1 12% 27% 35% 23%	477
	21st to end	Day	4 3 12% 27% 31% 23%	539
September	1st to 10th	Day	4 2 11% 21% 34% 28%	490
	11th to 20th	Day	5% 4 11% 27% 28% 25%	490
	21st to end	Day	4 3 15% 27% 32% 19%	490
October	1st to 10th	Day	8% 4 14% 23% 26% 25%	490
	11th to 20th	Day	10% 4 16% 27% 24% 19%	397
	21st to end	Day	13% 4 18% 29% 27% 10%	330
November	1st to 10th	Day	18% 5% 16% 27% 26% 7%	300
	11th to 20th	Day	13% 7% 15% 32% 25% 8%	300
	21st to end	Day	14% 4 13% 32% 27% 9%	267
December	1st to 10th	Day	21% 4 15% 29% 16% 16%	190
	11th to 20th	Day	19% 7% 21% 28% 19% 4	180
	21st to end	Day	17% 7% 20% 30% 19% 7%	198
January	1st to 10th	Night	21% 7% 20% 30% 19% 3	760
	11th to 20th	Night	19% 5% 20% 30% 24% 2	760
	21st to end	Night	19% 4 15% 36% 23% 3	836
February	1st to 10th	Night	20% 6% 20% 37% 15% 2	760
	11th to 20th	Night	15% 5% 21% 39% 18% 2	744
	21st to end	Night	15% 7% 25% 37% 14% 1	628
March	1st to 10th	Night	15% 7% 28% 34% 14% 2	760
	11th to 20th	Night	15% 6% 21% 39% 17% 2	760
	21st to end	Night	15% 8% 25% 38% 13% 2	836
April	1st to 10th	Night	13% 6% 22% 38% 20% 1	760
	11th to 20th	Night	11% 8% 26% 35% 19% 1	723
	21st to end	Night	10% 8% 23% 40% 18% 1	570
May	1st to 10th	Night	8% 8% 24% 39% 19% 2	570
	11th to 20th	Night	10% 6% 23% 32% 27% 4	450
	21st to end	Night	7% 8% 17% 38% 26% 5%	411
June	1st to 10th	Night	12% 5% 19% 35% 26% 3	380
	11th to 20th	Night	9% 8% 22% 37% 22% 2	380
	21st to end	Night	3 3 23% 40% 29% 2	380
July	1st to 10th	Night	1 1 18% 51% 28% 1	370
	11th to 20th	Night	1 1 19% 55% 24%	368
	21st to end	Night	3 1 16% 46% 33% 1	416
August	1st to 10th	Night	4 1 14% 48% 30% 2	453
	11th to 20th	Night	1 2 12% 47% 36% 2	573
	21st to end	Night	4 3 13% 42% 33% 5%	836
September	1st to 10th	Night	3 1 11% 43% 37% 5%	760
	11th to 20th	Night	6% 2 12% 38% 39% 4	760
	21st to end	Night	8% 3 14% 37% 31% 8%	760
October	1st to 10th	Night	8% 3 16% 41% 29% 4	760
	11th to 20th	Night	8% 4 15% 40% 28% 6%	760
	21st to end	Night	11% 3 18% 41% 24% 3	836
November	1st to 10th	Night	16% 5% 16% 38% 24% 2	780
	11th to 20th	Night	20% 4 19% 38% 17% 2	800
	21st to end	Night	16% 4 16% 38% 21% 4	800
December	1st to 10th	Night	21% 4 17% 36% 18% 4	782
	11th to 20th	Night	22% 6% 16% 38% 16% 2	760
	21st to end	Night	25% 6% 21% 35% 11% 2	836

Page generated at 2024-12-03 04:45:10. Version ac07

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