Fenton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fenton clear sky chart from 2005-11-06 to 2024-11-04.

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	14% 10% 3 8% 5% 5% 4 4 5% 7% 34%	100876
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 35%	98095
Transparency	Day	48% 6% 12% 21% 12% 1	104476
	Night	48% 5% 12% 21% 12% 1	102635
Seeing	Day	18% 12% 29% 23% 13% 5%	15496
	Night	19% 10% 29% 29% 11% 1	25337

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	14% 22% 6% 13% 5% 4 4 3 3 5% 21%	2527
	11th to 20th	Day	15% 22% 6% 15% 10% 7% 3 2 4 4 12%	2530
	21st to end	Day	27% 21% 7% 12% 5% 4 3 2 3 3 14%	2999
February	1st to 10th	Day	13% 15% 6% 13% 7% 5% 5% 3 5% 6% 22%	1710
	11th to 20th	Day	13% 14% 6% 13% 8% 6% 4 3 4 5% 24%	1803
	21st to end	Day	13% 17% 6% 12% 7% 4 3 4 4 5% 25%	1570
March	1st to 10th	Day	17% 15% 4 9% 5% 3 3 3 4 6% 28%	3173
	11th to 20th	Day	12% 14% 6% 10% 5% 4 4 3 5% 6% 30%	3480
	21st to end	Day	18% 15% 3 10% 5% 4 4 3 4 5% 29%	3815
April	1st to 10th	Day	17% 13% 4 8% 6% 4 5% 3 5% 6% 30%	2232
	11th to 20th	Day	17% 11% 3 7% 4 4 4 4 5% 6% 35%	2398
	21st to end	Day	17% 8% 3 8% 5% 5% 4 3 4 7% 34%	2470
May	1st to 10th	Day	18% 9% 2 7% 4 4 4 4 5% 7% 35%	4082
	11th to 20th	Day	17% 8% 2 5% 4 4 4 4 6% 8% 37%	4081
	21st to end	Day	11% 6% 2 7% 4 4 4 3 5% 7% 46%	4540
June	1st to 10th	Day	11% 6% 3 6% 5% 5% 5% 5% 7% 8% 40%	2674
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 9% 41%	2828
	21st to end	Day	11% 6% 2 6% 5% 6% 5% 5% 7% 9% 38%	2660
July	1st to 10th	Day	11% 7% 2 7% 5% 5% 5% 5% 7% 9% 37%	4440
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 9% 48%	4440
	21st to end	Day	8% 5% 2 7% 5% 6% 6% 5% 7% 9% 41%	4605
August	1st to 10th	Day	13% 5% 2 6% 4 5% 5% 4 6% 8% 41%	4104
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 5% 7% 8% 41%	4044
	21st to end	Day	8% 6% 2 7% 5% 6% 5% 4 6% 9% 40%	4452
September	1st to 10th	Day	11% 7% 2 7% 5% 5% 5% 4 6% 8% 40%	2163
	11th to 20th	Day	10% 6% 2 5% 3 3 4 4 6% 8% 48%	2090
	21st to end	Day	16% 7% 2 6% 4 5% 5% 5% 6% 8% 35%	2090
October	1st to 10th	Day	14% 7% 3 7% 4 4 4 4 5% 6% 42%	2048
	11th to 20th	Day	18% 12% 3 7% 5% 4 5% 4 4 7% 32%	1900
	21st to end	Day	21% 11% 3 7% 5% 4 4 3 5% 7% 28%	1910
November	1st to 10th	Day	12% 11% 3 8% 5% 4 3 4 7% 7% 36%	1699
	11th to 20th	Day	13% 15% 5% 8% 6% 4 4 4 5% 6% 29%	1710
	21st to end	Day	18% 15% 6% 8% 5% 5% 4 3 5% 6% 26%	1629
December	1st to 10th	Day	14% 18% 7% 13% 7% 5% 4 3 4 5% 21%	1520
	11th to 20th	Day	16% 17% 6% 10% 6% 4 4 5% 5% 6% 21%	1704
	21st to end	Day	23% 22% 7% 14% 5% 4 3 2 4 4 11%	2756
January	1st to 10th	Night	16% 17% 8% 13% 5% 4 4 3 4 4 22%	4428
	11th to 20th	Night	14% 18% 8% 16% 6% 7% 5% 4 4 4 14%	4440
	21st to end	Night	23% 17% 9% 11% 5% 4 4 3 3 5% 16%	4660
February	1st to 10th	Night	16% 17% 5% 11% 8% 5% 4 3 4 4 22%	2470
	11th to 20th	Night	13% 16% 6% 11% 7% 5% 4 4 5% 5% 26%	2261
	21st to end	Night	18% 14% 4 10% 6% 4 4 3 5% 6% 28%	1884
March	1st to 10th	Night	14% 14% 4 8% 5% 4 3 3 4 7% 35%	3680
	11th to 20th	Night	10% 10% 3 6% 5% 4 5% 4 5% 7% 41%	3480
	21st to end	Night	16% 10% 3 9% 5% 4 4 4 4 6% 34%	3817
April	1st to 10th	Night	16% 12% 3 6% 4 5% 4 3 5% 6% 36%	1963
	11th to 20th	Night	19% 10% 2 6% 4 3 5% 3 6% 6% 36%	1730
	21st to end	Night	17% 8% 3 7% 4 4 4 4 5% 6% 38%	1710
May	1st to 10th	Night	16% 9% 3 6% 5% 4 4 4 5% 8% 37%	2813
	11th to 20th	Night	16% 8% 2 6% 4 4 4 3 4 6% 44%	2812
	21st to end	Night	11% 6% 2 5% 4 4 4 4 5% 8% 48%	3001
June	1st to 10th	Night	11% 5% 2 6% 4 3 4 3 6% 9% 46%	1492
	11th to 20th	Night	10% 6% 2 5% 5% 4 3 4 7% 9% 45%	1335
	21st to end	Night	10% 6% 2 5% 4 3 3 3 6% 9% 48%	1520
July	1st to 10th	Night	9% 4 2 5% 4 4 5% 4 7% 11% 45%	2530
	11th to 20th	Night	10% 4 2 4 4 4 3 3 5% 7% 54%	2530
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 7% 9% 48%	2951
August	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 7% 8% 48%	2825
	11th to 20th	Night	11% 6% 1 5% 4 4 5% 3 5% 7% 49%	2785
	21st to end	Night	9% 5% 2 6% 5% 4 4 3 4 8% 50%	3188
September	1st to 10th	Night	10% 6% 2 6% 5% 3 4 3 6% 7% 48%	1996
	11th to 20th	Night	10% 5% 2 4 3 3 4 3 4 7% 54%	2090
	21st to end	Night	15% 6% 3 5% 4 4 5% 4 5% 6% 42%	2090
October	1st to 10th	Night	15% 6% 3 6% 4 3 4 3 5% 6% 45%	2131
	11th to 20th	Night	19% 11% 3 7% 5% 4 4 3 5% 5% 34%	2280
	21st to end	Night	21% 10% 3 7% 5% 5% 4 3 5% 6% 31%	2684
November	1st to 10th	Night	14% 10% 2 6% 4 4 4 3 5% 6% 41%	2452
	11th to 20th	Night	16% 13% 4 7% 5% 6% 5% 4 5% 6% 29%	2470
	21st to end	Night	20% 15% 4 8% 5% 4 3 3 5% 6% 27%	2547
December	1st to 10th	Night	17% 18% 6% 11% 6% 5% 5% 3 4 5% 20%	2660
	11th to 20th	Night	14% 17% 5% 13% 6% 5% 4 3 5% 5% 22%	3488
	21st to end	Night	25% 23% 7% 10% 5% 3 3 3 3 4 12%	4902

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	67% 3 12% 13% 5%	2528
	11th to 20th	Day	76% 5% 11% 6% 3	2530
	21st to end	Day	78% 3 9% 7% 3	2999
February	1st to 10th	Day	63% 5% 11% 14% 7%	1710
	11th to 20th	Day	63% 5% 8% 15% 9% 1	1813
	21st to end	Day	62% 4 11% 14% 6% 2	1570
March	1st to 10th	Day	56% 5% 12% 19% 7%	3173
	11th to 20th	Day	53% 6% 13% 19% 8% 1	3480
	21st to end	Day	58% 4 11% 15% 9% 2	3815
April	1st to 10th	Day	54% 6% 10% 19% 11%	2232
	11th to 20th	Day	49% 6% 11% 21% 12% 2	2398
	21st to end	Day	49% 6% 13% 17% 14% 1	2470
May	1st to 10th	Day	46% 7% 11% 23% 11% 2	4120
	11th to 20th	Day	43% 7% 15% 25% 9% 1	4085
	21st to end	Day	37% 5% 11% 20% 24% 3	4553
June	1st to 10th	Day	37% 7% 13% 26% 14% 2	2674
	11th to 20th	Day	40% 6% 11% 24% 16% 2	2828
	21st to end	Day	40% 7% 14% 23% 15% 1	2660
July	1st to 10th	Day	42% 7% 14% 20% 16% 2	4371
	11th to 20th	Day	30% 6% 13% 34% 16% 1	4365
	21st to end	Day	36% 7% 15% 19% 21% 2	4459
August	1st to 10th	Day	39% 7% 13% 24% 16% 1	4091
	11th to 20th	Day	38% 7% 11% 32% 12% 1	4083
	21st to end	Day	38% 6% 14% 28% 13% 1	4451
September	1st to 10th	Day	40% 8% 13% 25% 12% 2	2163
	11th to 20th	Day	33% 6% 13% 32% 15% 2	2090
	21st to end	Day	43% 7% 13% 25% 12%	2090
October	1st to 10th	Day	33% 5% 10% 32% 20% 1	3399
	11th to 20th	Day	42% 4 11% 26% 17%	3140
	21st to end	Day	47% 4 13% 24% 11% 1	3122
November	1st to 10th	Day	45% 7% 14% 22% 11% 1	1699
	11th to 20th	Day	54% 5% 14% 18% 8% 1	1710
	21st to end	Day	59% 5% 13% 16% 6% 1	1629
December	1st to 10th	Day	66% 4 11% 15% 3	1520
	11th to 20th	Day	63% 5% 13% 15% 4	1700
	21st to end	Day	79% 3 9% 6% 3	2756
January	1st to 10th	Night	65% 4 11% 13% 5% 1	4428
	11th to 20th	Night	72% 5% 11% 8% 4	4440
	21st to end	Night	71% 5% 9% 12% 3	4660
February	1st to 10th	Night	64% 6% 10% 12% 7% 1	2470
	11th to 20th	Night	59% 6% 9% 17% 9% 1	2262
	21st to end	Night	58% 4 12% 16% 8% 1	1884
March	1st to 10th	Night	50% 4 14% 25% 7% 1	3680
	11th to 20th	Night	40% 6% 14% 22% 16% 1	3480
	21st to end	Night	50% 6% 12% 21% 10% 1	3817
April	1st to 10th	Night	49% 5% 10% 21% 13% 2	1963
	11th to 20th	Night	46% 5% 11% 18% 17% 2	1730
	21st to end	Night	46% 5% 12% 19% 16% 2	1710
May	1st to 10th	Night	45% 6% 12% 22% 13% 3	2840
	11th to 20th	Night	41% 5% 10% 28% 13% 3	2813
	21st to end	Night	35% 6% 12% 22% 19% 6%	3009
June	1st to 10th	Night	34% 6% 10% 29% 17% 3	1492
	11th to 20th	Night	34% 7% 14% 24% 19% 2	1335
	21st to end	Night	33% 6% 14% 26% 19% 1	1520
July	1st to 10th	Night	32% 5% 13% 28% 15% 6%	2490
	11th to 20th	Night	30% 5% 12% 30% 22% 1	2482
	21st to end	Night	31% 8% 17% 19% 22% 2	2857
August	1st to 10th	Night	34% 6% 14% 28% 17% 1	2814
	11th to 20th	Night	34% 6% 11% 36% 11% 2	2812
	21st to end	Night	35% 6% 12% 32% 15% 1	3188
September	1st to 10th	Night	34% 7% 12% 28% 16% 2	1996
	11th to 20th	Night	31% 5% 11% 30% 21% 2	2090
	21st to end	Night	41% 5% 12% 27% 14% 1	2090
October	1st to 10th	Night	26% 4 10% 34% 25% 1	3560
	11th to 20th	Night	45% 4 11% 23% 17% 1	3779
	21st to end	Night	42% 4 11% 30% 12%	4422
November	1st to 10th	Night	43% 6% 11% 26% 14% 1	2452
	11th to 20th	Night	54% 6% 13% 19% 8% 1	2470
	21st to end	Night	57% 5% 12% 19% 6% 1	2547
December	1st to 10th	Night	67% 5% 11% 13% 5%	2660
	11th to 20th	Night	62% 6% 12% 14% 6% 1	3491
	21st to end	Night	77% 4 11% 7% 2	4902

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% 17% 39% 16% 6%	270
	11th to 20th	Day	22% 16% 43% 14% 3 1	270
	21st to end	Day	31% 16% 31% 16% 5% 1	297
February	1st to 10th	Day	27% 21% 35% 14% 1 1	270
	11th to 20th	Day	27% 20% 37% 15% 1	270
	21st to end	Day	26% 28% 35% 9% 2	225
March	1st to 10th	Day	25% 21% 36% 14% 3	297
	11th to 20th	Day	22% 13% 35% 22% 7%	460
	21st to end	Day	29% 13% 32% 20% 6% 1	506
April	1st to 10th	Day	18% 18% 32% 23% 8% 1	460
	11th to 20th	Day	26% 18% 31% 15% 6% 5%	452
	21st to end	Day	23% 13% 33% 20% 10% 2	460
May	1st to 10th	Day	25% 14% 26% 22% 10% 2	463
	11th to 20th	Day	20% 10% 29% 20% 14% 7%	487
	21st to end	Day	17% 6% 22% 29% 18% 8%	567
June	1st to 10th	Day	12% 9% 29% 28% 17% 4	680
	11th to 20th	Day	13% 8% 31% 26% 17% 4	680
	21st to end	Day	13% 9% 28% 30% 15% 5%	680
July	1st to 10th	Day	10% 5% 22% 30% 22% 11%	671
	11th to 20th	Day	11% 6% 28% 28% 18% 9%	668
	21st to end	Day	8% 5% 24% 31% 22% 9%	619
August	1st to 10th	Day	12% 3 22% 24% 25% 14%	486
	11th to 20th	Day	14% 4 18% 28% 24% 12%	479
	21st to end	Day	12% 6% 20% 26% 24% 12%	539
September	1st to 10th	Day	13% 7% 24% 24% 21% 11%	490
	11th to 20th	Day	12% 3 20% 22% 29% 14%	490
	21st to end	Day	19% 11% 21% 22% 19% 8%	490
October	1st to 10th	Day	17% 9% 28% 22% 16% 7%	490
	11th to 20th	Day	21% 17% 26% 28% 7% 1	490
	21st to end	Day	30% 15% 36% 15% 4	359
November	1st to 10th	Day	18% 21% 34% 18% 8% 1	279
	11th to 20th	Day	22% 21% 34% 17% 6% 1	270
	21st to end	Day	29% 20% 34% 12% 4	231
December	1st to 10th	Day	26% 20% 32% 15% 7%	180
	11th to 20th	Day	24% 23% 39% 10% 3 1	180
	21st to end	Day	25% 25% 34% 14% 1	291
January	1st to 10th	Night	22% 16% 36% 20% 5% 1	950
	11th to 20th	Night	25% 15% 33% 21% 5% 1	950
	21st to end	Night	21% 12% 34% 27% 6%	912
February	1st to 10th	Night	25% 13% 36% 24% 3	760
	11th to 20th	Night	21% 16% 34% 24% 4	743
	21st to end	Night	25% 17% 35% 19% 3	628
March	1st to 10th	Night	21% 15% 34% 24% 6% 1	760
	11th to 20th	Night	17% 15% 36% 26% 5% 1	760
	21st to end	Night	23% 12% 30% 27% 7% 1	836
April	1st to 10th	Night	21% 17% 35% 23% 4 1	633
	11th to 20th	Night	22% 12% 34% 25% 6% 2	563
	21st to end	Night	21% 9% 33% 30% 7%	570
May	1st to 10th	Night	20% 6% 33% 32% 8% 1	570
	11th to 20th	Night	22% 5% 29% 32% 12% 1	561
	21st to end	Night	12% 4 24% 40% 17% 2	617
June	1st to 10th	Night	12% 5% 25% 44% 14%	542
	11th to 20th	Night	10% 6% 28% 42% 14%	385
	21st to end	Night	12% 4 23% 44% 15% 2	570
July	1st to 10th	Night	9% 2 18% 40% 27% 3	555
	11th to 20th	Night	12% 3 20% 40% 23% 3	552
	21st to end	Night	6% 3 19% 48% 22% 2	624
August	1st to 10th	Night	9% 3 15% 43% 28% 2	567
	11th to 20th	Night	10% 2 21% 36% 26% 5%	564
	21st to end	Night	11% 4 17% 37% 29% 3	627
September	1st to 10th	Night	12% 4 21% 35% 24% 4	666
	11th to 20th	Night	12% 4 17% 35% 28% 4	760
	21st to end	Night	17% 7% 20% 32% 20% 4	760
October	1st to 10th	Night	18% 7% 26% 30% 17% 2	760
	11th to 20th	Night	26% 12% 27% 27% 8% 1	760
	21st to end	Night	26% 11% 35% 24% 4	836
November	1st to 10th	Night	20% 13% 29% 28% 10% 1	755
	11th to 20th	Night	23% 17% 32% 21% 6% 1	760
	21st to end	Night	27% 12% 34% 22% 5%	760
December	1st to 10th	Night	24% 17% 35% 19% 5% 1	760
	11th to 20th	Night	23% 14% 39% 21% 3	916
	21st to end	Night	31% 15% 35% 17% 2	1045

Page generated at 2024-11-01 22:47:38. Version ac07

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