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 2024-03-28.

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	15% 10% 4 7% 6% 3 5% 5% 5% 7% 32%	78464
	Night	16% 11% 5% 7% 6% 3 4 4 5% 6% 33%	81532
Transparency	Day	51% 6% 12% 20% 11% 1	78172
	Night	52% 5% 11% 19% 11% 1	81345
Seeing	Day	19% 12% 29% 22% 13% 5%	14569
	Night	20% 10% 29% 29% 11% 1	24616

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	15% 21% 7% 11% 6% 3 5% 3 4 5% 21%	2527
	11th to 20th	Day	15% 21% 6% 12% 12% 6% 4 3 4 4 12%	2530
	21st to end	Day	27% 19% 8% 11% 6% 3 3 3 3 3 14%	2999
February	1st to 10th	Day	14% 14% 7% 10% 10% 4 6% 4 5% 6% 22%	1710
	11th to 20th	Day	14% 13% 7% 12% 9% 5% 4 4 4 5% 24%	1803
	21st to end	Day	13% 15% 7% 12% 8% 3 4 4 4 5% 25%	1570
March	1st to 10th	Day	15% 12% 5% 8% 9% 3 4 4 5% 7% 29%	1927
	11th to 20th	Day	13% 13% 6% 8% 6% 3 5% 4 5% 7% 31%	2090
	21st to end	Day	19% 13% 4 9% 6% 3 5% 4 4 4 28%	2255
April	1st to 10th	Day	17% 12% 5% 7% 6% 3 4 4 5% 6% 30%	2114
	11th to 20th	Day	18% 10% 3 6% 5% 3 4 5% 6% 6% 34%	2270
	21st to end	Day	18% 8% 4 7% 6% 4 4 5% 4 7% 34%	2340
May	1st to 10th	Day	17% 9% 3 6% 6% 3 5% 5% 5% 7% 33%	2340
	11th to 20th	Day	19% 7% 3 5% 6% 3 4 4 5% 6% 37%	2301
	21st to end	Day	14% 6% 2 5% 5% 3 5% 5% 6% 8% 40%	2567
June	1st to 10th	Day	11% 5% 3 6% 6% 4 5% 6% 6% 8% 41%	2533
	11th to 20th	Day	11% 5% 3 6% 6% 4 5% 5% 5% 9% 41%	2680
	21st to end	Day	11% 5% 3 5% 5% 5% 6% 6% 7% 9% 39%	2520
July	1st to 10th	Day	7% 5% 2 4 5% 3 5% 6% 7% 9% 46%	2520
	11th to 20th	Day	11% 4 2 5% 6% 3 6% 5% 6% 8% 44%	2520
	21st to end	Day	9% 5% 2 5% 6% 4 7% 6% 7% 10% 41%	2630
August	1st to 10th	Day	11% 4 2 6% 6% 4 6% 6% 6% 9% 40%	2327
	11th to 20th	Day	11% 5% 3 5% 6% 4 6% 7% 7% 8% 39%	2303
	21st to end	Day	10% 6% 3 5% 5% 5% 5% 5% 6% 8% 42%	2536
September	1st to 10th	Day	12% 6% 3 6% 6% 4 5% 5% 6% 9% 38%	2050
	11th to 20th	Day	11% 5% 3 5% 4 3 4 5% 6% 8% 46%	1980
	21st to end	Day	16% 6% 2 5% 5% 3 5% 7% 6% 9% 36%	1980
October	1st to 10th	Day	15% 7% 3 6% 6% 3 5% 5% 5% 6% 40%	1941
	11th to 20th	Day	19% 11% 3 7% 6% 4 4 5% 4 7% 31%	1800
	21st to end	Day	23% 11% 3 6% 6% 3 4 3 4 7% 28%	1810
November	1st to 10th	Day	12% 10% 4 7% 6% 3 3 5% 6% 7% 37%	1672
	11th to 20th	Day	14% 14% 5% 7% 7% 4 4 5% 5% 6% 29%	1710
	21st to end	Day	19% 14% 6% 7% 5% 3 5% 3 4 6% 26%	1629
December	1st to 10th	Day	14% 16% 9% 12% 8% 3 4 4 3 5% 22%	1520
	11th to 20th	Day	16% 16% 7% 9% 6% 3 4 6% 4 6% 21%	1704
	21st to end	Day	24% 21% 8% 12% 7% 3 4 3 4 4 11%	2756
January	1st to 10th	Night	16% 16% 8% 12% 6% 3 4 4 4 4 22%	4428
	11th to 20th	Night	14% 17% 9% 14% 8% 5% 6% 5% 4 4 14%	4440
	21st to end	Night	23% 16% 10% 10% 6% 3 4 3 3 5% 16%	4660
February	1st to 10th	Night	16% 16% 6% 9% 8% 4 5% 5% 4 5% 23%	2470
	11th to 20th	Night	13% 14% 6% 10% 8% 4 4 5% 5% 5% 26%	2261
	21st to end	Night	18% 13% 4 8% 8% 3 4 4 4 6% 28%	1884
March	1st to 10th	Night	15% 11% 5% 8% 6% 4 4 3 5% 6% 33%	2253
	11th to 20th	Night	13% 9% 4 6% 5% 3 5% 5% 5% 6% 39%	2090
	21st to end	Night	20% 9% 3 7% 5% 3 4 4 4 6% 33%	2256
April	1st to 10th	Night	16% 10% 4 5% 5% 4 5% 4 5% 6% 36%	1860
	11th to 20th	Night	19% 9% 3 5% 4 3 4 4 6% 6% 37%	1638
	21st to end	Night	18% 7% 3 6% 5% 3 4 5% 5% 6% 39%	1620
May	1st to 10th	Night	17% 8% 4 6% 6% 3 4 4 6% 8% 34%	1620
	11th to 20th	Night	19% 6% 2 6% 4 3 4 4 5% 7% 41%	1592
	21st to end	Night	10% 5% 2 5% 6% 3 5% 5% 5% 10% 45%	1705
June	1st to 10th	Night	12% 4 3 5% 4 3 4 4 6% 9% 47%	1414
	11th to 20th	Night	11% 6% 1 4 5% 3 4 5% 6% 9% 46%	1264
	21st to end	Night	10% 5% 3 5% 4 3 4 4 5% 9% 48%	1440
July	1st to 10th	Night	8% 3 2 4 5% 3 3 4 5% 9% 53%	1440
	11th to 20th	Night	9% 4 2 5% 5% 3 4 4 5% 9% 50%	1440
	21st to end	Night	6% 3 2 4 4 3 6% 6% 6% 9% 51%	1687
August	1st to 10th	Night	8% 4 2 4 5% 3 4 5% 9% 9% 47%	1611
	11th to 20th	Night	9% 4 1 5% 5% 3 6% 5% 6% 7% 50%	1598
	21st to end	Night	9% 5% 3 5% 5% 3 4 3 4 8% 53%	1818
September	1st to 10th	Night	11% 6% 2 5% 5% 3 4 4 6% 7% 47%	1890
	11th to 20th	Night	11% 5% 2 4 4 3 5% 4 4 6% 53%	1980
	21st to end	Night	15% 5% 3 4 5% 3 4 6% 5% 6% 44%	1980
October	1st to 10th	Night	16% 7% 3 6% 5% 3 4 4 4 7% 43%	2018
	11th to 20th	Night	20% 11% 4 6% 6% 3 4 4 5% 5% 33%	2160
	21st to end	Night	23% 10% 3 7% 6% 4 4 4 4 5% 30%	2542
November	1st to 10th	Night	14% 9% 3 6% 4 3 5% 4 4 7% 42%	2406
	11th to 20th	Night	16% 12% 4 6% 5% 4 6% 5% 5% 7% 29%	2470
	21st to end	Night	20% 14% 5% 7% 5% 3 4 4 5% 6% 28%	2547
December	1st to 10th	Night	17% 16% 7% 11% 6% 3 5% 4 4 6% 20%	2660
	11th to 20th	Night	14% 16% 6% 12% 7% 3 5% 4 5% 5% 22%	3488
	21st to end	Night	25% 22% 7% 9% 6% 2 4 3 3 4 13%	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	54% 6% 13% 19% 8% 1	1927
	11th to 20th	Day	52% 5% 11% 18% 11% 2	2090
	21st to end	Day	58% 4 10% 18% 8% 1	2255
April	1st to 10th	Day	55% 6% 10% 19% 10%	2114
	11th to 20th	Day	49% 6% 11% 19% 13% 2	2270
	21st to end	Day	50% 5% 13% 16% 14% 2	2340
May	1st to 10th	Day	49% 7% 11% 22% 9% 2	2340
	11th to 20th	Day	47% 6% 11% 21% 13% 2	2305
	21st to end	Day	41% 6% 15% 23% 14% 2	2567
June	1st to 10th	Day	37% 7% 13% 26% 14% 2	2533
	11th to 20th	Day	40% 6% 12% 24% 16% 2	2680
	21st to end	Day	39% 7% 14% 23% 16% 2	2520
July	1st to 10th	Day	32% 7% 12% 27% 18% 3	2451
	11th to 20th	Day	36% 6% 13% 26% 17% 2	2445
	21st to end	Day	36% 7% 14% 23% 17% 3	2484
August	1st to 10th	Day	37% 8% 14% 26% 13% 2	2314
	11th to 20th	Day	38% 8% 15% 24% 13% 2	2303
	21st to end	Day	38% 6% 11% 26% 17% 2	2536
September	1st to 10th	Day	41% 8% 14% 23% 12% 2	2050
	11th to 20th	Day	34% 6% 14% 32% 13% 1	1980
	21st to end	Day	42% 7% 13% 26% 12%	1980
October	1st to 10th	Day	44% 6% 10% 25% 13% 1	1941
	11th to 20th	Day	53% 6% 13% 19% 9% 1	1800
	21st to end	Day	55% 6% 13% 18% 8%	1810
November	1st to 10th	Day	45% 7% 14% 23% 11% 1	1672
	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	52% 5% 11% 22% 9% 1	2253
	11th to 20th	Night	45% 5% 11% 21% 15% 2	2090
	21st to end	Night	52% 5% 10% 21% 10% 2	2256
April	1st to 10th	Night	49% 5% 10% 21% 14% 2	1860
	11th to 20th	Night	46% 5% 11% 17% 18% 2	1638
	21st to end	Night	46% 5% 12% 19% 15% 3	1620
May	1st to 10th	Night	48% 6% 12% 21% 11% 2	1620
	11th to 20th	Night	43% 5% 10% 21% 17% 4	1593
	21st to end	Night	36% 7% 14% 25% 15% 3	1706
June	1st to 10th	Night	34% 6% 10% 29% 17% 3	1414
	11th to 20th	Night	34% 7% 14% 24% 19% 2	1264
	21st to end	Night	33% 6% 14% 27% 19% 2	1440
July	1st to 10th	Night	29% 5% 12% 29% 21% 4	1400
	11th to 20th	Night	32% 5% 13% 27% 21% 2	1392
	21st to end	Night	28% 8% 16% 24% 20% 3	1593
August	1st to 10th	Night	30% 7% 16% 30% 15% 1	1600
	11th to 20th	Night	32% 7% 14% 31% 12% 4	1598
	21st to end	Night	32% 6% 13% 28% 20% 1	1818
September	1st to 10th	Night	35% 8% 12% 28% 16% 2	1890
	11th to 20th	Night	32% 5% 12% 31% 20% 1	1980
	21st to end	Night	39% 5% 13% 28% 14% 1	1980
October	1st to 10th	Night	41% 5% 10% 25% 17% 1	2018
	11th to 20th	Night	52% 5% 12% 19% 11% 1	2160
	21st to end	Night	56% 5% 11% 20% 8% 1	2542
November	1st to 10th	Night	43% 6% 11% 26% 14% 1	2406
	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% 31% 20% 6% 1	490
April	1st to 10th	Day	19% 17% 32% 23% 8% 1	420
	11th to 20th	Day	26% 17% 30% 15% 7% 5%	412
	21st to end	Day	23% 13% 33% 20% 10% 2	420
May	1st to 10th	Day	26% 14% 26% 21% 11% 2	423
	11th to 20th	Day	21% 10% 29% 20% 14% 6%	447
	21st to end	Day	18% 6% 21% 29% 18% 9%	521
June	1st to 10th	Day	12% 8% 30% 29% 18% 4	630
	11th to 20th	Day	14% 8% 31% 25% 18% 5%	630
	21st to end	Day	13% 7% 28% 30% 17% 6%	630
July	1st to 10th	Day	9% 4 22% 30% 23% 12%	621
	11th to 20th	Day	11% 6% 28% 28% 18% 9%	618
	21st to end	Day	9% 5% 25% 31% 22% 9%	571
August	1st to 10th	Day	11% 3 21% 24% 25% 16%	446
	11th to 20th	Day	14% 4 18% 27% 24% 13%	439
	21st to end	Day	13% 6% 21% 25% 24% 12%	495
September	1st to 10th	Day	13% 7% 22% 24% 22% 11%	450
	11th to 20th	Day	13% 4 20% 21% 28% 14%	450
	21st to end	Day	17% 12% 20% 23% 20% 9%	450
October	1st to 10th	Day	18% 9% 28% 21% 17% 7%	450
	11th to 20th	Day	22% 17% 26% 27% 7% 1	450
	21st to end	Day	31% 14% 36% 15% 3	325
November	1st to 10th	Day	19% 20% 34% 17% 8% 1	270
	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	821
April	1st to 10th	Night	20% 16% 35% 24% 4 1	600
	11th to 20th	Night	22% 10% 34% 26% 7% 2	533
	21st to end	Night	21% 9% 33% 30% 7%	540
May	1st to 10th	Night	20% 6% 32% 33% 8% 1	540
	11th to 20th	Night	22% 5% 29% 31% 12% 1	531
	21st to end	Night	13% 4 23% 40% 18% 2	584
June	1st to 10th	Night	12% 4 25% 45% 14%	514
	11th to 20th	Night	11% 5% 27% 42% 15%	364
	21st to end	Night	12% 3 23% 45% 15% 2	540
July	1st to 10th	Night	9% 2 17% 40% 29% 3	525
	11th to 20th	Night	12% 2 19% 41% 23% 3	522
	21st to end	Night	6% 3 20% 48% 21% 2	591
August	1st to 10th	Night	9% 2 15% 43% 28% 3	537
	11th to 20th	Night	10% 2 20% 36% 27% 5%	534
	21st to end	Night	11% 4 17% 36% 29% 3	594
September	1st to 10th	Night	13% 3 21% 35% 24% 4	630
	11th to 20th	Night	13% 5% 18% 35% 26% 4	720
	21st to end	Night	16% 7% 21% 31% 21% 4	720
October	1st to 10th	Night	19% 7% 25% 30% 17% 2	720
	11th to 20th	Night	26% 12% 27% 27% 7% 1	720
	21st to end	Night	27% 11% 34% 23% 4	792
November	1st to 10th	Night	19% 13% 29% 28% 10% 1	740
	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 2024-03-24 23:37:01. Version ac07

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