Pennyrile Forest Observing Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pennyrile Forest Observing Field clear sky chart from 2005-11-06 to 2024-11-02.

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% 7% 3 6% 4 4 4 4 5% 7% 41%	100928
	Night	14% 8% 3 6% 4 4 4 3 5% 6% 44%	98031
Transparency	Day	41% 6% 11% 24% 16% 3	100722
	Night	40% 5% 10% 24% 17% 3	97908
Seeing	Day	17% 12% 25% 24% 15% 6%	15381
	Night	18% 10% 25% 28% 16% 2	25148

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% 14% 5% 9% 5% 4 4 3 5% 4 32%	2527
	11th to 20th	Day	19% 9% 3 9% 6% 4 6% 3 4 4 34%	2530
	21st to end	Day	24% 12% 6% 7% 4 4 4 3 4 5% 28%	3243
February	1st to 10th	Day	18% 13% 4 6% 4 3 2 4 5% 6% 37%	1900
	11th to 20th	Day	19% 10% 3 7% 4 4 3 3 4 5% 37%	1848
	21st to end	Day	18% 11% 3 7% 5% 4 4 3 4 6% 34%	1570
March	1st to 10th	Day	21% 14% 4 8% 4 3 3 3 4 5% 33%	3120
	11th to 20th	Day	15% 8% 2 6% 3 3 3 2 4 6% 49%	3246
	21st to end	Day	12% 9% 3 8% 4 4 4 4 6% 6% 41%	4163
April	1st to 10th	Day	14% 6% 2 6% 5% 4 4 3 5% 7% 44%	2280
	11th to 20th	Day	17% 7% 3 7% 5% 4 4 3 5% 6% 40%	2254
	21st to end	Day	17% 7% 2 5% 4 4 5% 3 5% 8% 40%	2285
May	1st to 10th	Day	18% 7% 2 7% 5% 4 6% 4 6% 9% 31%	4082
	11th to 20th	Day	18% 7% 2 6% 5% 4 4 3 5% 8% 37%	4081
	21st to end	Day	12% 6% 3 7% 5% 5% 4 4 7% 8% 40%	4501
June	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 46%	2660
	11th to 20th	Day	5% 4 2 5% 5% 5% 5% 5% 7% 9% 48%	2660
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 7% 11% 44%	2660
July	1st to 10th	Day	10% 5% 2 7% 5% 6% 6% 5% 7% 10% 38%	4440
	11th to 20th	Day	7% 4 2 4 3 4 5% 5% 7% 11% 46%	4440
	21st to end	Day	12% 10% 4 9% 7% 6% 5% 5% 7% 8% 28%	4642
August	1st to 10th	Day	5% 3 2 5% 4 4 4 4 6% 9% 55%	3831
	11th to 20th	Day	9% 5% 2 6% 4 5% 6% 4 7% 10% 41%	3729
	21st to end	Day	5% 4 2 5% 4 4 3 4 5% 9% 57%	4180
September	1st to 10th	Day	11% 5% 2 5% 5% 4 6% 4 5% 8% 45%	2280
	11th to 20th	Day	11% 5% 2 6% 5% 5% 4 4 5% 7% 46%	2114
	21st to end	Day	12% 5% 2 5% 4 3 3 3 5% 6% 49%	2090
October	1st to 10th	Day	10% 5% 2 5% 2 3 3 2 4 8% 57%	2090
	11th to 20th	Day	12% 5% 2 6% 4 3 4 3 4 6% 52%	1957
	21st to end	Day	20% 7% 2 5% 3 2 3 3 4 5% 47%	1932
November	1st to 10th	Day	10% 5% 2 6% 3 3 4 2 4 6% 56%	1681
	11th to 20th	Day	16% 7% 2 4 4 3 4 2 5% 6% 48%	1710
	21st to end	Day	18% 8% 3 5% 3 3 4 3 4 5% 43%	1710
December	1st to 10th	Day	20% 10% 2 6% 3 3 4 4 4 5% 37%	1710
	11th to 20th	Day	16% 13% 3 8% 4 5% 3 4 6% 5% 35%	1999
	21st to end	Day	17% 14% 5% 8% 5% 5% 4 3 4 6% 29%	2783
January	1st to 10th	Night	18% 12% 3 6% 4 3 4 3 6% 5% 36%	4428
	11th to 20th	Night	17% 13% 4 9% 5% 5% 4 2 4 4 33%	4440
	21st to end	Night	25% 12% 5% 6% 3 3 3 2 4 5% 31%	4402
February	1st to 10th	Night	23% 10% 4 7% 4 4 3 3 4 4 33%	2280
	11th to 20th	Night	20% 8% 3 8% 4 4 3 2 4 5% 38%	2218
	21st to end	Night	22% 9% 3 8% 4 4 3 3 5% 4 35%	1884
March	1st to 10th	Night	23% 11% 2 7% 3 4 3 3 4 4 35%	3733
	11th to 20th	Night	13% 8% 3 5% 3 3 3 3 4 5% 49%	3712
	21st to end	Night	15% 8% 3 7% 5% 3 3 3 5% 6% 42%	3483
April	1st to 10th	Night	13% 5% 2 5% 3 3 4 4 6% 7% 48%	1900
	11th to 20th	Night	15% 7% 2 5% 4 4 4 3 4 6% 45%	1875
	21st to end	Night	15% 7% 3 5% 5% 3 4 3 6% 8% 40%	1895
May	1st to 10th	Night	20% 8% 3 5% 4 4 3 3 6% 7% 37%	2813
	11th to 20th	Night	14% 7% 2 6% 4 4 5% 4 6% 8% 41%	2812
	21st to end	Night	9% 6% 2 6% 5% 5% 5% 4 7% 9% 44%	3049
June	1st to 10th	Night	13% 5% 2 5% 4 3 4 4 5% 9% 46%	1520
	11th to 20th	Night	5% 3 1 4 4 4 4 5% 7% 9% 55%	1520
	21st to end	Night	2 3 1 5% 4 4 4 5% 8% 13% 50%	1520
July	1st to 10th	Night	6% 5% 2 6% 4 4 5% 5% 6% 9% 46%	2530
	11th to 20th	Night	6% 4 2 5% 3 3 4 3 6% 9% 55%	2530
	21st to end	Night	9% 8% 3 10% 6% 6% 6% 5% 8% 8% 31%	2903
August	1st to 10th	Night	5% 3 1 4 3 4 4 3 6% 8% 60%	3080
	11th to 20th	Night	5% 4 1 6% 4 4 5% 4 7% 9% 52%	3100
	21st to end	Night	5% 3 1 4 3 3 4 4 5% 8% 61%	3476
September	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 4 6% 54%	1900
	11th to 20th	Night	9% 5% 3 5% 4 3 4 4 5% 7% 51%	2047
	21st to end	Night	11% 6% 2 4 3 4 3 3 4 7% 53%	2090
October	1st to 10th	Night	8% 5% 1 5% 2 3 4 2 3 6% 61%	2090
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 5% 54%	2218
	21st to end	Night	18% 7% 2 4 3 3 3 3 4 6% 47%	2665
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 2 4 6% 54%	2431
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 5% 6% 50%	2470
	21st to end	Night	17% 8% 2 4 4 3 3 3 4 6% 46%	2470
December	1st to 10th	Night	21% 10% 3 5% 4 4 4 3 5% 5% 36%	2470
	11th to 20th	Night	18% 9% 3 6% 4 4 3 3 4 5% 41%	3193
	21st to end	Night	18% 12% 5% 9% 5% 5% 5% 4 4 6% 28%	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	52% 7% 7% 23% 9% 2	2528
	11th to 20th	Day	52% 6% 7% 22% 12% 1	2530
	21st to end	Day	57% 5% 9% 19% 9% 1	3243
February	1st to 10th	Day	49% 5% 9% 23% 13% 2	1900
	11th to 20th	Day	50% 4 7% 21% 13% 4	1858
	21st to end	Day	51% 4 9% 16% 15% 5%	1570
March	1st to 10th	Day	55% 4 5% 17% 12% 6%	3120
	11th to 20th	Day	37% 5% 9% 27% 17% 4	3246
	21st to end	Day	42% 6% 12% 23% 17% 1	4163
April	1st to 10th	Day	39% 6% 11% 23% 19% 2	2280
	11th to 20th	Day	44% 5% 8% 21% 18% 4	2254
	21st to end	Day	42% 6% 10% 27% 13% 2	2285
May	1st to 10th	Day	46% 10% 13% 20% 11% 1	4120
	11th to 20th	Day	44% 9% 11% 24% 13% 1	4085
	21st to end	Day	39% 9% 12% 18% 21% 1	4514
June	1st to 10th	Day	33% 7% 13% 24% 19% 3	2660
	11th to 20th	Day	29% 9% 14% 26% 19% 3	2660
	21st to end	Day	31% 9% 15% 23% 17% 5%	2660
July	1st to 10th	Day	40% 6% 14% 27% 11% 2	4371
	11th to 20th	Day	32% 5% 13% 37% 11% 2	4365
	21st to end	Day	53% 6% 13% 20% 8% 1	4495
August	1st to 10th	Day	26% 5% 14% 33% 22% 1	3818
	11th to 20th	Day	38% 5% 12% 25% 18% 1	3765
	21st to end	Day	26% 5% 10% 36% 20% 3	4179
September	1st to 10th	Day	36% 8% 10% 23% 19% 4	2280
	11th to 20th	Day	36% 6% 11% 22% 22% 3	2114
	21st to end	Day	35% 5% 9% 24% 22% 6%	2090
October	1st to 10th	Day	28% 4 9% 23% 30% 5%	2090
	11th to 20th	Day	34% 5% 7% 24% 23% 7%	1957
	21st to end	Day	41% 4 6% 24% 20% 5%	1932
November	1st to 10th	Day	31% 4 10% 24% 26% 5%	1681
	11th to 20th	Day	37% 4 8% 24% 21% 5%	1710
	21st to end	Day	44% 4 6% 26% 15% 5%	1710
December	1st to 10th	Day	48% 5% 10% 22% 13% 2	1710
	11th to 20th	Day	49% 6% 9% 21% 12% 2	1996
	21st to end	Day	54% 7% 12% 16% 10%	2783
January	1st to 10th	Night	48% 5% 9% 26% 12% 1	4428
	11th to 20th	Night	54% 6% 7% 19% 12% 2	4440
	21st to end	Night	55% 4 9% 21% 10% 1	4402
February	1st to 10th	Night	55% 4 9% 18% 13% 1	2280
	11th to 20th	Night	49% 4 6% 22% 15% 3	2219
	21st to end	Night	52% 5% 8% 16% 15% 4	1884
March	1st to 10th	Night	52% 5% 7% 14% 18% 4	3733
	11th to 20th	Night	37% 5% 11% 23% 14% 9%	3712
	21st to end	Night	43% 5% 11% 24% 17% 1	3483
April	1st to 10th	Night	34% 5% 11% 26% 20% 3	1900
	11th to 20th	Night	38% 5% 9% 20% 21% 7%	1875
	21st to end	Night	41% 6% 9% 25% 17% 2	1895
May	1st to 10th	Night	44% 8% 13% 23% 11% 1	2840
	11th to 20th	Night	40% 8% 14% 23% 14% 1	2813
	21st to end	Night	34% 9% 15% 22% 18% 2	3057
June	1st to 10th	Night	36% 5% 12% 24% 20% 3	1520
	11th to 20th	Night	23% 7% 16% 26% 25% 4	1520
	21st to end	Night	23% 9% 17% 27% 19% 6%	1520
July	1st to 10th	Night	33% 6% 13% 30% 15% 3	2490
	11th to 20th	Night	26% 5% 13% 37% 16% 3	2482
	21st to end	Night	49% 7% 14% 21% 9% 1	2810
August	1st to 10th	Night	23% 5% 12% 38% 21% 1	3069
	11th to 20th	Night	28% 5% 16% 29% 19% 1	3130
	21st to end	Night	22% 5% 9% 37% 24% 3	3476
September	1st to 10th	Night	31% 6% 9% 26% 23% 5%	1900
	11th to 20th	Night	33% 5% 8% 26% 24% 4	2047
	21st to end	Night	31% 5% 9% 23% 25% 7%	2090
October	1st to 10th	Night	26% 4 8% 22% 32% 7%	2090
	11th to 20th	Night	34% 4 7% 21% 27% 7%	2218
	21st to end	Night	39% 4 7% 23% 22% 6%	2665
November	1st to 10th	Night	33% 3 7% 25% 26% 6%	2431
	11th to 20th	Night	34% 4 6% 24% 22% 9%	2470
	21st to end	Night	40% 4 8% 24% 20% 4	2470
December	1st to 10th	Night	49% 5% 10% 21% 13% 2	2470
	11th to 20th	Night	45% 5% 8% 23% 18% 3	3195
	21st to end	Night	55% 8% 8% 16% 10% 2	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	28% 25% 30% 14% 3	270
	11th to 20th	Day	28% 28% 34% 9% 2	270
	21st to end	Day	25% 26% 39% 9% 1	297
February	1st to 10th	Day	28% 26% 33% 10% 3 1	270
	11th to 20th	Day	33% 29% 31% 6% 1	270
	21st to end	Day	36% 23% 31% 9% 1	225
March	1st to 10th	Day	26% 26% 34% 11% 3	270
	11th to 20th	Day	27% 26% 32% 11% 3	317
	21st to end	Day	27% 19% 34% 14% 5%	506
April	1st to 10th	Day	22% 20% 29% 22% 5% 1	460
	11th to 20th	Day	24% 18% 29% 21% 7% 2	452
	21st to end	Day	20% 18% 30% 20% 8% 2	460
May	1st to 10th	Day	20% 19% 29% 21% 7% 3	463
	11th to 20th	Day	18% 9% 25% 30% 12% 5%	487
	21st to end	Day	10% 8% 27% 28% 16% 11%	541
June	1st to 10th	Day	11% 6% 23% 28% 22% 10%	680
	11th to 20th	Day	5% 4 23% 36% 22% 9%	680
	21st to end	Day	6% 4 26% 34% 20% 10%	680
July	1st to 10th	Day	11% 3 16% 28% 25% 17%	671
	11th to 20th	Day	9% 4 18% 31% 28% 11%	668
	21st to end	Day	9% 3 17% 32% 26% 13%	643
August	1st to 10th	Day	12% 2 13% 33% 26% 14%	486
	11th to 20th	Day	14% 3 16% 35% 26% 7%	479
	21st to end	Day	10% 2 13% 28% 31% 17%	539
September	1st to 10th	Day	10% 3 18% 29% 28% 12%	490
	11th to 20th	Day	10% 3 14% 28% 32% 12%	490
	21st to end	Day	19% 8% 20% 26% 20% 8%	490
October	1st to 10th	Day	9% 6% 26% 32% 21% 6%	490
	11th to 20th	Day	14% 14% 34% 22% 12% 4	357
	21st to end	Day	26% 17% 29% 20% 6% 1	330
November	1st to 10th	Day	14% 15% 37% 21% 12% 1	273
	11th to 20th	Day	17% 22% 34% 21% 4 1	270
	21st to end	Day	25% 14% 32% 21% 7% 1	270
December	1st to 10th	Day	23% 23% 30% 17% 6%	270
	11th to 20th	Day	25% 17% 34% 19% 4	270
	21st to end	Day	27% 27% 33% 12% 2	297
January	1st to 10th	Night	27% 19% 30% 21% 4	950
	11th to 20th	Night	28% 18% 33% 18% 3	950
	21st to end	Night	23% 19% 35% 21% 2	963
February	1st to 10th	Night	26% 17% 33% 21% 2	760
	11th to 20th	Night	26% 20% 34% 18% 2	743
	21st to end	Night	28% 19% 35% 18% 1	628
March	1st to 10th	Night	22% 18% 31% 24% 5%	760
	11th to 20th	Night	22% 17% 33% 22% 5%	760
	21st to end	Night	22% 14% 28% 29% 6%	644
April	1st to 10th	Night	16% 13% 36% 27% 8% 1	570
	11th to 20th	Night	20% 13% 30% 25% 12%	563
	21st to end	Night	18% 12% 32% 27% 10% 1	570
May	1st to 10th	Night	20% 9% 31% 24% 14% 2	570
	11th to 20th	Night	13% 6% 22% 35% 20% 2	561
	21st to end	Night	9% 4 22% 33% 28% 4	617
June	1st to 10th	Night	14% 3 17% 34% 29% 4	570
	11th to 20th	Night	5% 2 15% 44% 30% 3	570
	21st to end	Night	3 2 19% 39% 33% 4	570
July	1st to 10th	Night	8% 1 11% 33% 38% 10%	555
	11th to 20th	Night	9% 2 12% 28% 42% 7%	552
	21st to end	Night	8% 3 13% 35% 32% 9%	624
August	1st to 10th	Night	8% 1 9% 34% 40% 7%	567
	11th to 20th	Night	8% 2 11% 41% 34% 5%	564
	21st to end	Night	8% 2 7% 33% 41% 8%	627
September	1st to 10th	Night	12% 2 13% 33% 34% 5%	570
	11th to 20th	Night	11% 2 12% 30% 38% 6%	717
	21st to end	Night	13% 5% 22% 30% 26% 5%	760
October	1st to 10th	Night	11% 6% 19% 33% 27% 5%	760
	11th to 20th	Night	17% 8% 26% 31% 16% 2	760
	21st to end	Night	20% 11% 29% 26% 12% 1	836
November	1st to 10th	Night	13% 11% 29% 32% 14% 1	748
	11th to 20th	Night	15% 14% 33% 28% 9% 1	760
	21st to end	Night	23% 14% 27% 26% 10% 1	760
December	1st to 10th	Night	26% 12% 32% 24% 5%	760
	11th to 20th	Night	25% 12% 31% 25% 6%	864
	21st to end	Night	28% 15% 30% 23% 4	1045

Page generated at 2024-10-30 12:19:21. Version ac07

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