Clearfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clearfield 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	16% 10% 4 9% 5% 5% 5% 4 5% 7% 31%	101330
	Night	16% 10% 4 9% 5% 4 4 4 5% 6% 32%	97713
Transparency	Day	51% 7% 12% 20% 10% 1	104969
	Night	50% 7% 11% 19% 10% 1	102213
Seeing	Day	23% 17% 27% 19% 10% 4	14741
	Night	22% 16% 26% 24% 10% 1	24209

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% 19% 10% 12% 6% 4 4 3 4 5% 19%	2555
	11th to 20th	Day	11% 18% 9% 18% 7% 6% 4 3 4 4 16%	2840
	21st to end	Day	24% 18% 8% 13% 7% 4 3 3 3 4 13%	3124
February	1st to 10th	Day	16% 16% 5% 11% 8% 5% 5% 4 5% 4 21%	1710
	11th to 20th	Day	14% 13% 5% 12% 7% 5% 6% 4 6% 7% 21%	1663
	21st to end	Day	18% 16% 3 10% 5% 4 4 4 4 6% 26%	1533
March	1st to 10th	Day	19% 11% 4 8% 5% 4 4 3 6% 7% 30%	3435
	11th to 20th	Day	12% 11% 6% 11% 5% 5% 5% 4 5% 6% 31%	3480
	21st to end	Day	15% 9% 3 8% 6% 5% 6% 4 5% 6% 33%	3815
April	1st to 10th	Day	16% 13% 3 8% 6% 4 5% 4 6% 7% 30%	2270
	11th to 20th	Day	15% 12% 3 8% 5% 5% 4 4 4 6% 34%	2254
	21st to end	Day	20% 10% 3 7% 6% 4 4 3 5% 6% 32%	2400
May	1st to 10th	Day	25% 9% 3 7% 5% 5% 4 4 5% 6% 28%	4082
	11th to 20th	Day	22% 10% 3 8% 5% 4 4 4 6% 8% 27%	4288
	21st to end	Day	13% 7% 2 6% 5% 4 6% 4 7% 9% 38%	4823
June	1st to 10th	Day	15% 8% 2 7% 5% 6% 6% 4 5% 8% 34%	2660
	11th to 20th	Day	13% 7% 3 8% 6% 5% 4 4 7% 9% 35%	2660
	21st to end	Day	14% 6% 2 7% 4 6% 5% 4 6% 9% 36%	2660
July	1st to 10th	Day	8% 7% 2 8% 5% 5% 6% 5% 6% 9% 38%	4440
	11th to 20th	Day	9% 6% 2 8% 6% 5% 5% 5% 7% 10% 37%	4328
	21st to end	Day	10% 6% 3 8% 5% 6% 5% 4 7% 7% 38%	4466
August	1st to 10th	Day	19% 9% 3 8% 5% 5% 5% 4 6% 8% 28%	4104
	11th to 20th	Day	12% 6% 3 8% 5% 6% 7% 5% 7% 8% 33%	4044
	21st to end	Day	13% 6% 2 6% 4 5% 6% 5% 7% 10% 38%	4190
September	1st to 10th	Day	17% 7% 3 6% 4 4 4 2 5% 6% 42%	2280
	11th to 20th	Day	14% 7% 1 6% 4 3 4 4 5% 8% 43%	2225
	21st to end	Day	20% 9% 3 7% 5% 4 5% 3 5% 6% 34%	2014
October	1st to 10th	Day	15% 9% 3 9% 3 4 5% 4 5% 8% 36%	1900
	11th to 20th	Day	19% 11% 2 7% 5% 4 4 3 5% 6% 33%	1900
	21st to end	Day	19% 11% 3 6% 5% 4 4 4 5% 7% 32%	2090
November	1st to 10th	Day	12% 8% 3 8% 5% 4 4 4 6% 6% 39%	1845
	11th to 20th	Day	16% 15% 5% 8% 5% 4 5% 3 5% 5% 29%	1530
	21st to end	Day	18% 16% 4 8% 5% 4 6% 4 4 6% 24%	1520
December	1st to 10th	Day	17% 21% 6% 13% 7% 4 4 3 5% 4 16%	1520
	11th to 20th	Day	18% 17% 8% 10% 5% 4 4 3 4 7% 20%	1910
	21st to end	Day	24% 22% 6% 11% 4 4 4 3 4 5% 15%	2772
January	1st to 10th	Night	15% 18% 7% 13% 6% 5% 4 3 4 5% 19%	4388
	11th to 20th	Night	14% 15% 7% 15% 6% 7% 5% 4 5% 5% 15%	4120
	21st to end	Night	24% 15% 6% 14% 5% 5% 3 2 4 5% 17%	4532
February	1st to 10th	Night	16% 13% 4 10% 7% 5% 5% 5% 4 5% 25%	2470
	11th to 20th	Night	14% 12% 5% 10% 7% 6% 5% 4 5% 6% 25%	2403
	21st to end	Night	18% 11% 4 10% 6% 5% 4 3 5% 6% 28%	1917
March	1st to 10th	Night	21% 12% 4 8% 4 4 3 4 4 6% 30%	3418
	11th to 20th	Night	12% 11% 8% 9% 5% 4 4 4 6% 6% 31%	3480
	21st to end	Night	16% 10% 3 6% 4 3 4 3 4 6% 40%	3817
April	1st to 10th	Night	16% 13% 4 9% 5% 3 4 3 5% 7% 31%	1910
	11th to 20th	Night	15% 9% 3 7% 4 4 5% 3 6% 5% 37%	1875
	21st to end	Night	16% 9% 3 8% 5% 4 4 4 6% 7% 35%	1796
May	1st to 10th	Night	26% 9% 3 8% 4 4 3 3 5% 6% 29%	2813
	11th to 20th	Night	22% 11% 3 7% 5% 4 3 3 5% 7% 30%	2602
	21st to end	Night	12% 7% 3 7% 4 5% 4 4 7% 10% 38%	2732
June	1st to 10th	Night	11% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	1520
	11th to 20th	Night	10% 6% 2 7% 6% 4 5% 4 7% 10% 40%	1520
	21st to end	Night	12% 7% 2 5% 4 4 4 4 6% 9% 42%	1520
July	1st to 10th	Night	12% 7% 3 8% 5% 5% 4 5% 6% 8% 38%	2520
	11th to 20th	Night	8% 4 2 6% 5% 5% 5% 5% 7% 9% 43%	2614
	21st to end	Night	12% 7% 2 6% 5% 5% 5% 4 6% 7% 42%	3087
August	1st to 10th	Night	18% 6% 2 6% 6% 5% 4 3 5% 7% 36%	2825
	11th to 20th	Night	15% 7% 2 7% 5% 4 4 4 6% 6% 40%	2785
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 45%	3432
September	1st to 10th	Night	16% 5% 2 6% 4 4 4 3 4 6% 46%	1900
	11th to 20th	Night	11% 5% 2 6% 4 4 3 3 5% 7% 50%	1952
	21st to end	Night	19% 7% 3 7% 4 4 4 4 4 6% 38%	2166
October	1st to 10th	Night	15% 7% 2 7% 4 4 4 3 5% 7% 43%	2280
	11th to 20th	Night	17% 8% 3 7% 4 4 4 3 5% 7% 39%	2280
	21st to end	Night	20% 9% 3 7% 4 4 4 4 5% 6% 34%	2508
November	1st to 10th	Night	11% 9% 3 6% 4 4 4 3 6% 7% 44%	2394
	11th to 20th	Night	16% 12% 4 8% 6% 5% 4 3 6% 7% 30%	2648
	21st to end	Night	16% 13% 4 8% 6% 4 4 4 6% 7% 28%	2660
December	1st to 10th	Night	19% 14% 6% 10% 7% 6% 5% 5% 6% 5% 18%	2660
	11th to 20th	Night	18% 14% 6% 11% 6% 5% 4 3 5% 5% 24%	3285
	21st to end	Night	21% 16% 6% 11% 6% 5% 5% 4 6% 6% 16%	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	69% 5% 10% 12% 4 1	2556
	11th to 20th	Day	72% 5% 8% 10% 4	2840
	21st to end	Day	76% 5% 7% 8% 3 1	3124
February	1st to 10th	Day	66% 6% 11% 11% 6%	1710
	11th to 20th	Day	62% 7% 10% 14% 6%	1672
	21st to end	Day	60% 5% 11% 16% 6% 1	1533
March	1st to 10th	Day	53% 7% 12% 22% 6%	3435
	11th to 20th	Day	52% 8% 15% 17% 6% 1	3480
	21st to end	Day	49% 9% 12% 19% 11% 1	3815
April	1st to 10th	Day	53% 8% 10% 17% 10% 1	2270
	11th to 20th	Day	50% 7% 11% 17% 14% 2	2254
	21st to end	Day	53% 6% 9% 19% 11% 1	2400
May	1st to 10th	Day	55% 7% 10% 19% 8% 1	4120
	11th to 20th	Day	54% 10% 11% 17% 6% 1	4292
	21st to end	Day	38% 10% 15% 24% 12% 1	4837
June	1st to 10th	Day	47% 8% 12% 21% 11% 1	2660
	11th to 20th	Day	45% 8% 14% 19% 12% 1	2660
	21st to end	Day	42% 8% 15% 24% 11%	2660
July	1st to 10th	Day	41% 8% 14% 24% 12% 2	4370
	11th to 20th	Day	39% 8% 14% 25% 13%	4253
	21st to end	Day	43% 6% 11% 24% 14% 1	4324
August	1st to 10th	Day	52% 8% 14% 19% 7%	4091
	11th to 20th	Day	45% 8% 12% 26% 8%	4083
	21st to end	Day	39% 8% 13% 27% 11% 2	4190
September	1st to 10th	Day	44% 5% 9% 23% 16% 3	2280
	11th to 20th	Day	38% 7% 12% 24% 18% 1	2225
	21st to end	Day	50% 7% 11% 18% 13% 1	2014
October	1st to 10th	Day	41% 6% 10% 23% 17% 2	3160
	11th to 20th	Day	44% 6% 10% 22% 15% 3	3140
	21st to end	Day	37% 5% 13% 29% 15% 1	3428
November	1st to 10th	Day	44% 7% 12% 19% 15% 3	1845
	11th to 20th	Day	56% 5% 13% 15% 8% 2	1530
	21st to end	Day	60% 7% 11% 16% 7%	1520
December	1st to 10th	Day	72% 6% 10% 9% 3	1520
	11th to 20th	Day	66% 6% 10% 15% 4	1906
	21st to end	Day	74% 6% 9% 10% 2	2772
January	1st to 10th	Night	67% 6% 9% 13% 4	4388
	11th to 20th	Night	70% 8% 11% 9% 2	4120
	21st to end	Night	72% 5% 8% 11% 4 1	4532
February	1st to 10th	Night	60% 7% 10% 16% 7%	2470
	11th to 20th	Night	59% 6% 11% 16% 7%	2405
	21st to end	Night	58% 6% 10% 16% 10% 1	1917
March	1st to 10th	Night	55% 7% 11% 20% 7%	3418
	11th to 20th	Night	49% 11% 15% 18% 6% 1	3480
	21st to end	Night	44% 6% 9% 23% 16% 2	3817
April	1st to 10th	Night	53% 7% 10% 17% 12% 1	1910
	11th to 20th	Night	46% 8% 11% 20% 13% 2	1875
	21st to end	Night	47% 7% 10% 21% 12% 2	1796
May	1st to 10th	Night	55% 7% 9% 17% 10% 2	2840
	11th to 20th	Night	51% 10% 12% 18% 8% 1	2603
	21st to end	Night	37% 13% 14% 19% 13% 4	2739
June	1st to 10th	Night	38% 9% 13% 25% 13% 1	1520
	11th to 20th	Night	38% 10% 13% 24% 13% 2	1520
	21st to end	Night	37% 9% 14% 25% 14% 1	1520
July	1st to 10th	Night	43% 7% 12% 20% 16% 2	2480
	11th to 20th	Night	35% 9% 17% 24% 16% 1	2566
	21st to end	Night	41% 8% 12% 20% 18% 1	2988
August	1st to 10th	Night	47% 9% 13% 23% 9%	2814
	11th to 20th	Night	42% 7% 11% 29% 10% 1	2812
	21st to end	Night	37% 7% 12% 32% 10% 2	3432
September	1st to 10th	Night	39% 7% 10% 25% 17% 3	1900
	11th to 20th	Night	33% 6% 13% 28% 19% 1	1952
	21st to end	Night	46% 7% 12% 20% 15% 1	2166
October	1st to 10th	Night	39% 7% 10% 24% 19% 1	3800
	11th to 20th	Night	37% 6% 11% 23% 18% 5%	3779
	21st to end	Night	37% 5% 13% 26% 17% 2	4120
November	1st to 10th	Night	39% 7% 14% 21% 17% 3	2394
	11th to 20th	Night	52% 8% 11% 18% 9% 2	2648
	21st to end	Night	55% 7% 12% 19% 6% 1	2660
December	1st to 10th	Night	67% 8% 11% 11% 4	2660
	11th to 20th	Night	63% 6% 10% 16% 4	3288
	21st to end	Night	68% 8% 11% 11% 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	31% 31% 26% 8% 4 1	193
	11th to 20th	Day	36% 29% 29% 4 1 1	270
	21st to end	Day	31% 30% 28% 9% 2	297
February	1st to 10th	Day	30% 30% 30% 7% 3	270
	11th to 20th	Day	38% 28% 28% 6%	270
	21st to end	Day	39% 25% 27% 9% 1	329
March	1st to 10th	Day	30% 25% 29% 12% 3	460
	11th to 20th	Day	32% 24% 27% 12% 4 1	460
	21st to end	Day	31% 26% 27% 10% 4 1	506
April	1st to 10th	Day	30% 24% 26% 16% 4 1	460
	11th to 20th	Day	23% 26% 25% 14% 8% 3	452
	21st to end	Day	30% 20% 30% 14% 4 1	460
May	1st to 10th	Day	31% 16% 28% 15% 7% 2	463
	11th to 20th	Day	25% 16% 31% 15% 8% 5%	487
	21st to end	Day	16% 14% 27% 22% 15% 5%	529
June	1st to 10th	Day	20% 14% 28% 24% 11% 3	490
	11th to 20th	Day	17% 16% 26% 23% 14% 4	490
	21st to end	Day	15% 14% 32% 27% 9% 3	490
July	1st to 10th	Day	11% 9% 27% 27% 16% 10%	485
	11th to 20th	Day	9% 8% 31% 29% 16% 7%	484
	21st to end	Day	13% 7% 31% 29% 14% 6%	532
August	1st to 10th	Day	13% 9% 25% 26% 20% 6%	486
	11th to 20th	Day	13% 8% 26% 28% 15% 10%	479
	21st to end	Day	15% 8% 26% 27% 14% 10%	539
September	1st to 10th	Day	20% 9% 22% 26% 16% 8%	490
	11th to 20th	Day	13% 7% 21% 28% 21% 10%	490
	21st to end	Day	26% 14% 23% 19% 13% 5%	490
October	1st to 10th	Day	22% 14% 23% 20% 18% 4	490
	11th to 20th	Day	26% 18% 28% 17% 9% 2	490
	21st to end	Day	28% 20% 28% 17% 7% 1	539
November	1st to 10th	Day	19% 20% 29% 18% 12% 1	443
	11th to 20th	Day	31% 25% 27% 12% 4 1	190
	21st to end	Day	27% 28% 34% 9% 2	180
December	1st to 10th	Day	33% 31% 25% 7% 3 1	180
	11th to 20th	Day	36% 22% 28% 12% 1	180
	21st to end	Day	37% 25% 27% 9% 3	198
January	1st to 10th	Night	30% 26% 30% 11% 3	760
	11th to 20th	Night	29% 25% 28% 15% 3	760
	21st to end	Night	26% 27% 29% 15% 2	836
February	1st to 10th	Night	31% 20% 29% 18% 2	760
	11th to 20th	Night	30% 29% 31% 9% 1	743
	21st to end	Night	31% 24% 29% 15% 2	628
March	1st to 10th	Night	26% 22% 30% 19% 3	760
	11th to 20th	Night	30% 22% 24% 18% 5% 1	760
	21st to end	Night	23% 21% 34% 16% 5% 1	836
April	1st to 10th	Night	26% 21% 31% 19% 4	760
	11th to 20th	Night	23% 19% 30% 19% 8% 1	751
	21st to end	Night	21% 15% 30% 28% 6%	656
May	1st to 10th	Night	24% 12% 25% 30% 9% 1	570
	11th to 20th	Night	19% 9% 31% 30% 10%	442
	21st to end	Night	11% 9% 26% 32% 21% 1	411
June	1st to 10th	Night	12% 8% 28% 37% 16%	380
	11th to 20th	Night	13% 7% 26% 39% 15% 1	380
	21st to end	Night	13% 6% 30% 38% 13% 1	380
July	1st to 10th	Night	12% 5% 19% 40% 20% 3	370
	11th to 20th	Night	8% 4 22% 40% 25% 2	423
	21st to end	Night	12% 4 21% 39% 22% 1	624
August	1st to 10th	Night	11% 3 19% 40% 25% 2	567
	11th to 20th	Night	13% 7% 12% 38% 25% 4	564
	21st to end	Night	13% 4 19% 35% 25% 4	805
September	1st to 10th	Night	18% 6% 19% 32% 22% 3	760
	11th to 20th	Night	14% 5% 17% 32% 29% 4	760
	21st to end	Night	21% 11% 21% 27% 17% 3	760
October	1st to 10th	Night	18% 12% 23% 27% 18% 2	760
	11th to 20th	Night	23% 16% 28% 23% 9% 1	760
	21st to end	Night	26% 15% 28% 25% 5%	836
November	1st to 10th	Night	19% 15% 29% 27% 10% 1	771
	11th to 20th	Night	27% 19% 28% 20% 5% 2	760
	21st to end	Night	26% 19% 31% 18% 5%	760
December	1st to 10th	Night	31% 24% 28% 13% 4	760
	11th to 20th	Night	29% 24% 27% 17% 3	760
	21st to end	Night	29% 23% 29% 17% 1	836

Page generated at 2024-11-05 08:15:52. Version ac07

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