PropBusters Flying Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the PropBusters Flying Field clear sky chart from 2005-11-06 to 2024-11-10.

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	18% 7% 2 6% 4 4 4 3 5% 7% 39%	101238
	Night	19% 8% 2 6% 4 4 4 3 5% 6% 40%	97923
Transparency	Day	46% 2 11% 23% 16% 2	104789
	Night	46% 2 11% 23% 16% 2	102448
Seeing	Day	26% 15% 32% 18% 7% 2	15091
	Night	24% 14% 31% 23% 7% 1	24072

By Month

Percentage Cloud Cover NE (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	16% 8% 2 5% 4 4 4 3 4 5% 45%	2517
	11th to 20th	Day	17% 9% 2 6% 4 5% 4 4 5% 6% 38%	2520
	21st to end	Day	23% 13% 3 5% 3 3 3 3 4 5% 35%	2781
February	1st to 10th	Day	19% 8% 2 5% 5% 5% 4 4 6% 6% 38%	1818
	11th to 20th	Day	15% 7% 2 5% 5% 5% 4 3 6% 7% 41%	1848
	21st to end	Day	21% 9% 3 5% 4 4 4 4 4 5% 38%	1570
March	1st to 10th	Day	27% 10% 3 6% 4 3 3 2 4 5% 35%	3116
	11th to 20th	Day	11% 5% 2 5% 5% 5% 5% 4 7% 8% 43%	3274
	21st to end	Day	21% 8% 3 6% 4 4 4 3 6% 6% 36%	4124
April	1st to 10th	Day	19% 9% 3 5% 4 4 4 3 5% 7% 38%	2280
	11th to 20th	Day	20% 7% 2 5% 3 4 4 4 5% 6% 41%	2254
	21st to end	Day	21% 6% 2 5% 4 5% 4 4 4 6% 39%	2419
May	1st to 10th	Day	29% 8% 3 6% 4 3 4 4 5% 7% 29%	4106
	11th to 20th	Day	24% 9% 3 6% 4 4 4 3 4 6% 33%	4192
	21st to end	Day	17% 5% 2 5% 4 3 4 4 6% 8% 45%	4837
June	1st to 10th	Day	18% 5% 2 6% 5% 4 5% 4 6% 8% 35%	2660
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 6% 9% 36%	2660
	21st to end	Day	14% 8% 2 6% 5% 4 5% 4 5% 8% 38%	2660
July	1st to 10th	Day	15% 6% 2 7% 5% 6% 5% 5% 6% 8% 35%	4440
	11th to 20th	Day	15% 5% 2 5% 4 5% 5% 4 8% 9% 38%	4440
	21st to end	Day	21% 8% 3 6% 4 4 5% 4 6% 7% 32%	4814
August	1st to 10th	Day	21% 7% 2 7% 5% 4 6% 4 6% 8% 30%	4183
	11th to 20th	Day	13% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	3830
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 4 7% 9% 42%	4180
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 3 4 6% 45%	2280
	11th to 20th	Day	14% 6% 2 5% 3 3 4 3 5% 6% 50%	2119
	21st to end	Day	19% 7% 2 6% 3 4 4 3 4 6% 41%	2090
October	1st to 10th	Day	22% 8% 2 6% 3 3 3 3 5% 5% 42%	2090
	11th to 20th	Day	14% 7% 1 4 4 3 3 3 5% 6% 48%	1866
	21st to end	Day	19% 6% 3 6% 4 3 3 3 4 6% 44%	1881
November	1st to 10th	Day	14% 6% 2 6% 4 3 4 2 4 6% 49%	1752
	11th to 20th	Day	19% 5% 2 4 3 3 3 3 5% 6% 46%	1710
	21st to end	Day	16% 6% 2 6% 4 4 4 3 4 6% 44%	1710
December	1st to 10th	Day	19% 8% 3 5% 4 5% 4 3 6% 6% 37%	1539
	11th to 20th	Day	22% 6% 2 5% 3 3 2 2 4 5% 45%	1906
	21st to end	Day	20% 10% 3 7% 4 4 3 3 4 5% 36%	2772
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 5% 6% 47%	4429
	11th to 20th	Night	17% 10% 3 8% 4 3 3 2 4 4 43%	4440
	21st to end	Night	23% 12% 3 7% 4 3 3 3 4 5% 32%	4874
February	1st to 10th	Night	16% 9% 3 7% 4 3 3 3 4 6% 41%	2361
	11th to 20th	Night	16% 8% 3 6% 4 4 3 3 5% 6% 41%	2218
	21st to end	Night	20% 9% 2 6% 4 3 4 3 5% 5% 41%	1884
March	1st to 10th	Night	27% 12% 2 5% 3 3 2 2 5% 5% 34%	3724
	11th to 20th	Night	11% 7% 2 6% 5% 4 5% 4 6% 6% 44%	3684
	21st to end	Night	22% 9% 2 5% 3 3 4 3 5% 5% 38%	3503
April	1st to 10th	Night	20% 8% 2 6% 4 4 4 4 5% 6% 37%	1900
	11th to 20th	Night	19% 7% 2 6% 4 4 4 3 4 6% 40%	1875
	21st to end	Night	22% 7% 2 6% 4 4 3 2 4 5% 41%	1759
May	1st to 10th	Night	25% 10% 3 8% 4 4 4 3 5% 6% 28%	2834
	11th to 20th	Night	24% 9% 3 7% 5% 4 5% 4 6% 7% 28%	2730
	21st to end	Night	18% 6% 3 5% 4 3 4 3 5% 8% 41%	2738
June	1st to 10th	Night	18% 7% 2 6% 5% 4 4 4 4 7% 39%	1520
	11th to 20th	Night	19% 6% 2 5% 4 3 4 3 6% 8% 39%	1520
	21st to end	Night	15% 7% 2 6% 4 5% 5% 3 7% 8% 39%	1520
July	1st to 10th	Night	17% 6% 3 7% 5% 5% 6% 4 6% 8% 32%	2520
	11th to 20th	Night	19% 7% 2 6% 4 4 4 3 7% 9% 36%	2520
	21st to end	Night	21% 9% 2 7% 5% 4 4 4 5% 6% 33%	2739
August	1st to 10th	Night	24% 7% 3 7% 5% 4 5% 4 6% 7% 27%	2714
	11th to 20th	Night	12% 7% 3 7% 6% 5% 5% 4 5% 8% 38%	2995
	21st to end	Night	9% 4 2 4 4 3 4 3 5% 7% 55%	3476
September	1st to 10th	Night	14% 6% 3 6% 5% 4 5% 3 5% 6% 43%	1900
	11th to 20th	Night	14% 6% 2 5% 3 3 2 3 3 7% 52%	2061
	21st to end	Night	18% 7% 4 6% 5% 4 4 3 4 5% 40%	2090
October	1st to 10th	Night	19% 7% 2 6% 4 3 4 3 4 5% 42%	2090
	11th to 20th	Night	16% 5% 2 5% 3 3 4 3 5% 6% 48%	2308
	21st to end	Night	22% 7% 2 5% 3 3 3 2 4 7% 41%	2717
November	1st to 10th	Night	14% 5% 2 5% 3 4 3 3 4 7% 49%	2531
	11th to 20th	Night	19% 7% 2 4 3 3 3 3 4 6% 45%	2470
	21st to end	Night	16% 7% 2 5% 4 4 4 2 5% 7% 46%	2470
December	1st to 10th	Night	21% 8% 2 5% 4 4 4 3 5% 6% 39%	2637
	11th to 20th	Night	21% 7% 2 4 4 4 4 3 5% 5% 42%	3288
	21st to end	Night	22% 11% 3 6% 3 3 3 3 3 5% 37%	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	44% 1 7% 31% 14% 3	2518
	11th to 20th	Day	48% 2 9% 25% 13% 2	2520
	21st to end	Day	54% 2 7% 23% 12% 2	2781
February	1st to 10th	Day	48% 2 12% 21% 14% 2	1818
	11th to 20th	Day	44% 3 9% 25% 16% 3	1857
	21st to end	Day	51% 2 10% 20% 14% 4	1570
March	1st to 10th	Day	56% 1 10% 18% 13% 3	3119
	11th to 20th	Day	40% 2 9% 32% 16% 2	3274
	21st to end	Day	51% 1 5% 19% 19% 6%	4124
April	1st to 10th	Day	48% 2 9% 21% 17% 4	2280
	11th to 20th	Day	45% 2 9% 21% 20% 3	2254
	21st to end	Day	47% 3 9% 22% 16% 4	2419
May	1st to 10th	Day	58% 2 13% 15% 11% 2	4120
	11th to 20th	Day	55% 1 13% 19% 10% 2	4196
	21st to end	Day	39% 2 12% 26% 19% 2	4837
June	1st to 10th	Day	47% 3 11% 25% 12% 1	2660
	11th to 20th	Day	44% 3 14% 24% 13% 2	2660
	21st to end	Day	44% 5% 12% 23% 15% 1	2660
July	1st to 10th	Day	48% 4 11% 21% 15% 1	4370
	11th to 20th	Day	43% 3 16% 24% 12% 2	4365
	21st to end	Day	51% 3 11% 18% 15% 2	4661
August	1st to 10th	Day	52% 3 16% 20% 8%	4169
	11th to 20th	Day	42% 3 14% 30% 11% 1	3869
	21st to end	Day	38% 3 12% 26% 19% 2	4180
September	1st to 10th	Day	40% 3 11% 23% 20% 2	2280
	11th to 20th	Day	35% 2 9% 25% 25% 3	2119
	21st to end	Day	46% 2 6% 21% 22% 2	2090
October	1st to 10th	Day	42% 1 7% 21% 23% 5%	3480
	11th to 20th	Day	30% 1 8% 24% 32% 4	3069
	21st to end	Day	34% 2 13% 27% 21% 3	3081
November	1st to 10th	Day	39% 2 13% 21% 23% 3	1752
	11th to 20th	Day	39% 2 11% 22% 22% 4	1710
	21st to end	Day	42% 2 11% 28% 14% 3	1710
December	1st to 10th	Day	48% 2 12% 19% 17% 2	1539
	11th to 20th	Day	45% 1 13% 18% 20% 3	1906
	21st to end	Day	52% 2 10% 24% 12% 1	2772
January	1st to 10th	Night	40% 1 10% 32% 13% 4	4429
	11th to 20th	Night	48% 2 10% 24% 13% 3	4440
	21st to end	Night	57% 1 7% 21% 12% 2	4874
February	1st to 10th	Night	47% 2 11% 24% 13% 2	2361
	11th to 20th	Night	45% 2 9% 22% 17% 5%	2220
	21st to end	Night	47% 2 6% 24% 16% 4	1884
March	1st to 10th	Night	55% 1 7% 22% 12% 2	3734
	11th to 20th	Night	42% 2 14% 24% 16% 3	3685
	21st to end	Night	50% 1 5% 13% 24% 6%	3503
April	1st to 10th	Night	49% 2 8% 21% 16% 3	1900
	11th to 20th	Night	47% 2 8% 21% 20% 2	1875
	21st to end	Night	48% 2 8% 23% 15% 4	1759
May	1st to 10th	Night	58% 2 12% 17% 9% 2	2840
	11th to 20th	Night	58% 3 12% 16% 9% 2	2731
	21st to end	Night	43% 3 15% 25% 13% 1	2739
June	1st to 10th	Night	46% 4 12% 22% 15% 2	1520
	11th to 20th	Night	44% 3 13% 27% 11% 1	1520
	21st to end	Night	43% 4 13% 26% 14% 1	1520
July	1st to 10th	Night	51% 4 12% 20% 12% 1	2480
	11th to 20th	Night	44% 3 18% 26% 9% 1	2472
	21st to end	Night	53% 2 12% 15% 16% 2	2651
August	1st to 10th	Night	56% 4 13% 17% 9% 1	2704
	11th to 20th	Night	46% 2 14% 29% 8%	3022
	21st to end	Night	31% 2 16% 32% 19% 1	3476
September	1st to 10th	Night	43% 4 8% 26% 19% 1	1900
	11th to 20th	Night	36% 2 10% 25% 25% 3	2061
	21st to end	Night	49% 3 7% 19% 21% 3	2090
October	1st to 10th	Night	41% 2 11% 24% 20% 3	3480
	11th to 20th	Night	27% 2 8% 26% 33% 3	3831
	21st to end	Night	34% 1 12% 29% 21% 3	4467
November	1st to 10th	Night	38% 3 11% 23% 21% 4	2531
	11th to 20th	Night	42% 2 8% 23% 20% 4	2470
	21st to end	Night	40% 2 12% 30% 14% 2	2470
December	1st to 10th	Night	48% 2 12% 21% 16% 1	2637
	11th to 20th	Night	46% 2 13% 19% 19% 2	3288
	21st to end	Night	52% 2 8% 24% 14% 1	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	32% 22% 29% 16% 1	180
	11th to 20th	Day	36% 21% 31% 9% 3	180
	21st to end	Day	29% 23% 32% 11% 4 1	202
February	1st to 10th	Day	34% 24% 27% 13% 2	378
	11th to 20th	Day	33% 27% 30% 8% 2	456
	21st to end	Day	34% 22% 30% 10% 4	382
March	1st to 10th	Day	32% 21% 32% 12% 2	460
	11th to 20th	Day	32% 21% 32% 11% 3 1	460
	21st to end	Day	34% 21% 29% 11% 4 1	506
April	1st to 10th	Day	36% 22% 27% 11% 4 1	460
	11th to 20th	Day	34% 20% 30% 12% 4	452
	21st to end	Day	35% 17% 32% 11% 5% 2	460
May	1st to 10th	Day	39% 15% 27% 13% 5% 1	463
	11th to 20th	Day	28% 14% 38% 14% 5% 1	487
	21st to end	Day	24% 11% 32% 23% 8% 2	529
June	1st to 10th	Day	23% 11% 35% 21% 9% 2	490
	11th to 20th	Day	20% 14% 37% 20% 7% 1	490
	21st to end	Day	21% 12% 36% 22% 7% 3	490
July	1st to 10th	Day	20% 7% 31% 27% 12% 2	485
	11th to 20th	Day	16% 7% 34% 30% 11% 3	484
	21st to end	Day	17% 10% 38% 26% 8% 1	532
August	1st to 10th	Day	17% 7% 32% 30% 10% 3	486
	11th to 20th	Day	17% 9% 30% 25% 14% 4	479
	21st to end	Day	13% 9% 34% 24% 14% 6%	539
September	1st to 10th	Day	19% 11% 28% 24% 13% 4	490
	11th to 20th	Day	17% 8% 34% 20% 13% 8%	490
	21st to end	Day	24% 9% 37% 18% 8% 4	490
October	1st to 10th	Day	28% 11% 27% 19% 9% 5%	490
	11th to 20th	Day	21% 18% 30% 19% 8% 3	463
	21st to end	Day	28% 14% 31% 17% 7% 2	429
November	1st to 10th	Day	23% 13% 34% 21% 8% 2	392
	11th to 20th	Day	32% 19% 27% 17% 5% 1	370
	21st to end	Day	26% 18% 30% 19% 6% 1	370
December	1st to 10th	Day	29% 24% 30% 14% 4	199
	11th to 20th	Day	36% 23% 30% 8% 3	180
	21st to end	Day	30% 24% 29% 13% 3 1	198
January	1st to 10th	Night	24% 23% 33% 17% 3	760
	11th to 20th	Night	33% 19% 29% 17% 2	760
	21st to end	Night	25% 22% 31% 19% 2	836
February	1st to 10th	Night	25% 20% 33% 21% 2	760
	11th to 20th	Night	28% 23% 34% 14% 1	743
	21st to end	Night	32% 21% 30% 15% 3	628
March	1st to 10th	Night	29% 18% 34% 16% 3	760
	11th to 20th	Night	24% 22% 33% 18% 3	760
	21st to end	Night	29% 20% 31% 16% 3 1	836
April	1st to 10th	Night	28% 18% 34% 18% 3	760
	11th to 20th	Night	24% 18% 34% 21% 3	751
	21st to end	Night	27% 16% 34% 18% 5%	619
May	1st to 10th	Night	30% 12% 29% 23% 5%	570
	11th to 20th	Night	24% 15% 37% 19% 5%	518
	21st to end	Night	21% 7% 30% 32% 8% 1	411
June	1st to 10th	Night	22% 7% 30% 30% 10% 1	380
	11th to 20th	Night	24% 5% 30% 32% 8%	380
	21st to end	Night	19% 7% 32% 33% 8% 1	380
July	1st to 10th	Night	17% 5% 32% 31% 16% 1	370
	11th to 20th	Night	18% 2 27% 40% 11% 1	368
	21st to end	Night	18% 4 28% 39% 10%	416
August	1st to 10th	Night	13% 3 33% 38% 12% 1	495
	11th to 20th	Night	15% 4 27% 35% 17% 2	684
	21st to end	Night	16% 4 26% 34% 18% 3	836
September	1st to 10th	Night	18% 4 33% 30% 13% 2	760
	11th to 20th	Night	19% 6% 25% 29% 17% 4	760
	21st to end	Night	23% 6% 29% 26% 14% 2	760
October	1st to 10th	Night	24% 9% 29% 23% 13% 2	760
	11th to 20th	Night	20% 13% 32% 25% 10% 1	760
	21st to end	Night	28% 14% 31% 19% 8%	836
November	1st to 10th	Night	18% 16% 32% 23% 10% 2	779
	11th to 20th	Night	27% 18% 30% 19% 5% 1	760
	21st to end	Night	25% 17% 31% 19% 7%	760
December	1st to 10th	Night	30% 17% 27% 21% 5%	760
	11th to 20th	Night	29% 20% 29% 18% 3	760
	21st to end	Night	28% 17% 36% 16% 3	836

Page generated at 2024-11-07 06:55:43. Version ac07

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