"Flying F" Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the "Flying F" Observatory 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	3 7% 3 7% 5% 5% 5% 4 6% 7% 47%	105063
	Night	2 5% 2 6% 4 4 4 4 6% 8% 56%	102692
Transparency	Day	34% 4 9% 21% 23% 8%	104820
	Night	26% 4 12% 26% 25% 8%	102525
Seeing	Day	18% 21% 24% 21% 13% 3	15317
	Night	8% 11% 29% 33% 17% 2	25411

By Month

Percentage Cloud Cover SW (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	2 2 11% 5% 4 4 3 7% 8% 54%	2697
	11th to 20th	Day	4 6% 6% 4 4 4 3 6% 8% 55%	2860
	21st to end	Day	6% 4 9% 5% 4 4 4 6% 8% 50%	3146
February	1st to 10th	Day	6% 3 11% 4 4 4 3 5% 8% 52%	1710
	11th to 20th	Day	1 6% 2 7% 5% 4 4 4 6% 9% 51%	1759
	21st to end	Day	5% 4 11% 6% 5% 3 4 6% 9% 48%	1570
March	1st to 10th	Day	6% 6% 9% 6% 4 4 4 5% 6% 49%	3353
	11th to 20th	Day	1 12% 8% 9% 4 4 4 3 6% 7% 40%	3490
	21st to end	Day	1 13% 5% 11% 6% 6% 5% 3 5% 6% 37%	3903
April	1st to 10th	Day	1 8% 2 6% 5% 5% 5% 4 5% 8% 50%	2280
	11th to 20th	Day	2 11% 4 8% 5% 5% 4 4 6% 6% 45%	2251
	21st to end	Day	3 9% 4 8% 6% 4 5% 4 6% 6% 45%	2280
May	1st to 10th	Day	3 12% 3 8% 5% 6% 5% 4 5% 6% 45%	3909
	11th to 20th	Day	3 9% 3 8% 6% 6% 6% 5% 7% 8% 39%	4215
	21st to end	Day	4 7% 2 7% 5% 5% 5% 4 6% 6% 48%	4825
June	1st to 10th	Day	4 6% 2 5% 5% 4 5% 4 5% 8% 51%	2660
	11th to 20th	Day	4 4 2 5% 4 4 4 4 5% 6% 58%	2660
	21st to end	Day	4 6% 2 7% 6% 6% 6% 5% 6% 7% 47%	2660
July	1st to 10th	Day	5% 5% 2 6% 5% 5% 6% 4 5% 6% 52%	4430
	11th to 20th	Day	5% 5% 2 8% 7% 7% 8% 8% 9% 9% 32%	4187
	21st to end	Day	7% 6% 2 9% 7% 7% 7% 6% 7% 8% 34%	4454
August	1st to 10th	Day	9% 8% 3 10% 8% 8% 7% 6% 7% 9% 25%	4092
	11th to 20th	Day	6% 6% 3 8% 6% 7% 7% 7% 8% 8% 35%	3818
	21st to end	Day	6% 7% 3 9% 7% 8% 7% 6% 8% 8% 31%	4180
September	1st to 10th	Day	8% 7% 3 9% 6% 5% 5% 4 6% 6% 41%	2280
	11th to 20th	Day	7% 6% 3 8% 5% 4 5% 4 5% 6% 47%	2280
	21st to end	Day	6% 7% 2 6% 4 4 4 3 4 5% 55%	2025
October	1st to 10th	Day	5% 6% 1 5% 3 3 3 3 3 4 63%	3170
	11th to 20th	Day	3 8% 3 7% 5% 4 5% 4 5% 6% 50%	3150
	21st to end	Day	2 4 2 4 2 2 3 2 4 4 70%	3438
November	1st to 10th	Day	1 4 2 4 3 2 3 3 4 6% 70%	1813
	11th to 20th	Day	3 1 3 2 2 3 3 4 5% 72%	1710
	21st to end	Day	4 2 5% 4 3 3 3 4 7% 63%	1568
December	1st to 10th	Day	1 5% 3 6% 4 3 4 2 5% 8% 60%	1520
	11th to 20th	Day	5% 3 5% 5% 4 4 5% 6% 9% 55%	1926
	21st to end	Day	5% 3 7% 4 3 4 3 5% 9% 58%	2794
January	1st to 10th	Night	2 2 9% 8% 6% 5% 4 6% 7% 51%	4288
	11th to 20th	Night	3 2 10% 5% 4 5% 3 5% 6% 56%	4110
	21st to end	Night	6% 4 8% 4 4 5% 4 6% 9% 50%	4521
February	1st to 10th	Night	4 3 7% 4 3 4 4 5% 7% 59%	2470
	11th to 20th	Night	4 2 5% 4 3 4 4 5% 6% 62%	2308
	21st to end	Night	4 3 7% 4 4 4 2 5% 8% 59%	1884
March	1st to 10th	Night	6% 3 7% 4 3 4 4 6% 8% 55%	3504
	11th to 20th	Night	1 9% 6% 12% 5% 5% 5% 4 7% 8% 40%	3490
	21st to end	Night	1 9% 3 8% 5% 5% 5% 3 6% 7% 47%	3747
April	1st to 10th	Night	5% 2 5% 3 4 3 4 6% 7% 61%	1900
	11th to 20th	Night	1 8% 2 4 4 5% 5% 3 6% 8% 54%	1877
	21st to end	Night	1 6% 2 4 3 4 4 4 6% 7% 59%	1900
May	1st to 10th	Night	2 9% 3 4 3 3 3 3 4 6% 59%	3058
	11th to 20th	Night	3 7% 2 5% 4 3 4 4 8% 9% 51%	2686
	21st to end	Night	3 4 1 3 3 2 3 3 4 5% 69%	2762
June	1st to 10th	Night	1 3 1 3 2 4 4 3 6% 8% 66%	1520
	11th to 20th	Night	2 3 1 2 3 2 3 2 5% 6% 70%	1520
	21st to end	Night	2 4 2 3 3 3 5% 4 7% 8% 59%	1520
July	1st to 10th	Night	4 4 1 5% 4 4 5% 3 5% 8% 57%	2540
	11th to 20th	Night	2 4 1 3 3 3 5% 6% 9% 17% 46%	2779
	21st to end	Night	3 6% 3 7% 5% 4 5% 5% 8% 12% 42%	3109
August	1st to 10th	Night	4 4 2 8% 6% 6% 7% 6% 11% 13% 33%	2847
	11th to 20th	Night	3 4 1 4 4 4 5% 6% 11% 16% 42%	3018
	21st to end	Night	5% 8% 4 9% 6% 5% 6% 5% 6% 10% 38%	3487
September	1st to 10th	Night	5% 5% 2 5% 5% 4 5% 5% 7% 9% 48%	1900
	11th to 20th	Night	5% 4 1 5% 4 4 4 3 6% 8% 56%	1900
	21st to end	Night	4 3 1 5% 3 3 2 3 5% 5% 65%	2151
October	1st to 10th	Night	3 3 1 3 2 2 3 2 3 5% 72%	3800
	11th to 20th	Night	2 6% 3 6% 3 3 3 3 4 7% 59%	3778
	21st to end	Night	1 4 2 5% 2 2 2 2 3 6% 71%	4120
November	1st to 10th	Night	1 3 2 2 2 2 3 3 4 8% 70%	2316
	11th to 20th	Night	2 1 2 2 2 3 3 5% 6% 74%	2470
	21st to end	Night	1 5% 3 4 4 3 2 3 5% 6% 64%	2608
December	1st to 10th	Night	4 2 4 4 3 4 4 4 8% 63%	2660
	11th to 20th	Night	4 2 6% 3 3 4 4 6% 10% 57%	3271
	21st to end	Night	5% 3 7% 4 4 4 3 5% 7% 58%	4873

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	28% 2 14% 25% 26% 6%	2698
	11th to 20th	Day	29% 2 13% 26% 26% 4	2860
	21st to end	Day	36% 2 6% 28% 23% 5%	3146
February	1st to 10th	Day	30% 4 12% 26% 18% 10%	1710
	11th to 20th	Day	29% 4 7% 25% 26% 9%	1768
	21st to end	Day	35% 4 6% 20% 24% 11%	1570
March	1st to 10th	Day	34% 2 5% 26% 26% 8%	3353
	11th to 20th	Day	43% 2 6% 31% 16% 3	3490
	21st to end	Day	45% 2 8% 23% 19% 3	3903
April	1st to 10th	Day	32% 4 9% 23% 24% 9%	2280
	11th to 20th	Day	36% 3 8% 24% 23% 7%	2254
	21st to end	Day	37% 3 8% 29% 21% 3	2280
May	1st to 10th	Day	36% 2 8% 18% 25% 11%	3909
	11th to 20th	Day	42% 2 6% 23% 21% 5%	4219
	21st to end	Day	33% 2 4 18% 36% 7%	4825
June	1st to 10th	Day	29% 3 9% 26% 22% 10%	2660
	11th to 20th	Day	24% 4 7% 18% 29% 19%	2660
	21st to end	Day	34% 4 7% 17% 24% 14%	2660
July	1st to 10th	Day	31% 5% 9% 10% 18% 26%	4361
	11th to 20th	Day	40% 9% 18% 19% 11% 3	4115
	21st to end	Day	42% 9% 16% 13% 12% 8%	4314
August	1st to 10th	Day	52% 10% 16% 11% 8% 4	4078
	11th to 20th	Day	41% 10% 14% 13% 17% 5%	3856
	21st to end	Day	42% 9% 13% 16% 17% 4	4179
September	1st to 10th	Day	43% 4 10% 15% 21% 8%	2280
	11th to 20th	Day	37% 3 7% 18% 25% 9%	2280
	21st to end	Day	29% 3 6% 23% 33% 7%	2025
October	1st to 10th	Day	24% 3 5% 19% 32% 17%	3170
	11th to 20th	Day	28% 7% 7% 24% 26% 7%	3150
	21st to end	Day	18% 2 7% 25% 39% 8%	3438
November	1st to 10th	Day	16% 3 8% 28% 35% 11%	1813
	11th to 20th	Day	14% 2 8% 33% 33% 10%	1710
	21st to end	Day	22% 3 8% 26% 28% 13%	1568
December	1st to 10th	Day	24% 3 14% 28% 23% 8%	1520
	11th to 20th	Day	24% 5% 11% 28% 25% 6%	1924
	21st to end	Day	26% 3 8% 21% 25% 17%	2794
January	1st to 10th	Night	32% 2 8% 30% 24% 5%	4288
	11th to 20th	Night	25% 1 12% 27% 29% 5%	4110
	21st to end	Night	34% 2 6% 32% 21% 4	4521
February	1st to 10th	Night	25% 3 13% 26% 24% 9%	2470
	11th to 20th	Night	21% 3 9% 30% 28% 9%	2309
	21st to end	Night	26% 2 7% 25% 30% 10%	1884
March	1st to 10th	Night	27% 2 7% 25% 37% 3	3504
	11th to 20th	Night	44% 1 8% 29% 15% 3	3490
	21st to end	Night	36% 2 12% 27% 21% 2	3747
April	1st to 10th	Night	20% 5% 13% 28% 27% 7%	1900
	11th to 20th	Night	28% 2 10% 28% 27% 6%	1877
	21st to end	Night	24% 4 11% 36% 22% 3	1900
May	1st to 10th	Night	25% 2 8% 21% 35% 9%	3058
	11th to 20th	Night	31% 2 8% 33% 21% 5%	2687
	21st to end	Night	19% 2 6% 24% 40% 10%	2762
June	1st to 10th	Night	18% 3 13% 27% 29% 10%	1520
	11th to 20th	Night	15% 3 6% 23% 32% 21%	1520
	21st to end	Night	21% 5% 9% 22% 26% 17%	1520
July	1st to 10th	Night	26% 4 14% 10% 19% 28%	2500
	11th to 20th	Night	22% 12% 33% 22% 7% 5%	2728
	21st to end	Night	30% 13% 27% 16% 9% 5%	3011
August	1st to 10th	Night	39% 16% 19% 11% 10% 5%	2838
	11th to 20th	Night	27% 16% 24% 12% 17% 4	3046
	21st to end	Night	39% 10% 16% 18% 15% 2	3487
September	1st to 10th	Night	31% 5% 16% 19% 22% 7%	1900
	11th to 20th	Night	27% 4 12% 20% 28% 10%	1900
	21st to end	Night	21% 3 7% 30% 34% 6%	2151
October	1st to 10th	Night	18% 2 8% 29% 29% 14%	3800
	11th to 20th	Night	19% 8% 10% 32% 24% 7%	3778
	21st to end	Night	15% 3 14% 34% 29% 6%	4120
November	1st to 10th	Night	14% 3 11% 33% 31% 9%	2316
	11th to 20th	Night	12% 3 9% 35% 33% 8%	2470
	21st to end	Night	22% 3 7% 28% 31% 10%	2608
December	1st to 10th	Night	21% 3 16% 27% 24% 8%	2660
	11th to 20th	Night	22% 5% 12% 27% 28% 6%	3272
	21st to end	Night	28% 3 8% 21% 26% 13%	4873

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	17% 17% 34% 20% 10% 1	270
	11th to 20th	Day	21% 23% 25% 24% 6% 1	270
	21st to end	Day	8% 22% 35% 25% 10% 1	297
February	1st to 10th	Day	22% 27% 31% 17% 2 1	270
	11th to 20th	Day	21% 29% 29% 16% 4 1	270
	21st to end	Day	31% 26% 24% 16% 2	225
March	1st to 10th	Day	27% 28% 26% 13% 5% 1	403
	11th to 20th	Day	24% 30% 25% 15% 5% 1	460
	21st to end	Day	33% 31% 26% 7% 3	506
April	1st to 10th	Day	27% 31% 27% 12% 3 1	460
	11th to 20th	Day	32% 36% 19% 9% 4	452
	21st to end	Day	30% 32% 23% 12% 3	460
May	1st to 10th	Day	26% 34% 24% 9% 5% 1	463
	11th to 20th	Day	18% 28% 27% 16% 10% 2	567
	21st to end	Day	21% 24% 21% 21% 12% 2	734
June	1st to 10th	Day	9% 20% 24% 25% 18% 3	680
	11th to 20th	Day	11% 24% 25% 23% 13% 4	680
	21st to end	Day	7% 19% 22% 24% 22% 5%	680
July	1st to 10th	Day	9% 10% 18% 32% 25% 6%	671
	11th to 20th	Day	10% 7% 18% 30% 27% 8%	532
	21st to end	Day	13% 8% 16% 32% 23% 8%	531
August	1st to 10th	Day	19% 8% 20% 28% 20% 6%	487
	11th to 20th	Day	13% 9% 22% 32% 18% 5%	477
	21st to end	Day	12% 10% 25% 28% 20% 4	539
September	1st to 10th	Day	12% 12% 24% 24% 23% 5%	490
	11th to 20th	Day	13% 22% 29% 22% 12% 2	490
	21st to end	Day	17% 16% 23% 21% 20% 3	367
October	1st to 10th	Day	18% 15% 23% 20% 20% 5%	300
	11th to 20th	Day	16% 20% 26% 20% 16% 2	300
	21st to end	Day	18% 22% 23% 21% 12% 4	330
November	1st to 10th	Day	21% 19% 24% 25% 10% 1	279
	11th to 20th	Day	14% 20% 27% 26% 10% 2	270
	21st to end	Day	16% 19% 30% 20% 13% 3	270
December	1st to 10th	Day	17% 20% 32% 18% 9% 3	270
	11th to 20th	Day	17% 19% 32% 20% 10% 1	270
	21st to end	Day	21% 22% 32% 19% 6% 1	297
January	1st to 10th	Night	6% 14% 35% 33% 10% 2	873
	11th to 20th	Night	9% 13% 35% 32% 10% 1	760
	21st to end	Night	5% 12% 39% 34% 9% 2	836
February	1st to 10th	Night	6% 15% 44% 29% 6% 1	760
	11th to 20th	Night	7% 13% 44% 28% 7%	744
	21st to end	Night	10% 15% 45% 27% 3	628
March	1st to 10th	Night	10% 21% 33% 29% 7%	760
	11th to 20th	Night	6% 13% 36% 32% 12% 1	760
	21st to end	Night	10% 16% 40% 30% 5%	793
April	1st to 10th	Night	11% 19% 38% 28% 5%	570
	11th to 20th	Night	13% 18% 35% 26% 7%	563
	21st to end	Night	8% 18% 35% 28% 9% 1	570
May	1st to 10th	Night	9% 13% 36% 30% 11% 1	570
	11th to 20th	Night	9% 11% 25% 37% 15% 2	561
	21st to end	Night	11% 15% 25% 30% 17% 2	617
June	1st to 10th	Night	5% 8% 23% 38% 25% 1	570
	11th to 20th	Night	5% 9% 29% 37% 18% 2	570
	21st to end	Night	4 8% 16% 40% 29% 2	570
July	1st to 10th	Night	5% 4 11% 37% 40% 3	555
	11th to 20th	Night	6% 2 5% 33% 48% 7%	552
	21st to end	Night	8% 2 4 28% 50% 8%	624
August	1st to 10th	Night	7% 3 6% 29% 49% 6%	567
	11th to 20th	Night	5% 2 8% 38% 41% 5%	564
	21st to end	Night	7% 3 11% 37% 37% 5%	627
September	1st to 10th	Night	6% 3 13% 38% 36% 4	570
	11th to 20th	Night	8% 4 19% 39% 27% 3	570
	21st to end	Night	6% 8% 17% 38% 27% 4	698
October	1st to 10th	Night	9% 9% 24% 37% 19% 2	760
	11th to 20th	Night	6% 9% 31% 36% 15% 3	760
	21st to end	Night	8% 11% 27% 35% 16% 3	836
November	1st to 10th	Night	6% 13% 30% 35% 14% 2	808
	11th to 20th	Night	8% 11% 36% 32% 11% 2	950
	21st to end	Night	9% 13% 32% 33% 12% 1	950
December	1st to 10th	Night	8% 14% 40% 29% 8% 1	950
	11th to 20th	Night	9% 17% 35% 29% 9% 1	950
	21st to end	Night	10% 13% 41% 29% 6% 1	1045

Page generated at 2024-11-01 20:47:38. Version ac07

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