FWAS Rising Star
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the FWAS Rising Star clear sky chart from 2005-11-06 to 2025-09-19.

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	8% 5% 2 4 3 3 4 3 5% 7% 56%	126210
	Night	8% 5% 2 4 3 3 3 3 4 7% 59%	123163
Transparency	Day	28% 2 8% 23% 25% 12%	130015
	Night	27% 2 8% 22% 26% 15%	127421
Seeing	Day	9% 6% 22% 30% 24% 9%	16245
	Night	10% 6% 30% 38% 15% 1	26089

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	10% 6% 3 5% 3 2 3 3 4 5% 56%	4077
	11th to 20th	Day	5% 5% 2 2 2 2 2 2 4 5% 67%	4080
	21st to end	Day	18% 6% 1 4 3 3 3 3 4 5% 52%	4826
February	1st to 10th	Day	12% 5% 2 4 3 3 3 4 5% 6% 54%	2000
	11th to 20th	Day	11% 8% 3 5% 3 2 3 3 3 5% 53%	1949
	21st to end	Day	13% 7% 2 4 3 2 2 2 3 5% 57%	1650
March	1st to 10th	Day	11% 6% 2 4 3 2 3 3 5% 6% 56%	4692
	11th to 20th	Day	10% 4 2 4 3 3 3 3 4 5% 58%	4980
	21st to end	Day	6% 4 1 5% 4 4 5% 4 6% 6% 55%	5462
April	1st to 10th	Day	8% 5% 3 5% 3 4 4 3 5% 7% 53%	2200
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 3 6% 53%	2349
	21st to end	Day	9% 5% 2 4 4 3 3 3 4 6% 57%	2526
May	1st to 10th	Day	12% 6% 2 6% 4 3 4 3 5% 5% 50%	5862
	11th to 20th	Day	12% 6% 2 6% 3 3 3 3 5% 6% 50%	5862
	21st to end	Day	10% 6% 3 6% 5% 5% 4 4 5% 7% 46%	6434
June	1st to 10th	Day	5% 3 1 4 4 4 4 4 6% 8% 58%	2600
	11th to 20th	Day	4 3 1 4 4 3 4 4 5% 8% 60%	2600
	21st to end	Day	5% 3 1 3 4 3 4 4 7% 8% 58%	2600
July	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 4 6% 7% 43%	5900
	11th to 20th	Day	3 3 1 3 3 3 3 3 6% 9% 62%	5900
	21st to end	Day	3 2 1 3 3 3 4 4 6% 10% 61%	6422
August	1st to 10th	Day	1 2 1 2 2 2 3 3 4 7% 73%	4181
	11th to 20th	Day	4 2 1 3 3 3 3 3 6% 9% 62%	3846
	21st to end	Day	2 3 1 4 3 4 4 4 6% 9% 60%	4289
September	1st to 10th	Day	10% 4 2 5% 4 4 5% 3 5% 6% 53%	2200
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 5% 7% 50%	2178
	21st to end	Day	7% 4 1 4 3 3 4 3 5% 7% 59%	2090
October	1st to 10th	Day	5% 4 1 3 3 3 3 3 6% 5% 65%	2090
	11th to 20th	Day	9% 3 1 4 2 3 3 2 4 4 65%	2000
	21st to end	Day	11% 4 1 3 2 2 3 2 3 4 64%	2090
November	1st to 10th	Day	10% 6% 2 4 3 3 2 2 4 5% 60%	1856
	11th to 20th	Day	4 4 1 4 3 2 3 2 5% 7% 64%	1800
	21st to end	Day	12% 5% 2 5% 4 3 3 3 4 5% 56%	1800
December	1st to 10th	Day	14% 6% 3 5% 3 4 4 3 4 6% 49%	2940
	11th to 20th	Day	10% 4 2 6% 4 4 4 3 5% 5% 54%	3391
	21st to end	Day	10% 6% 1 4 3 3 3 2 3 4 61%	4488
January	1st to 10th	Night	12% 6% 2 4 3 2 2 2 4 5% 58%	5888
	11th to 20th	Night	6% 4 1 3 2 2 2 2 3 4 71%	5900
	21st to end	Night	16% 8% 2 5% 3 3 3 3 3 5% 49%	6196
February	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 3 5% 58%	2400
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 4 6% 53%	2338
	21st to end	Night	11% 6% 2 4 3 2 3 3 3 5% 59%	1980
March	1st to 10th	Night	8% 5% 2 5% 3 3 3 3 5% 6% 56%	5172
	11th to 20th	Night	10% 5% 2 4 3 2 3 3 5% 6% 58%	4980
	21st to end	Night	6% 6% 2 4 3 3 3 3 5% 6% 58%	5467
April	1st to 10th	Night	6% 4 2 5% 4 3 3 4 5% 8% 56%	2200
	11th to 20th	Night	9% 6% 1 5% 5% 3 3 3 4 6% 53%	1996
	21st to end	Night	8% 5% 2 3 3 3 3 3 4 6% 61%	1870
May	1st to 10th	Night	15% 6% 2 4 3 3 3 3 4 6% 51%	4053
	11th to 20th	Night	6% 5% 2 6% 4 4 4 4 5% 6% 53%	4053
	21st to end	Night	10% 5% 2 5% 4 3 4 4 6% 9% 48%	4443
June	1st to 10th	Night	3 2 1 4 2 4 4 3 7% 9% 60%	1800
	11th to 20th	Night	3 2 1 3 2 3 3 4 6% 9% 64%	1800
	21st to end	Night	3 3 1 3 3 3 2 4 5% 7% 65%	1800
July	1st to 10th	Night	8% 5% 2 6% 4 4 4 3 5% 9% 50%	4078
	11th to 20th	Night	2 1 1 2 2 3 3 3 5% 10% 70%	4077
	21st to end	Night	2 2 1 3 2 3 4 3 6% 9% 65%	4449
August	1st to 10th	Night	1 1 1 2 2 2 3 2 4 7% 75%	2974
	11th to 20th	Night	3 2 1 2 3 2 3 2 5% 10% 66%	3213
	21st to end	Night	2 2 1 3 3 4 4 3 6% 10% 61%	3618
September	1st to 10th	Night	8% 4 1 5% 3 4 4 4 5% 8% 55%	2200
	11th to 20th	Night	9% 4 2 4 3 3 4 3 7% 8% 53%	2178
	21st to end	Night	6% 3 1 3 3 3 4 3 5% 7% 61%	2090
October	1st to 10th	Night	5% 3 1 3 3 3 3 3 4 6% 67%	2090
	11th to 20th	Night	8% 4 1 4 2 2 3 3 3 5% 65%	2158
	21st to end	Night	10% 4 2 4 2 3 3 2 3 4 63%	2508
November	1st to 10th	Night	10% 5% 1 4 2 3 3 3 3 4 62%	2438
	11th to 20th	Night	5% 3 1 4 2 3 4 3 3 5% 66%	2600
	21st to end	Night	13% 5% 2 4 3 3 3 3 5% 7% 54%	2600
December	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 4 6% 54%	4250
	11th to 20th	Night	8% 6% 2 5% 4 4 4 3 4 6% 54%	4816
	21st to end	Night	11% 6% 2 4 3 3 3 2 3 4 61%	6490

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	33% 1 5% 21% 29% 11%	4078
	11th to 20th	Day	23% 1 4 22% 37% 14%	4080
	21st to end	Day	38% 1 3 15% 25% 18%	4826
February	1st to 10th	Day	32% 2 5% 17% 25% 20%	2000
	11th to 20th	Day	36% 2 5% 21% 22% 14%	1959
	21st to end	Day	33% 2 3 12% 28% 22%	1650
March	1st to 10th	Day	32% 1 4 10% 26% 26%	4692
	11th to 20th	Day	30% 2 9% 11% 20% 28%	4980
	21st to end	Day	31% 1 8% 20% 26% 14%	5464
April	1st to 10th	Day	32% 2 9% 20% 20% 16%	2200
	11th to 20th	Day	34% 2 7% 18% 23% 17%	2349
	21st to end	Day	31% 2 8% 19% 30% 10%	2526
May	1st to 10th	Day	36% 2 8% 19% 23% 12%	5900
	11th to 20th	Day	36% 3 6% 16% 30% 10%	5866
	21st to end	Day	38% 3 10% 27% 15% 8%	6447
June	1st to 10th	Day	24% 4 15% 30% 22% 5%	2600
	11th to 20th	Day	23% 4 10% 32% 24% 7%	2600
	21st to end	Day	23% 4 12% 30% 23% 8%	2600
July	1st to 10th	Day	39% 4 12% 31% 13% 1	5836
	11th to 20th	Day	20% 2 19% 33% 23% 3	5831
	21st to end	Day	18% 4 15% 37% 24% 2	6240
August	1st to 10th	Day	13% 2 11% 33% 36% 5%	4167
	11th to 20th	Day	19% 3 14% 34% 26% 4	3882
	21st to end	Day	21% 4 17% 31% 23% 4	4288
September	1st to 10th	Day	32% 3 7% 22% 25% 10%	2200
	11th to 20th	Day	33% 4 10% 22% 24% 7%	2178
	21st to end	Day	26% 3 7% 22% 27% 16%	2090
October	1st to 10th	Day	13% 2 6% 14% 35% 30%	3480
	11th to 20th	Day	19% 2 6% 24% 27% 22%	3305
	21st to end	Day	18% 2 3 25% 37% 14%	3428
November	1st to 10th	Day	29% 2 6% 23% 26% 14%	1856
	11th to 20th	Day	22% 2 7% 24% 27% 18%	1800
	21st to end	Day	33% 2 4 21% 27% 14%	1800
December	1st to 10th	Day	39% 2 4 17% 28% 10%	2940
	11th to 20th	Day	34% 2 6% 15% 26% 16%	3389
	21st to end	Day	29% 1 3 22% 28% 17%	4488
January	1st to 10th	Night	32% 1 4 20% 32% 11%	5888
	11th to 20th	Night	20% 1 3 19% 35% 22%	5900
	21st to end	Night	40% 1 4 15% 23% 17%	6196
February	1st to 10th	Night	31% 2 6% 17% 24% 21%	2400
	11th to 20th	Night	34% 2 7% 17% 24% 17%	2338
	21st to end	Night	31% 2 4 15% 23% 24%	1980
March	1st to 10th	Night	30% 2 4 15% 26% 23%	5172
	11th to 20th	Night	29% 1 8% 16% 15% 30%	4980
	21st to end	Night	29% 1 7% 21% 28% 14%	5467
April	1st to 10th	Night	27% 3 10% 21% 19% 21%	2200
	11th to 20th	Night	33% 3 8% 17% 23% 17%	1996
	21st to end	Night	26% 3 11% 23% 28% 10%	1870
May	1st to 10th	Night	37% 2 7% 22% 19% 11%	4080
	11th to 20th	Night	33% 2 10% 19% 20% 16%	4054
	21st to end	Night	33% 2 14% 26% 15% 9%	4452
June	1st to 10th	Night	21% 4 17% 33% 21% 4	1800
	11th to 20th	Night	17% 3 13% 34% 25% 8%	1800
	21st to end	Night	19% 3 12% 31% 26% 9%	1800
July	1st to 10th	Night	33% 4 12% 33% 16% 2	4035
	11th to 20th	Night	13% 3 14% 36% 30% 4	4026
	21st to end	Night	16% 4 16% 36% 26% 2	4320
August	1st to 10th	Night	11% 2 10% 30% 42% 6%	2964
	11th to 20th	Night	16% 2 16% 37% 24% 4	3243
	21st to end	Night	20% 5% 21% 28% 23% 4	3618
September	1st to 10th	Night	28% 4 9% 23% 25% 11%	2200
	11th to 20th	Night	28% 4 13% 23% 22% 10%	2178
	21st to end	Night	24% 2 7% 24% 25% 18%	2090
October	1st to 10th	Night	12% 1 6% 16% 30% 36%	3480
	11th to 20th	Night	18% 2 7% 18% 34% 23%	3579
	21st to end	Night	20% 1 3 23% 38% 15%	4120
November	1st to 10th	Night	27% 2 6% 21% 24% 19%	2438
	11th to 20th	Night	22% 2 6% 23% 27% 19%	2600
	21st to end	Night	32% 2 6% 18% 27% 16%	2600
December	1st to 10th	Night	33% 1 5% 23% 25% 13%	4250
	11th to 20th	Night	34% 2 5% 14% 29% 16%	4817
	21st to end	Night	29% 1 3 22% 25% 19%	6490

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	11% 14% 38% 30% 7%	300
	11th to 20th	Day	13% 14% 29% 33% 8% 3	300
	21st to end	Day	13% 10% 42% 22% 11% 1	330
February	1st to 10th	Day	17% 11% 37% 27% 8% 1	300
	11th to 20th	Day	19% 11% 40% 25% 5%	300
	21st to end	Day	20% 9% 42% 23% 5% 1	249
March	1st to 10th	Day	16% 13% 36% 28% 6%	300
	11th to 20th	Day	14% 14% 37% 27% 6% 2	300
	21st to end	Day	8% 12% 46% 25% 8%	330
April	1st to 10th	Day	11% 15% 39% 25% 9%	300
	11th to 20th	Day	14% 13% 47% 21% 5%	467
	21st to end	Day	12% 11% 41% 27% 9% 1	626
May	1st to 10th	Day	11% 10% 36% 35% 8%	703
	11th to 20th	Day	15% 6% 28% 32% 16% 3	725
	21st to end	Day	10% 5% 28% 37% 18% 3	789
June	1st to 10th	Day	6% 2 14% 43% 28% 6%	730
	11th to 20th	Day	5% 1 18% 47% 24% 6%	730
	21st to end	Day	4 1 9% 35% 38% 13%	730
July	1st to 10th	Day	7% 2 4 31% 41% 15%	721
	11th to 20th	Day	4 1 4 26% 48% 17%	718
	21st to end	Day	2 1 3 26% 46% 22%	794
August	1st to 10th	Day	1 1 2 25% 49% 22%	699
	11th to 20th	Day	7% 1 3 27% 40% 22%	517
	21st to end	Day	4 1 4 24% 38% 28%	573
September	1st to 10th	Day	11% 1 6% 16% 38% 28%	330
	11th to 20th	Day	5% 2 4 21% 44% 25%	324
	21st to end	Day	10% 1 4 28% 33% 24%	300
October	1st to 10th	Day	5% 12% 35% 31% 17%	300
	11th to 20th	Day	9% 2 26% 36% 26% 2	300
	21st to end	Day	18% 7% 24% 25% 24% 2	330
November	1st to 10th	Day	16% 5% 26% 33% 14% 6%	300
	11th to 20th	Day	8% 11% 28% 31% 17% 5%	300
	21st to end	Day	15% 9% 36% 25% 13% 2	300
December	1st to 10th	Day	17% 8% 28% 31% 13% 4	300
	11th to 20th	Day	7% 12% 41% 28% 11% 1	300
	21st to end	Day	20% 8% 35% 27% 9% 1	330
January	1st to 10th	Night	11% 8% 37% 36% 7%	1000
	11th to 20th	Night	13% 10% 34% 36% 7% 1	1000
	21st to end	Night	14% 9% 36% 33% 8%	975
February	1st to 10th	Night	14% 8% 39% 33% 6%	800
	11th to 20th	Night	15% 9% 41% 30% 4	784
	21st to end	Night	15% 10% 47% 24% 3	660
March	1st to 10th	Night	14% 12% 43% 28% 4	715
	11th to 20th	Night	16% 8% 41% 30% 5%	600
	21st to end	Night	9% 9% 49% 29% 4	660
April	1st to 10th	Night	7% 12% 50% 27% 4	600
	11th to 20th	Night	11% 10% 49% 26% 4	593
	21st to end	Night	9% 8% 50% 26% 7%	600
May	1st to 10th	Night	10% 10% 44% 33% 4	600
	11th to 20th	Night	10% 4 39% 36% 10% 1	591
	21st to end	Night	8% 4 36% 41% 10% 1	650
June	1st to 10th	Night	3 3 24% 51% 19% 2	600
	11th to 20th	Night	4 2 27% 55% 12% 1	600
	21st to end	Night	5% 1 13% 53% 27% 1	600
July	1st to 10th	Night	8% 1 7% 50% 30% 3	585
	11th to 20th	Night	4 1 7% 52% 36% 1	582
	21st to end	Night	2 5% 49% 42% 1	657
August	1st to 10th	Night	1 5% 50% 41% 3	597
	11th to 20th	Night	6% 1 3 45% 40% 4	594
	21st to end	Night	3 1 4 43% 46% 4	660
September	1st to 10th	Night	9% 1 8% 46% 34% 3	600
	11th to 20th	Night	10% 1 10% 43% 35% 1	594
	21st to end	Night	7% 1 12% 47% 32% 2	570
October	1st to 10th	Night	6% 2 19% 46% 26% 1	570
	11th to 20th	Night	9% 3 26% 46% 16% 1	638
	21st to end	Night	13% 6% 28% 36% 16% 1	836
November	1st to 10th	Night	12% 3 27% 42% 16%	878
	11th to 20th	Night	6% 7% 33% 40% 13% 1	1000
	21st to end	Night	15% 8% 33% 33% 11% 1	1000
December	1st to 10th	Night	12% 8% 32% 40% 8% 1	1000
	11th to 20th	Night	15% 8% 34% 35% 8%	1000
	21st to end	Night	13% 7% 37% 35% 8%	1100

Page generated at 2025-09-16 00:49:15. Version ac07

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