FoxStar II Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the FoxStar II Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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% 8% 3 5% 5% 3 4 4 5% 7% 43%	78566
	Night	13% 8% 3 5% 4 3 4 4 4 7% 46%	80779
Transparency	Day	41% 4 11% 25% 16% 3	78289
	Night	40% 4 11% 25% 17% 3	80576
Seeing	Day	17% 12% 28% 26% 14% 3	14552
	Night	17% 12% 32% 27% 12% 1	24592

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	13% 12% 4 6% 5% 2 4 3 4 6% 42%	2847
	11th to 20th	Day	12% 13% 4 7% 5% 3 4 3 4 5% 40%	2850
	21st to end	Day	19% 12% 4 7% 4 2 3 3 4 5% 37%	3135
February	1st to 10th	Day	15% 11% 4 8% 6% 3 4 4 3 6% 36%	1710
	11th to 20th	Day	15% 8% 5% 6% 5% 3 3 3 4 6% 41%	1678
	21st to end	Day	16% 10% 3 5% 4 3 3 6% 4 6% 38%	1574
March	1st to 10th	Day	15% 10% 4 6% 3 3 3 4 3 6% 42%	1980
	11th to 20th	Day	22% 10% 4 6% 4 2 4 3 4 6% 36%	1980
	21st to end	Day	21% 11% 4 7% 5% 2 4 5% 4 6% 30%	2178
April	1st to 10th	Day	13% 7% 2 6% 6% 3 5% 4 4 7% 43%	2137
	11th to 20th	Day	17% 9% 2 5% 5% 3 4 4 5% 5% 40%	2134
	21st to end	Day	20% 8% 3 6% 6% 3 4 4 5% 7% 35%	2160
May	1st to 10th	Day	20% 6% 3 5% 5% 3 5% 6% 5% 6% 36%	2319
	11th to 20th	Day	16% 5% 3 5% 5% 3 4 5% 5% 7% 42%	2302
	21st to end	Day	13% 6% 4 5% 7% 4 7% 6% 5% 9% 34%	2673
June	1st to 10th	Day	8% 5% 3 4 5% 3 5% 6% 6% 9% 47%	2520
	11th to 20th	Day	7% 5% 2 5% 5% 4 7% 5% 6% 9% 45%	2520
	21st to end	Day	5% 2 1 4 5% 3 5% 5% 6% 10% 54%	2520
July	1st to 10th	Day	10% 5% 2 5% 6% 3 6% 6% 7% 11% 41%	2421
	11th to 20th	Day	3 4 2 4 5% 4 6% 7% 8% 10% 49%	2340
	21st to end	Day	9% 5% 2 5% 5% 4 7% 6% 7% 9% 41%	2546
August	1st to 10th	Day	7% 5% 2 5% 6% 4 6% 6% 7% 10% 42%	2328
	11th to 20th	Day	8% 5% 3 4 5% 4 5% 6% 6% 9% 44%	2257
	21st to end	Day	8% 5% 2 4 4 3 5% 4 5% 7% 53%	2376
September	1st to 10th	Day	11% 4 3 4 5% 3 4 4 5% 7% 49%	2160
	11th to 20th	Day	10% 6% 2 5% 5% 3 4 4 5% 7% 49%	2107
	21st to end	Day	8% 5% 2 3 5% 3 4 5% 5% 7% 53%	1904
October	1st to 10th	Day	11% 5% 2 4 4 2 4 4 4 6% 54%	1800
	11th to 20th	Day	16% 5% 2 4 3 2 3 3 3 7% 52%	1800
	21st to end	Day	20% 8% 2 5% 3 2 2 3 4 4 46%	1980
November	1st to 10th	Day	12% 5% 2 3 3 2 2 3 4 5% 57%	1858
	11th to 20th	Day	14% 7% 2 6% 4 2 3 4 4 7% 47%	1699
	21st to end	Day	17% 7% 3 4 4 2 3 4 4 6% 46%	1520
December	1st to 10th	Day	14% 9% 4 4 4 2 4 5% 5% 6% 43%	1520
	11th to 20th	Day	14% 11% 4 7% 4 3 3 3 3 6% 42%	1918
	21st to end	Day	17% 17% 5% 7% 4 3 4 4 4 5% 29%	2815
January	1st to 10th	Night	12% 11% 4 10% 6% 3 4 4 4 4 39%	4108
	11th to 20th	Night	12% 7% 3 8% 9% 5% 6% 5% 4 5% 35%	4120
	21st to end	Night	22% 12% 5% 7% 4 2 2 3 3 5% 36%	4532
February	1st to 10th	Night	14% 12% 4 6% 5% 2 4 4 5% 7% 38%	2470
	11th to 20th	Night	14% 9% 5% 6% 3 2 3 4 4 7% 44%	2388
	21st to end	Night	16% 9% 3 5% 5% 3 3 3 4 6% 42%	1792
March	1st to 10th	Night	16% 8% 3 5% 4 3 4 3 4 5% 46%	1980
	11th to 20th	Night	20% 8% 3 6% 5% 2 3 4 4 5% 40%	1980
	21st to end	Night	21% 8% 4 6% 6% 3 4 4 5% 6% 33%	2178
April	1st to 10th	Night	9% 6% 2 5% 4 2 4 3 5% 8% 52%	1821
	11th to 20th	Night	14% 7% 3 4 5% 3 4 3 4 6% 47%	1775
	21st to end	Night	18% 6% 3 6% 4 3 5% 5% 4 7% 40%	1800
May	1st to 10th	Night	15% 5% 3 5% 4 2 5% 5% 5% 7% 43%	1638
	11th to 20th	Night	15% 5% 2 5% 4 3 4 4 4 7% 46%	1593
	21st to end	Night	12% 6% 4 6% 5% 3 5% 5% 5% 10% 40%	1599
June	1st to 10th	Night	6% 3 2 4 5% 3 4 4 8% 9% 53%	1440
	11th to 20th	Night	4 3 1 4 3 4 5% 5% 8% 10% 51%	1440
	21st to end	Night	3 2 1 2 3 2 3 4 6% 10% 63%	1440
July	1st to 10th	Night	8% 4 2 4 5% 2 4 4 7% 10% 49%	1534
	11th to 20th	Night	3 3 1 2 4 2 4 5% 5% 12% 58%	1620
	21st to end	Night	6% 3 2 3 5% 3 4 5% 7% 10% 52%	1772
August	1st to 10th	Night	5% 3 2 5% 4 3 5% 5% 6% 9% 53%	1611
	11th to 20th	Night	5% 4 2 4 3 3 4 4 6% 7% 57%	1644
	21st to end	Night	4 4 2 4 4 2 4 4 6% 8% 58%	1980
September	1st to 10th	Night	12% 4 1 4 4 3 3 4 4 7% 55%	1800
	11th to 20th	Night	10% 4 2 3 4 2 4 4 5% 8% 54%	1849
	21st to end	Night	7% 4 1 4 4 2 3 4 4 7% 59%	2037
October	1st to 10th	Night	8% 5% 1 3 3 2 3 3 5% 7% 60%	2160
	11th to 20th	Night	16% 5% 2 3 3 2 3 3 3 6% 54%	2160
	21st to end	Night	17% 7% 2 4 3 2 3 4 3 6% 49%	2376
November	1st to 10th	Night	12% 5% 2 3 3 2 3 3 4 5% 59%	2220
	11th to 20th	Night	13% 7% 2 5% 4 2 3 4 3 6% 51%	2474
	21st to end	Night	16% 9% 3 4 3 2 3 3 3 5% 48%	2660
December	1st to 10th	Night	14% 8% 3 5% 6% 3 4 4 5% 6% 41%	2660
	11th to 20th	Night	15% 10% 5% 6% 4 2 4 3 4 5% 42%	3279
	21st to end	Night	19% 17% 6% 7% 4 3 3 4 4 5% 29%	4849

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	46% 2 7% 28% 16% 1	2848
	11th to 20th	Day	47% 3 9% 27% 12% 1	2850
	21st to end	Day	52% 2 8% 19% 16% 4	3135
February	1st to 10th	Day	52% 4 9% 22% 12% 1	1710
	11th to 20th	Day	45% 3 13% 19% 15% 4	1687
	21st to end	Day	47% 4 7% 23% 14% 5%	1574
March	1st to 10th	Day	45% 3 9% 21% 17% 5%	1980
	11th to 20th	Day	52% 3 9% 20% 13% 3	1980
	21st to end	Day	56% 4 12% 18% 9% 1	2178
April	1st to 10th	Day	41% 4 11% 26% 16% 2	2137
	11th to 20th	Day	45% 4 13% 22% 14% 2	2134
	21st to end	Day	50% 4 11% 23% 11% 1	2160
May	1st to 10th	Day	48% 6% 12% 21% 12% 1	2319
	11th to 20th	Day	42% 5% 14% 24% 14% 1	2306
	21st to end	Day	47% 6% 13% 22% 11% 1	2673
June	1st to 10th	Day	33% 5% 17% 27% 16% 1	2520
	11th to 20th	Day	34% 6% 14% 29% 14% 3	2520
	21st to end	Day	25% 6% 17% 33% 16% 4	2520
July	1st to 10th	Day	36% 7% 15% 26% 13% 3	2357
	11th to 20th	Day	26% 7% 16% 27% 20% 4	2271
	21st to end	Day	36% 7% 14% 31% 12% 1	2405
August	1st to 10th	Day	35% 7% 19% 25% 14% 1	2314
	11th to 20th	Day	34% 6% 14% 30% 15% 1	2257
	21st to end	Day	30% 5% 11% 26% 21% 7%	2376
September	1st to 10th	Day	34% 4 12% 28% 16% 5%	2160
	11th to 20th	Day	34% 5% 7% 26% 26% 2	2107
	21st to end	Day	30% 6% 9% 28% 24% 4	1904
October	1st to 10th	Day	33% 3 9% 27% 23% 5%	1800
	11th to 20th	Day	35% 3 7% 29% 21% 6%	1800
	21st to end	Day	43% 3 7% 23% 18% 5%	1980
November	1st to 10th	Day	32% 3 10% 28% 23% 5%	1858
	11th to 20th	Day	38% 3 9% 22% 24% 4	1699
	21st to end	Day	41% 4 8% 27% 18% 2	1520
December	1st to 10th	Day	42% 4 10% 30% 13% 1	1520
	11th to 20th	Day	46% 3 8% 24% 18% 2	1915
	21st to end	Day	59% 3 9% 19% 10% 1	2815
January	1st to 10th	Night	49% 3 11% 23% 13% 1	4108
	11th to 20th	Night	51% 5% 9% 24% 10% 1	4120
	21st to end	Night	54% 3 9% 21% 12% 1	4532
February	1st to 10th	Night	46% 3 11% 24% 14% 2	2470
	11th to 20th	Night	42% 3 10% 25% 16% 3	2389
	21st to end	Night	45% 3 8% 23% 16% 5%	1792
March	1st to 10th	Night	42% 3 8% 22% 20% 6%	1980
	11th to 20th	Night	48% 4 9% 21% 16% 3	1980
	21st to end	Night	53% 4 11% 21% 9% 1	2178
April	1st to 10th	Night	32% 3 14% 26% 21% 4	1821
	11th to 20th	Night	39% 3 10% 24% 18% 5%	1775
	21st to end	Night	45% 4 11% 24% 15% 1	1800
May	1st to 10th	Night	39% 6% 12% 25% 17% 1	1638
	11th to 20th	Night	39% 5% 14% 24% 16% 2	1594
	21st to end	Night	40% 7% 14% 26% 11% 2	1600
June	1st to 10th	Night	26% 5% 18% 31% 18% 3	1440
	11th to 20th	Night	25% 6% 15% 29% 21% 4	1440
	21st to end	Night	17% 5% 18% 34% 21% 6%	1440
July	1st to 10th	Night	28% 6% 16% 30% 15% 5%	1489
	11th to 20th	Night	19% 5% 14% 34% 25% 3	1566
	21st to end	Night	27% 5% 14% 38% 16% 1	1673
August	1st to 10th	Night	25% 7% 18% 35% 13% 1	1601
	11th to 20th	Night	26% 4 10% 36% 22% 2	1644
	21st to end	Night	24% 4 14% 28% 24% 7%	1980
September	1st to 10th	Night	30% 4 10% 30% 20% 6%	1800
	11th to 20th	Night	29% 5% 10% 24% 27% 5%	1849
	21st to end	Night	26% 3 9% 28% 29% 4	2037
October	1st to 10th	Night	25% 3 11% 29% 26% 6%	2160
	11th to 20th	Night	33% 3 7% 27% 23% 6%	2160
	21st to end	Night	38% 3 8% 23% 22% 6%	2376
November	1st to 10th	Night	30% 2 10% 28% 23% 7%	2220
	11th to 20th	Night	36% 3 6% 26% 24% 5%	2474
	21st to end	Night	41% 3 8% 26% 19% 3	2660
December	1st to 10th	Night	45% 3 11% 23% 17% 2	2660
	11th to 20th	Night	46% 3 9% 24% 17% 1	3281
	21st to end	Night	59% 4 10% 16% 9% 2	4849

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	23% 20% 40% 16% 1	270
	11th to 20th	Day	30% 22% 38% 9% 1	270
	21st to end	Day	21% 24% 42% 10% 2	297
February	1st to 10th	Day	26% 24% 37% 12% 1	270
	11th to 20th	Day	27% 28% 31% 13% 1	270
	21st to end	Day	29% 26% 36% 8% 2	210
March	1st to 10th	Day	26% 23% 38% 11% 2	240
	11th to 20th	Day	34% 20% 29% 15% 2	240
	21st to end	Day	33% 27% 31% 8% 2	264
April	1st to 10th	Day	20% 22% 36% 17% 5%	397
	11th to 20th	Day	28% 18% 33% 17% 4	412
	21st to end	Day	26% 15% 38% 16% 5%	420
May	1st to 10th	Day	25% 14% 36% 20% 5%	582
	11th to 20th	Day	21% 12% 32% 25% 9% 2	625
	21st to end	Day	16% 10% 32% 26% 12% 4	679
June	1st to 10th	Day	10% 5% 24% 35% 21% 6%	630
	11th to 20th	Day	8% 5% 27% 37% 20% 3	630
	21st to end	Day	7% 6% 32% 36% 16% 3	630
July	1st to 10th	Day	11% 3 17% 32% 30% 7%	621
	11th to 20th	Day	5% 3 21% 40% 26% 6%	618
	21st to end	Day	11% 2 15% 39% 29% 5%	684
August	1st to 10th	Day	9% 3 17% 43% 24% 4	626
	11th to 20th	Day	10% 3 19% 38% 25% 6%	571
	21st to end	Day	11% 3 15% 33% 29% 9%	495
September	1st to 10th	Day	12% 5% 15% 39% 24% 5%	450
	11th to 20th	Day	9% 2 23% 37% 23% 6%	397
	21st to end	Day	11% 7% 29% 33% 16% 4	270
October	1st to 10th	Day	15% 11% 30% 27% 13% 4	270
	11th to 20th	Day	18% 19% 41% 19% 3	270
	21st to end	Day	35% 15% 30% 16% 3	297
November	1st to 10th	Day	19% 12% 43% 18% 6% 2	270
	11th to 20th	Day	19% 23% 32% 20% 5% 1	270
	21st to end	Day	30% 17% 27% 20% 5%	270
December	1st to 10th	Day	21% 21% 34% 16% 6% 2	270
	11th to 20th	Day	26% 18% 36% 16% 4 1	270
	21st to end	Day	25% 28% 36% 9% 2	297
January	1st to 10th	Night	19% 19% 37% 20% 5%	950
	11th to 20th	Night	21% 23% 36% 17% 3	950
	21st to end	Night	19% 21% 38% 22% 2	1045
February	1st to 10th	Night	21% 20% 40% 16% 3	950
	11th to 20th	Night	22% 19% 39% 18% 2	914
	21st to end	Night	25% 21% 37% 15% 3	572
March	1st to 10th	Night	21% 17% 38% 21% 3	540
	11th to 20th	Night	25% 13% 36% 22% 4	540
	21st to end	Night	27% 15% 35% 19% 4	594
April	1st to 10th	Night	15% 18% 40% 22% 5%	540
	11th to 20th	Night	18% 14% 36% 25% 6%	533
	21st to end	Night	22% 10% 38% 24% 6%	540
May	1st to 10th	Night	16% 8% 38% 31% 7%	540
	11th to 20th	Night	18% 7% 28% 32% 13% 1	531
	21st to end	Night	16% 7% 30% 29% 17% 2	584
June	1st to 10th	Night	8% 4 19% 41% 25% 2	540
	11th to 20th	Night	7% 2 28% 41% 21% 2	540
	21st to end	Night	4 2 31% 43% 18% 2	540
July	1st to 10th	Night	11% 1 14% 40% 30% 4	525
	11th to 20th	Night	3 2 20% 44% 28% 2	522
	21st to end	Night	7% 1 16% 40% 33% 2	591
August	1st to 10th	Night	8% 1 16% 43% 30% 2	537
	11th to 20th	Night	7% 2 15% 46% 27% 4	534
	21st to end	Night	5% 2 16% 37% 36% 4	594
September	1st to 10th	Night	12% 2 16% 41% 25% 3	540
	11th to 20th	Night	13% 2 17% 37% 27% 4	540
	21st to end	Night	10% 5% 23% 38% 21% 3	597
October	1st to 10th	Night	11% 7% 29% 29% 21% 3	720
	11th to 20th	Night	20% 9% 38% 26% 7%	720
	21st to end	Night	22% 13% 35% 23% 8%	792
November	1st to 10th	Night	14% 12% 41% 24% 9% 1	740
	11th to 20th	Night	18% 16% 35% 24% 7%	802
	21st to end	Night	23% 14% 37% 20% 6%	950
December	1st to 10th	Night	21% 14% 39% 20% 5%	950
	11th to 20th	Night	24% 15% 35% 22% 4	950
	21st to end	Night	23% 19% 37% 19% 2	1045

Page generated at 2024-02-22 05:05:41. Version ac07

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