Starfest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starfest clear sky chart from 2005-11-06 to 2024-01-16.

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% 12% 5% 8% 6% 3 5% 4 5% 7% 29%	74852
	Night	16% 13% 6% 9% 7% 3 5% 4 5% 6% 27%	74915
Transparency	Day	55% 7% 11% 17% 9% 1	74559
	Night	58% 6% 10% 16% 9% 1	74743
Seeing	Day	21% 12% 29% 22% 12% 4	13908
	Night	22% 11% 29% 27% 10% 1	23237

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	15% 16% 10% 18% 11% 5% 4 3 3 3 12%	1351
	11th to 20th	Day	15% 20% 10% 16% 10% 5% 4 4 3 4 11%	1624
	21st to end	Day	12% 18% 10% 16% 10% 4 6% 4 4 4 12%	1782
February	1st to 10th	Day	14% 19% 8% 18% 11% 5% 4 3 3 4 10%	1620
	11th to 20th	Day	14% 15% 9% 17% 11% 3 4 4 5% 5% 13%	1573
	21st to end	Day	16% 20% 8% 12% 9% 4 6% 3 3 4 16%	1435
March	1st to 10th	Day	14% 14% 5% 12% 9% 4 4 4 4 5% 25%	1931
	11th to 20th	Day	13% 12% 8% 10% 7% 4 5% 4 3 6% 27%	1980
	21st to end	Day	18% 12% 5% 7% 6% 3 5% 5% 4 6% 28%	2178
April	1st to 10th	Day	18% 15% 6% 10% 5% 3 4 4 5% 6% 25%	2072
	11th to 20th	Day	19% 12% 4 6% 4 2 4 4 5% 6% 35%	2291
	21st to end	Day	21% 11% 4 6% 5% 3 4 3 4 7% 31%	2340
May	1st to 10th	Day	19% 8% 4 8% 4 3 3 4 6% 6% 34%	2340
	11th to 20th	Day	17% 9% 3 6% 5% 3 4 4 4 7% 38%	2387
	21st to end	Day	14% 5% 3 5% 5% 3 5% 5% 6% 8% 41%	2725
June	1st to 10th	Day	15% 7% 3 5% 5% 3 5% 5% 6% 7% 38%	2564
	11th to 20th	Day	13% 6% 2 5% 5% 3 5% 5% 6% 9% 41%	2700
	21st to end	Day	17% 6% 2 5% 4 3 4 5% 6% 9% 39%	2700
July	1st to 10th	Day	10% 5% 2 6% 4 3 5% 6% 7% 8% 45%	2700
	11th to 20th	Day	12% 7% 2 6% 6% 3 6% 5% 7% 8% 37%	2560
	21st to end	Day	11% 6% 3 6% 6% 4 5% 5% 6% 10% 37%	2547
August	1st to 10th	Day	12% 6% 2 6% 6% 4 5% 6% 8% 11% 35%	2327
	11th to 20th	Day	13% 6% 3 6% 7% 5% 6% 7% 7% 8% 34%	2303
	21st to end	Day	13% 7% 2 6% 6% 3 4 5% 7% 9% 37%	2540
September	1st to 10th	Day	15% 7% 3 7% 5% 4 4 4 6% 9% 37%	2150
	11th to 20th	Day	14% 6% 3 6% 5% 4 5% 4 6% 8% 41%	1980
	21st to end	Day	17% 9% 3 6% 6% 3 4 6% 6% 7% 33%	1980
October	1st to 10th	Day	20% 11% 3 6% 6% 3 5% 4 4 5% 33%	1816
	11th to 20th	Day	26% 14% 4 7% 6% 4 5% 4 5% 6% 20%	1800
	21st to end	Day	28% 17% 5% 7% 6% 3 4 4 4 5% 17%	1941
November	1st to 10th	Day	17% 19% 4 8% 6% 3 5% 4 4 6% 25%	1634
	11th to 20th	Day	17% 17% 7% 11% 7% 3 4 6% 4 6% 19%	1520
	21st to end	Day	19% 22% 9% 9% 7% 3 4 4 4 5% 13%	1520
December	1st to 10th	Day	15% 24% 12% 17% 8% 3 4 3 2 4 7%	1520
	11th to 20th	Day	19% 20% 9% 14% 8% 3 4 4 4 5% 11%	1906
	21st to end	Day	25% 22% 9% 13% 7% 3 3 3 3 4 9%	2515
January	1st to 10th	Night	17% 17% 9% 16% 10% 4 4 3 4 4 11%	2810
	11th to 20th	Night	19% 19% 8% 15% 10% 4 5% 3 3 4 10%	2441
	21st to end	Night	12% 16% 9% 14% 12% 6% 6% 5% 4 4 12%	2574
February	1st to 10th	Night	15% 19% 7% 14% 11% 5% 6% 4 4 4 12%	2340
	11th to 20th	Night	14% 15% 10% 13% 9% 4 5% 4 4 4 18%	2273
	21st to end	Night	16% 14% 7% 12% 9% 3 5% 4 4 5% 20%	1816
March	1st to 10th	Night	14% 11% 6% 12% 7% 3 5% 4 5% 4 28%	2015
	11th to 20th	Night	13% 14% 5% 9% 7% 4 5% 4 4 6% 29%	1979
	21st to end	Night	17% 11% 5% 7% 6% 3 5% 4 4 5% 33%	2178
April	1st to 10th	Night	19% 13% 5% 8% 5% 3 4 4 5% 6% 28%	1886
	11th to 20th	Night	17% 11% 3 5% 5% 3 4 4 4 7% 36%	1633
	21st to end	Night	16% 13% 4 7% 6% 4 4 5% 4 6% 31%	1620
May	1st to 10th	Night	16% 8% 4 7% 5% 3 4 5% 5% 7% 36%	1620
	11th to 20th	Night	15% 7% 3 5% 5% 3 5% 4 5% 6% 41%	1505
	21st to end	Night	10% 4 2 5% 5% 3 5% 4 6% 8% 47%	1550
June	1st to 10th	Night	14% 6% 3 6% 5% 3 6% 3 5% 9% 41%	1390
	11th to 20th	Night	12% 5% 2 4 6% 4 4 7% 5% 9% 42%	1260
	21st to end	Night	15% 4 3 5% 4 3 4 5% 5% 8% 44%	1260
July	1st to 10th	Night	8% 4 3 3 4 2 4 3 6% 8% 54%	1260
	11th to 20th	Night	11% 5% 2 5% 4 2 4 5% 6% 9% 47%	1393
	21st to end	Night	9% 5% 2 6% 6% 3 5% 5% 6% 8% 45%	1771
August	1st to 10th	Night	10% 5% 2 5% 6% 3 4 5% 5% 8% 47%	1611
	11th to 20th	Night	11% 4 2 5% 4 3 4 5% 6% 8% 48%	1598
	21st to end	Night	12% 5% 2 6% 6% 3 5% 5% 4 8% 43%	1797
September	1st to 10th	Night	12% 5% 3 6% 5% 3 4 5% 6% 7% 44%	1808
	11th to 20th	Night	13% 6% 2 4 5% 3 4 3 6% 7% 48%	1980
	21st to end	Night	15% 8% 4 6% 5% 3 3 4 5% 7% 39%	1980
October	1st to 10th	Night	18% 9% 3 7% 5% 3 4 3 5% 7% 36%	2142
	11th to 20th	Night	25% 12% 3 7% 5% 4 4 4 5% 7% 24%	2160
	21st to end	Night	25% 15% 3 6% 7% 3 5% 4 5% 5% 21%	2412
November	1st to 10th	Night	18% 13% 4 8% 6% 4 4 4 4 5% 28%	2441
	11th to 20th	Night	18% 17% 5% 9% 6% 4 4 5% 5% 6% 20%	2660
	21st to end	Night	20% 19% 7% 9% 7% 3 4 4 4 6% 16%	2660
December	1st to 10th	Night	20% 24% 11% 12% 6% 4 3 4 3 4 10%	2660
	11th to 20th	Night	15% 20% 10% 13% 8% 3 4 4 4 5% 14%	3288
	21st to end	Night	23% 21% 8% 15% 8% 3 4 3 3 3 7%	5144

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	79% 3 9% 7% 2	1352
	11th to 20th	Day	79% 5% 4 6% 4 1	1624
	21st to end	Day	75% 5% 8% 7% 5% 1	1782
February	1st to 10th	Day	80% 5% 4 8% 2	1620
	11th to 20th	Day	73% 5% 7% 9% 5% 1	1582
	21st to end	Day	72% 5% 7% 10% 5%	1435
March	1st to 10th	Day	62% 5% 11% 13% 8% 1	1934
	11th to 20th	Day	58% 6% 9% 15% 9% 2	1980
	21st to end	Day	56% 6% 10% 16% 11% 2	2178
April	1st to 10th	Day	60% 6% 9% 16% 9%	2072
	11th to 20th	Day	50% 6% 10% 20% 13% 1	2291
	21st to end	Day	54% 6% 10% 17% 11% 2	2340
May	1st to 10th	Day	49% 6% 9% 21% 14% 1	2340
	11th to 20th	Day	47% 5% 10% 22% 13% 1	2391
	21st to end	Day	40% 6% 15% 22% 14% 2	2725
June	1st to 10th	Day	44% 7% 11% 23% 15% 1	2564
	11th to 20th	Day	40% 7% 11% 25% 16% 1	2700
	21st to end	Day	41% 8% 13% 24% 13% 1	2700
July	1st to 10th	Day	35% 8% 13% 23% 19% 2	2626
	11th to 20th	Day	40% 9% 13% 25% 11% 1	2479
	21st to end	Day	41% 9% 12% 23% 13% 2	2405
August	1st to 10th	Day	41% 9% 16% 23% 10% 2	2314
	11th to 20th	Day	44% 10% 14% 22% 10%	2303
	21st to end	Day	42% 9% 14% 23% 11% 1	2540
September	1st to 10th	Day	44% 8% 13% 22% 11% 3	2150
	11th to 20th	Day	40% 7% 13% 29% 11%	1980
	21st to end	Day	48% 8% 13% 23% 7% 1	1980
October	1st to 10th	Day	53% 7% 10% 16% 12% 2	1816
	11th to 20th	Day	64% 7% 10% 13% 6% 1	1800
	21st to end	Day	69% 7% 8% 11% 5%	1941
November	1st to 10th	Day	60% 6% 11% 16% 7%	1634
	11th to 20th	Day	66% 7% 11% 9% 6% 1	1520
	21st to end	Day	73% 6% 9% 9% 2	1520
December	1st to 10th	Day	82% 6% 5% 6% 1	1520
	11th to 20th	Day	76% 7% 8% 7% 3	1906
	21st to end	Day	81% 7% 6% 5% 1	2515
January	1st to 10th	Night	77% 4 8% 7% 4	2810
	11th to 20th	Night	79% 5% 8% 4 4	2441
	21st to end	Night	74% 6% 9% 6% 4 1	2574
February	1st to 10th	Night	77% 5% 7% 9% 1	2340
	11th to 20th	Night	69% 4 9% 12% 5%	2275
	21st to end	Night	66% 6% 8% 12% 7%	1816
March	1st to 10th	Night	58% 6% 10% 16% 8% 1	2025
	11th to 20th	Night	55% 7% 8% 17% 11% 2	1980
	21st to end	Night	55% 4 8% 18% 13% 2	2178
April	1st to 10th	Night	58% 5% 8% 17% 11% 1	1886
	11th to 20th	Night	49% 6% 8% 20% 16% 1	1633
	21st to end	Night	53% 7% 9% 15% 14% 2	1620
May	1st to 10th	Night	47% 7% 8% 22% 14% 2	1620
	11th to 20th	Night	43% 6% 9% 24% 16% 3	1506
	21st to end	Night	34% 8% 14% 25% 15% 4	1551
June	1st to 10th	Night	41% 6% 11% 25% 17% 1	1390
	11th to 20th	Night	38% 7% 13% 25% 16% 2	1260
	21st to end	Night	38% 8% 11% 26% 16% 1	1260
July	1st to 10th	Night	26% 7% 12% 28% 23% 3	1225
	11th to 20th	Night	34% 7% 12% 29% 17% 1	1351
	21st to end	Night	35% 8% 14% 25% 15% 2	1672
August	1st to 10th	Night	34% 8% 15% 28% 13% 1	1600
	11th to 20th	Night	32% 8% 15% 29% 15% 2	1598
	21st to end	Night	40% 8% 10% 28% 13% 1	1797
September	1st to 10th	Night	37% 8% 12% 27% 13% 2	1808
	11th to 20th	Night	36% 6% 14% 29% 15% 1	1980
	21st to end	Night	45% 7% 13% 24% 10% 1	1980
October	1st to 10th	Night	48% 8% 11% 18% 14% 1	2142
	11th to 20th	Night	58% 7% 11% 17% 6%	2160
	21st to end	Night	64% 7% 11% 12% 7%	2412
November	1st to 10th	Night	57% 8% 11% 17% 7% 1	2441
	11th to 20th	Night	63% 8% 11% 13% 5% 2	2660
	21st to end	Night	69% 7% 11% 10% 3	2660
December	1st to 10th	Night	80% 6% 7% 5% 1	2660
	11th to 20th	Night	73% 6% 10% 9% 2	3288
	21st to end	Night	83% 6% 6% 4 1	5144

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	24% 14% 39% 17% 5% 1	191
	11th to 20th	Day	21% 19% 39% 14% 6%	255
	21st to end	Day	25% 17% 33% 21% 4	264
February	1st to 10th	Day	29% 20% 37% 10% 4	240
	11th to 20th	Day	23% 22% 42% 12% 1	240
	21st to end	Day	29% 32% 28% 10% 1	198
March	1st to 10th	Day	25% 16% 38% 13% 7% 1	374
	11th to 20th	Day	23% 13% 39% 18% 6% 2	420
	21st to end	Day	29% 12% 33% 19% 7% 1	462
April	1st to 10th	Day	24% 15% 34% 20% 6% 1	420
	11th to 20th	Day	29% 14% 26% 16% 10% 5%	412
	21st to end	Day	26% 13% 29% 23% 6% 3	420
May	1st to 10th	Day	25% 10% 26% 24% 12% 2	423
	11th to 20th	Day	20% 10% 28% 23% 15% 4	447
	21st to end	Day	18% 8% 24% 27% 17% 6%	485
June	1st to 10th	Day	15% 12% 25% 31% 15% 2	494
	11th to 20th	Day	16% 8% 30% 30% 13% 4	630
	21st to end	Day	18% 6% 32% 28% 13% 2	630
July	1st to 10th	Day	11% 6% 26% 28% 23% 7%	621
	11th to 20th	Day	15% 7% 26% 29% 15% 8%	538
	21st to end	Day	10% 5% 29% 34% 16% 6%	488
August	1st to 10th	Day	12% 6% 23% 28% 20% 12%	446
	11th to 20th	Day	15% 4 18% 26% 23% 13%	439
	21st to end	Day	14% 6% 23% 26% 20% 9%	495
September	1st to 10th	Day	16% 7% 25% 26% 15% 11%	450
	11th to 20th	Day	10% 7% 21% 27% 24% 11%	450
	21st to end	Day	17% 11% 26% 24% 15% 6%	450
October	1st to 10th	Day	24% 10% 28% 18% 16% 4	450
	11th to 20th	Day	28% 19% 29% 19% 4 1	450
	21st to end	Day	35% 16% 27% 16% 5% 1	456
November	1st to 10th	Day	33% 13% 29% 17% 8%	252
	11th to 20th	Day	25% 22% 35% 12% 3 3	180
	21st to end	Day	29% 21% 36% 13% 2	180
December	1st to 10th	Day	29% 27% 28% 14% 1	180
	11th to 20th	Day	26% 25% 34% 12% 3	180
	21st to end	Day	36% 18% 34% 11% 1	198
January	1st to 10th	Night	22% 18% 36% 18% 5% 1	950
	11th to 20th	Night	29% 15% 32% 20% 4 1	776
	21st to end	Night	19% 11% 36% 27% 6% 1	792
February	1st to 10th	Night	24% 16% 37% 20% 2	720
	11th to 20th	Night	22% 14% 37% 23% 4	703
	21st to end	Night	24% 18% 35% 20% 3 1	592
March	1st to 10th	Night	19% 15% 38% 21% 6% 1	720
	11th to 20th	Night	20% 16% 36% 22% 6% 1	720
	21st to end	Night	23% 11% 31% 25% 9% 1	792
April	1st to 10th	Night	26% 13% 30% 27% 4	720
	11th to 20th	Night	22% 14% 28% 23% 11% 1	569
	21st to end	Night	24% 10% 29% 28% 9% 1	540
May	1st to 10th	Night	20% 6% 26% 34% 12% 2	540
	11th to 20th	Night	20% 5% 27% 35% 12% 1	444
	21st to end	Night	12% 4 28% 39% 18%	389
June	1st to 10th	Night	16% 3 29% 39% 12%	360
	11th to 20th	Night	13% 7% 28% 39% 12%	360
	21st to end	Night	17% 5% 24% 38% 15% 1	360
July	1st to 10th	Night	7% 3 17% 50% 22% 1	350
	11th to 20th	Night	15% 3 21% 37% 23% 1	405
	21st to end	Night	11% 4 20% 43% 21% 1	591
August	1st to 10th	Night	12% 3 16% 39% 29% 1	537
	11th to 20th	Night	10% 3 17% 37% 30% 4	534
	21st to end	Night	15% 3 22% 31% 27% 2	609
September	1st to 10th	Night	14% 5% 23% 34% 18% 5%	720
	11th to 20th	Night	16% 3 22% 33% 21% 5%	720
	21st to end	Night	18% 8% 23% 30% 18% 4	720
October	1st to 10th	Night	22% 8% 26% 27% 14% 2	720
	11th to 20th	Night	28% 10% 27% 26% 7% 1	720
	21st to end	Night	33% 11% 30% 22% 4	792
November	1st to 10th	Night	25% 14% 28% 25% 7% 1	740
	11th to 20th	Night	26% 18% 31% 18% 6% 1	760
	21st to end	Night	28% 15% 32% 22% 3	760
December	1st to 10th	Night	32% 17% 30% 18% 4	760
	11th to 20th	Night	22% 19% 39% 16% 3 1	760
	21st to end	Night	31% 15% 34% 17% 2	992

Page generated at 2024-01-13 01:38:13. Version ac07

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