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 2024-12-06.

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	15% 12% 4 10% 5% 5% 4 3 5% 6% 29%	101916
	Night	15% 13% 5% 11% 6% 5% 4 3 4 5% 28%	97814
Transparency	Day	53% 7% 11% 18% 10% 1	105476
	Night	56% 7% 10% 17% 9% 1	102331
Seeing	Day	21% 12% 29% 22% 12% 4	15134
	Night	21% 11% 29% 27% 10% 1	24337

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	14% 21% 11% 19% 7% 5% 4 2 3 3 12%	2244
	11th to 20th	Day	10% 22% 9% 21% 13% 9% 3 2 2 2 6%	2775
	21st to end	Day	17% 23% 10% 17% 6% 5% 4 2 3 4 10%	3124
February	1st to 10th	Day	13% 20% 7% 19% 10% 6% 4 3 3 4 11%	1710
	11th to 20th	Day	13% 16% 10% 18% 9% 4 4 3 5% 5% 13%	1663
	21st to end	Day	15% 20% 7% 13% 7% 5% 5% 3 4 4 16%	1522
March	1st to 10th	Day	17% 15% 5% 12% 6% 4 3 3 3 5% 26%	3362
	11th to 20th	Day	12% 17% 9% 13% 5% 4 4 3 4 5% 24%	3480
	21st to end	Day	16% 14% 5% 10% 6% 4 5% 4 5% 5% 26%	3815
April	1st to 10th	Day	17% 16% 5% 10% 5% 4 3 3 5% 5% 26%	2188
	11th to 20th	Day	19% 13% 3 6% 4 3 3 3 5% 5% 35%	2420
	21st to end	Day	21% 12% 4 7% 4 4 3 3 4 7% 32%	2470
May	1st to 10th	Day	18% 9% 3 8% 4 4 4 3 6% 7% 34%	4108
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 4 5% 8% 33%	4237
	21st to end	Day	16% 5% 2 5% 4 4 4 3 4 7% 46%	4837
June	1st to 10th	Day	15% 8% 3 7% 4 5% 4 4 6% 7% 36%	2707
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 9% 41%	2850
	21st to end	Day	18% 7% 2 6% 4 4 4 4 6% 8% 37%	2850
July	1st to 10th	Day	13% 6% 3 8% 4 6% 6% 5% 7% 8% 35%	4760
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 7% 41%	4494
	21st to end	Day	9% 6% 3 6% 4 5% 5% 4 7% 9% 42%	4466
August	1st to 10th	Day	14% 7% 2 7% 5% 6% 6% 4 7% 8% 34%	4104
	11th to 20th	Day	14% 8% 3 7% 5% 6% 5% 5% 7% 8% 31%	4044
	21st to end	Day	10% 6% 2 7% 4 5% 5% 4 8% 9% 41%	4470
September	1st to 10th	Day	15% 7% 3 8% 4 5% 4 3 6% 8% 38%	2269
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 6% 8% 43%	2090
	21st to end	Day	16% 9% 3 7% 4 4 5% 4 6% 7% 33%	2090
October	1st to 10th	Day	19% 11% 3 7% 5% 4 5% 3 4 5% 33%	1916
	11th to 20th	Day	24% 14% 4 8% 5% 5% 5% 3 5% 6% 22%	1900
	21st to end	Day	26% 18% 4 8% 5% 4 4 3 5% 5% 17%	2048
November	1st to 10th	Day	16% 20% 3 9% 5% 4 4 3 4 6% 26%	1722
	11th to 20th	Day	16% 19% 5% 12% 6% 4 5% 4 4 6% 19%	1600
	21st to end	Day	18% 24% 9% 11% 6% 4 4 3 4 5% 12%	1600
December	1st to 10th	Day	15% 27% 10% 17% 7% 4 4 2 3 4 7%	1560
	11th to 20th	Day	18% 21% 8% 15% 6% 4 4 4 4 5% 11%	1906
	21st to end	Day	25% 23% 8% 14% 5% 4 3 2 4 4 9%	2515
January	1st to 10th	Night	15% 22% 10% 22% 7% 5% 3 2 3 3 8%	4707
	11th to 20th	Night	13% 16% 10% 23% 14% 8% 4 2 2 3 6%	4181
	21st to end	Night	17% 19% 10% 16% 9% 6% 4 3 3 3 8%	4532
February	1st to 10th	Night	14% 21% 6% 15% 10% 6% 5% 3 4 4 13%	2470
	11th to 20th	Night	13% 16% 10% 14% 8% 5% 5% 3 5% 4 18%	2403
	21st to end	Night	15% 15% 5% 13% 7% 5% 5% 4 5% 5% 20%	1927
March	1st to 10th	Night	14% 14% 5% 9% 5% 4 4 3 5% 5% 31%	3477
	11th to 20th	Night	10% 17% 6% 10% 5% 5% 5% 3 4 6% 30%	3479
	21st to end	Night	15% 11% 5% 12% 6% 5% 4 3 4 5% 31%	3817
April	1st to 10th	Night	19% 15% 4 9% 4 4 4 3 4 6% 28%	1990
	11th to 20th	Night	18% 12% 3 5% 4 4 4 3 4 6% 35%	1725
	21st to end	Night	16% 13% 4 8% 5% 5% 4 4 4 5% 31%	1710
May	1st to 10th	Night	15% 8% 3 7% 4 3 4 4 5% 7% 40%	2833
	11th to 20th	Night	16% 8% 2 7% 5% 5% 5% 3 5% 6% 38%	2655
	21st to end	Night	11% 5% 2 6% 4 4 4 3 5% 7% 48%	2738
June	1st to 10th	Night	14% 7% 3 7% 4 4 5% 3 5% 8% 40%	1467
	11th to 20th	Night	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 40%	1330
	21st to end	Night	15% 5% 3 5% 4 3 5% 4 5% 8% 43%	1330
July	1st to 10th	Night	8% 6% 2 6% 4 4 4 3 6% 8% 49%	2210
	11th to 20th	Night	14% 6% 1 5% 3 3 3 4 5% 7% 50%	2464
	21st to end	Night	7% 7% 2 7% 5% 4 5% 4 6% 8% 46%	3087
August	1st to 10th	Night	12% 6% 3 7% 5% 4 4 3 5% 6% 46%	2825
	11th to 20th	Night	17% 8% 3 6% 4 4 5% 3 5% 7% 39%	2785
	21st to end	Night	14% 5% 2 6% 4 4 4 3 4 7% 46%	3153
September	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 6% 7% 45%	1909
	11th to 20th	Night	13% 6% 2 4 4 3 4 2 5% 7% 49%	2090
	21st to end	Night	15% 9% 3 8% 4 4 3 3 5% 7% 38%	2090
October	1st to 10th	Night	18% 8% 3 8% 4 4 4 3 5% 7% 37%	2262
	11th to 20th	Night	23% 12% 3 8% 4 5% 4 3 5% 7% 26%	2280
	21st to end	Night	24% 15% 3 8% 5% 5% 4 3 5% 6% 22%	2546
November	1st to 10th	Night	18% 15% 4 9% 6% 5% 4 3 5% 5% 27%	2573
	11th to 20th	Night	17% 19% 5% 10% 6% 5% 4 4 5% 6% 20%	2800
	21st to end	Night	20% 20% 7% 10% 6% 5% 3 3 5% 6% 15%	2800
December	1st to 10th	Night	19% 26% 8% 13% 5% 5% 4 3 4 4 9%	2737
	11th to 20th	Night	14% 22% 10% 15% 6% 4 4 3 4 5% 14%	3288
	21st to end	Night	23% 22% 8% 16% 6% 5% 4 2 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	76% 6% 9% 7% 3	2245
	11th to 20th	Day	87% 4 3 3 2 1	2775
	21st to end	Day	79% 5% 7% 5% 3	3124
February	1st to 10th	Day	78% 5% 4 9% 3	1710
	11th to 20th	Day	73% 5% 7% 9% 5% 1	1672
	21st to end	Day	71% 5% 7% 11% 5%	1522
March	1st to 10th	Day	61% 5% 11% 14% 8% 1	3365
	11th to 20th	Day	61% 7% 10% 16% 5% 1	3480
	21st to end	Day	56% 7% 12% 14% 9% 2	3815
April	1st to 10th	Day	60% 5% 8% 17% 9%	2188
	11th to 20th	Day	50% 6% 9% 20% 13% 1	2420
	21st to end	Day	53% 6% 10% 17% 12% 2	2470
May	1st to 10th	Day	46% 8% 13% 18% 14% 1	4120
	11th to 20th	Day	47% 9% 13% 22% 8% 1	4241
	21st to end	Day	38% 7% 12% 20% 18% 5%	4837
June	1st to 10th	Day	45% 7% 11% 22% 14% 1	2707
	11th to 20th	Day	39% 7% 11% 25% 16% 1	2850
	21st to end	Day	43% 7% 13% 23% 13% 1	2850
July	1st to 10th	Day	44% 7% 13% 19% 16% 2	4686
	11th to 20th	Day	38% 7% 12% 30% 12% 1	4413
	21st to end	Day	37% 8% 12% 23% 19% 2	4324
August	1st to 10th	Day	45% 8% 13% 21% 13% 1	4091
	11th to 20th	Day	47% 8% 13% 23% 9%	4083
	21st to end	Day	37% 7% 14% 30% 12% 1	4470
September	1st to 10th	Day	44% 8% 12% 23% 11% 2	2269
	11th to 20th	Day	38% 7% 13% 28% 13% 1	2090
	21st to end	Day	48% 8% 13% 23% 8% 1	2090
October	1st to 10th	Day	47% 6% 11% 22% 12% 1	3176
	11th to 20th	Day	50% 6% 12% 20% 11% 1	3140
	21st to end	Day	61% 6% 11% 17% 5%	3350
November	1st to 10th	Day	60% 6% 10% 16% 7%	1722
	11th to 20th	Day	65% 7% 11% 9% 7% 1	1600
	21st to end	Day	74% 6% 9% 9% 2	1600
December	1st to 10th	Day	82% 6% 5% 6% 1	1560
	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	81% 6% 6% 5% 2	4707
	11th to 20th	Night	84% 6% 5% 2 2	4181
	21st to end	Night	79% 7% 7% 4 2 1	4532
February	1st to 10th	Night	75% 5% 7% 10% 2	2470
	11th to 20th	Night	68% 5% 10% 12% 5%	2405
	21st to end	Night	64% 6% 9% 12% 8%	1927
March	1st to 10th	Night	52% 8% 13% 19% 7% 1	3487
	11th to 20th	Night	51% 10% 11% 17% 9% 1	3480
	21st to end	Night	52% 7% 10% 19% 11% 1	3817
April	1st to 10th	Night	58% 5% 8% 16% 11% 1	1990
	11th to 20th	Night	50% 6% 8% 19% 16% 1	1725
	21st to end	Night	53% 7% 9% 15% 15% 2	1710
May	1st to 10th	Night	42% 8% 10% 21% 14% 4	2840
	11th to 20th	Night	43% 9% 12% 22% 12% 2	2656
	21st to end	Night	34% 7% 12% 23% 21% 3	2739
June	1st to 10th	Night	42% 6% 10% 24% 16% 1	1467
	11th to 20th	Night	38% 7% 12% 25% 16% 1	1330
	21st to end	Night	39% 8% 11% 26% 15% 1	1330
July	1st to 10th	Night	34% 5% 14% 24% 18% 5%	2175
	11th to 20th	Night	34% 6% 11% 33% 16% 1	2422
	21st to end	Night	35% 8% 14% 26% 16% 1	2988
August	1st to 10th	Night	39% 6% 12% 27% 16% 1	2814
	11th to 20th	Night	43% 7% 14% 23% 11% 1	2812
	21st to end	Night	38% 6% 10% 32% 13% 1	3153
September	1st to 10th	Night	37% 8% 12% 28% 14% 2	1909
	11th to 20th	Night	34% 6% 14% 28% 17% 1	2090
	21st to end	Night	45% 7% 13% 24% 11% 1	2090
October	1st to 10th	Night	38% 7% 10% 25% 19% 1	3782
	11th to 20th	Night	50% 6% 13% 18% 13%	3779
	21st to end	Night	52% 6% 16% 19% 7%	4182
November	1st to 10th	Night	57% 8% 10% 17% 7% 1	2573
	11th to 20th	Night	63% 7% 11% 12% 5% 2	2800
	21st to end	Night	70% 6% 11% 10% 2	2800
December	1st to 10th	Night	80% 6% 8% 5% 1	2737
	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	20% 20% 38% 15% 6%	270
	21st to end	Day	26% 15% 32% 22% 4	297
February	1st to 10th	Day	26% 21% 37% 11% 5%	270
	11th to 20th	Day	23% 21% 41% 14% 1	270
	21st to end	Day	28% 31% 29% 11% 1	225
March	1st to 10th	Day	25% 16% 38% 14% 7%	412
	11th to 20th	Day	23% 14% 38% 18% 5% 2	460
	21st to end	Day	27% 13% 33% 19% 7% 1	506
April	1st to 10th	Day	24% 15% 35% 19% 6% 1	460
	11th to 20th	Day	30% 16% 25% 15% 9% 4	452
	21st to end	Day	26% 13% 29% 22% 7% 3	460
May	1st to 10th	Day	25% 11% 26% 25% 11% 3	463
	11th to 20th	Day	20% 10% 27% 23% 16% 4	487
	21st to end	Day	18% 8% 26% 26% 17% 5%	529
June	1st to 10th	Day	15% 13% 25% 30% 14% 2	537
	11th to 20th	Day	15% 8% 31% 30% 13% 3	680
	21st to end	Day	20% 6% 32% 27% 13% 2	680
July	1st to 10th	Day	11% 7% 27% 27% 22% 6%	671
	11th to 20th	Day	14% 7% 27% 28% 15% 8%	583
	21st to end	Day	10% 5% 28% 33% 17% 7%	532
August	1st to 10th	Day	12% 6% 23% 28% 19% 12%	486
	11th to 20th	Day	15% 5% 19% 25% 23% 13%	479
	21st to end	Day	14% 6% 23% 27% 21% 9%	539
September	1st to 10th	Day	17% 8% 24% 25% 16% 11%	490
	11th to 20th	Day	10% 7% 20% 27% 24% 14%	490
	21st to end	Day	17% 11% 26% 25% 15% 6%	490
October	1st to 10th	Day	23% 10% 29% 19% 15% 4	490
	11th to 20th	Day	26% 19% 29% 20% 5% 1	490
	21st to end	Day	34% 16% 27% 17% 5% 1	497
November	1st to 10th	Day	34% 14% 29% 16% 7%	280
	11th to 20th	Day	26% 22% 35% 12% 3 3	200
	21st to end	Day	30% 22% 34% 13% 2	200
December	1st to 10th	Day	29% 27% 28% 14% 3	190
	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	28% 15% 32% 20% 4 1	795
	21st to end	Night	19% 11% 36% 27% 6%	836
February	1st to 10th	Night	23% 17% 36% 21% 3	760
	11th to 20th	Night	21% 14% 37% 24% 4	743
	21st to end	Night	23% 18% 35% 20% 3	628
March	1st to 10th	Night	19% 15% 39% 20% 6% 1	760
	11th to 20th	Night	19% 16% 37% 21% 6% 1	760
	21st to end	Night	23% 11% 32% 24% 9% 1	836
April	1st to 10th	Night	26% 13% 31% 26% 4	760
	11th to 20th	Night	24% 13% 29% 22% 10% 1	601
	21st to end	Night	24% 10% 29% 28% 8% 1	570
May	1st to 10th	Night	19% 6% 27% 34% 12% 2	570
	11th to 20th	Night	19% 5% 27% 36% 12% 1	469
	21st to end	Night	12% 4 27% 39% 18%	411
June	1st to 10th	Night	17% 4 29% 38% 12%	380
	11th to 20th	Night	13% 7% 28% 40% 12%	380
	21st to end	Night	18% 6% 23% 38% 15% 1	380
July	1st to 10th	Night	6% 4 18% 50% 21% 1	370
	11th to 20th	Night	15% 3 21% 37% 23% 1	429
	21st to end	Night	11% 4 20% 43% 22% 1	624
August	1st to 10th	Night	13% 3 16% 39% 29% 1	567
	11th to 20th	Night	11% 3 17% 36% 29% 3	564
	21st to end	Night	15% 3 21% 31% 27% 2	643
September	1st to 10th	Night	14% 6% 24% 34% 19% 5%	760
	11th to 20th	Night	15% 3 21% 34% 22% 5%	760
	21st to end	Night	18% 8% 23% 30% 18% 4	760
October	1st to 10th	Night	21% 8% 27% 28% 14% 2	760
	11th to 20th	Night	28% 10% 26% 26% 8% 2	760
	21st to end	Night	32% 11% 30% 23% 4	836
November	1st to 10th	Night	26% 14% 28% 25% 7% 1	780
	11th to 20th	Night	26% 18% 30% 19% 6% 1	800
	21st to end	Night	28% 15% 32% 22% 3	800
December	1st to 10th	Night	31% 16% 30% 18% 4	783
	11th to 20th	Night	22% 19% 39% 16% 3 1	760
	21st to end	Night	31% 15% 34% 17% 2	992

Page generated at 2024-12-03 06:45:14. Version ac07

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