Golden State Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Golden State Star Party clear sky chart from 2005-11-06 to 2024-11-30.

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	6% 8% 3 5% 3 3 3 3 4 5% 57%	105503
	Night	7% 10% 3 6% 3 3 3 3 4 5% 53%	102806
Transparency	Day	28% 5% 9% 19% 22% 18%	105249
	Night	32% 6% 10% 19% 21% 13%	102649
Seeing	Day	11% 14% 27% 27% 16% 4	14989
	Night	11% 7% 20% 38% 22% 3	24201

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	10% 22% 8% 9% 4 4 4 3 4 4 28%	2539
	11th to 20th	Day	13% 21% 5% 9% 4 4 3 3 3 5% 29%	2576
	21st to end	Day	15% 18% 5% 9% 6% 4 3 2 4 5% 30%	3146
February	1st to 10th	Day	10% 13% 3 6% 5% 4 4 4 4 6% 41%	1710
	11th to 20th	Day	8% 14% 4 8% 5% 3 3 3 4 6% 42%	1745
	21st to end	Day	7% 15% 5% 7% 4 4 5% 4 5% 6% 39%	1570
March	1st to 10th	Day	8% 23% 8% 11% 5% 5% 4 2 4 4 26%	3186
	11th to 20th	Day	7% 11% 3 6% 3 3 2 2 3 5% 54%	3490
	21st to end	Day	9% 16% 5% 11% 6% 5% 5% 3 5% 5% 29%	4000
April	1st to 10th	Day	11% 14% 4 8% 6% 4 4 3 4 7% 35%	2280
	11th to 20th	Day	9% 12% 3 6% 4 4 4 3 5% 5% 45%	2249
	21st to end	Day	7% 10% 2 6% 4 4 3 3 4 8% 49%	2280
May	1st to 10th	Day	7% 9% 3 5% 3 3 3 2 4 5% 56%	4185
	11th to 20th	Day	5% 4 1 4 3 2 3 2 3 5% 68%	4377
	21st to end	Day	7% 5% 1 4 3 3 3 3 5% 6% 59%	4813
June	1st to 10th	Day	7% 6% 2 5% 4 4 5% 4 6% 8% 50%	2660
	11th to 20th	Day	4 3 2 4 3 3 3 3 5% 5% 67%	2660
	21st to end	Day	3 2 1 2 2 2 3 2 3 4 76%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 2 3 87%	4420
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 3 78%	4420
	21st to end	Day	1 1 1 1 1 2 2 2 3 4 83%	4709
August	1st to 10th	Day	2 2 1 3 2 2 2 2 5% 5% 72%	4091
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 87%	3855
	21st to end	Day	2 2 1 1 1 1 2 2 3 4 82%	4180
September	1st to 10th	Day	1 1 1 2 2 2 2 2 3 5% 80%	2280
	11th to 20th	Day	4 2 1 4 3 3 3 3 4 6% 68%	2280
	21st to end	Day	3 3 2 3 2 2 2 2 4 6% 71%	2048
October	1st to 10th	Day	4 3 1 3 2 2 3 2 4 5% 72%	3180
	11th to 20th	Day	6% 5% 1 5% 3 3 2 3 5% 7% 61%	3161
	21st to end	Day	7% 7% 3 7% 4 3 4 4 6% 7% 48%	3387
November	1st to 10th	Day	11% 10% 3 6% 4 3 4 3 5% 7% 45%	1764
	11th to 20th	Day	12% 11% 3 7% 5% 4 5% 3 7% 8% 37%	1765
	21st to end	Day	9% 12% 4 6% 3 3 4 3 4 9% 44%	1595
December	1st to 10th	Day	10% 12% 3 5% 4 3 4 3 5% 6% 44%	1520
	11th to 20th	Day	15% 15% 4 9% 5% 5% 4 4 6% 6% 27%	1928
	21st to end	Day	10% 11% 4 9% 5% 5% 5% 4 7% 9% 31%	2794
January	1st to 10th	Night	7% 17% 6% 11% 5% 5% 4 4 6% 7% 29%	4406
	11th to 20th	Night	12% 21% 7% 9% 5% 3 3 2 4 4 30%	4383
	21st to end	Night	11% 20% 4 9% 5% 5% 4 3 4 5% 30%	4521
February	1st to 10th	Night	8% 13% 4 6% 4 4 4 4 5% 7% 42%	2470
	11th to 20th	Night	8% 12% 3 7% 4 5% 4 3 5% 6% 42%	2321
	21st to end	Night	8% 14% 3 8% 4 4 5% 3 4 6% 41%	1884
March	1st to 10th	Night	9% 24% 7% 9% 4 3 3 2 3 5% 29%	3686
	11th to 20th	Night	6% 13% 3 6% 3 3 2 2 4 5% 53%	3490
	21st to end	Night	9% 18% 5% 9% 6% 4 5% 3 5% 6% 30%	3651
April	1st to 10th	Night	9% 12% 4 7% 6% 5% 4 3 5% 8% 37%	1900
	11th to 20th	Night	9% 13% 3 5% 4 3 4 3 5% 6% 45%	1879
	21st to end	Night	10% 9% 2 4 3 3 3 3 5% 7% 51%	1900
May	1st to 10th	Night	6% 10% 3 4 3 2 3 2 3 5% 59%	2775
	11th to 20th	Night	6% 3 1 3 3 3 3 2 4 5% 68%	2516
	21st to end	Night	9% 5% 2 4 3 2 3 3 6% 6% 57%	2762
June	1st to 10th	Night	9% 6% 2 5% 4 3 4 4 5% 8% 51%	1520
	11th to 20th	Night	6% 3 1 3 3 2 3 3 3 6% 67%	1520
	21st to end	Night	3 3 1 3 3 2 3 2 3 5% 73%	1520
July	1st to 10th	Night	1 1 1 1 2 1 2 3 87%	2540
	11th to 20th	Night	2 2 1 2 2 2 2 1 3 3 80%	2540
	21st to end	Night	1 1 1 1 2 2 2 3 3 85%	2842
August	1st to 10th	Night	2 3 1 3 2 2 2 2 4 6% 72%	2848
	11th to 20th	Night	1 1 1 1 1 1 1 2 2 3 86%	2989
	21st to end	Night	2 3 1 2 1 1 1 1 2 3 84%	3498
September	1st to 10th	Night	1 1 1 1 2 1 2 1 2 4 83%	1900
	11th to 20th	Night	4 3 1 3 2 3 2 2 3 5% 71%	1900
	21st to end	Night	4 2 1 3 2 3 3 2 5% 6% 70%	2127
October	1st to 10th	Night	3 3 2 4 2 2 2 1 2 3 76%	3800
	11th to 20th	Night	6% 4 1 4 2 3 3 2 4 5% 67%	3777
	21st to end	Night	6% 6% 2 5% 3 3 3 4 6% 7% 54%	4178
November	1st to 10th	Night	11% 11% 3 6% 4 4 4 3 4 6% 44%	2535
	11th to 20th	Night	11% 10% 2 7% 5% 5% 4 4 5% 7% 40%	2630
	21st to end	Night	8% 10% 2 6% 4 4 4 3 6% 7% 46%	2800
December	1st to 10th	Night	12% 11% 2 5% 4 3 3 3 5% 8% 45%	2660
	11th to 20th	Night	13% 16% 3 7% 5% 4 6% 4 6% 8% 29%	3276
	21st to end	Night	12% 15% 5% 9% 5% 4 5% 3 5% 6% 31%	4862

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	56% 8% 10% 19% 6% 1	2539
	11th to 20th	Day	56% 7% 11% 13% 8% 5%	2576
	21st to end	Day	56% 6% 11% 16% 8% 2	3146
February	1st to 10th	Day	43% 5% 12% 22% 13% 5%	1710
	11th to 20th	Day	42% 5% 13% 21% 17% 2	1754
	21st to end	Day	44% 7% 15% 19% 12% 4	1570
March	1st to 10th	Day	58% 8% 7% 13% 12% 1	3186
	11th to 20th	Day	33% 5% 11% 28% 22% 1	3490
	21st to end	Day	51% 8% 13% 19% 6% 2	4000
April	1st to 10th	Day	47% 6% 12% 19% 13% 3	2280
	11th to 20th	Day	38% 6% 12% 23% 16% 5%	2252
	21st to end	Day	34% 5% 15% 23% 19% 3	2280
May	1st to 10th	Day	27% 6% 10% 26% 26% 4	4185
	11th to 20th	Day	19% 4 7% 17% 38% 15%	4380
	21st to end	Day	23% 6% 13% 31% 25% 2	4814
June	1st to 10th	Day	29% 7% 12% 23% 23% 5%	2660
	11th to 20th	Day	18% 3 9% 22% 34% 13%	2660
	21st to end	Day	13% 2 6% 18% 34% 26%	2660
July	1st to 10th	Day	5% 1 3 8% 19% 64%	4351
	11th to 20th	Day	10% 2 3 9% 19% 56%	4345
	21st to end	Day	7% 2 3 11% 30% 48%	4560
August	1st to 10th	Day	13% 3 4 10% 25% 45%	4076
	11th to 20th	Day	5% 1 3 12% 43% 36%	3894
	21st to end	Day	9% 1 3 18% 36% 32%	4179
September	1st to 10th	Day	10% 2 4 11% 30% 44%	2280
	11th to 20th	Day	17% 3 8% 20% 31% 20%	2280
	21st to end	Day	16% 2 8% 22% 28% 24%	2048
October	1st to 10th	Day	16% 3 6% 17% 25% 34%	3180
	11th to 20th	Day	22% 3 7% 30% 29% 8%	3161
	21st to end	Day	30% 5% 11% 24% 21% 9%	3387
November	1st to 10th	Day	38% 5% 11% 18% 21% 6%	1764
	11th to 20th	Day	41% 7% 13% 21% 15% 3	1765
	21st to end	Day	37% 5% 13% 19% 19% 7%	1595
December	1st to 10th	Day	39% 8% 11% 21% 18% 3	1520
	11th to 20th	Day	55% 8% 10% 15% 10% 1	1928
	21st to end	Day	46% 10% 13% 20% 10% 1	2794
January	1st to 10th	Night	51% 11% 15% 17% 5% 1	4406
	11th to 20th	Night	54% 7% 11% 13% 9% 5%	4383
	21st to end	Night	57% 6% 9% 15% 11% 3	4521
February	1st to 10th	Night	40% 7% 13% 20% 16% 4	2470
	11th to 20th	Night	41% 6% 14% 21% 15% 3	2323
	21st to end	Night	42% 6% 16% 19% 13% 4	1884
March	1st to 10th	Night	55% 8% 11% 14% 10% 2	3686
	11th to 20th	Night	32% 6% 10% 26% 24% 1	3490
	21st to end	Night	49% 10% 14% 17% 8% 1	3651
April	1st to 10th	Night	43% 8% 14% 21% 11% 3	1900
	11th to 20th	Night	38% 7% 16% 20% 15% 4	1879
	21st to end	Night	32% 6% 16% 27% 16% 2	1900
May	1st to 10th	Night	27% 6% 10% 29% 21% 6%	2775
	11th to 20th	Night	19% 4 9% 21% 36% 11%	2516
	21st to end	Night	25% 6% 17% 29% 21% 2	2762
June	1st to 10th	Night	31% 5% 15% 29% 17% 2	1520
	11th to 20th	Night	19% 5% 11% 23% 34% 9%	1520
	21st to end	Night	14% 4 6% 20% 34% 22%	1520
July	1st to 10th	Night	5% 2 4 9% 19% 62%	2500
	11th to 20th	Night	10% 2 3 10% 21% 56%	2492
	21st to end	Night	6% 2 4 10% 33% 46%	2753
August	1st to 10th	Night	13% 2 4 12% 26% 43%	2839
	11th to 20th	Night	6% 2 3 15% 41% 33%	3016
	21st to end	Night	10% 1 3 20% 41% 25%	3498
September	1st to 10th	Night	7% 3 5% 10% 29% 45%	1900
	11th to 20th	Night	16% 3 7% 20% 32% 22%	1900
	21st to end	Night	16% 3 7% 22% 28% 25%	2127
October	1st to 10th	Night	17% 2 5% 13% 31% 32%	3800
	11th to 20th	Night	20% 4 7% 30% 30% 9%	3777
	21st to end	Night	25% 5% 11% 25% 24% 10%	4178
November	1st to 10th	Night	39% 7% 12% 18% 18% 7%	2535
	11th to 20th	Night	42% 7% 13% 20% 15% 4	2630
	21st to end	Night	35% 6% 14% 17% 20% 7%	2800
December	1st to 10th	Night	37% 7% 12% 19% 20% 4	2660
	11th to 20th	Night	52% 8% 9% 16% 14% 1	3276
	21st to end	Night	51% 9% 11% 15% 11% 2	4862

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	27% 22% 26% 21% 4 1	180
	11th to 20th	Day	20% 20% 27% 23% 8% 2	203
	21st to end	Day	19% 16% 27% 24% 13% 2	407
February	1st to 10th	Day	17% 19% 29% 26% 9%	370
	11th to 20th	Day	20% 24% 26% 25% 5%	403
	21st to end	Day	19% 17% 32% 26% 7%	382
March	1st to 10th	Day	22% 29% 28% 16% 6%	460
	11th to 20th	Day	21% 18% 27% 23% 9% 1	460
	21st to end	Day	20% 24% 30% 19% 7%	506
April	1st to 10th	Day	20% 22% 28% 22% 7% 2	460
	11th to 20th	Day	20% 19% 28% 21% 10% 2	452
	21st to end	Day	12% 22% 28% 22% 14% 2	460
May	1st to 10th	Day	13% 19% 33% 24% 10% 2	463
	11th to 20th	Day	16% 17% 30% 20% 13% 5%	488
	21st to end	Day	14% 12% 25% 26% 18% 6%	529
June	1st to 10th	Day	9% 16% 26% 24% 20% 6%	490
	11th to 20th	Day	8% 16% 34% 25% 14% 3	490
	21st to end	Day	3 10% 24% 32% 24% 7%	490
July	1st to 10th	Day	2 7% 28% 37% 20% 6%	486
	11th to 20th	Day	1 7% 28% 32% 25% 8%	484
	21st to end	Day	1 7% 26% 34% 22% 9%	531
August	1st to 10th	Day	3 6% 27% 29% 23% 11%	487
	11th to 20th	Day	3 10% 19% 33% 23% 12%	477
	21st to end	Day	2 7% 27% 31% 25% 8%	539
September	1st to 10th	Day	2 5% 29% 31% 27% 6%	490
	11th to 20th	Day	7% 9% 26% 29% 24% 6%	490
	21st to end	Day	5% 10% 27% 33% 20% 4	490
October	1st to 10th	Day	7% 12% 27% 28% 21% 5%	490
	11th to 20th	Day	10% 12% 20% 30% 23% 4	490
	21st to end	Day	12% 13% 25% 31% 15% 5%	502
November	1st to 10th	Day	16% 11% 21% 31% 19% 2	300
	11th to 20th	Day	11% 10% 31% 27% 17% 4	283
	21st to end	Day	15% 12% 29% 29% 15% 2	199
December	1st to 10th	Day	16% 15% 26% 24% 18% 2	180
	11th to 20th	Day	19% 17% 24% 24% 14% 2	180
	21st to end	Day	19% 17% 24% 27% 13% 1	198
January	1st to 10th	Night	16% 9% 26% 31% 16% 3	760
	11th to 20th	Night	15% 9% 24% 32% 18% 2	760
	21st to end	Night	17% 7% 24% 33% 16% 3	836
February	1st to 10th	Night	14% 9% 24% 37% 15% 1	760
	11th to 20th	Night	13% 10% 22% 40% 14% 2	744
	21st to end	Night	14% 13% 26% 37% 11% 1	628
March	1st to 10th	Night	22% 12% 24% 29% 11% 3	760
	11th to 20th	Night	15% 9% 22% 34% 19% 2	760
	21st to end	Night	17% 13% 26% 32% 11% 1	836
April	1st to 10th	Night	12% 11% 28% 36% 12% 1	760
	11th to 20th	Night	14% 13% 26% 27% 17% 3	751
	21st to end	Night	13% 10% 23% 33% 19% 2	760
May	1st to 10th	Night	10% 9% 30% 33% 17% 1	524
	11th to 20th	Night	11% 6% 19% 37% 22% 5%	374
	21st to end	Night	13% 8% 19% 35% 23% 2	411
June	1st to 10th	Night	11% 5% 18% 42% 24% 2	380
	11th to 20th	Night	7% 6% 25% 42% 20% 1	380
	21st to end	Night	4 1 15% 51% 29% 1	380
July	1st to 10th	Night	1 1 10% 54% 33% 1	370
	11th to 20th	Night	1 1 10% 59% 29% 1	368
	21st to end	Night	1 4 53% 39% 3	461
August	1st to 10th	Night	3 1 5% 48% 39% 4	567
	11th to 20th	Night	2 1 10% 45% 37% 5%	663
	21st to end	Night	2 1 12% 45% 37% 3	836
September	1st to 10th	Night	1 2 13% 47% 33% 4	760
	11th to 20th	Night	5% 2 13% 34% 39% 7%	760
	21st to end	Night	5% 3 15% 38% 32% 8%	760
October	1st to 10th	Night	7% 3 18% 38% 29% 4	760
	11th to 20th	Night	7% 6% 13% 40% 29% 5%	760
	21st to end	Night	10% 5% 18% 38% 23% 6%	836
November	1st to 10th	Night	15% 8% 17% 36% 20% 4	780
	11th to 20th	Night	13% 7% 25% 38% 15% 2	800
	21st to end	Night	12% 8% 23% 36% 19% 3	800
December	1st to 10th	Night	14% 9% 23% 35% 17% 2	760
	11th to 20th	Night	22% 7% 21% 33% 16% 1	760
	21st to end	Night	21% 13% 24% 33% 8% 1	836

Page generated at 2024-11-27 14:30:53. Version ac07

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