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 2024-01-15.

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	7% 7% 3 4 4 2 3 4 4 6% 55%	74773
	Night	8% 9% 3 5% 4 2 4 4 4 6% 52%	75010
Transparency	Day	30% 5% 10% 19% 21% 15%	74479
	Night	33% 6% 11% 19% 20% 11%	74825
Seeing	Day	11% 14% 27% 27% 16% 4	13788
	Night	11% 7% 19% 37% 22% 3	23105

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	11% 15% 4 7% 5% 4 5% 5% 5% 6% 33%	1519
	11th to 20th	Day	11% 11% 4 6% 5% 3 5% 4 5% 6% 40%	1494
	21st to end	Day	11% 15% 3 6% 5% 2 3 4 5% 6% 40%	1782
February	1st to 10th	Day	10% 11% 3 6% 5% 3 5% 5% 4 6% 42%	1620
	11th to 20th	Day	8% 12% 5% 6% 5% 2 3 4 4 6% 44%	1651
	21st to end	Day	7% 13% 6% 7% 5% 3 5% 4 5% 6% 38%	1480
March	1st to 10th	Day	11% 15% 7% 7% 6% 4 5% 4 5% 6% 31%	1822
	11th to 20th	Day	12% 14% 5% 6% 5% 3 3 4 5% 8% 36%	1980
	21st to end	Day	12% 16% 5% 6% 5% 3 4 4 5% 6% 34%	2276
April	1st to 10th	Day	12% 13% 5% 7% 6% 3 4 4 4 7% 34%	2160
	11th to 20th	Day	10% 10% 4 6% 4 3 4 4 5% 6% 45%	2129
	21st to end	Day	8% 9% 3 6% 5% 3 3 4 4 7% 49%	2160
May	1st to 10th	Day	7% 6% 2 5% 4 4 4 4 5% 6% 54%	2376
	11th to 20th	Day	8% 7% 2 5% 5% 3 4 4 5% 7% 50%	2477
	21st to end	Day	11% 7% 2 6% 5% 3 5% 4 5% 7% 44%	2723
June	1st to 10th	Day	7% 5% 3 5% 4 3 5% 5% 6% 8% 50%	2520
	11th to 20th	Day	4 3 2 3 3 2 3 3 4 6% 67%	2520
	21st to end	Day	3 2 1 2 2 1 2 3 3 4 76%	2520
July	1st to 10th	Day	1 1 1 2 2 1 2 3 3 5% 78%	2520
	11th to 20th	Day	1 1 1 1 2 1 2 2 3 3 83%	2520
	21st to end	Day	2 1 1 2 2 2 3 3 4 4 77%	2696
August	1st to 10th	Day	2 2 1 2 2 2 3 3 4 5% 74%	2328
	11th to 20th	Day	1 2 1 1 2 1 2 3 3 4 80%	2205
	21st to end	Day	2 1 1 1 1 1 2 2 3 3 84%	2376
September	1st to 10th	Day	1 1 1 2 2 1 2 2 3 4 80%	2160
	11th to 20th	Day	3 2 1 2 3 2 3 3 4 6% 69%	2160
	21st to end	Day	4 4 2 2 3 1 2 2 4 6% 70%	1941
October	1st to 10th	Day	7% 4 2 4 3 2 3 3 4 5% 64%	1800
	11th to 20th	Day	6% 6% 2 4 4 2 3 4 4 5% 61%	1800
	21st to end	Day	8% 6% 1 4 4 2 3 4 5% 7% 56%	1945
November	1st to 10th	Day	12% 9% 3 5% 5% 2 3 4 5% 7% 44%	1674
	11th to 20th	Day	12% 10% 3 5% 6% 2 4 4 6% 8% 39%	1677
	21st to end	Day	9% 11% 4 6% 4 2 4 4 4 9% 44%	1520
December	1st to 10th	Day	11% 11% 3 5% 4 2 4 5% 5% 7% 44%	1520
	11th to 20th	Day	15% 14% 4 8% 6% 3 5% 5% 6% 6% 27%	1928
	21st to end	Day	10% 11% 4 8% 5% 4 6% 5% 7% 9% 31%	2794
January	1st to 10th	Night	9% 14% 5% 7% 6% 3 4 5% 6% 7% 34%	2646
	11th to 20th	Night	9% 13% 4 7% 6% 3 4 4 5% 6% 40%	2552
	21st to end	Night	10% 15% 3 5% 5% 3 3 3 4 6% 43%	2574
February	1st to 10th	Night	9% 12% 4 5% 4 2 4 4 5% 7% 44%	2340
	11th to 20th	Night	8% 11% 4 6% 5% 3 4 3 5% 6% 44%	2195
	21st to end	Night	9% 14% 4 7% 5% 3 4 4 5% 6% 40%	1776
March	1st to 10th	Night	13% 17% 6% 6% 4 3 4 4 4 6% 33%	2136
	11th to 20th	Night	9% 12% 4 6% 5% 3 4 5% 6% 9% 37%	1980
	21st to end	Night	11% 16% 4 5% 5% 2 4 4 4 7% 39%	2078
April	1st to 10th	Night	10% 11% 5% 7% 6% 4 5% 4 5% 8% 36%	1800
	11th to 20th	Night	9% 12% 3 5% 4 2 4 4 4 6% 46%	1779
	21st to end	Night	10% 8% 3 4 3 2 4 4 5% 7% 52%	1800
May	1st to 10th	Night	9% 5% 2 3 3 2 4 4 4 6% 57%	1577
	11th to 20th	Night	10% 5% 2 4 5% 3 5% 5% 5% 8% 48%	1416
	21st to end	Night	11% 8% 3 5% 5% 3 4 4 5% 7% 45%	1552
June	1st to 10th	Night	10% 6% 2 4 4 2 4 4 5% 8% 52%	1440
	11th to 20th	Night	6% 3 1 3 4 2 3 3 4 6% 66%	1440
	21st to end	Night	3 2 1 3 3 1 3 3 3 5% 73%	1440
July	1st to 10th	Night	1 1 1 2 2 1 3 3 3 5% 78%	1440
	11th to 20th	Night	1 2 1 1 1 1 2 2 2 3 84%	1440
	21st to end	Night	1 1 1 1 2 2 3 3 3 4 80%	1618
August	1st to 10th	Night	2 2 1 3 2 2 3 2 4 4 75%	1611
	11th to 20th	Night	2 2 1 2 2 1 2 3 2 5% 78%	1695
	21st to end	Night	1 1 1 1 1 2 2 3 4 84%	1980
September	1st to 10th	Night	1 1 1 1 2 1 2 2 3 4 83%	1800
	11th to 20th	Night	4 3 1 2 3 2 2 3 3 5% 73%	1800
	21st to end	Night	4 2 1 3 2 2 3 3 5% 6% 69%	2015
October	1st to 10th	Night	5% 5% 2 4 3 2 3 2 3 4 67%	2160
	11th to 20th	Night	7% 3 2 3 3 2 2 3 4 5% 65%	2160
	21st to end	Night	7% 6% 2 3 3 2 2 4 6% 6% 60%	2409
November	1st to 10th	Night	12% 10% 3 5% 4 3 5% 4 4 6% 44%	2405
	11th to 20th	Night	11% 9% 2 5% 6% 3 5% 5% 5% 8% 41%	2498
	21st to end	Night	8% 9% 3 5% 5% 3 4 4 6% 8% 46%	2660
December	1st to 10th	Night	12% 10% 3 4 5% 2 3 4 5% 8% 45%	2660
	11th to 20th	Night	13% 16% 3 6% 6% 3 5% 6% 6% 8% 29%	3276
	21st to end	Night	12% 15% 5% 8% 6% 3 5% 4 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	49% 8% 15% 20% 8% 1	1519
	11th to 20th	Day	44% 7% 11% 19% 11% 8%	1494
	21st to end	Day	45% 5% 9% 23% 14% 4	1782
February	1st to 10th	Day	41% 5% 13% 22% 13% 5%	1620
	11th to 20th	Day	40% 5% 14% 22% 17% 2	1660
	21st to end	Day	45% 6% 14% 19% 12% 4	1480
March	1st to 10th	Day	52% 8% 9% 19% 10% 2	1822
	11th to 20th	Day	46% 6% 12% 17% 17% 2	1980
	21st to end	Day	50% 6% 16% 17% 8% 3	2276
April	1st to 10th	Day	48% 6% 12% 18% 13% 3	2160
	11th to 20th	Day	38% 6% 12% 23% 17% 5%	2132
	21st to end	Day	34% 5% 15% 23% 19% 3	2160
May	1st to 10th	Day	29% 5% 11% 26% 23% 4	2376
	11th to 20th	Day	33% 6% 11% 25% 20% 6%	2480
	21st to end	Day	37% 7% 12% 24% 17% 3	2724
June	1st to 10th	Day	29% 7% 12% 23% 22% 6%	2520
	11th to 20th	Day	19% 4 10% 22% 34% 12%	2520
	21st to end	Day	13% 2 7% 18% 35% 25%	2520
July	1st to 10th	Day	10% 2 6% 14% 32% 37%	2451
	11th to 20th	Day	8% 2 4 13% 27% 46%	2445
	21st to end	Day	11% 3 4 11% 22% 48%	2546
August	1st to 10th	Day	13% 4 6% 16% 28% 33%	2312
	11th to 20th	Day	8% 2 5% 14% 34% 36%	2205
	21st to end	Day	8% 2 3 14% 35% 38%	2376
September	1st to 10th	Day	10% 2 4 11% 30% 43%	2160
	11th to 20th	Day	16% 3 8% 19% 32% 21%	2160
	21st to end	Day	17% 2 8% 23% 27% 23%	1941
October	1st to 10th	Day	23% 4 9% 22% 25% 18%	1800
	11th to 20th	Day	25% 4 9% 21% 28% 13%	1800
	21st to end	Day	26% 5% 12% 21% 21% 14%	1945
November	1st to 10th	Day	39% 5% 11% 18% 21% 6%	1674
	11th to 20th	Day	40% 7% 13% 22% 15% 3	1677
	21st to end	Day	37% 6% 13% 19% 19% 6%	1520
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	47% 8% 16% 19% 8% 2	2646
	11th to 20th	Night	43% 6% 13% 17% 12% 9%	2552
	21st to end	Night	43% 5% 9% 18% 20% 5%	2574
February	1st to 10th	Night	40% 6% 13% 21% 16% 4	2340
	11th to 20th	Night	40% 5% 14% 22% 16% 3	2197
	21st to end	Night	43% 5% 15% 19% 12% 4	1776
March	1st to 10th	Night	51% 7% 13% 16% 11% 3	2136
	11th to 20th	Night	40% 8% 13% 19% 18% 2	1980
	21st to end	Night	44% 7% 17% 19% 10% 2	2078
April	1st to 10th	Night	44% 8% 13% 20% 11% 3	1800
	11th to 20th	Night	39% 7% 15% 19% 16% 5%	1779
	21st to end	Night	32% 6% 17% 27% 16% 3	1800
May	1st to 10th	Night	28% 6% 12% 28% 23% 4	1577
	11th to 20th	Night	34% 7% 15% 25% 14% 6%	1416
	21st to end	Night	37% 6% 16% 26% 14% 1	1552
June	1st to 10th	Night	31% 5% 15% 28% 18% 3	1440
	11th to 20th	Night	20% 5% 11% 23% 33% 8%	1440
	21st to end	Night	15% 4 6% 21% 34% 21%	1440
July	1st to 10th	Night	9% 3 7% 16% 32% 34%	1400
	11th to 20th	Night	8% 1 4 15% 28% 44%	1392
	21st to end	Night	9% 3 5% 12% 25% 46%	1528
August	1st to 10th	Night	13% 4 6% 19% 29% 30%	1602
	11th to 20th	Night	11% 3 5% 16% 32% 34%	1695
	21st to end	Night	7% 1 5% 16% 37% 34%	1980
September	1st to 10th	Night	7% 3 5% 11% 28% 46%	1800
	11th to 20th	Night	15% 3 8% 19% 32% 23%	1800
	21st to end	Night	17% 3 7% 22% 27% 24%	2015
October	1st to 10th	Night	23% 3 8% 21% 27% 18%	2160
	11th to 20th	Night	21% 5% 9% 21% 28% 16%	2160
	21st to end	Night	23% 5% 13% 24% 20% 14%	2409
November	1st to 10th	Night	39% 7% 11% 18% 18% 7%	2405
	11th to 20th	Night	41% 7% 12% 20% 15% 4	2498
	21st to end	Night	35% 6% 15% 17% 20% 7%	2660
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	19% 19% 28% 23% 8% 2	190
	21st to end	Day	19% 15% 26% 24% 14% 2	374
February	1st to 10th	Day	16% 19% 29% 26% 9%	340
	11th to 20th	Day	20% 23% 25% 27% 5%	369
	21st to end	Day	18% 18% 33% 25% 6%	346
March	1st to 10th	Day	20% 29% 28% 17% 6%	420
	11th to 20th	Day	21% 18% 28% 23% 9% 1	420
	21st to end	Day	20% 23% 29% 20% 8%	462
April	1st to 10th	Day	21% 22% 29% 20% 6% 1	420
	11th to 20th	Day	20% 21% 29% 19% 10% 1	412
	21st to end	Day	12% 22% 28% 22% 14% 2	420
May	1st to 10th	Day	11% 18% 34% 25% 10% 3	423
	11th to 20th	Day	17% 18% 29% 19% 13% 4	448
	21st to end	Day	15% 11% 25% 26% 19% 5%	485
June	1st to 10th	Day	9% 16% 26% 24% 19% 6%	450
	11th to 20th	Day	8% 16% 33% 25% 14% 3	450
	21st to end	Day	3 10% 23% 32% 24% 7%	450
July	1st to 10th	Day	2 7% 28% 38% 20% 5%	446
	11th to 20th	Day	8% 27% 33% 25% 7%	444
	21st to end	Day	1 7% 26% 34% 23% 9%	487
August	1st to 10th	Day	4 7% 27% 29% 23% 11%	447
	11th to 20th	Day	2 9% 17% 34% 24% 13%	437
	21st to end	Day	2 6% 28% 33% 24% 7%	495
September	1st to 10th	Day	2 5% 30% 31% 26% 6%	450
	11th to 20th	Day	6% 9% 26% 28% 25% 6%	450
	21st to end	Day	6% 11% 28% 33% 19% 2	450
October	1st to 10th	Day	7% 12% 28% 26% 21% 5%	450
	11th to 20th	Day	11% 12% 20% 31% 22% 4	450
	21st to end	Day	12% 12% 26% 30% 16% 5%	460
November	1st to 10th	Day	17% 11% 20% 30% 19% 1	270
	11th to 20th	Day	10% 9% 31% 27% 19% 4	255
	21st to end	Day	14% 11% 31% 31% 13% 2	180
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	736
	21st to end	Night	17% 7% 23% 34% 17% 3	792
February	1st to 10th	Night	14% 8% 24% 37% 15% 1	720
	11th to 20th	Night	13% 9% 21% 40% 14% 2	704
	21st to end	Night	14% 13% 25% 36% 11% 1	592
March	1st to 10th	Night	21% 12% 23% 30% 12% 3	720
	11th to 20th	Night	15% 9% 21% 35% 18% 2	720
	21st to end	Night	18% 12% 25% 32% 12% 1	792
April	1st to 10th	Night	12% 11% 28% 37% 12% 2	720
	11th to 20th	Night	14% 13% 25% 27% 17% 3	711
	21st to end	Night	13% 10% 23% 33% 19% 2	720
May	1st to 10th	Night	10% 8% 28% 34% 18% 1	497
	11th to 20th	Night	12% 6% 19% 36% 22% 5%	354
	21st to end	Night	14% 8% 19% 34% 24% 2	389
June	1st to 10th	Night	11% 4 17% 41% 25% 2	360
	11th to 20th	Night	7% 6% 24% 41% 21% 1	360
	21st to end	Night	4 1 15% 50% 30% 1	360
July	1st to 10th	Night	1 1 11% 53% 34% 1	350
	11th to 20th	Night	1 1 10% 57% 30% 1	348
	21st to end	Night	1 4 52% 39% 3	436
August	1st to 10th	Night	2 1 6% 47% 40% 4	537
	11th to 20th	Night	2 1 9% 44% 39% 6%	627
	21st to end	Night	1 1 12% 45% 37% 3	792
September	1st to 10th	Night	1 2 12% 46% 34% 4	720
	11th to 20th	Night	4 2 13% 34% 40% 7%	720
	21st to end	Night	5% 3 16% 37% 32% 8%	720
October	1st to 10th	Night	8% 4 18% 37% 29% 5%	720
	11th to 20th	Night	8% 6% 13% 40% 29% 5%	720
	21st to end	Night	10% 6% 17% 37% 24% 7%	792
November	1st to 10th	Night	16% 8% 16% 36% 20% 4	740
	11th to 20th	Night	13% 6% 24% 39% 16% 2	760
	21st to end	Night	13% 7% 23% 37% 19% 3	760
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 2024-01-11 19:33:50. Version ac07

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