Shaver Recreation Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shaver Recreation Center clear sky chart from 2005-11-06 to 2026-09-29.

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% 5% 2 6% 4 4 5% 4 6% 8% 43%	148777
	Night	15% 6% 2 6% 4 4 4 4 6% 7% 43%	142636
Transparency	Day	38% 5% 12% 21% 18% 6%	152501
	Night	40% 4 10% 19% 20% 7%	146971
Seeing	Day	18% 8% 21% 25% 19% 9%	17571
	Night	17% 6% 21% 31% 20% 4	27565

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	17% 6% 2 5% 3 3 3 3 4 6% 48%	5258
	11th to 20th	Day	11% 5% 1 4 3 2 2 2 3 3 64%	5280
	21st to end	Day	23% 7% 3 5% 3 3 3 3 4 6% 40%	5780
February	1st to 10th	Day	16% 5% 2 5% 4 4 4 4 5% 7% 44%	2048
	11th to 20th	Day	22% 6% 2 4 4 3 3 3 5% 6% 43%	2048
	21st to end	Day	20% 5% 2 6% 3 4 3 3 5% 5% 43%	1730
March	1st to 10th	Day	21% 7% 2 6% 4 4 3 3 4 6% 40%	4900
	11th to 20th	Day	11% 4 2 5% 3 3 3 3 4 6% 55%	5090
	21st to end	Day	18% 5% 2 5% 4 4 4 3 4 5% 46%	5586
April	1st to 10th	Day	13% 4 1 4 4 4 4 4 7% 8% 46%	2310
	11th to 20th	Day	11% 4 2 5% 4 4 4 3 5% 7% 50%	2488
	21st to end	Day	12% 4 1 5% 3 4 4 3 6% 8% 51%	2730
May	1st to 10th	Day	14% 7% 3 7% 4 4 5% 4 6% 8% 38%	7616
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 4 6% 8% 37%	7626
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 6% 8% 33%	8391
June	1st to 10th	Day	10% 6% 3 7% 5% 6% 5% 6% 8% 11% 34%	2730
	11th to 20th	Day	5% 4 2 5% 5% 5% 7% 7% 10% 12% 39%	2730
	21st to end	Day	6% 4 2 6% 6% 6% 5% 5% 8% 12% 40%	2730
July	1st to 10th	Day	4 4 2 6% 5% 5% 6% 6% 8% 12% 41%	7680
	11th to 20th	Day	7% 4 2 7% 5% 6% 7% 6% 9% 13% 34%	7680
	21st to end	Day	8% 6% 3 8% 6% 7% 7% 6% 9% 11% 28%	8340
August	1st to 10th	Day	13% 7% 3 7% 5% 6% 6% 6% 8% 11% 27%	6014
	11th to 20th	Day	6% 3 1 5% 3 5% 5% 4 8% 11% 49%	5951
	21st to end	Day	7% 4 2 6% 4 4 4 4 6% 9% 49%	5949
September	1st to 10th	Day	8% 4 2 7% 5% 5% 6% 5% 7% 9% 43%	2310
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 4 6% 8% 41%	2310
	21st to end	Day	16% 6% 2 5% 3 3 4 3 5% 8% 46%	2288
October	1st to 10th	Day	14% 5% 2 4 2 3 3 3 3 6% 55%	2199
	11th to 20th	Day	12% 4 2 4 3 3 2 2 4 5% 59%	2000
	21st to end	Day	14% 5% 1 4 3 3 2 3 4 4 58%	2200
November	1st to 10th	Day	14% 5% 2 3 3 3 2 2 4 5% 57%	1957
	11th to 20th	Day	14% 5% 1 3 3 3 3 3 4 7% 54%	1890
	21st to end	Day	16% 4 2 4 4 3 3 3 6% 7% 50%	1890
December	1st to 10th	Day	20% 6% 1 4 3 3 3 2 4 6% 49%	3020
	11th to 20th	Day	19% 5% 2 5% 4 4 4 4 5% 5% 43%	3463
	21st to end	Day	24% 4 1 3 2 2 3 3 4 6% 46%	4565
January	1st to 10th	Night	16% 4 2 4 3 3 3 3 4 5% 54%	7635
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 5% 54%	7680
	21st to end	Night	21% 6% 2 4 3 3 3 3 4 5% 46%	8401
February	1st to 10th	Night	15% 6% 2 5% 3 4 3 3 4 6% 48%	2569
	11th to 20th	Night	22% 6% 2 5% 5% 3 3 3 4 4 44%	2458
	21st to end	Night	19% 6% 2 5% 3 4 3 3 5% 5% 44%	2076
March	1st to 10th	Night	20% 5% 2 5% 4 3 4 4 6% 7% 40%	5170
	11th to 20th	Night	9% 3 1 4 3 3 4 4 6% 8% 55%	5090
	21st to end	Night	17% 4 2 5% 4 4 4 3 4 6% 47%	5588
April	1st to 10th	Night	14% 4 2 5% 3 4 4 3 5% 7% 49%	2310
	11th to 20th	Night	12% 5% 2 5% 3 3 2 3 5% 7% 52%	2094
	21st to end	Night	11% 5% 2 5% 4 4 4 4 4 7% 50%	1890
May	1st to 10th	Night	14% 6% 3 8% 5% 5% 5% 4 6% 9% 35%	5237
	11th to 20th	Night	19% 6% 3 6% 4 4 5% 4 6% 7% 36%	5234
	21st to end	Night	20% 7% 2 7% 5% 5% 4 3 7% 8% 33%	5761
June	1st to 10th	Night	10% 7% 2 7% 5% 6% 7% 5% 7% 10% 34%	1890
	11th to 20th	Night	9% 5% 2 6% 5% 5% 6% 5% 8% 11% 40%	1890
	21st to end	Night	8% 5% 2 6% 5% 5% 6% 5% 8% 12% 40%	1890
July	1st to 10th	Night	9% 6% 3 7% 6% 6% 7% 5% 8% 11% 32%	5278
	11th to 20th	Night	11% 6% 2 8% 5% 6% 7% 7% 10% 11% 28%	5277
	21st to end	Night	13% 9% 4 10% 6% 6% 6% 5% 7% 10% 25%	5736
August	1st to 10th	Night	16% 7% 3 9% 5% 6% 6% 5% 7% 9% 25%	4135
	11th to 20th	Night	9% 6% 3 7% 5% 5% 5% 5% 8% 13% 34%	4095
	21st to end	Night	10% 5% 2 7% 5% 5% 5% 4 6% 9% 41%	5122
September	1st to 10th	Night	9% 7% 2 7% 5% 6% 5% 4 7% 9% 39%	2310
	11th to 20th	Night	17% 7% 2 6% 5% 4 5% 4 6% 7% 35%	2310
	21st to end	Night	16% 5% 2 6% 4 4 4 3 6% 5% 44%	2289
October	1st to 10th	Night	14% 4 2 5% 3 4 4 3 5% 6% 51%	2200
	11th to 20th	Night	13% 4 2 5% 3 3 3 3 5% 5% 55%	2400
	21st to end	Night	14% 3 1 4 3 3 2 3 4 5% 58%	2640
November	1st to 10th	Night	15% 4 2 5% 3 3 3 2 3 5% 56%	2556
	11th to 20th	Night	16% 6% 2 4 3 2 3 3 4 6% 53%	2730
	21st to end	Night	17% 4 2 4 3 3 3 4 5% 5% 49%	2730
December	1st to 10th	Night	18% 5% 2 5% 3 3 3 3 4 5% 50%	4380
	11th to 20th	Night	21% 6% 2 6% 4 3 3 3 3 5% 44%	4952
	21st to end	Night	22% 5% 2 4 3 3 4 3 4 5% 44%	6633

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	39% 2 6% 24% 24% 5%	5259
	11th to 20th	Day	28% 2 4 13% 38% 15%	5280
	21st to end	Day	47% 1 4 15% 20% 12%	5780
February	1st to 10th	Day	41% 3 7% 22% 20% 6%	2048
	11th to 20th	Day	43% 2 6% 20% 22% 6%	2058
	21st to end	Day	43% 3 7% 16% 22% 9%	1730
March	1st to 10th	Day	47% 2 5% 15% 18% 13%	4900
	11th to 20th	Day	32% 2 6% 14% 26% 20%	5090
	21st to end	Day	42% 2 5% 24% 21% 6%	5586
April	1st to 10th	Day	35% 4 10% 21% 24% 6%	2310
	11th to 20th	Day	35% 3 7% 23% 23% 9%	2488
	21st to end	Day	32% 3 11% 29% 21% 4	2730
May	1st to 10th	Day	44% 4 13% 24% 13% 2	7651
	11th to 20th	Day	44% 4 16% 21% 13% 2	7630
	21st to end	Day	49% 5% 12% 16% 16% 2	8405
June	1st to 10th	Day	41% 6% 17% 24% 10% 3	2730
	11th to 20th	Day	33% 7% 20% 25% 12% 2	2730
	21st to end	Day	33% 8% 19% 22% 14% 4	2730
July	1st to 10th	Day	32% 9% 24% 27% 7% 1	7615
	11th to 20th	Day	37% 11% 28% 19% 3 1	7611
	21st to end	Day	45% 9% 19% 18% 8% 1	8156
August	1st to 10th	Day	46% 8% 19% 21% 5%	6001
	11th to 20th	Day	27% 6% 25% 26% 13% 1	5990
	21st to end	Day	30% 6% 16% 26% 19% 2	5949
September	1st to 10th	Day	35% 6% 15% 20% 20% 3	2310
	11th to 20th	Day	41% 5% 11% 22% 19% 2	2310
	21st to end	Day	38% 4 12% 21% 20% 6%	2288
October	1st to 10th	Day	28% 3 6% 18% 34% 10%	3576
	11th to 20th	Day	21% 1 5% 16% 30% 26%	3240
	21st to end	Day	29% 2 4 22% 29% 14%	3538
November	1st to 10th	Day	31% 3 7% 20% 29% 10%	1957
	11th to 20th	Day	33% 2 6% 23% 27% 9%	1890
	21st to end	Day	35% 2 7% 23% 26% 7%	1890
December	1st to 10th	Day	39% 2 5% 18% 26% 10%	3020
	11th to 20th	Day	44% 3 6% 17% 19% 9%	3460
	21st to end	Day	41% 2 6% 29% 20% 2	4565
January	1st to 10th	Night	34% 2 9% 23% 24% 8%	7636
	11th to 20th	Night	34% 2 4 16% 32% 12%	7680
	21st to end	Night	42% 2 4 16% 26% 10%	8401
February	1st to 10th	Night	39% 3 7% 22% 23% 7%	2569
	11th to 20th	Night	45% 2 5% 18% 23% 7%	2459
	21st to end	Night	42% 3 7% 18% 21% 9%	2076
March	1st to 10th	Night	44% 2 6% 14% 27% 7%	5170
	11th to 20th	Night	28% 3 7% 14% 29% 18%	5090
	21st to end	Night	40% 2 6% 22% 21% 10%	5588
April	1st to 10th	Night	36% 3 8% 21% 25% 7%	2310
	11th to 20th	Night	32% 3 6% 25% 25% 10%	2094
	21st to end	Night	35% 3 9% 27% 22% 4	1890
May	1st to 10th	Night	46% 4 13% 22% 13% 2	5264
	11th to 20th	Night	47% 4 15% 20% 13% 1	5235
	21st to end	Night	50% 5% 11% 19% 13% 2	5771
June	1st to 10th	Night	42% 8% 16% 20% 12% 2	1890
	11th to 20th	Night	36% 7% 18% 24% 13% 1	1890
	21st to end	Night	35% 8% 20% 19% 15% 4	1890
July	1st to 10th	Night	42% 10% 24% 19% 4	5235
	11th to 20th	Night	44% 12% 24% 15% 3 1	5226
	21st to end	Night	52% 8% 19% 14% 5% 2	5606
August	1st to 10th	Night	52% 10% 18% 16% 4	4124
	11th to 20th	Night	40% 8% 23% 21% 8% 1	4122
	21st to end	Night	38% 7% 14% 23% 16% 1	5122
September	1st to 10th	Night	40% 7% 14% 20% 16% 3	2310
	11th to 20th	Night	46% 6% 12% 18% 16% 2	2310
	21st to end	Night	42% 4 11% 18% 19% 6%	2289
October	1st to 10th	Night	30% 4 10% 15% 33% 8%	3590
	11th to 20th	Night	21% 3 5% 17% 30% 25%	3899
	21st to end	Night	29% 2 4 21% 27% 17%	4252
November	1st to 10th	Night	34% 2 6% 20% 27% 11%	2556
	11th to 20th	Night	34% 2 4 18% 29% 12%	2730
	21st to end	Night	36% 4 5% 21% 25% 8%	2730
December	1st to 10th	Night	38% 2 5% 19% 29% 8%	4380
	11th to 20th	Night	45% 2 8% 16% 21% 9%	4954
	21st to end	Night	43% 2 6% 26% 20% 3	6633

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% 14% 39% 19% 4	330
	11th to 20th	Day	26% 19% 30% 20% 5% 1	330
	21st to end	Day	25% 15% 40% 16% 3	363
February	1st to 10th	Day	24% 13% 35% 24% 5%	330
	11th to 20th	Day	34% 17% 32% 15% 2	330
	21st to end	Day	28% 21% 36% 11% 4	273
March	1st to 10th	Day	21% 13% 29% 26% 9% 1	468
	11th to 20th	Day	21% 14% 38% 20% 6% 1	540
	21st to end	Day	23% 13% 31% 23% 9%	594
April	1st to 10th	Day	21% 12% 28% 24% 13% 2	540
	11th to 20th	Day	14% 11% 34% 23% 15% 3	532
	21st to end	Day	20% 6% 23% 28% 17% 7%	540
May	1st to 10th	Day	15% 10% 29% 26% 12% 7%	543
	11th to 20th	Day	18% 5% 20% 27% 21% 10%	567
	21st to end	Day	18% 7% 18% 24% 19% 13%	617
June	1st to 10th	Day	15% 5% 14% 31% 24% 12%	570
	11th to 20th	Day	7% 4 15% 30% 25% 19%	570
	21st to end	Day	9% 2 14% 30% 26% 19%	570
July	1st to 10th	Day	10% 2 9% 23% 32% 25%	565
	11th to 20th	Day	7% 3 7% 26% 34% 23%	564
	21st to end	Day	7% 2 7% 31% 34% 20%	620
August	1st to 10th	Day	18% 3 11% 24% 26% 17%	566
	11th to 20th	Day	10% 3 7% 26% 33% 20%	559
	21st to end	Day	14% 3 8% 26% 30% 19%	627
September	1st to 10th	Day	10% 2 11% 30% 29% 18%	570
	11th to 20th	Day	20% 4 9% 21% 30% 17%	570
	21st to end	Day	21% 3 15% 27% 25% 9%	562
October	1st to 10th	Day	19% 2 15% 32% 22% 9%	530
	11th to 20th	Day	14% 6% 18% 31% 26% 5%	530
	21st to end	Day	20% 5% 23% 29% 18% 5%	583
November	1st to 10th	Day	21% 7% 23% 27% 17% 5%	435
	11th to 20th	Day	17% 13% 31% 30% 8% 2	330
	21st to end	Day	14% 14% 31% 28% 11% 2	330
December	1st to 10th	Day	33% 11% 29% 21% 6%	330
	11th to 20th	Day	22% 13% 31% 26% 7% 1	330
	21st to end	Day	31% 13% 31% 16% 7% 3	363
January	1st to 10th	Night	22% 11% 31% 30% 5%	840
	11th to 20th	Night	21% 13% 32% 28% 6%	840
	21st to end	Night	21% 12% 37% 27% 3	924
February	1st to 10th	Night	18% 10% 29% 38% 5%	840
	11th to 20th	Night	26% 10% 33% 27% 3	823
	21st to end	Night	22% 12% 34% 28% 4	692
March	1st to 10th	Night	18% 10% 30% 35% 6%	840
	11th to 20th	Night	16% 9% 35% 32% 8%	840
	21st to end	Night	20% 9% 29% 31% 10%	924
April	1st to 10th	Night	17% 11% 26% 34% 12%	840
	11th to 20th	Night	14% 9% 25% 36% 15% 1	707
	21st to end	Night	14% 4 23% 37% 20% 1	630
May	1st to 10th	Night	13% 5% 23% 37% 21% 1	630
	11th to 20th	Night	18% 4 19% 32% 24% 3	621
	21st to end	Night	18% 2 12% 30% 32% 6%	683
June	1st to 10th	Night	13% 3 11% 32% 35% 6%	630
	11th to 20th	Night	10% 2 12% 28% 33% 14%	630
	21st to end	Night	8% 3 6% 34% 40% 9%	630
July	1st to 10th	Night	12% 3 7% 24% 40% 14%	615
	11th to 20th	Night	13% 3 4 22% 42% 16%	612
	21st to end	Night	9% 3 6% 28% 43% 12%	690
August	1st to 10th	Night	20% 2 6% 23% 37% 13%	627
	11th to 20th	Night	15% 3 6% 27% 38% 11%	624
	21st to end	Night	15% 2 5% 27% 41% 11%	736
September	1st to 10th	Night	12% 2 9% 30% 37% 10%	840
	11th to 20th	Night	20% 3 10% 26% 35% 6%	840
	21st to end	Night	19% 3 11% 32% 30% 3	833
October	1st to 10th	Night	16% 4 17% 30% 28% 7%	800
	11th to 20th	Night	14% 5% 23% 34% 22% 3	800
	21st to end	Night	17% 6% 19% 35% 21% 3	880
November	1st to 10th	Night	16% 6% 19% 38% 18% 3	820
	11th to 20th	Night	18% 8% 27% 32% 13% 1	840
	21st to end	Night	18% 7% 25% 36% 14% 1	840
December	1st to 10th	Night	25% 7% 26% 33% 9% 1	840
	11th to 20th	Night	22% 7% 29% 32% 11% 1	840
	21st to end	Night	26% 9% 25% 32% 8%	924

Page generated at 2026-09-26 04:18:44. Version ac07

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