Gilbert-Baker Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gilbert-Baker Campground clear sky chart from 2005-11-06 to 2026-07-31.

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% 5% 2 5% 3 4 4 4 6% 8% 53%	147141
	Night	6% 6% 2 6% 4 4 4 4 6% 7% 51%	143384
Transparency	Day	28% 6% 13% 27% 20% 6%	141967
	Night	30% 7% 13% 27% 18% 5%	139570
Seeing	Day	11% 12% 32% 28% 14% 3	18253
	Night	9% 12% 38% 32% 8% 1	28179

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	2 6% 4 9% 6% 5% 4 4 6% 7% 48%	4720
	11th to 20th	Day	3 8% 5% 8% 5% 5% 5% 5% 6% 7% 42%	4740
	21st to end	Day	2 5% 2 9% 3 4 4 3 6% 7% 54%	5404
February	1st to 10th	Day	4 11% 4 7% 5% 5% 4 4 6% 7% 42%	1890
	11th to 20th	Day	3 9% 5% 8% 4 4 5% 4 6% 7% 45%	2012
	21st to end	Day	3 8% 4 6% 5% 3 4 3 5% 7% 52%	1730
March	1st to 10th	Day	5% 10% 2 5% 4 3 3 3 5% 7% 52%	4600
	11th to 20th	Day	5% 7% 2 4 3 3 3 3 4 7% 59%	4820
	21st to end	Day	9% 9% 3 8% 4 4 4 4 5% 8% 42%	6089
April	1st to 10th	Day	8% 8% 3 5% 4 4 5% 4 6% 8% 45%	2520
	11th to 20th	Day	10% 8% 3 6% 5% 4 4 4 6% 7% 42%	2491
	21st to end	Day	13% 10% 2 5% 4 3 5% 3 5% 6% 44%	2609
May	1st to 10th	Day	11% 7% 2 5% 3 3 4 3 5% 6% 50%	7768
	11th to 20th	Day	11% 5% 1 4 3 4 4 4 6% 8% 49%	8191
	21st to end	Day	12% 5% 2 5% 3 4 4 4 6% 9% 46%	9026
June	1st to 10th	Day	7% 3 1 4 3 4 5% 5% 6% 9% 53%	2940
	11th to 20th	Day	8% 4 1 4 3 4 4 3 7% 9% 53%	2940
	21st to end	Day	6% 3 1 3 3 3 4 3 6% 9% 58%	2940
July	1st to 10th	Day	3 3 1 4 3 3 4 4 7% 9% 59%	6479
	11th to 20th	Day	6% 2 1 3 3 4 5% 4 6% 9% 58%	6480
	21st to end	Day	7% 4 1 4 3 4 4 3 6% 9% 56%	7044
August	1st to 10th	Day	6% 3 1 4 3 4 4 4 6% 9% 55%	6192
	11th to 20th	Day	3 2 1 4 3 3 4 4 6% 8% 62%	5413
	21st to end	Day	5% 5% 2 6% 4 4 4 4 6% 8% 52%	5984
September	1st to 10th	Day	7% 4 1 4 3 2 3 3 4 6% 63%	2400
	11th to 20th	Day	7% 4 1 3 2 2 3 3 4 8% 63%	2332
	21st to end	Day	7% 4 1 3 2 2 2 2 4 7% 65%	2200
October	1st to 10th	Day	6% 3 1 2 2 2 2 2 3 3 74%	3382
	11th to 20th	Day	8% 5% 1 4 2 3 3 2 4 7% 61%	3250
	21st to end	Day	7% 7% 2 4 3 3 3 3 5% 7% 56%	3203
November	1st to 10th	Day	4 5% 2 4 3 4 3 4 8% 8% 54%	1853
	11th to 20th	Day	4 5% 2 6% 4 3 4 3 5% 8% 57%	1890
	21st to end	Day	4 8% 2 4 3 4 4 4 5% 8% 54%	1711
December	1st to 10th	Day	2 5% 3 6% 4 4 3 2 5% 7% 60%	2700
	11th to 20th	Day	2 5% 2 5% 3 3 4 4 7% 9% 55%	3106
	21st to end	Day	3 7% 4 8% 5% 5% 5% 3 4 7% 50%	4092
January	1st to 10th	Night	2 9% 4 9% 5% 5% 4 3 5% 7% 46%	8201
	11th to 20th	Night	2 7% 3 9% 5% 4 4 4 6% 8% 49%	8250
	21st to end	Night	1 5% 3 9% 4 4 4 4 5% 6% 55%	8869
February	1st to 10th	Night	4 10% 4 9% 5% 5% 5% 5% 6% 7% 40%	2730
	11th to 20th	Night	3 10% 4 7% 6% 5% 6% 5% 6% 7% 41%	2493
	21st to end	Night	3 7% 3 7% 4 4 5% 4 5% 6% 51%	2076
March	1st to 10th	Night	6% 8% 3 7% 4 3 3 3 4 5% 54%	5494
	11th to 20th	Night	4 7% 2 5% 3 4 4 3 5% 7% 56%	5385
	21st to end	Night	9% 9% 3 9% 5% 5% 5% 4 5% 8% 38%	5105
April	1st to 10th	Night	11% 9% 2 5% 4 4 4 3 4 7% 48%	2100
	11th to 20th	Night	11% 8% 2 5% 5% 4 4 3 5% 7% 45%	2077
	21st to end	Night	14% 9% 2 6% 4 4 4 3 6% 7% 41%	2009
May	1st to 10th	Night	10% 7% 2 6% 4 4 4 3 5% 7% 48%	5163
	11th to 20th	Night	11% 6% 2 4 3 3 4 4 6% 8% 48%	4701
	21st to end	Night	14% 5% 2 5% 4 4 5% 4 6% 9% 43%	5181
June	1st to 10th	Night	7% 4 2 4 3 5% 4 6% 6% 10% 49%	1680
	11th to 20th	Night	9% 3 1 3 3 3 4 4 8% 10% 52%	1680
	21st to end	Night	6% 4 1 3 3 4 4 3 8% 8% 55%	1680
July	1st to 10th	Night	5% 3 2 6% 4 5% 5% 4 7% 8% 52%	3720
	11th to 20th	Night	7% 3 1 4 4 4 5% 4 7% 10% 49%	3720
	21st to end	Night	4 4 2 6% 5% 5% 5% 5% 7% 9% 49%	4050
August	1st to 10th	Night	8% 3 2 5% 4 5% 4 5% 6% 10% 49%	3617
	11th to 20th	Night	3 4 2 5% 4 4 6% 5% 7% 9% 53%	4436
	21st to end	Night	6% 6% 2 7% 5% 5% 5% 4 6% 7% 47%	4993
September	1st to 10th	Night	7% 4 2 4 3 2 4 3 3 7% 61%	2000
	11th to 20th	Night	7% 4 1 4 3 4 3 3 5% 6% 59%	2067
	21st to end	Night	9% 4 1 3 3 3 3 2 4 5% 62%	2200
October	1st to 10th	Night	7% 3 1 3 2 2 2 2 3 4 72%	3788
	11th to 20th	Night	6% 5% 2 4 3 4 3 2 5% 8% 58%	3898
	21st to end	Night	7% 5% 2 4 3 3 3 4 6% 8% 55%	4563
November	1st to 10th	Night	7% 5% 2 5% 4 4 3 3 5% 8% 53%	2665
	11th to 20th	Night	4 6% 2 6% 5% 4 5% 4 6% 7% 53%	2730
	21st to end	Night	4 7% 3 5% 3 3 3 3 6% 8% 55%	2904
December	1st to 10th	Night	2 4 2 5% 3 4 4 3 5% 7% 59%	4710
	11th to 20th	Night	2 7% 3 6% 4 4 5% 4 7% 8% 52%	5321
	21st to end	Night	3 9% 4 8% 5% 4 5% 3 6% 7% 46%	7128

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	32% 6% 15% 28% 18% 1	4723
	11th to 20th	Day	37% 7% 14% 24% 15% 3	4740
	21st to end	Day	28% 5% 14% 28% 19% 6%	5404
February	1st to 10th	Day	39% 7% 15% 22% 14% 2	1890
	11th to 20th	Day	37% 7% 14% 23% 14% 5%	2022
	21st to end	Day	30% 5% 16% 27% 18% 4	1730
March	1st to 10th	Day	30% 5% 8% 29% 23% 5%	4600
	11th to 20th	Day	25% 5% 14% 28% 25% 2	4820
	21st to end	Day	38% 9% 15% 27% 11% 1	6089
April	1st to 10th	Day	34% 8% 16% 26% 13% 4	2520
	11th to 20th	Day	38% 7% 13% 19% 20% 4	2494
	21st to end	Day	39% 6% 14% 27% 13% 1	2609
May	1st to 10th	Day	32% 7% 15% 29% 16% 3	7768
	11th to 20th	Day	29% 7% 12% 26% 21% 4	8195
	21st to end	Day	31% 9% 14% 29% 16% 1	9027
June	1st to 10th	Day	25% 9% 19% 29% 15% 4	2940
	11th to 20th	Day	27% 6% 15% 25% 19% 7%	2940
	21st to end	Day	21% 7% 11% 28% 25% 9%	2940
July	1st to 10th	Day	19% 7% 10% 26% 28% 10%	6411
	11th to 20th	Day	20% 7% 11% 27% 23% 13%	6405
	21st to end	Day	24% 5% 10% 18% 22% 20%	6846
August	1st to 10th	Day	25% 7% 14% 25% 22% 7%	4509
	11th to 20th	Day	21% 8% 13% 23% 25% 11%	3917
	21st to end	Day	21% 6% 10% 19% 26% 18%	4311
September	1st to 10th	Day	23% 4 8% 24% 28% 14%	2400
	11th to 20th	Day	21% 4 9% 27% 27% 13%	2332
	21st to end	Day	21% 3 9% 30% 30% 7%	2200
October	1st to 10th	Day	18% 3 8% 16% 35% 20%	3382
	11th to 20th	Day	25% 5% 11% 30% 23% 6%	3250
	21st to end	Day	28% 4 11% 33% 19% 5%	3203
November	1st to 10th	Day	25% 7% 16% 27% 20% 6%	1853
	11th to 20th	Day	25% 5% 14% 30% 23% 4	1890
	21st to end	Day	27% 6% 14% 29% 20% 4	1711
December	1st to 10th	Day	25% 5% 18% 31% 20% 2	2700
	11th to 20th	Day	23% 6% 15% 36% 17% 2	3104
	21st to end	Day	32% 6% 10% 35% 16% 1	4092
January	1st to 10th	Night	36% 6% 11% 32% 12% 2	8202
	11th to 20th	Night	30% 7% 18% 26% 16% 4	8250
	21st to end	Night	29% 6% 14% 30% 17% 4	8869
February	1st to 10th	Night	39% 7% 16% 23% 13% 2	2730
	11th to 20th	Night	39% 8% 14% 22% 13% 5%	2493
	21st to end	Night	31% 7% 13% 27% 18% 5%	2076
March	1st to 10th	Night	31% 5% 9% 24% 24% 7%	5494
	11th to 20th	Night	27% 6% 15% 24% 27% 2	5385
	21st to end	Night	40% 10% 17% 21% 12% 1	5105
April	1st to 10th	Night	36% 6% 14% 24% 17% 3	2100
	11th to 20th	Night	37% 6% 12% 24% 17% 4	2077
	21st to end	Night	41% 7% 12% 24% 14% 1	2009
May	1st to 10th	Night	34% 7% 12% 27% 18% 1	5164
	11th to 20th	Night	31% 8% 13% 31% 13% 4	4702
	21st to end	Night	33% 11% 16% 28% 11% 1	5182
June	1st to 10th	Night	27% 11% 23% 25% 11% 3	1680
	11th to 20th	Night	25% 9% 18% 27% 15% 6%	1680
	21st to end	Night	23% 8% 14% 27% 21% 7%	1680
July	1st to 10th	Night	26% 7% 11% 25% 21% 10%	3680
	11th to 20th	Night	27% 7% 15% 27% 17% 7%	3672
	21st to end	Night	29% 8% 13% 20% 20% 9%	3936
August	1st to 10th	Night	31% 9% 15% 22% 18% 5%	2624
	11th to 20th	Night	27% 10% 14% 21% 22% 6%	3208
	21st to end	Night	24% 6% 12% 20% 26% 11%	3597
September	1st to 10th	Night	24% 4 8% 26% 28% 10%	2000
	11th to 20th	Night	25% 5% 10% 26% 24% 10%	2067
	21st to end	Night	25% 5% 8% 27% 25% 11%	2200
October	1st to 10th	Night	18% 4 7% 19% 31% 21%	3788
	11th to 20th	Night	26% 4 12% 30% 23% 6%	3898
	21st to end	Night	27% 5% 11% 29% 20% 8%	4563
November	1st to 10th	Night	28% 5% 15% 26% 21% 5%	2665
	11th to 20th	Night	28% 6% 12% 28% 21% 5%	2730
	21st to end	Night	27% 5% 13% 29% 21% 5%	2904
December	1st to 10th	Night	23% 6% 17% 31% 20% 3	4710
	11th to 20th	Night	28% 6% 15% 36% 12% 2	5322
	21st to end	Night	35% 6% 10% 34% 12% 2	7128

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	8% 21% 32% 26% 12% 2	330
	11th to 20th	Day	14% 21% 39% 20% 6% 1	330
	21st to end	Day	10% 23% 45% 16% 4 2	363
February	1st to 10th	Day	11% 22% 45% 18% 3 1	330
	11th to 20th	Day	7% 23% 41% 23% 5%	330
	21st to end	Day	9% 24% 43% 21% 3	273
March	1st to 10th	Day	8% 21% 36% 27% 6% 1	330
	11th to 20th	Day	12% 18% 42% 21% 6% 1	406
	21st to end	Day	15% 19% 37% 22% 7% 1	594
April	1st to 10th	Day	16% 19% 36% 22% 5% 1	540
	11th to 20th	Day	15% 25% 36% 17% 7% 1	532
	21st to end	Day	20% 11% 34% 24% 9% 2	629
May	1st to 10th	Day	16% 12% 32% 24% 13% 3	753
	11th to 20th	Day	19% 10% 26% 27% 16% 3	775
	21st to end	Day	16% 11% 30% 27% 14% 3	844
June	1st to 10th	Day	7% 7% 27% 32% 22% 6%	780
	11th to 20th	Day	10% 12% 34% 30% 12% 3	780
	21st to end	Day	10% 6% 29% 32% 20% 3	780
July	1st to 10th	Day	5% 4 24% 38% 23% 6%	771
	11th to 20th	Day	7% 3 25% 42% 20% 4	768
	21st to end	Day	7% 3 22% 39% 26% 3	845
August	1st to 10th	Day	5% 4 27% 37% 24% 4	712
	11th to 20th	Day	5% 4 25% 34% 26% 6%	517
	21st to end	Day	6% 6% 24% 34% 24% 6%	583
September	1st to 10th	Day	8% 7% 22% 35% 21% 7%	530
	11th to 20th	Day	7% 8% 22% 35% 23% 5%	462
	21st to end	Day	8% 8% 31% 28% 15% 9%	330
October	1st to 10th	Day	12% 10% 26% 27% 17% 9%	330
	11th to 20th	Day	12% 16% 38% 18% 13% 3	330
	21st to end	Day	11% 14% 39% 23% 10% 2	363
November	1st to 10th	Day	7% 17% 43% 22% 9% 3	330
	11th to 20th	Day	9% 18% 41% 22% 9%	330
	21st to end	Day	11% 12% 42% 25% 8% 3	330
December	1st to 10th	Day	10% 18% 45% 20% 6%	330
	11th to 20th	Day	12% 19% 49% 14% 5%	330
	21st to end	Day	10% 24% 40% 20% 6%	363
January	1st to 10th	Night	7% 19% 39% 27% 8% 1	1050
	11th to 20th	Night	10% 22% 41% 21% 5%	1050
	21st to end	Night	7% 19% 44% 26% 4	1102
February	1st to 10th	Night	8% 18% 47% 23% 4	840
	11th to 20th	Night	9% 15% 43% 28% 5%	824
	21st to end	Night	8% 17% 48% 23% 4	692
March	1st to 10th	Night	10% 15% 41% 29% 5%	840
	11th to 20th	Night	10% 9% 43% 30% 7% 1	840
	21st to end	Night	13% 14% 37% 31% 4 1	704
April	1st to 10th	Night	15% 13% 39% 30% 4	630
	11th to 20th	Night	16% 14% 39% 27% 3	623
	21st to end	Night	18% 13% 27% 33% 9%	630
May	1st to 10th	Night	15% 10% 30% 32% 11% 1	630
	11th to 20th	Night	17% 6% 30% 35% 11% 1	621
	21st to end	Night	16% 10% 33% 33% 7%	683
June	1st to 10th	Night	8% 6% 36% 37% 11% 1	630
	11th to 20th	Night	10% 7% 42% 36% 5%	630
	21st to end	Night	7% 6% 35% 43% 9% 1	630
July	1st to 10th	Night	6% 3 29% 44% 16% 1	615
	11th to 20th	Night	4 4 30% 48% 14%	612
	21st to end	Night	5% 3 27% 48% 17%	687
August	1st to 10th	Night	6% 4 29% 46% 15% 1	597
	11th to 20th	Night	4 2 30% 48% 16% 1	594
	21st to end	Night	4 4 29% 48% 15%	660
September	1st to 10th	Night	8% 4 26% 46% 15% 1	600
	11th to 20th	Night	8% 8% 32% 37% 15% 2	600
	21st to end	Night	12% 6% 31% 37% 14%	600
October	1st to 10th	Night	14% 10% 32% 30% 14% 1	720
	11th to 20th	Night	11% 11% 34% 35% 9% 1	800
	21st to end	Night	9% 12% 40% 30% 8% 1	1065
November	1st to 10th	Night	9% 9% 44% 29% 8% 1	1025
	11th to 20th	Night	6% 18% 43% 28% 5% 1	1050
	21st to end	Night	8% 15% 40% 30% 6%	1050
December	1st to 10th	Night	7% 17% 47% 24% 5%	1050
	11th to 20th	Night	8% 15% 44% 28% 4	1050
	21st to end	Night	10% 18% 44% 22% 5%	1155

Page generated at 2026-07-28 01:25:25. Version ac07

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