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 2025-03-27.

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% 6% 2 5% 4 4 4 4 6% 7% 54%	112872
	Night	5% 6% 2 6% 4 4 4 4 6% 7% 52%	115295
Transparency	Day	27% 6% 13% 27% 20% 7%	112613
	Night	29% 7% 14% 27% 18% 5%	115144
Seeing	Day	10% 12% 32% 28% 15% 3	16270
	Night	9% 12% 38% 32% 8% 1	26442

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 10% 7% 5% 4 4 6% 6% 45%	3638
	11th to 20th	Day	3 10% 5% 7% 5% 5% 5% 5% 7% 8% 39%	3640
	21st to end	Day	2 5% 2 8% 3 3 3 3 5% 6% 60%	4164
February	1st to 10th	Day	4 11% 4 7% 5% 5% 5% 4 6% 6% 42%	1800
	11th to 20th	Day	3 9% 5% 8% 4 4 4 4 6% 7% 45%	1914
	21st to end	Day	3 9% 4 6% 5% 3 4 3 5% 7% 51%	1650
March	1st to 10th	Day	4 9% 2 5% 4 4 4 3 6% 7% 53%	3230
	11th to 20th	Day	5% 7% 2 4 3 3 3 3 5% 7% 58%	3394
	21st to end	Day	10% 10% 3 8% 4 4 4 4 5% 8% 40%	4227
April	1st to 10th	Day	9% 8% 2 5% 4 4 5% 4 6% 8% 44%	2280
	11th to 20th	Day	11% 9% 3 6% 5% 4 4 4 6% 7% 41%	2251
	21st to end	Day	13% 9% 2 5% 4 3 5% 3 5% 7% 44%	2361
May	1st to 10th	Day	16% 10% 3 6% 4 4 4 3 5% 6% 38%	4182
	11th to 20th	Day	11% 6% 1 4 3 4 4 4 6% 8% 48%	4388
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 8% 46%	4825
June	1st to 10th	Day	6% 3 1 4 4 4 5% 5% 7% 10% 52%	2660
	11th to 20th	Day	8% 4 1 4 3 3 4 3 7% 9% 52%	2660
	21st to end	Day	5% 3 1 3 3 3 4 3 6% 9% 59%	2660
July	1st to 10th	Day	4 2 1 3 3 3 4 4 7% 8% 61%	4430
	11th to 20th	Day	3 2 1 3 3 4 4 4 7% 10% 60%	4430
	21st to end	Day	3 2 1 3 3 4 4 3 6% 9% 62%	4802
August	1st to 10th	Day	9% 3 1 4 3 4 4 4 6% 8% 54%	4385
	11th to 20th	Day	4 3 1 4 3 4 5% 5% 7% 8% 57%	3760
	21st to end	Day	4 3 1 4 3 3 4 4 6% 7% 61%	4180
September	1st to 10th	Day	7% 4 1 4 3 2 3 3 4 6% 63%	2280
	11th to 20th	Day	6% 3 1 3 2 2 3 3 3 8% 65%	2216
	21st to end	Day	7% 4 1 3 2 2 2 2 4 7% 65%	2090
October	1st to 10th	Day	6% 3 1 2 2 2 2 2 3 3 74%	3278
	11th to 20th	Day	8% 5% 1 4 2 3 3 2 4 7% 61%	3150
	21st to end	Day	8% 7% 2 5% 3 3 3 3 5% 7% 55%	3104
November	1st to 10th	Day	5% 6% 2 4 3 4 3 4 8% 7% 54%	1763
	11th to 20th	Day	3 6% 2 6% 4 3 4 3 5% 8% 57%	1800
	21st to end	Day	5% 8% 2 4 3 3 4 3 5% 8% 55%	1630
December	1st to 10th	Day	2 5% 3 5% 4 3 3 2 4 6% 61%	2620
	11th to 20th	Day	2 5% 2 5% 3 3 4 4 7% 9% 56%	3026
	21st to end	Day	3 7% 4 8% 5% 5% 4 3 4 7% 50%	4004
January	1st to 10th	Night	2 9% 4 10% 5% 4 4 3 5% 7% 46%	6327
	11th to 20th	Night	2 8% 4 8% 5% 4 4 4 6% 8% 48%	6340
	21st to end	Night	1 4 3 8% 4 4 4 3 5% 6% 58%	6859
February	1st to 10th	Night	4 10% 4 10% 5% 5% 5% 5% 6% 7% 39%	2600
	11th to 20th	Night	4 11% 4 8% 7% 5% 6% 5% 6% 7% 40%	2372
	21st to end	Night	3 8% 3 7% 4 4 4 4 5% 6% 50%	1980
March	1st to 10th	Night	4 7% 4 7% 4 3 4 3 5% 6% 52%	3854
	11th to 20th	Night	5% 8% 2 5% 3 4 3 3 5% 7% 53%	3797
	21st to end	Night	9% 9% 3 9% 6% 6% 5% 4 5% 8% 37%	3552
April	1st to 10th	Night	11% 8% 2 5% 3 4 4 4 4 7% 48%	1900
	11th to 20th	Night	12% 8% 2 5% 5% 4 5% 3 5% 7% 44%	1877
	21st to end	Night	13% 9% 2 6% 4 4 4 3 6% 7% 42%	1818
May	1st to 10th	Night	13% 9% 3 5% 4 4 5% 4 5% 7% 41%	2772
	11th to 20th	Night	9% 5% 2 4 3 3 4 4 7% 10% 51%	2517
	21st to end	Night	13% 5% 2 5% 4 4 4 4 6% 9% 44%	2762
June	1st to 10th	Night	6% 4 2 4 3 5% 4 6% 6% 11% 49%	1520
	11th to 20th	Night	9% 3 1 4 3 3 4 4 8% 10% 51%	1520
	21st to end	Night	6% 3 1 3 3 4 4 3 7% 9% 57%	1520
July	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 7% 53%	2540
	11th to 20th	Night	4 2 1 4 4 4 5% 5% 8% 11% 52%	2540
	21st to end	Night	3 3 1 5% 4 4 5% 5% 7% 9% 54%	2761
August	1st to 10th	Night	9% 3 2 6% 4 5% 4 5% 6% 9% 46%	2551
	11th to 20th	Night	3 4 2 5% 4 5% 6% 5% 7% 9% 50%	3079
	21st to end	Night	3 3 1 5% 3 4 5% 4 6% 8% 57%	3487
September	1st to 10th	Night	7% 5% 2 4 3 2 4 3 3 7% 61%	1900
	11th to 20th	Night	6% 4 2 4 3 3 3 3 5% 6% 61%	1963
	21st to end	Night	9% 4 1 3 2 3 3 2 4 5% 62%	2090
October	1st to 10th	Night	7% 3 1 3 1 2 2 2 2 4 73%	3672
	11th to 20th	Night	6% 5% 2 4 3 4 3 2 5% 8% 58%	3778
	21st to end	Night	7% 5% 2 4 3 3 3 4 6% 8% 54%	4422
November	1st to 10th	Night	7% 5% 2 5% 4 4 3 3 5% 8% 53%	2535
	11th to 20th	Night	4 6% 2 6% 4 4 5% 4 6% 7% 53%	2600
	21st to end	Night	4 7% 3 5% 3 3 3 3 6% 8% 55%	2765
December	1st to 10th	Night	2 4 2 5% 3 4 4 3 5% 7% 60%	4570
	11th to 20th	Night	2 7% 3 6% 4 4 5% 4 6% 8% 52%	5181
	21st to end	Night	3 9% 4 8% 5% 4 5% 3 5% 7% 45%	6974

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	35% 6% 14% 28% 16% 1	3639
	11th to 20th	Day	39% 8% 15% 21% 15% 2	3640
	21st to end	Day	24% 5% 15% 29% 19% 7%	4164
February	1st to 10th	Day	40% 7% 16% 21% 14% 3	1800
	11th to 20th	Day	37% 7% 15% 22% 14% 5%	1924
	21st to end	Day	31% 5% 16% 26% 17% 5%	1650
March	1st to 10th	Day	28% 5% 10% 27% 24% 5%	3230
	11th to 20th	Day	24% 7% 19% 33% 16% 2	3394
	21st to end	Day	40% 9% 15% 28% 7% 1	4227
April	1st to 10th	Day	35% 8% 16% 24% 13% 4	2280
	11th to 20th	Day	39% 7% 14% 19% 17% 3	2254
	21st to end	Day	38% 6% 15% 28% 13% 1	2361
May	1st to 10th	Day	41% 9% 15% 22% 10% 3	4182
	11th to 20th	Day	30% 8% 16% 31% 14% 2	4392
	21st to end	Day	32% 9% 16% 30% 11% 2	4825
June	1st to 10th	Day	25% 9% 20% 29% 14% 4	2660
	11th to 20th	Day	27% 6% 15% 25% 19% 7%	2660
	21st to end	Day	20% 6% 11% 29% 26% 9%	2660
July	1st to 10th	Day	19% 7% 10% 24% 30% 10%	4361
	11th to 20th	Day	17% 6% 12% 27% 24% 14%	4355
	21st to end	Day	18% 5% 10% 21% 24% 21%	4651
August	1st to 10th	Day	25% 7% 14% 25% 22% 7%	4370
	11th to 20th	Day	21% 8% 13% 23% 25% 10%	3796
	21st to end	Day	20% 5% 10% 19% 26% 19%	4179
September	1st to 10th	Day	23% 4 8% 22% 28% 15%	2280
	11th to 20th	Day	19% 4 9% 26% 28% 13%	2216
	21st to end	Day	21% 3 9% 31% 30% 6%	2090
October	1st to 10th	Day	17% 3 8% 16% 35% 20%	3278
	11th to 20th	Day	25% 4 11% 31% 23% 6%	3150
	21st to end	Day	29% 4 12% 32% 18% 5%	3104
November	1st to 10th	Day	25% 6% 16% 27% 19% 6%	1763
	11th to 20th	Day	25% 5% 13% 29% 23% 4	1800
	21st to end	Day	27% 5% 14% 29% 20% 4	1630
December	1st to 10th	Day	25% 5% 18% 31% 20% 2	2620
	11th to 20th	Day	23% 6% 16% 37% 17% 1	3024
	21st to end	Day	32% 6% 10% 34% 16% 1	4004
January	1st to 10th	Night	37% 6% 11% 30% 13% 3	6327
	11th to 20th	Night	31% 7% 18% 23% 18% 3	6340
	21st to end	Night	26% 6% 16% 30% 18% 4	6859
February	1st to 10th	Night	40% 7% 16% 22% 12% 3	2600
	11th to 20th	Night	40% 8% 14% 21% 12% 4	2372
	21st to end	Night	31% 7% 13% 27% 17% 5%	1980
March	1st to 10th	Night	30% 6% 11% 26% 21% 5%	3854
	11th to 20th	Night	29% 6% 18% 27% 19% 2	3797
	21st to end	Night	40% 12% 17% 22% 8% 1	3552
April	1st to 10th	Night	36% 6% 15% 23% 17% 3	1900
	11th to 20th	Night	38% 6% 13% 25% 15% 3	1877
	21st to end	Night	40% 8% 12% 25% 14% 1	1818
May	1st to 10th	Night	38% 10% 14% 22% 15% 2	2772
	11th to 20th	Night	26% 9% 16% 36% 10% 3	2518
	21st to end	Night	31% 13% 18% 25% 10% 2	2762
June	1st to 10th	Night	27% 11% 23% 25% 11% 3	1520
	11th to 20th	Night	26% 9% 18% 27% 15% 6%	1520
	21st to end	Night	21% 8% 15% 29% 22% 6%	1520
July	1st to 10th	Night	27% 7% 10% 26% 21% 9%	2500
	11th to 20th	Night	21% 8% 17% 24% 21% 8%	2492
	21st to end	Night	23% 8% 13% 25% 21% 11%	2674
August	1st to 10th	Night	31% 9% 15% 21% 19% 5%	2543
	11th to 20th	Night	28% 9% 14% 21% 22% 6%	3109
	21st to end	Night	23% 6% 12% 21% 27% 11%	3487
September	1st to 10th	Night	24% 4 8% 24% 29% 11%	1900
	11th to 20th	Night	23% 5% 10% 27% 24% 11%	1963
	21st to end	Night	25% 5% 8% 27% 25% 11%	2090
October	1st to 10th	Night	18% 3 7% 19% 32% 21%	3672
	11th to 20th	Night	25% 5% 12% 30% 23% 6%	3778
	21st to end	Night	27% 5% 12% 29% 19% 8%	4422
November	1st to 10th	Night	28% 5% 15% 26% 21% 5%	2535
	11th to 20th	Night	27% 6% 12% 28% 21% 5%	2600
	21st to end	Night	27% 5% 13% 29% 21% 5%	2765
December	1st to 10th	Night	23% 5% 17% 31% 21% 3	4570
	11th to 20th	Night	29% 6% 15% 37% 13% 1	5182
	21st to end	Night	36% 6% 10% 34% 12% 2	6974

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% 18% 33% 27% 12% 2	300
	11th to 20th	Day	12% 21% 39% 21% 6% 1	300
	21st to end	Day	10% 22% 46% 16% 5% 2	330
February	1st to 10th	Day	12% 22% 47% 16% 3	300
	11th to 20th	Day	7% 25% 43% 21% 5%	300
	21st to end	Day	10% 24% 42% 21% 3	249
March	1st to 10th	Day	8% 22% 36% 27% 6% 1	300
	11th to 20th	Day	12% 17% 41% 21% 6% 1	372
	21st to end	Day	15% 18% 36% 21% 8% 1	531
April	1st to 10th	Day	16% 19% 35% 23% 5%	460
	11th to 20th	Day	15% 25% 36% 17% 6%	452
	21st to end	Day	19% 12% 34% 23% 10% 2	541
May	1st to 10th	Day	18% 13% 31% 23% 13% 2	653
	11th to 20th	Day	19% 9% 24% 27% 17% 3	675
	21st to end	Day	16% 12% 28% 28% 13% 3	734
June	1st to 10th	Day	6% 6% 27% 32% 23% 6%	680
	11th to 20th	Day	10% 11% 34% 30% 11% 3	680
	21st to end	Day	9% 5% 29% 33% 21% 3	680
July	1st to 10th	Day	5% 4 25% 38% 23% 6%	671
	11th to 20th	Day	6% 4 26% 41% 19% 3	668
	21st to end	Day	7% 2 22% 40% 27% 3	739
August	1st to 10th	Day	5% 3 27% 37% 24% 4	663
	11th to 20th	Day	5% 4 26% 34% 25% 6%	477
	21st to end	Day	5% 6% 24% 33% 25% 7%	539
September	1st to 10th	Day	8% 7% 22% 35% 21% 6%	490
	11th to 20th	Day	7% 8% 23% 34% 23% 6%	426
	21st to end	Day	8% 9% 32% 27% 16% 8%	300
October	1st to 10th	Day	11% 9% 26% 27% 18% 9%	300
	11th to 20th	Day	11% 14% 38% 19% 14% 3	300
	21st to end	Day	12% 15% 39% 23% 10% 2	330
November	1st to 10th	Day	7% 17% 43% 22% 9% 3	300
	11th to 20th	Day	9% 20% 41% 22% 8%	300
	21st to end	Day	11% 12% 44% 24% 6% 3	300
December	1st to 10th	Day	10% 18% 44% 22% 6%	300
	11th to 20th	Day	10% 19% 51% 14% 5%	300
	21st to end	Day	11% 24% 38% 20% 7%	330
January	1st to 10th	Night	7% 19% 38% 27% 8% 1	1000
	11th to 20th	Night	9% 22% 41% 22% 6% 1	1000
	21st to end	Night	7% 19% 43% 27% 4	1050
February	1st to 10th	Night	8% 19% 46% 23% 4	800
	11th to 20th	Night	9% 15% 43% 28% 5%	784
	21st to end	Night	8% 17% 47% 23% 5%	660
March	1st to 10th	Night	9% 15% 41% 29% 5% 1	800
	11th to 20th	Night	10% 9% 42% 31% 7% 1	800
	21st to end	Night	13% 13% 37% 32% 4 1	657
April	1st to 10th	Night	16% 13% 38% 29% 4	570
	11th to 20th	Night	16% 15% 39% 27% 3 1	563
	21st to end	Night	17% 13% 27% 33% 10%	570
May	1st to 10th	Night	16% 11% 31% 31% 11% 1	570
	11th to 20th	Night	17% 6% 28% 36% 12% 1	561
	21st to end	Night	15% 10% 33% 34% 7%	617
June	1st to 10th	Night	8% 5% 36% 36% 12% 2	570
	11th to 20th	Night	9% 7% 42% 36% 5%	570
	21st to end	Night	6% 4 35% 44% 9% 1	570
July	1st to 10th	Night	6% 3 29% 43% 17% 1	555
	11th to 20th	Night	4 4 31% 48% 14%	552
	21st to end	Night	4 2 27% 48% 18%	624
August	1st to 10th	Night	6% 3 28% 47% 15% 1	567
	11th to 20th	Night	4 2 30% 47% 16% 1	564
	21st to end	Night	3 3 28% 49% 16%	627
September	1st to 10th	Night	8% 5% 26% 45% 15% 1	570
	11th to 20th	Night	7% 8% 33% 36% 15% 2	570
	21st to end	Night	12% 6% 32% 37% 13%	570
October	1st to 10th	Night	14% 10% 31% 30% 14% 1	684
	11th to 20th	Night	11% 10% 34% 35% 10% 1	760
	21st to end	Night	10% 11% 40% 29% 8% 1	1012
November	1st to 10th	Night	9% 8% 43% 30% 9% 1	975
	11th to 20th	Night	6% 18% 43% 26% 5% 1	1000
	21st to end	Night	8% 15% 41% 30% 6%	1000
December	1st to 10th	Night	7% 17% 47% 24% 5%	1000
	11th to 20th	Night	8% 15% 45% 28% 5%	1000
	21st to end	Night	10% 19% 43% 23% 5%	1100

Page generated at 2025-03-24 07:04:30. Version ac07

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