Martis Creek Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Martis Creek Campground clear sky chart from 2005-11-06 to 2025-10-19.

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	2 6% 2 4 3 3 3 3 4 6% 65%	135235
	Night	2 6% 2 5% 3 3 3 3 5% 6% 61%	131847
Transparency	Day	12% 39% 5% 11% 18% 14%	130198
	Night	14% 40% 6% 13% 17% 10%	127866
Seeing	Day	14% 20% 29% 22% 12% 3	16303
	Night	11% 13% 23% 31% 19% 4	25589

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 10% 4 6% 3 4 4 3 6% 7% 52%	3639
	11th to 20th	Day	1 8% 3 4 4 3 4 3 4 5% 59%	3759
	21st to end	Day	4 12% 4 7% 4 4 4 4 4 6% 49%	4510
February	1st to 10th	Day	4 11% 4 7% 4 4 4 3 6% 6% 48%	1800
	11th to 20th	Day	2 10% 4 8% 5% 3 4 4 6% 7% 47%	1935
	21st to end	Day	1 11% 4 7% 5% 3 4 3 6% 7% 47%	1650
March	1st to 10th	Day	2 17% 8% 12% 4 4 4 3 5% 7% 35%	4518
	11th to 20th	Day	1 10% 3 5% 4 3 3 3 5% 7% 54%	4955
	21st to end	Day	2 16% 4 7% 4 4 4 4 5% 6% 43%	5823
April	1st to 10th	Day	3 10% 3 7% 5% 4 4 4 6% 8% 46%	2400
	11th to 20th	Day	3 10% 3 6% 4 4 4 3 5% 7% 51%	2369
	21st to end	Day	4 10% 2 5% 3 3 3 2 6% 7% 55%	2400
May	1st to 10th	Day	3 6% 1 4 2 2 2 2 3 5% 70%	5691
	11th to 20th	Day	2 5% 1 4 3 3 3 3 4 5% 68%	6228
	21st to end	Day	3 4 2 4 3 2 2 2 3 5% 69%	6902
June	1st to 10th	Day	4 4 2 5% 4 4 3 3 5% 7% 59%	2800
	11th to 20th	Day	2 2 1 3 2 2 3 3 3 5% 76%	2800
	21st to end	Day	2 2 1 3 1 2 2 2 3 5% 77%	2800
July	1st to 10th	Day	1 1 1 1 2 1 2 2 89%	6319
	11th to 20th	Day	1 1 2 2 2 2 2 3 3 82%	6320
	21st to end	Day	2 1 1 2 1 3 3 3 4 5% 76%	6707
August	1st to 10th	Day	2 1 1 2 1 1 2 1 3 4 82%	5744
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 89%	5364
	21st to end	Day	2 1 1 3 2 3 3 2 3 3 77%	5984
September	1st to 10th	Day	2 1 2 2 2 2 2 3 5% 80%	2400
	11th to 20th	Day	2 3 1 3 2 2 2 2 4 5% 72%	2378
	21st to end	Day	3 3 1 2 2 2 2 2 4 5% 75%	2200
October	1st to 10th	Day	3 3 1 3 2 2 3 2 5% 6% 71%	3295
	11th to 20th	Day	3 4 1 3 2 2 2 2 3 4 73%	3242
	21st to end	Day	2 4 1 4 3 3 3 3 5% 7% 65%	3372
November	1st to 10th	Day	4 8% 2 5% 4 3 5% 3 4 6% 56%	1764
	11th to 20th	Day	2 7% 2 4 4 4 5% 4 7% 9% 53%	1800
	21st to end	Day	2 8% 3 6% 5% 3 4 4 6% 8% 53%	1715
December	1st to 10th	Day	2 5% 2 4 3 4 3 3 6% 8% 60%	2620
	11th to 20th	Day	5% 15% 4 7% 5% 5% 6% 5% 7% 7% 35%	3028
	21st to end	Day	7% 11% 3 7% 4 4 4 4 7% 10% 38%	4004
January	1st to 10th	Night	1 6% 3 6% 4 4 5% 5% 8% 10% 49%	6306
	11th to 20th	Night	1 9% 3 7% 4 3 4 3 4 6% 55%	6192
	21st to end	Night	2 13% 4 6% 5% 4 4 4 5% 5% 49%	6468
February	1st to 10th	Night	2 9% 3 8% 6% 5% 5% 4 6% 6% 46%	2600
	11th to 20th	Night	1 9% 3 6% 5% 5% 5% 5% 7% 9% 45%	2352
	21st to end	Night	2 8% 4 8% 4 4 4 3 5% 8% 48%	1980
March	1st to 10th	Night	1 13% 7% 10% 5% 4 4 4 5% 7% 39%	5376
	11th to 20th	Night	2 12% 5% 7% 4 4 3 3 5% 6% 51%	5031
	21st to end	Night	1 15% 5% 8% 5% 5% 5% 5% 6% 6% 38%	5151
April	1st to 10th	Night	2 8% 3 7% 5% 4 5% 4 7% 8% 48%	2000
	11th to 20th	Night	2 9% 2 4 4 4 4 3 5% 7% 55%	1979
	21st to end	Night	3 7% 3 4 3 3 3 3 4 6% 59%	2000
May	1st to 10th	Night	2 3 2 3 2 2 2 2 3 5% 73%	4294
	11th to 20th	Night	1 5% 1 3 2 3 2 2 4 5% 71%	3662
	21st to end	Night	2 4 1 3 2 2 3 2 3 5% 73%	3972
June	1st to 10th	Night	3 4 1 5% 3 3 4 3 4 8% 61%	1600
	11th to 20th	Night	1 2 1 2 1 3 2 2 4 4 79%	1600
	21st to end	Night	2 2 1 3 2 2 3 2 3 4 78%	1600
July	1st to 10th	Night	1 1 1 1 1 1 2 91%	3640
	11th to 20th	Night	2 2 2 2 2 2 1 3 2 82%	3640
	21st to end	Night	3 1 2 2 2 3 3 4 5% 74%	4146
August	1st to 10th	Night	2 1 1 2 2 2 2 1 3 4 81%	4069
	11th to 20th	Night	1 1 1 1 1 1 1 2 3 87%	4506
	21st to end	Night	2 2 2 2 2 3 2 4 3 78%	5015
September	1st to 10th	Night	2 1 1 1 1 1 2 2 3 4 83%	2000
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 5% 76%	2021
	21st to end	Night	2 2 1 3 1 2 2 2 4 4 76%	2200
October	1st to 10th	Night	2 3 1 2 2 2 2 2 3 4 77%	3888
	11th to 20th	Night	2 2 1 3 2 2 2 1 3 5% 77%	3873
	21st to end	Night	3 5% 1 4 2 3 3 3 5% 7% 64%	4181
November	1st to 10th	Night	3 6% 2 4 4 4 4 4 6% 7% 56%	2535
	11th to 20th	Night	2 6% 2 5% 3 3 3 4 6% 9% 57%	2600
	21st to end	Night	2 6% 3 5% 5% 4 4 4 5% 7% 55%	2682
December	1st to 10th	Night	2 4 2 4 3 3 4 4 5% 6% 62%	4560
	11th to 20th	Night	2 13% 3 8% 4 5% 6% 5% 7% 11% 35%	5176
	21st to end	Night	5% 11% 4 9% 6% 5% 6% 5% 6% 8% 36%	6952

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	21% 31% 16% 17% 16% 1	3639
	11th to 20th	Day	20% 31% 5% 12% 24% 7%	3759
	21st to end	Day	23% 32% 7% 12% 17% 8%	4510
February	1st to 10th	Day	20% 63% 4 7% 3 3	1800
	11th to 20th	Day	15% 63% 4 10% 6% 2	1945
	21st to end	Day	11% 64% 5% 10% 6% 4	1650
March	1st to 10th	Day	32% 36% 6% 8% 13% 5%	4518
	11th to 20th	Day	13% 34% 9% 29% 15% 1	4955
	21st to end	Day	25% 35% 10% 17% 12% 1	5823
April	1st to 10th	Day	13% 63% 5% 11% 6% 1	2400
	11th to 20th	Day	10% 64% 4 11% 8% 3	2372
	21st to end	Day	11% 63% 6% 11% 9% 1	2400
May	1st to 10th	Day	12% 30% 5% 19% 30% 5%	5691
	11th to 20th	Day	11% 30% 8% 14% 33% 5%	6231
	21st to end	Day	8% 29% 5% 16% 36% 6%	6904
June	1st to 10th	Day	6% 62% 4 9% 15% 5%	2800
	11th to 20th	Day	4 61% 2 10% 13% 10%	2800
	21st to end	Day	3 60% 1 4 13% 18%	2800
July	1st to 10th	Day	3 24% 1 4 13% 54%	6251
	11th to 20th	Day	6% 26% 2 5% 7% 54%	6245
	21st to end	Day	8% 26% 4 11% 23% 28%	6512
August	1st to 10th	Day	9% 35% 2 4 15% 35%	4184
	11th to 20th	Day	3 35% 1 4 20% 37%	3880
	21st to end	Day	4 36% 2 7% 29% 22%	4311
September	1st to 10th	Day	6% 56% 2 5% 17% 15%	2400
	11th to 20th	Day	8% 57% 3 10% 15% 7%	2378
	21st to end	Day	8% 56% 3 10% 15% 8%	2200
October	1st to 10th	Day	6% 35% 3 8% 27% 21%	3295
	11th to 20th	Day	10% 36% 2 8% 36% 7%	3242
	21st to end	Day	11% 38% 6% 17% 21% 7%	3372
November	1st to 10th	Day	8% 57% 4 13% 13% 5%	1764
	11th to 20th	Day	11% 59% 6% 11% 11% 3	1800
	21st to end	Day	16% 59% 6% 8% 7% 5%	1715
December	1st to 10th	Day	12% 37% 6% 19% 21% 5%	2620
	11th to 20th	Day	30% 37% 7% 11% 10% 4	3028
	21st to end	Day	24% 32% 15% 16% 11% 1	4004
January	1st to 10th	Night	17% 34% 17% 17% 15% 1	6306
	11th to 20th	Night	22% 31% 6% 13% 23% 5%	6192
	21st to end	Night	25% 32% 5% 10% 22% 5%	6468
February	1st to 10th	Night	17% 65% 4 6% 4 3	2600
	11th to 20th	Night	12% 64% 4 9% 9% 2	2353
	21st to end	Night	10% 64% 6% 9% 7% 5%	1980
March	1st to 10th	Night	30% 33% 6% 15% 12% 4	5376
	11th to 20th	Night	18% 34% 8% 28% 11% 1	5031
	21st to end	Night	29% 38% 12% 16% 4 1	5151
April	1st to 10th	Night	11% 64% 6% 11% 7%	2000
	11th to 20th	Night	11% 64% 4 12% 8% 2	1979
	21st to end	Night	10% 63% 6% 13% 7% 1	2000
May	1st to 10th	Night	8% 31% 6% 26% 26% 3	4291
	11th to 20th	Night	10% 29% 7% 20% 29% 5%	3662
	21st to end	Night	6% 29% 5% 21% 34% 5%	3972
June	1st to 10th	Night	4 62% 3 13% 13% 5%	1600
	11th to 20th	Night	2 62% 3 10% 12% 11%	1600
	21st to end	Night	3 59% 2 4 14% 17%	1600
July	1st to 10th	Night	3 24% 1 3 17% 53%	3600
	11th to 20th	Night	7% 24% 2 4 10% 53%	3592
	21st to end	Night	8% 26% 3 15% 22% 27%	4030
August	1st to 10th	Night	8% 35% 1 5% 20% 30%	2951
	11th to 20th	Night	3 35% 1 4 24% 32%	3256
	21st to end	Night	5% 35% 2 10% 27% 21%	3608
September	1st to 10th	Night	4 56% 2 6% 20% 14%	2000
	11th to 20th	Night	6% 57% 3 11% 19% 5%	2021
	21st to end	Night	7% 56% 2 9% 18% 8%	2200
October	1st to 10th	Night	4 35% 2 8% 27% 24%	3888
	11th to 20th	Night	6% 37% 4 12% 34% 8%	3873
	21st to end	Night	12% 38% 5% 18% 19% 8%	4181
November	1st to 10th	Night	9% 56% 4 13% 13% 4	2535
	11th to 20th	Night	11% 57% 5% 13% 11% 3	2600
	21st to end	Night	15% 58% 5% 9% 8% 6%	2682
December	1st to 10th	Night	12% 38% 6% 16% 19% 9%	4560
	11th to 20th	Night	25% 39% 8% 13% 14% 2	5176
	21st to end	Night	29% 33% 12% 15% 9% 2	6952

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	33% 21% 24% 14% 9% 1	200
	11th to 20th	Day	26% 19% 23% 21% 10% 1	254
	21st to end	Day	15% 25% 29% 20% 8% 3	440
February	1st to 10th	Day	25% 24% 26% 17% 8% 1	400
	11th to 20th	Day	25% 24% 27% 19% 4	488
	21st to end	Day	23% 21% 32% 19% 4	414
March	1st to 10th	Day	28% 30% 24% 12% 4 1	500
	11th to 20th	Day	26% 25% 24% 15% 8% 1	500
	21st to end	Day	24% 30% 25% 16% 5%	550
April	1st to 10th	Day	20% 28% 27% 16% 8% 1	500
	11th to 20th	Day	22% 28% 26% 15% 6% 2	492
	21st to end	Day	17% 24% 28% 19% 10% 2	500
May	1st to 10th	Day	19% 27% 25% 20% 7% 2	503
	11th to 20th	Day	19% 23% 26% 21% 9% 3	528
	21st to end	Day	16% 18% 27% 23% 13% 4	573
June	1st to 10th	Day	11% 19% 31% 22% 13% 4	530
	11th to 20th	Day	12% 22% 35% 19% 11% 2	530
	21st to end	Day	4 15% 35% 28% 15% 4	530
July	1st to 10th	Day	3 13% 40% 27% 14% 3	526
	11th to 20th	Day	1 10% 40% 30% 15% 3	524
	21st to end	Day	2 10% 34% 31% 17% 6%	575
August	1st to 10th	Day	4 12% 34% 29% 16% 5%	527
	11th to 20th	Day	3 14% 34% 26% 18% 5%	517
	21st to end	Day	4 11% 39% 26% 16% 3	583
September	1st to 10th	Day	3 12% 37% 29% 16% 2	530
	11th to 20th	Day	8% 17% 28% 29% 15% 3	530
	21st to end	Day	7% 16% 34% 28% 13% 2	530
October	1st to 10th	Day	8% 21% 25% 27% 15% 3	530
	11th to 20th	Day	12% 18% 22% 29% 15% 4	523
	21st to end	Day	12% 20% 29% 21% 16% 2	499
November	1st to 10th	Day	19% 18% 22% 19% 19% 4	300
	11th to 20th	Day	15% 17% 26% 22% 15% 5%	300
	21st to end	Day	16% 21% 23% 21% 16% 3	257
December	1st to 10th	Day	22% 17% 20% 19% 17% 6%	200
	11th to 20th	Day	21% 26% 21% 18% 11% 5%	200
	21st to end	Day	30% 20% 25% 16% 8% 1	220
January	1st to 10th	Night	15% 17% 26% 23% 13% 7%	800
	11th to 20th	Night	15% 14% 23% 33% 12% 4	800
	21st to end	Night	11% 15% 28% 26% 16% 4	880
February	1st to 10th	Night	18% 14% 26% 27% 14% 2	800
	11th to 20th	Night	14% 15% 27% 26% 13% 5%	784
	21st to end	Night	18% 15% 22% 33% 10% 2	660
March	1st to 10th	Night	19% 20% 26% 21% 12% 3	800
	11th to 20th	Night	14% 23% 19% 22% 19% 3	800
	21st to end	Night	15% 26% 23% 23% 11% 1	880
April	1st to 10th	Night	10% 21% 28% 27% 13% 1	800
	11th to 20th	Night	14% 19% 25% 27% 13% 3	791
	21st to end	Night	10% 16% 26% 28% 17% 3	800
May	1st to 10th	Night	12% 17% 27% 25% 16% 3	690
	11th to 20th	Night	9% 12% 23% 35% 19% 2	414
	21st to end	Night	9% 9% 20% 35% 24% 3	433
June	1st to 10th	Night	6% 10% 22% 37% 24% 3	400
	11th to 20th	Night	3 11% 23% 38% 25% 1	400
	21st to end	Night	3 6% 22% 42% 25% 3	400
July	1st to 10th	Night	2 3 19% 47% 27% 2	390
	11th to 20th	Night	2 4 22% 40% 32% 1	388
	21st to end	Night	2 3 16% 40% 35% 6%	513
August	1st to 10th	Night	3 2 17% 43% 32% 4	606
	11th to 20th	Night	2 5% 21% 41% 28% 4	792
	21st to end	Night	2 5% 25% 41% 25% 3	880
September	1st to 10th	Night	2 6% 22% 39% 28% 4	800
	11th to 20th	Night	4 10% 19% 31% 31% 6%	800
	21st to end	Night	4 10% 22% 34% 22% 9%	800
October	1st to 10th	Night	7% 11% 19% 35% 23% 6%	800
	11th to 20th	Night	10% 7% 18% 36% 23% 6%	792
	21st to end	Night	10% 11% 18% 28% 22% 10%	836
November	1st to 10th	Night	14% 13% 18% 25% 24% 7%	780
	11th to 20th	Night	12% 15% 23% 29% 16% 5%	800
	21st to end	Night	14% 14% 21% 28% 19% 5%	800
December	1st to 10th	Night	16% 13% 21% 30% 16% 5%	800
	11th to 20th	Night	17% 17% 24% 26% 12% 4	800
	21st to end	Night	19% 19% 26% 24% 10% 2	880

Page generated at 2025-10-15 22:50:25. Version ac07

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