Tripod Reservoir
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tripod Reservoir clear sky chart from 2005-11-06 to 2025-04-11.

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	8% 11% 3 7% 4 4 4 3 4 5% 47%	117196
	Night	9% 11% 3 6% 4 3 4 3 5% 6% 46%	119893
Transparency	Day	38% 6% 10% 19% 17% 11%	116940
	Night	39% 6% 11% 20% 16% 8%	119738
Seeing	Day	15% 13% 29% 28% 13% 2	14870
	Night	16% 5% 20% 36% 20% 3	24315

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	10% 22% 9% 11% 5% 4 3 3 4 5% 26%	3639
	11th to 20th	Day	10% 13% 6% 8% 3 3 3 3 4 5% 42%	3640
	21st to end	Day	13% 16% 3 5% 3 3 3 2 3 6% 43%	4004
February	1st to 10th	Day	14% 20% 6% 10% 5% 4 3 3 4 4 27%	1722
	11th to 20th	Day	11% 22% 6% 8% 5% 5% 4 3 5% 5% 26%	1950
	21st to end	Day	11% 23% 7% 11% 5% 4 3 3 5% 4 24%	1650
March	1st to 10th	Day	7% 15% 7% 11% 5% 5% 5% 4 6% 6% 28%	4518
	11th to 20th	Day	9% 18% 5% 8% 4 3 4 2 3 4 39%	4818
	21st to end	Day	10% 20% 5% 11% 7% 6% 6% 4 5% 7% 20%	5736
April	1st to 10th	Day	12% 17% 4 9% 5% 5% 4 3 5% 6% 29%	2400
	11th to 20th	Day	10% 14% 4 8% 6% 5% 4 3 4 7% 36%	2311
	21st to end	Day	10% 13% 3 8% 5% 4 5% 4 5% 6% 37%	2470
May	1st to 10th	Day	8% 13% 4 9% 5% 5% 4 3 4 5% 39%	4110
	11th to 20th	Day	7% 5% 2 5% 3 4 4 3 5% 7% 55%	4242
	21st to end	Day	8% 10% 2 7% 5% 4 5% 4 6% 7% 42%	4813
June	1st to 10th	Day	12% 9% 3 8% 6% 5% 5% 4 7% 7% 34%	2660
	11th to 20th	Day	11% 7% 2 6% 5% 4 4 3 5% 6% 46%	2660
	21st to end	Day	4 4 2 4 3 3 3 3 4 5% 64%	2660
July	1st to 10th	Day	2 1 1 2 2 2 3 2 3 3 79%	4420
	11th to 20th	Day	2 2 1 2 2 2 3 2 3 4 76%	4420
	21st to end	Day	2 2 1 3 2 3 3 2 4 5% 73%	4790
August	1st to 10th	Day	5% 5% 2 6% 4 4 4 3 4 5% 59%	4256
	11th to 20th	Day	2 2 1 2 2 3 2 2 4 5% 76%	4028
	21st to end	Day	3 4 1 3 2 2 2 2 3 4 72%	4243
September	1st to 10th	Day	4 2 1 3 2 3 3 3 4 5% 70%	2280
	11th to 20th	Day	7% 5% 2 4 3 4 3 2 5% 7% 58%	2104
	21st to end	Day	7% 4 2 4 3 3 4 3 4 6% 61%	2090
October	1st to 10th	Day	7% 6% 2 4 3 3 3 2 3 5% 63%	3490
	11th to 20th	Day	9% 7% 3 6% 4 4 3 2 5% 6% 50%	3015
	21st to end	Day	10% 13% 3 7% 5% 4 4 3 4 6% 41%	3101
November	1st to 10th	Day	16% 14% 4 8% 4 4 4 3 4 6% 34%	1764
	11th to 20th	Day	16% 15% 5% 7% 4 5% 3 3 5% 5% 31%	1800
	21st to end	Day	12% 14% 5% 7% 6% 4 4 3 5% 6% 34%	1740
December	1st to 10th	Day	9% 11% 3 7% 4 3 3 2 4 6% 49%	2620
	11th to 20th	Day	15% 22% 7% 10% 5% 5% 4 3 5% 5% 19%	3028
	21st to end	Day	14% 18% 5% 10% 4 4 4 3 4 6% 28%	4004
January	1st to 10th	Night	12% 19% 6% 9% 5% 4 4 3 5% 5% 29%	6306
	11th to 20th	Night	11% 14% 5% 7% 3 4 3 3 4 5% 42%	6320
	21st to end	Night	11% 17% 3 6% 4 4 3 2 3 5% 42%	6952
February	1st to 10th	Night	14% 19% 5% 9% 5% 4 4 3 4 5% 29%	2673
	11th to 20th	Night	11% 17% 5% 7% 5% 4 4 3 5% 5% 33%	2338
	21st to end	Night	12% 19% 7% 9% 5% 4 4 3 4 6% 28%	1980
March	1st to 10th	Night	8% 17% 5% 8% 4 3 3 2 5% 7% 39%	5376
	11th to 20th	Night	11% 17% 3 7% 4 3 4 3 4 4 40%	5181
	21st to end	Night	8% 15% 4 8% 5% 5% 5% 4 7% 9% 30%	5236
April	1st to 10th	Night	11% 12% 3 6% 4 4 4 4 5% 7% 40%	2000
	11th to 20th	Night	12% 11% 3 6% 4 4 5% 3 4 5% 44%	1823
	21st to end	Night	9% 7% 2 6% 4 4 4 4 4 7% 48%	1710
May	1st to 10th	Night	9% 10% 2 4 3 4 4 4 6% 6% 47%	2860
	11th to 20th	Night	4 5% 1 5% 3 4 3 2 6% 7% 59%	2652
	21st to end	Night	7% 9% 3 7% 4 4 3 3 5% 7% 49%	2762
June	1st to 10th	Night	12% 7% 2 4 4 4 6% 3 7% 9% 42%	1520
	11th to 20th	Night	10% 6% 2 4 3 3 3 3 6% 5% 56%	1520
	21st to end	Night	4 3 1 4 3 3 4 3 4 6% 64%	1520
July	1st to 10th	Night	1 1 2 1 2 3 3 4 4 79%	2540
	11th to 20th	Night	1 1 2 1 2 3 2 4 6% 78%	2540
	21st to end	Night	2 2 1 4 3 3 3 3 4 6% 69%	2761
August	1st to 10th	Night	5% 4 2 4 4 4 4 3 6% 6% 58%	2678
	11th to 20th	Night	2 2 1 2 2 2 2 2 4 5% 76%	2811
	21st to end	Night	5% 3 1 3 2 2 2 2 3 4 73%	3429
September	1st to 10th	Night	3 3 1 3 3 2 3 2 3 5% 72%	1900
	11th to 20th	Night	6% 5% 2 5% 3 3 3 3 5% 6% 60%	2076
	21st to end	Night	8% 4 1 4 3 3 2 2 3 5% 65%	2090
October	1st to 10th	Night	5% 4 2 5% 3 3 3 3 3 5% 67%	3490
	11th to 20th	Night	8% 6% 2 5% 3 3 4 3 5% 6% 56%	3913
	21st to end	Night	10% 9% 2 6% 4 4 5% 4 6% 6% 44%	4457
November	1st to 10th	Night	15% 12% 3 6% 4 3 4 3 5% 6% 38%	2535
	11th to 20th	Night	18% 12% 3 7% 4 4 4 4 5% 6% 35%	2600
	21st to end	Night	13% 13% 3 8% 4 4 4 3 4 6% 39%	2656
December	1st to 10th	Night	8% 10% 3 5% 3 3 3 2 4 6% 51%	4560
	11th to 20th	Night	13% 22% 6% 10% 6% 4 5% 4 5% 5% 20%	5176
	21st to end	Night	16% 17% 4 8% 5% 4 4 3 5% 5% 28%	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	60% 9% 11% 13% 6%	3639
	11th to 20th	Day	45% 6% 15% 24% 8% 1	3640
	21st to end	Day	45% 7% 12% 18% 15% 4	4004
February	1st to 10th	Day	60% 8% 13% 15% 3 1	1722
	11th to 20th	Day	58% 8% 13% 14% 7%	1960
	21st to end	Day	60% 7% 11% 15% 6% 1	1650
March	1st to 10th	Day	52% 7% 8% 19% 10% 3	4518
	11th to 20th	Day	48% 5% 8% 29% 10%	4818
	21st to end	Day	58% 10% 13% 15% 4	5736
April	1st to 10th	Day	54% 6% 14% 17% 8% 1	2400
	11th to 20th	Day	45% 7% 13% 20% 13% 2	2314
	21st to end	Day	44% 8% 13% 22% 12%	2470
May	1st to 10th	Day	42% 7% 10% 23% 16% 2	4110
	11th to 20th	Day	24% 5% 10% 29% 25% 7%	4245
	21st to end	Day	35% 9% 14% 29% 12% 2	4814
June	1st to 10th	Day	43% 9% 13% 21% 13% 1	2660
	11th to 20th	Day	36% 5% 10% 21% 21% 7%	2660
	21st to end	Day	21% 4 8% 18% 34% 14%	2660
July	1st to 10th	Day	10% 3 4 9% 20% 54%	4351
	11th to 20th	Day	13% 2 3 6% 22% 54%	4345
	21st to end	Day	14% 2 3 9% 31% 40%	4639
August	1st to 10th	Day	27% 3 5% 11% 26% 28%	4240
	11th to 20th	Day	13% 2 4 15% 43% 24%	4067
	21st to end	Day	17% 2 4 21% 33% 23%	4242
September	1st to 10th	Day	16% 3 6% 18% 32% 24%	2280
	11th to 20th	Day	26% 4 9% 20% 28% 12%	2104
	21st to end	Day	24% 5% 8% 27% 27% 9%	2090
October	1st to 10th	Day	25% 4 6% 19% 38% 8%	3490
	11th to 20th	Day	35% 3 13% 22% 25% 2	3015
	21st to end	Day	44% 5% 8% 24% 17% 1	3101
November	1st to 10th	Day	50% 7% 12% 21% 11% 1	1764
	11th to 20th	Day	53% 7% 15% 18% 6%	1800
	21st to end	Day	50% 6% 15% 17% 10% 2	1740
December	1st to 10th	Day	38% 5% 15% 35% 6% 1	2620
	11th to 20th	Day	67% 7% 12% 11% 3	3028
	21st to end	Day	57% 6% 14% 17% 6%	4004
January	1st to 10th	Night	56% 8% 14% 15% 6%	6306
	11th to 20th	Night	45% 6% 13% 23% 11% 2	6320
	21st to end	Night	45% 8% 10% 19% 11% 8%	6952
February	1st to 10th	Night	57% 7% 15% 15% 5% 1	2673
	11th to 20th	Night	51% 8% 15% 16% 10% 1	2339
	21st to end	Night	56% 6% 11% 18% 8% 2	1980
March	1st to 10th	Night	44% 6% 9% 25% 12% 6%	5376
	11th to 20th	Night	47% 5% 6% 27% 15% 1	5181
	21st to end	Night	46% 11% 17% 20% 6%	5236
April	1st to 10th	Night	42% 6% 13% 25% 13% 1	2000
	11th to 20th	Night	41% 7% 12% 23% 15% 3	1823
	21st to end	Night	35% 6% 14% 27% 17% 1	1710
May	1st to 10th	Night	32% 8% 11% 26% 21% 2	2860
	11th to 20th	Night	21% 5% 11% 32% 28% 3	2652
	21st to end	Night	33% 7% 12% 34% 13% 1	2762
June	1st to 10th	Night	35% 9% 15% 28% 13%	1520
	11th to 20th	Night	29% 4 11% 26% 23% 8%	1520
	21st to end	Night	19% 5% 8% 19% 34% 15%	1520
July	1st to 10th	Night	9% 3 4 10% 24% 52%	2500
	11th to 20th	Night	10% 2 3 7% 21% 56%	2492
	21st to end	Night	17% 2 3 10% 30% 39%	2674
August	1st to 10th	Night	25% 3 5% 9% 31% 26%	2670
	11th to 20th	Night	12% 3 3 13% 37% 32%	2838
	21st to end	Night	17% 2 3 18% 32% 27%	3429
September	1st to 10th	Night	15% 3 6% 18% 32% 26%	1900
	11th to 20th	Night	25% 4 8% 18% 28% 17%	2076
	21st to end	Night	23% 3 7% 26% 28% 13%	2090
October	1st to 10th	Night	21% 3 6% 18% 35% 15%	3490
	11th to 20th	Night	29% 3 12% 22% 28% 5%	3913
	21st to end	Night	38% 5% 11% 23% 21% 1	4457
November	1st to 10th	Night	44% 7% 13% 21% 14% 2	2535
	11th to 20th	Night	48% 7% 13% 22% 9%	2600
	21st to end	Night	46% 5% 14% 22% 11% 2	2656
December	1st to 10th	Night	35% 5% 18% 31% 10% 1	4560
	11th to 20th	Night	65% 6% 12% 14% 3	5176
	21st to end	Night	57% 6% 15% 16% 6% 1	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	21% 16% 28% 22% 12% 2	200
	11th to 20th	Day	23% 13% 23% 23% 12% 8%	200
	21st to end	Day	21% 10% 28% 25% 11% 5%	220
February	1st to 10th	Day	28% 17% 26% 19% 8% 2	277
	11th to 20th	Day	21% 17% 34% 21% 6%	495
	21st to end	Day	24% 19% 27% 21% 7% 1	414
March	1st to 10th	Day	24% 17% 31% 23% 4 1	500
	11th to 20th	Day	23% 15% 28% 25% 9% 1	500
	21st to end	Day	26% 17% 30% 20% 6% 1	550
April	1st to 10th	Day	22% 18% 27% 21% 9% 2	500
	11th to 20th	Day	21% 20% 30% 22% 7% 1	453
	21st to end	Day	17% 21% 30% 22% 10% 1	460
May	1st to 10th	Day	12% 19% 31% 25% 11% 1	463
	11th to 20th	Day	23% 13% 28% 24% 11% 1	488
	21st to end	Day	14% 12% 25% 30% 16% 3	529
June	1st to 10th	Day	14% 15% 28% 27% 14% 3	490
	11th to 20th	Day	16% 18% 32% 24% 9% 1	490
	21st to end	Day	6% 11% 35% 32% 15% 2	490
July	1st to 10th	Day	3 6% 41% 35% 12% 2	486
	11th to 20th	Day	1 11% 37% 37% 13% 2	484
	21st to end	Day	3 6% 33% 39% 18% 2	531
August	1st to 10th	Day	6% 8% 34% 33% 16% 2	487
	11th to 20th	Day	2 7% 28% 40% 20% 3	477
	21st to end	Day	6% 9% 29% 36% 19% 2	539
September	1st to 10th	Day	7% 6% 24% 41% 19% 3	490
	11th to 20th	Day	11% 8% 28% 32% 20% 1	490
	21st to end	Day	9% 10% 30% 33% 16% 2	490
October	1st to 10th	Day	13% 11% 25% 31% 19% 1	490
	11th to 20th	Day	16% 11% 23% 31% 16% 4	367
	21st to end	Day	18% 17% 22% 28% 12% 3	330
November	1st to 10th	Day	25% 10% 23% 28% 13% 1	300
	11th to 20th	Day	19% 13% 29% 25% 11% 3	300
	21st to end	Day	19% 7% 28% 26% 16% 3	270
December	1st to 10th	Day	29% 10% 17% 19% 16% 9%	200
	11th to 20th	Day	29% 14% 25% 23% 8% 2	200
	21st to end	Day	23% 16% 24% 23% 11% 2	220
January	1st to 10th	Night	25% 7% 22% 28% 16% 3	800
	11th to 20th	Night	24% 7% 21% 26% 18% 3	800
	21st to end	Night	21% 5% 21% 31% 19% 4	880
February	1st to 10th	Night	23% 8% 25% 31% 12% 2	800
	11th to 20th	Night	22% 5% 24% 33% 14% 1	784
	21st to end	Night	21% 7% 24% 33% 13% 2	660
March	1st to 10th	Night	20% 11% 23% 31% 13% 2	800
	11th to 20th	Night	18% 8% 22% 34% 16% 1	800
	21st to end	Night	21% 8% 22% 37% 11% 1	880
April	1st to 10th	Night	18% 8% 22% 34% 17% 2	800
	11th to 20th	Night	16% 9% 28% 32% 13% 2	693
	21st to end	Night	12% 6% 26% 39% 16% 2	570
May	1st to 10th	Night	10% 6% 24% 38% 20% 1	570
	11th to 20th	Night	10% 6% 18% 35% 27% 3	458
	21st to end	Night	13% 5% 17% 36% 27% 2	411
June	1st to 10th	Night	12% 5% 15% 40% 24% 4	380
	11th to 20th	Night	12% 3 20% 41% 22% 2	380
	21st to end	Night	5% 1 16% 50% 28% 1	380
July	1st to 10th	Night	2 2 14% 49% 31% 2	370
	11th to 20th	Night	1 2 17% 56% 22% 1	368
	21st to end	Night	4 1 11% 51% 32% 2	416
August	1st to 10th	Night	8% 2 10% 45% 32% 2	462
	11th to 20th	Night	1 2 11% 46% 37% 3	564
	21st to end	Night	5% 2 13% 45% 31% 4	793
September	1st to 10th	Night	5% 1 10% 48% 33% 3	760
	11th to 20th	Night	8% 3 13% 40% 31% 5%	760
	21st to end	Night	10% 2 18% 37% 26% 7%	760
October	1st to 10th	Night	11% 2 18% 43% 24% 2	760
	11th to 20th	Night	13% 5% 16% 40% 23% 5%	760
	21st to end	Night	18% 4 22% 36% 18% 3	836
November	1st to 10th	Night	24% 5% 19% 35% 16% 2	780
	11th to 20th	Night	25% 5% 21% 32% 16% 1	800
	21st to end	Night	19% 7% 22% 33% 16% 4	800
December	1st to 10th	Night	20% 6% 22% 34% 16% 2	800
	11th to 20th	Night	28% 6% 20% 31% 14% 2	800
	21st to end	Night	30% 8% 25% 27% 10% 2	880

Page generated at 2025-04-08 07:17:24. Version ac07

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