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 2026-08-15.

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	7% 10% 3 6% 4 4 4 3 4 6% 50%	152417
	Night	8% 10% 3 6% 4 3 4 3 5% 6% 49%	146807
Transparency	Day	35% 5% 8% 20% 20% 12%	147165
	Night	37% 5% 10% 21% 18% 9%	143061
Seeing	Day	15% 13% 29% 28% 13% 2	16646
	Night	16% 5% 20% 37% 19% 2	25864

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% 27% 8% 12% 4 4 3 3 4 4 22%	4722
	11th to 20th	Day	7% 10% 5% 6% 3 2 3 3 4 5% 51%	4740
	21st to end	Day	10% 14% 3 6% 4 4 4 2 4 6% 43%	5187
February	1st to 10th	Day	13% 19% 6% 10% 5% 4 3 3 4 4 27%	1809
	11th to 20th	Day	10% 22% 7% 9% 5% 5% 4 3 4 5% 26%	2050
	21st to end	Day	11% 22% 7% 11% 5% 4 3 3 5% 4 25%	1730
March	1st to 10th	Day	7% 15% 7% 11% 5% 5% 5% 4 6% 6% 28%	4618
	11th to 20th	Day	9% 18% 5% 8% 4 3 4 2 3 4 39%	4924
	21st to end	Day	10% 20% 5% 11% 7% 6% 6% 4 5% 7% 20%	5862
April	1st to 10th	Day	12% 17% 4 9% 5% 5% 4 3 5% 6% 29%	2520
	11th to 20th	Day	10% 14% 4 8% 6% 4 4 3 5% 7% 36%	2555
	21st to end	Day	10% 13% 3 8% 5% 5% 5% 4 5% 6% 36%	2730
May	1st to 10th	Day	5% 8% 2 6% 4 3 4 3 4 5% 56%	7626
	11th to 20th	Day	7% 7% 2 5% 3 4 4 4 5% 7% 51%	7910
	21st to end	Day	6% 6% 2 5% 4 4 4 3 5% 7% 53%	8992
June	1st to 10th	Day	11% 8% 2 8% 6% 5% 5% 4 6% 7% 37%	2940
	11th to 20th	Day	10% 7% 2 6% 5% 4 4 3 5% 6% 47%	2940
	21st to end	Day	4 5% 2 4 3 3 3 3 4 6% 63%	2940
July	1st to 10th	Day	3 1 1 2 2 2 2 2 3 4 77%	8219
	11th to 20th	Day	3 3 1 4 2 3 3 2 4 4 72%	8220
	21st to end	Day	3 3 1 3 2 2 3 2 5% 6% 71%	8922
August	1st to 10th	Day	3 3 1 5% 3 4 4 3 5% 7% 60%	6141
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 78%	5851
	21st to end	Day	6% 4 2 4 3 3 3 3 3 5% 66%	6073
September	1st to 10th	Day	4 2 1 3 2 3 3 3 4 6% 69%	2400
	11th to 20th	Day	7% 5% 2 5% 3 4 4 3 4 7% 57%	2215
	21st to end	Day	7% 4 2 4 3 3 3 3 3 6% 61%	2200
October	1st to 10th	Day	7% 6% 2 4 3 3 3 2 3 5% 63%	3600
	11th to 20th	Day	10% 7% 3 6% 4 4 3 3 5% 6% 50%	3110
	21st to end	Day	10% 12% 3 7% 5% 4 4 3 4 6% 41%	3200
November	1st to 10th	Day	15% 14% 4 8% 4 4 4 3 4 6% 34%	1854
	11th to 20th	Day	17% 15% 5% 7% 4 5% 3 3 5% 5% 31%	1890
	21st to end	Day	11% 14% 5% 7% 6% 4 5% 3 5% 6% 34%	1827
December	1st to 10th	Day	10% 12% 3 7% 4 3 3 2 4 6% 48%	2700
	11th to 20th	Day	16% 22% 6% 10% 5% 5% 4 3 5% 5% 19%	3108
	21st to end	Day	14% 18% 5% 10% 4 4 4 3 4 6% 28%	4092
January	1st to 10th	Night	11% 22% 6% 10% 5% 4 4 3 5% 5% 26%	8172
	11th to 20th	Night	8% 11% 4 6% 3 3 2 2 4 6% 52%	8220
	21st to end	Night	9% 13% 3 6% 4 4 4 3 5% 6% 43%	8994
February	1st to 10th	Night	14% 18% 5% 9% 5% 4 4 3 4 5% 30%	2806
	11th to 20th	Night	11% 17% 5% 8% 5% 4 4 3 5% 6% 32%	2458
	21st to end	Night	13% 18% 6% 9% 5% 4 4 3 4 6% 28%	2076
March	1st to 10th	Night	7% 17% 5% 8% 4 3 3 2 5% 7% 39%	5496
	11th to 20th	Night	11% 17% 3 7% 4 3 3 3 4 4 40%	5295
	21st to end	Night	9% 15% 4 8% 5% 5% 5% 4 7% 9% 31%	5352
April	1st to 10th	Night	11% 12% 3 5% 4 4 4 4 5% 7% 41%	2100
	11th to 20th	Night	11% 11% 3 6% 3 4 5% 3 4 5% 44%	2013
	21st to end	Night	8% 7% 2 7% 4 4 5% 4 4 7% 47%	1890
May	1st to 10th	Night	6% 6% 1 3 2 3 3 3 5% 7% 61%	5321
	11th to 20th	Night	6% 6% 2 6% 4 4 4 3 5% 7% 55%	4946
	21st to end	Night	5% 6% 2 6% 4 4 3 3 5% 6% 56%	5181
June	1st to 10th	Night	11% 6% 2 5% 4 4 5% 3 7% 9% 45%	1680
	11th to 20th	Night	9% 6% 2 4 3 3 3 3 5% 5% 57%	1680
	21st to end	Night	4 5% 1 4 3 3 4 3 5% 6% 63%	1680
July	1st to 10th	Night	2 2 1 3 2 2 3 3 3 5% 74%	4740
	11th to 20th	Night	2 2 1 3 2 2 3 2 4 5% 75%	4740
	21st to end	Night	2 3 1 3 2 3 3 4 5% 7% 68%	5153
August	1st to 10th	Night	4 3 2 4 3 4 4 3 6% 7% 60%	3880
	11th to 20th	Night	1 1 1 2 2 2 2 2 4 5% 78%	4087
	21st to end	Night	7% 4 2 4 2 2 3 3 4 5% 65%	4918
September	1st to 10th	Night	3 3 1 3 3 2 3 2 3 6% 71%	2000
	11th to 20th	Night	6% 5% 2 5% 3 3 3 3 5% 6% 60%	2185
	21st to end	Night	8% 4 1 4 3 3 2 2 3 5% 66%	2200
October	1st to 10th	Night	5% 4 2 5% 3 3 3 2 3 5% 66%	3600
	11th to 20th	Night	7% 6% 2 5% 3 3 3 3 5% 6% 56%	4038
	21st to end	Night	10% 9% 2 6% 4 4 5% 4 6% 6% 44%	4600
November	1st to 10th	Night	16% 12% 3 6% 4 3 4 3 5% 7% 38%	2665
	11th to 20th	Night	18% 11% 3 7% 4 4 4 4 5% 6% 34%	2730
	21st to end	Night	12% 12% 3 8% 5% 4 4 3 4 7% 39%	2789
December	1st to 10th	Night	9% 11% 3 5% 3 3 3 2 4 6% 50%	4700
	11th to 20th	Night	13% 21% 5% 10% 5% 4 5% 4 5% 5% 21%	5316
	21st to end	Night	16% 17% 4 8% 5% 4 4 3 5% 5% 28%	7106

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	65% 8% 11% 11% 5%	4723
	11th to 20th	Day	35% 5% 13% 31% 13% 3	4740
	21st to end	Day	45% 6% 10% 19% 16% 4	5187
February	1st to 10th	Day	59% 7% 14% 16% 4 1	1809
	11th to 20th	Day	59% 8% 12% 14% 7%	2060
	21st to end	Day	59% 7% 10% 16% 6% 1	1730
March	1st to 10th	Day	52% 7% 9% 19% 10% 3	4618
	11th to 20th	Day	48% 5% 8% 29% 10%	4924
	21st to end	Day	58% 10% 13% 15% 4	5862
April	1st to 10th	Day	53% 6% 14% 19% 7% 1	2520
	11th to 20th	Day	45% 6% 12% 21% 14% 2	2558
	21st to end	Day	44% 7% 12% 23% 13%	2730
May	1st to 10th	Day	29% 4 6% 30% 27% 3	7626
	11th to 20th	Day	30% 4 7% 27% 26% 5%	7913
	21st to end	Day	29% 5% 8% 29% 25% 3	8994
June	1st to 10th	Day	41% 8% 12% 21% 16% 1	2940
	11th to 20th	Day	35% 4 9% 21% 23% 8%	2940
	21st to end	Day	23% 4 7% 19% 34% 14%	2940
July	1st to 10th	Day	12% 2 3 11% 31% 42%	8151
	11th to 20th	Day	18% 2 2 8% 25% 46%	8145
	21st to end	Day	16% 2 3 15% 31% 34%	8723
August	1st to 10th	Day	26% 3 4 12% 26% 29%	4510
	11th to 20th	Day	13% 2 4 15% 43% 24%	4250
	21st to end	Day	18% 2 4 21% 32% 23%	4376
September	1st to 10th	Day	16% 3 6% 19% 32% 23%	2400
	11th to 20th	Day	27% 4 9% 21% 28% 12%	2215
	21st to end	Day	25% 4 8% 26% 28% 9%	2200
October	1st to 10th	Day	25% 4 6% 19% 38% 8%	3600
	11th to 20th	Day	35% 3 13% 22% 25% 2	3110
	21st to end	Day	43% 5% 8% 25% 17% 1	3200
November	1st to 10th	Day	49% 6% 13% 21% 10%	1854
	11th to 20th	Day	54% 6% 15% 18% 6%	1890
	21st to end	Day	50% 6% 15% 17% 10% 2	1827
December	1st to 10th	Day	39% 5% 15% 35% 6% 1	2700
	11th to 20th	Day	66% 7% 12% 12% 3	3108
	21st to end	Day	57% 6% 14% 17% 6%	4092
January	1st to 10th	Night	60% 7% 15% 13% 4	8172
	11th to 20th	Night	36% 4 12% 29% 15% 4	8220
	21st to end	Night	42% 7% 10% 22% 12% 7%	8994
February	1st to 10th	Night	56% 7% 15% 16% 5% 1	2806
	11th to 20th	Night	51% 8% 14% 17% 9% 1	2459
	21st to end	Night	55% 6% 10% 18% 9% 2	2076
March	1st to 10th	Night	44% 5% 9% 25% 12% 6%	5496
	11th to 20th	Night	47% 5% 6% 26% 15% 1	5295
	21st to end	Night	46% 11% 17% 20% 6%	5352
April	1st to 10th	Night	41% 6% 13% 27% 12% 1	2100
	11th to 20th	Night	41% 6% 11% 25% 15% 3	2013
	21st to end	Night	36% 6% 13% 27% 17% 1	1890
May	1st to 10th	Night	22% 4 7% 31% 33% 2	5319
	11th to 20th	Night	28% 4 7% 30% 29% 2	4946
	21st to end	Night	29% 4 8% 35% 21% 3	5182
June	1st to 10th	Night	33% 8% 14% 28% 16% 1	1680
	11th to 20th	Night	29% 4 10% 25% 25% 8%	1680
	21st to end	Night	21% 5% 8% 19% 33% 15%	1680
July	1st to 10th	Night	15% 2 2 13% 27% 42%	4700
	11th to 20th	Night	13% 2 3 8% 25% 49%	4692
	21st to end	Night	17% 2 3 15% 28% 35%	5040
August	1st to 10th	Night	25% 3 5% 10% 31% 27%	2839
	11th to 20th	Night	12% 2 3 13% 38% 31%	2964
	21st to end	Night	17% 2 4 18% 32% 27%	3537
September	1st to 10th	Night	16% 3 6% 18% 33% 25%	2000
	11th to 20th	Night	25% 4 8% 18% 28% 16%	2185
	21st to end	Night	22% 3 7% 25% 30% 13%	2200
October	1st to 10th	Night	21% 3 6% 19% 35% 15%	3600
	11th to 20th	Night	30% 3 12% 23% 28% 5%	4038
	21st to end	Night	38% 5% 11% 24% 21% 1	4600
November	1st to 10th	Night	45% 6% 13% 21% 13% 2	2665
	11th to 20th	Night	49% 7% 14% 22% 9%	2730
	21st to end	Night	46% 5% 15% 22% 11% 2	2789
December	1st to 10th	Night	36% 5% 18% 31% 10%	4700
	11th to 20th	Night	64% 6% 12% 14% 3	5316
	21st to end	Night	57% 6% 15% 16% 6% 1	7106

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% 16% 27% 20% 12% 1	220
	11th to 20th	Day	20% 11% 23% 25% 13% 7%	220
	21st to end	Day	19% 9% 29% 27% 12% 4	242
February	1st to 10th	Day	27% 16% 25% 20% 8% 3	304
	11th to 20th	Day	21% 17% 34% 20% 7% 1	535
	21st to end	Day	24% 19% 28% 21% 7% 1	446
March	1st to 10th	Day	24% 17% 32% 22% 4 1	540
	11th to 20th	Day	23% 14% 29% 24% 8% 1	540
	21st to end	Day	26% 17% 29% 20% 6% 1	594
April	1st to 10th	Day	22% 17% 26% 22% 10% 2	540
	11th to 20th	Day	21% 20% 30% 21% 7% 1	532
	21st to end	Day	17% 20% 30% 23% 9% 1	540
May	1st to 10th	Day	12% 18% 32% 26% 11% 1	543
	11th to 20th	Day	24% 15% 28% 22% 10% 1	568
	21st to end	Day	13% 13% 26% 29% 15% 3	617
June	1st to 10th	Day	14% 15% 28% 25% 14% 3	570
	11th to 20th	Day	16% 18% 33% 24% 9% 1	570
	21st to end	Day	7% 11% 35% 31% 14% 2	570
July	1st to 10th	Day	4 6% 42% 35% 12% 2	566
	11th to 20th	Day	2 11% 37% 36% 12% 2	564
	21st to end	Day	3 6% 33% 38% 17% 2	619
August	1st to 10th	Day	5% 9% 34% 34% 16% 2	567
	11th to 20th	Day	3 7% 28% 39% 19% 3	534
	21st to end	Day	7% 9% 28% 36% 19% 2	583
September	1st to 10th	Day	6% 6% 24% 41% 19% 4	530
	11th to 20th	Day	10% 8% 27% 33% 20% 1	530
	21st to end	Day	9% 10% 29% 32% 17% 2	530
October	1st to 10th	Day	13% 11% 25% 30% 18% 2	530
	11th to 20th	Day	17% 11% 24% 30% 15% 4	400
	21st to end	Day	18% 16% 22% 29% 13% 2	363
November	1st to 10th	Day	25% 11% 24% 27% 13% 2	330
	11th to 20th	Day	21% 13% 28% 25% 11% 3	330
	21st to end	Day	20% 7% 28% 27% 15% 3	297
December	1st to 10th	Day	30% 10% 19% 19% 15% 8%	220
	11th to 20th	Day	30% 13% 25% 23% 9% 1	220
	21st to end	Day	26% 15% 23% 23% 12% 2	242
January	1st to 10th	Night	25% 8% 22% 28% 15% 2	840
	11th to 20th	Night	23% 7% 21% 27% 18% 3	840
	21st to end	Night	20% 5% 22% 32% 18% 3	924
February	1st to 10th	Night	23% 8% 25% 31% 12% 2	840
	11th to 20th	Night	21% 6% 24% 33% 14% 1	824
	21st to end	Night	22% 6% 24% 33% 13% 2	692
March	1st to 10th	Night	20% 11% 24% 31% 12% 2	840
	11th to 20th	Night	18% 9% 24% 33% 15% 1	840
	21st to end	Night	21% 8% 24% 36% 10% 1	924
April	1st to 10th	Night	18% 7% 21% 35% 17% 2	840
	11th to 20th	Night	16% 9% 28% 33% 12% 2	765
	21st to end	Night	11% 6% 27% 39% 16% 1	630
May	1st to 10th	Night	10% 7% 24% 39% 19% 1	630
	11th to 20th	Night	11% 7% 20% 35% 25% 3	506
	21st to end	Night	12% 5% 18% 37% 25% 2	455
June	1st to 10th	Night	12% 5% 17% 40% 22% 3	420
	11th to 20th	Night	11% 5% 22% 41% 20% 1	420
	21st to end	Night	5% 2 17% 50% 26% 1	420
July	1st to 10th	Night	2 2 17% 49% 29% 2	410
	11th to 20th	Night	1 2 19% 55% 21% 1	408
	21st to end	Night	3 1 13% 51% 30% 2	460
August	1st to 10th	Night	7% 3 13% 46% 29% 2	511
	11th to 20th	Night	1 2 13% 46% 35% 3	606
	21st to end	Night	6% 2 13% 44% 30% 4	835
September	1st to 10th	Night	5% 1 11% 49% 32% 3	800
	11th to 20th	Night	7% 3 13% 41% 31% 5%	800
	21st to end	Night	10% 2 18% 38% 26% 6%	800
October	1st to 10th	Night	11% 3 19% 41% 24% 3	800
	11th to 20th	Night	12% 6% 17% 39% 21% 4	800
	21st to end	Night	18% 4 22% 36% 18% 3	880
November	1st to 10th	Night	24% 5% 19% 35% 16% 2	820
	11th to 20th	Night	25% 5% 21% 33% 15% 1	840
	21st to end	Night	19% 7% 22% 33% 16% 3	840
December	1st to 10th	Night	21% 6% 22% 33% 15% 2	840
	11th to 20th	Night	28% 6% 19% 32% 13% 2	840
	21st to end	Night	30% 7% 25% 26% 10% 2	924

Page generated at 2026-08-12 01:37:14. Version ac07

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