Tainter Lake Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tainter Lake Skies Observatory clear sky chart from 2005-11-06 to 2024-11-03.

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	13% 9% 3 8% 5% 4 5% 4 5% 7% 37%	101610
	Night	13% 9% 4 8% 5% 4 4 4 5% 6% 38%	97483
Transparency	Day	45% 6% 13% 24% 11% 1	101403
	Night	46% 6% 12% 23% 12% 1	97361
Seeing	Day	17% 10% 30% 26% 14% 4	16021
	Night	17% 9% 31% 32% 11% 1	25872

By Month

Percentage Cloud Cover SE (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% 19% 8% 13% 6% 4 5% 3 4 5% 24%	2527
	11th to 20th	Day	6% 12% 5% 13% 8% 9% 11% 7% 5% 5% 19%	2530
	21st to end	Day	11% 18% 7% 13% 6% 4 4 4 4 6% 23%	3016
February	1st to 10th	Day	9% 10% 4 10% 6% 5% 5% 5% 6% 7% 31%	1710
	11th to 20th	Day	9% 10% 4 9% 6% 6% 4 5% 5% 8% 35%	1664
	21st to end	Day	11% 12% 5% 10% 5% 4 4 4 6% 7% 32%	1535
March	1st to 10th	Day	13% 9% 3 6% 5% 4 4 3 4 6% 45%	3233
	11th to 20th	Day	10% 8% 3 9% 5% 5% 4 3 5% 8% 39%	3480
	21st to end	Day	22% 11% 4 11% 5% 4 4 3 5% 5% 26%	3959
April	1st to 10th	Day	16% 11% 3 7% 5% 4 4 3 5% 7% 33%	2280
	11th to 20th	Day	21% 10% 4 7% 5% 4 4 3 5% 5% 31%	2254
	21st to end	Day	21% 11% 3 7% 5% 5% 5% 4 5% 6% 29%	2394
May	1st to 10th	Day	18% 7% 2 6% 4 4 4 4 5% 6% 41%	4389
	11th to 20th	Day	14% 7% 2 6% 4 4 5% 4 6% 7% 42%	4399
	21st to end	Day	17% 9% 3 7% 5% 5% 4 3 5% 6% 36%	4824
June	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 9% 44%	2660
	11th to 20th	Day	12% 7% 2 7% 6% 5% 5% 4 6% 9% 36%	2660
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 8% 10% 39%	2660
July	1st to 10th	Day	13% 5% 2 6% 5% 5% 6% 5% 7% 9% 38%	4440
	11th to 20th	Day	6% 3 1 5% 4 3 4 4 6% 10% 55%	4440
	21st to end	Day	8% 5% 2 6% 4 5% 6% 4 7% 8% 45%	4813
August	1st to 10th	Day	13% 6% 2 6% 4 5% 5% 4 6% 7% 43%	4210
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	4041
	21st to end	Day	10% 7% 2 7% 5% 5% 5% 4 6% 8% 42%	4222
September	1st to 10th	Day	11% 6% 2 6% 4 4 3 3 5% 9% 47%	2280
	11th to 20th	Day	13% 5% 2 5% 5% 4 4 4 5% 8% 45%	2280
	21st to end	Day	16% 6% 3 6% 3 4 4 3 5% 8% 43%	2004
October	1st to 10th	Day	15% 7% 2 6% 4 3 4 3 6% 6% 43%	1900
	11th to 20th	Day	15% 10% 4 8% 5% 5% 5% 3 4 7% 36%	1900
	21st to end	Day	19% 11% 4 7% 4 3 3 3 5% 5% 36%	1993
November	1st to 10th	Day	13% 11% 4 7% 4 4 5% 3 5% 7% 38%	1652
	11th to 20th	Day	14% 14% 5% 9% 7% 4 4 4 7% 4 28%	1520
	21st to end	Day	15% 12% 4 6% 5% 4 4 3 5% 5% 37%	1520
December	1st to 10th	Day	11% 13% 5% 13% 8% 6% 6% 4 4 5% 24%	1520
	11th to 20th	Day	11% 15% 6% 11% 7% 5% 5% 3 5% 4 27%	1918
	21st to end	Day	21% 17% 7% 15% 5% 4 3 2 3 4 18%	2783
January	1st to 10th	Night	9% 16% 8% 13% 5% 4 4 3 4 5% 29%	4428
	11th to 20th	Night	8% 11% 5% 14% 8% 8% 7% 7% 6% 5% 21%	4440
	21st to end	Night	11% 20% 8% 13% 5% 4 4 3 4 5% 23%	4647
February	1st to 10th	Night	6% 13% 5% 11% 6% 5% 4 4 5% 6% 35%	2470
	11th to 20th	Night	8% 10% 4 8% 5% 6% 5% 4 6% 6% 39%	2403
	21st to end	Night	12% 10% 4 9% 6% 5% 5% 4 5% 5% 36%	1918
March	1st to 10th	Night	9% 7% 3 6% 5% 5% 4 3 6% 8% 45%	3651
	11th to 20th	Night	8% 8% 3 9% 6% 5% 5% 4 5% 6% 40%	3480
	21st to end	Night	24% 11% 4 12% 5% 3 3 2 3 4 28%	3672
April	1st to 10th	Night	17% 11% 3 7% 4 4 3 3 6% 6% 35%	1900
	11th to 20th	Night	23% 9% 2 6% 4 3 4 4 5% 5% 35%	1875
	21st to end	Night	20% 8% 3 6% 3 4 5% 3 5% 6% 36%	1782
May	1st to 10th	Night	16% 8% 2 7% 5% 5% 4 4 5% 7% 38%	2516
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 7% 51%	2506
	21st to end	Night	13% 7% 3 7% 5% 4 4 3 6% 7% 41%	2743
June	1st to 10th	Night	10% 6% 2 6% 4 4 4 4 7% 8% 46%	1520
	11th to 20th	Night	11% 6% 2 5% 4 4 5% 4 6% 8% 45%	1520
	21st to end	Night	8% 5% 1 5% 4 4 6% 4 7% 8% 47%	1520
July	1st to 10th	Night	11% 4 2 5% 4 4 4 4 6% 8% 47%	2530
	11th to 20th	Night	5% 3 1 4 4 4 4 4 6% 10% 56%	2530
	21st to end	Night	5% 4 2 5% 4 4 4 4 5% 7% 56%	2750
August	1st to 10th	Night	11% 5% 2 6% 5% 4 5% 3 6% 6% 45%	2726
	11th to 20th	Night	12% 5% 2 5% 4 3 3 3 6% 7% 50%	2798
	21st to end	Night	12% 6% 3 7% 5% 4 4 3 4 6% 45%	3434
September	1st to 10th	Night	9% 5% 2 6% 3 3 4 4 4 8% 52%	1900
	11th to 20th	Night	10% 5% 2 5% 3 3 4 3 6% 7% 51%	1900
	21st to end	Night	14% 5% 2 5% 3 3 4 3 5% 6% 49%	2152
October	1st to 10th	Night	13% 6% 2 6% 3 4 3 3 5% 6% 49%	2280
	11th to 20th	Night	16% 8% 3 6% 4 5% 4 3 5% 7% 41%	2280
	21st to end	Night	17% 11% 3 6% 4 4 4 3 5% 6% 36%	2603
November	1st to 10th	Night	13% 11% 4 6% 4 3 3 3 4 7% 41%	2466
	11th to 20th	Night	14% 10% 4 10% 5% 5% 4 3 5% 6% 33%	2660
	21st to end	Night	15% 11% 4 8% 5% 3 4 4 5% 6% 36%	2660
December	1st to 10th	Night	11% 12% 4 12% 7% 4 4 4 4 6% 30%	2660
	11th to 20th	Night	12% 15% 5% 11% 7% 6% 4 4 5% 6% 26%	3279
	21st to end	Night	24% 15% 6% 11% 5% 3 3 3 4 5% 21%	4884

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	63% 5% 11% 17% 4	2528
	11th to 20th	Day	65% 6% 9% 15% 6%	2530
	21st to end	Day	61% 5% 15% 15% 4	3016
February	1st to 10th	Day	50% 6% 13% 19% 10% 1	1710
	11th to 20th	Day	47% 6% 13% 24% 9% 1	1673
	21st to end	Day	50% 6% 13% 19% 10% 2	1535
March	1st to 10th	Day	40% 5% 15% 23% 14% 2	3233
	11th to 20th	Day	43% 4 11% 29% 11% 1	3480
	21st to end	Day	61% 5% 9% 19% 6% 1	3959
April	1st to 10th	Day	51% 5% 11% 20% 13% 1	2280
	11th to 20th	Day	54% 5% 9% 18% 12% 2	2254
	21st to end	Day	55% 6% 11% 18% 9% 1	2394
May	1st to 10th	Day	43% 5% 11% 26% 13% 2	4430
	11th to 20th	Day	40% 7% 14% 25% 14% 1	4403
	21st to end	Day	47% 7% 10% 24% 11% 1	4837
June	1st to 10th	Day	35% 7% 14% 29% 13% 2	2660
	11th to 20th	Day	43% 9% 12% 22% 13% 1	2660
	21st to end	Day	37% 8% 15% 28% 10% 1	2660
July	1st to 10th	Day	40% 8% 17% 24% 11% 1	4371
	11th to 20th	Day	24% 5% 16% 35% 18% 1	4365
	21st to end	Day	33% 8% 14% 27% 17% 1	4662
August	1st to 10th	Day	38% 6% 13% 27% 15% 1	4195
	11th to 20th	Day	36% 7% 13% 34% 10%	4080
	21st to end	Day	39% 7% 14% 28% 12% 1	4221
September	1st to 10th	Day	34% 7% 15% 30% 14%	2280
	11th to 20th	Day	36% 7% 16% 31% 8%	2280
	21st to end	Day	39% 5% 13% 31% 11%	2004
October	1st to 10th	Day	40% 5% 12% 31% 11%	1900
	11th to 20th	Day	48% 4 13% 21% 12% 2	1900
	21st to end	Day	50% 5% 14% 23% 9%	1993
November	1st to 10th	Day	46% 6% 13% 20% 13% 2	1652
	11th to 20th	Day	57% 6% 13% 16% 8% 1	1520
	21st to end	Day	48% 5% 17% 21% 7% 2	1520
December	1st to 10th	Day	61% 6% 13% 15% 5%	1520
	11th to 20th	Day	60% 5% 14% 15% 5% 1	1915
	21st to end	Day	71% 5% 8% 12% 5%	2783
January	1st to 10th	Night	58% 5% 12% 18% 6% 1	4428
	11th to 20th	Night	62% 6% 11% 13% 7%	4440
	21st to end	Night	63% 5% 9% 18% 5% 1	4647
February	1st to 10th	Night	50% 5% 12% 21% 10% 2	2470
	11th to 20th	Night	44% 6% 13% 26% 9% 2	2404
	21st to end	Night	48% 6% 11% 22% 10% 2	1918
March	1st to 10th	Night	37% 5% 14% 27% 15% 2	3651
	11th to 20th	Night	42% 5% 11% 26% 14% 1	3480
	21st to end	Night	61% 4 7% 19% 9% 1	3672
April	1st to 10th	Night	48% 6% 9% 19% 17% 2	1900
	11th to 20th	Night	50% 5% 8% 19% 15% 2	1875
	21st to end	Night	48% 5% 10% 21% 15% 2	1782
May	1st to 10th	Night	44% 7% 12% 16% 19% 1	2540
	11th to 20th	Night	33% 5% 8% 31% 19% 4	2507
	21st to end	Night	41% 8% 11% 23% 16% 1	2751
June	1st to 10th	Night	33% 8% 12% 28% 17% 2	1520
	11th to 20th	Night	34% 8% 14% 24% 18% 1	1520
	21st to end	Night	31% 9% 14% 32% 13% 3	1520
July	1st to 10th	Night	34% 6% 20% 26% 14% 1	2490
	11th to 20th	Night	22% 6% 14% 36% 20% 1	2482
	21st to end	Night	25% 7% 15% 30% 21% 3	2662
August	1st to 10th	Night	38% 5% 12% 28% 14% 3	2717
	11th to 20th	Night	33% 7% 13% 32% 13% 2	2825
	21st to end	Night	39% 6% 14% 27% 13% 2	3434
September	1st to 10th	Night	30% 7% 12% 34% 16% 1	1900
	11th to 20th	Night	31% 6% 15% 33% 16%	1900
	21st to end	Night	34% 6% 13% 32% 14% 1	2152
October	1st to 10th	Night	35% 5% 10% 32% 16% 2	2280
	11th to 20th	Night	43% 6% 11% 24% 15% 1	2280
	21st to end	Night	48% 6% 12% 22% 11% 1	2603
November	1st to 10th	Night	43% 5% 11% 26% 14% 1	2466
	11th to 20th	Night	52% 6% 13% 17% 12% 1	2660
	21st to end	Night	48% 6% 15% 23% 7% 1	2660
December	1st to 10th	Night	54% 6% 15% 20% 6%	2660
	11th to 20th	Night	58% 5% 13% 18% 6% 1	3281
	21st to end	Night	67% 4 10% 15% 5%	4884

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	15% 12% 34% 26% 10% 3	270
	11th to 20th	Day	17% 12% 37% 26% 7% 1	270
	21st to end	Day	15% 9% 39% 25% 10% 1	297
February	1st to 10th	Day	15% 13% 44% 19% 8% 2	270
	11th to 20th	Day	15% 19% 38% 19% 9%	270
	21st to end	Day	18% 12% 46% 22% 2	225
March	1st to 10th	Day	16% 14% 39% 20% 11% 1	270
	11th to 20th	Day	19% 13% 35% 24% 7% 3	270
	21st to end	Day	23% 14% 30% 21% 9% 3	378
April	1st to 10th	Day	26% 14% 33% 21% 6% 1	460
	11th to 20th	Day	30% 12% 28% 22% 8% 1	452
	21st to end	Day	26% 15% 28% 19% 10% 2	574
May	1st to 10th	Day	21% 14% 30% 26% 8% 2	653
	11th to 20th	Day	19% 13% 27% 25% 13% 4	675
	21st to end	Day	18% 11% 25% 25% 16% 4	734
June	1st to 10th	Day	11% 9% 27% 32% 18% 4	680
	11th to 20th	Day	16% 10% 33% 27% 12% 2	680
	21st to end	Day	14% 7% 29% 29% 16% 6%	680
July	1st to 10th	Day	9% 5% 22% 28% 26% 10%	671
	11th to 20th	Day	9% 5% 27% 29% 20% 10%	668
	21st to end	Day	6% 4 25% 36% 21% 9%	739
August	1st to 10th	Day	12% 5% 22% 32% 22% 7%	676
	11th to 20th	Day	13% 4 20% 29% 27% 7%	665
	21st to end	Day	13% 6% 24% 29% 23% 5%	568
September	1st to 10th	Day	13% 6% 28% 30% 18% 6%	490
	11th to 20th	Day	11% 6% 27% 31% 22% 3	490
	21st to end	Day	21% 13% 22% 25% 15% 4	363
October	1st to 10th	Day	19% 10% 32% 22% 15% 2	300
	11th to 20th	Day	22% 15% 34% 23% 5% 1	300
	21st to end	Day	25% 18% 34% 16% 6% 2	330
November	1st to 10th	Day	20% 11% 34% 25% 10% 1	276
	11th to 20th	Day	22% 14% 38% 20% 6% 1	270
	21st to end	Day	24% 12% 41% 15% 7%	270
December	1st to 10th	Day	17% 13% 37% 23% 9% 1	270
	11th to 20th	Day	18% 16% 37% 21% 7% 1	270
	21st to end	Day	28% 13% 37% 20% 2 1	297
January	1st to 10th	Night	13% 12% 33% 32% 9% 1	950
	11th to 20th	Night	18% 10% 35% 30% 6% 1	950
	21st to end	Night	18% 10% 33% 31% 7%	1045
February	1st to 10th	Night	13% 12% 37% 30% 7% 1	950
	11th to 20th	Night	13% 12% 40% 27% 8%	929
	21st to end	Night	18% 13% 33% 29% 7%	662
March	1st to 10th	Night	15% 11% 37% 30% 7% 1	717
	11th to 20th	Night	17% 9% 35% 32% 6%	570
	21st to end	Night	22% 9% 31% 26% 11% 2	627
April	1st to 10th	Night	24% 12% 32% 25% 5% 1	570
	11th to 20th	Night	27% 9% 30% 27% 6% 1	563
	21st to end	Night	24% 7% 34% 26% 8% 1	570
May	1st to 10th	Night	21% 10% 32% 31% 6%	570
	11th to 20th	Night	19% 7% 29% 32% 11% 1	561
	21st to end	Night	14% 6% 26% 39% 14% 1	617
June	1st to 10th	Night	10% 6% 29% 41% 14% 1	570
	11th to 20th	Night	12% 6% 31% 40% 11%	570
	21st to end	Night	9% 4 25% 44% 17% 1	570
July	1st to 10th	Night	8% 2 21% 39% 27% 2	555
	11th to 20th	Night	8% 5% 22% 41% 22% 2	552
	21st to end	Night	6% 2 19% 46% 24% 3	624
August	1st to 10th	Night	8% 3 16% 47% 25% 1	567
	11th to 20th	Night	13% 2 19% 35% 26% 3	564
	21st to end	Night	14% 2 22% 36% 24% 1	627
September	1st to 10th	Night	11% 4 24% 38% 18% 5%	570
	11th to 20th	Night	12% 4 27% 36% 19% 2	570
	21st to end	Night	15% 10% 28% 30% 16% 1	699
October	1st to 10th	Night	17% 8% 28% 31% 14% 1	760
	11th to 20th	Night	20% 9% 34% 29% 7%	760
	21st to end	Night	22% 11% 29% 30% 8%	836
November	1st to 10th	Night	18% 10% 34% 30% 8% 1	782
	11th to 20th	Night	19% 13% 35% 25% 8%	950
	21st to end	Night	20% 13% 34% 27% 6%	950
December	1st to 10th	Night	17% 11% 35% 29% 7% 1	950
	11th to 20th	Night	21% 9% 35% 25% 7% 2	950
	21st to end	Night	26% 9% 34% 25% 5%	1045

Page generated at 2024-10-31 02:39:26. Version ac07

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