Bass Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bass Lake clear sky chart from 2005-11-06 to 2024-11-02.

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	14% 10% 4 8% 5% 4 4 3 5% 6% 36%	101335
	Night	15% 13% 5% 10% 5% 4 4 3 4 5% 31%	97710
Transparency	Day	26% 49% 7% 11% 6% 1	101126
	Night	30% 50% 5% 9% 5% 1	97591
Seeing	Day	18% 13% 29% 26% 12% 3	15898
	Night	21% 12% 27% 27% 12% 2	25746

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	13% 29% 14% 17% 7% 4 2 2 2 2 8%	2527
	11th to 20th	Day	13% 19% 9% 20% 13% 10% 4 2 3 3 5%	2530
	21st to end	Day	18% 23% 10% 15% 7% 5% 4 3 3 4 9%	2783
February	1st to 10th	Day	10% 17% 7% 15% 13% 6% 4 3 4 4 16%	1678
	11th to 20th	Day	13% 16% 7% 18% 10% 6% 4 2 3 4 17%	1848
	21st to end	Day	13% 16% 6% 13% 8% 5% 4 3 5% 6% 21%	1570
March	1st to 10th	Day	12% 12% 6% 8% 5% 5% 5% 4 5% 5% 34%	3120
	11th to 20th	Day	12% 9% 8% 11% 5% 4 4 3 5% 6% 34%	3320
	21st to end	Day	20% 11% 6% 11% 5% 4 3 4 5% 5% 28%	4055
April	1st to 10th	Day	18% 14% 3 6% 4 4 4 4 5% 6% 33%	2280
	11th to 20th	Day	20% 10% 3 5% 4 4 4 4 5% 6% 36%	2291
	21st to end	Day	16% 9% 3 7% 5% 4 4 4 5% 6% 37%	2470
May	1st to 10th	Day	14% 7% 2 7% 3 4 4 3 6% 7% 43%	4082
	11th to 20th	Day	12% 7% 2 5% 4 4 4 3 6% 7% 47%	4257
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 8% 46%	4824
June	1st to 10th	Day	12% 6% 1 5% 4 4 4 3 6% 7% 48%	2660
	11th to 20th	Day	13% 5% 2 5% 3 4 4 3 5% 9% 47%	2660
	21st to end	Day	12% 5% 2 5% 4 4 4 3 6% 9% 46%	2660
July	1st to 10th	Day	15% 6% 2 6% 4 3 4 4 6% 8% 43%	4440
	11th to 20th	Day	6% 3 1 4 3 3 4 3 5% 8% 59%	4440
	21st to end	Day	8% 4 2 5% 4 4 5% 4 5% 9% 51%	4813
August	1st to 10th	Day	10% 4 2 5% 4 4 5% 5% 7% 9% 44%	4274
	11th to 20th	Day	11% 4 2 5% 3 4 3 3 5% 6% 54%	4044
	21st to end	Day	10% 5% 2 6% 4 4 4 4 5% 8% 48%	4188
September	1st to 10th	Day	13% 5% 2 6% 4 5% 3 4 5% 6% 46%	2280
	11th to 20th	Day	11% 5% 2 6% 4 3 3 3 6% 7% 49%	2098
	21st to end	Day	15% 7% 2 6% 4 4 4 4 5% 7% 41%	2090
October	1st to 10th	Day	16% 7% 3 6% 4 3 4 3 5% 7% 42%	2090
	11th to 20th	Day	25% 13% 3 8% 5% 4 4 4 5% 6% 23%	1812
	21st to end	Day	25% 14% 3 8% 4 4 4 4 5% 5% 24%	1881
November	1st to 10th	Day	16% 16% 3 7% 5% 4 4 3 4 6% 32%	1681
	11th to 20th	Day	14% 25% 7% 10% 5% 4 4 3 5% 5% 18%	1710
	21st to end	Day	20% 22% 8% 11% 5% 3 3 2 4 4 17%	1658
December	1st to 10th	Day	16% 25% 12% 15% 6% 3 3 2 3 3 12%	1520
	11th to 20th	Day	16% 23% 10% 16% 8% 3 3 3 4 4 10%	1918
	21st to end	Day	19% 23% 9% 14% 7% 5% 3 2 4 3 10%	2783
January	1st to 10th	Night	15% 26% 12% 15% 8% 4 2 2 2 3 12%	4428
	11th to 20th	Night	12% 20% 10% 21% 10% 10% 3 2 2 2 7%	4440
	21st to end	Night	17% 25% 10% 17% 8% 5% 3 2 3 3 8%	4884
February	1st to 10th	Night	12% 19% 6% 16% 12% 5% 4 3 3 3 17%	2499
	11th to 20th	Night	13% 14% 7% 16% 9% 7% 3 3 4 4 18%	2218
	21st to end	Night	15% 17% 5% 13% 7% 5% 4 2 4 6% 21%	1884
March	1st to 10th	Night	16% 11% 4 8% 5% 3 3 3 4 6% 38%	3733
	11th to 20th	Night	9% 12% 4 10% 6% 4 4 3 5% 7% 38%	3640
	21st to end	Night	16% 12% 4 12% 6% 5% 4 3 5% 5% 28%	3607
April	1st to 10th	Night	17% 12% 3 7% 4 4 3 3 6% 6% 33%	1900
	11th to 20th	Night	21% 9% 3 5% 4 4 4 3 6% 6% 36%	1838
	21st to end	Night	17% 10% 3 7% 4 3 4 3 5% 5% 38%	1710
May	1st to 10th	Night	14% 7% 2 8% 5% 5% 5% 4 5% 7% 38%	2813
	11th to 20th	Night	15% 7% 3 6% 5% 5% 5% 4 6% 7% 40%	2640
	21st to end	Night	18% 7% 3 6% 4 3 3 3 5% 6% 42%	2743
June	1st to 10th	Night	12% 6% 2 5% 4 4 5% 4 7% 8% 43%	1520
	11th to 20th	Night	11% 6% 2 6% 5% 4 3 3 5% 8% 46%	1520
	21st to end	Night	9% 6% 3 5% 4 4 5% 4 7% 10% 45%	1520
July	1st to 10th	Night	13% 8% 2 5% 4 5% 5% 5% 5% 8% 41%	2530
	11th to 20th	Night	6% 4 1 5% 4 3 3 3 6% 7% 57%	2530
	21st to end	Night	7% 5% 2 6% 5% 3 4 4 6% 7% 51%	2750
August	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 7% 8% 45%	2657
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 6% 52%	2785
	21st to end	Night	10% 5% 2 5% 4 5% 4 4 5% 6% 48%	3466
September	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 5% 6% 50%	1900
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 5% 6% 54%	2062
	21st to end	Night	16% 6% 2 5% 4 4 5% 3 5% 7% 42%	2090
October	1st to 10th	Night	17% 7% 2 5% 4 3 4 2 4 7% 45%	2090
	11th to 20th	Night	24% 11% 3 7% 4 4 4 2 4 5% 32%	2366
	21st to end	Night	26% 13% 2 7% 4 4 4 4 4 6% 26%	2717
November	1st to 10th	Night	15% 16% 4 8% 4 4 3 3 4 5% 33%	2420
	11th to 20th	Night	16% 23% 6% 12% 4 4 4 3 4 4 20%	2470
	21st to end	Night	19% 22% 7% 9% 4 4 3 3 4 4 20%	2517
December	1st to 10th	Night	17% 27% 10% 12% 5% 3 3 2 4 4 13%	2660
	11th to 20th	Night	16% 24% 9% 14% 6% 4 4 3 4 4 13%	3279
	21st to end	Night	23% 24% 8% 12% 5% 4 3 2 4 4 12%	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	59% 37% 2 2 1	2528
	11th to 20th	Day	59% 37% 2 2	2530
	21st to end	Day	49% 44% 5% 1 1	2783
February	1st to 10th	Day	27% 66% 2 4 1	1678
	11th to 20th	Day	25% 64% 3 5% 2	1858
	21st to end	Day	23% 66% 5% 4 1	1570
March	1st to 10th	Day	28% 44% 9% 13% 6%	3120
	11th to 20th	Day	31% 42% 11% 12% 4	3320
	21st to end	Day	38% 42% 5% 11% 4 1	4055
April	1st to 10th	Day	20% 66% 4 7% 3	2280
	11th to 20th	Day	18% 66% 4 6% 5% 1	2291
	21st to end	Day	16% 66% 5% 7% 6% 1	2470
May	1st to 10th	Day	23% 43% 8% 15% 9% 3	4120
	11th to 20th	Day	21% 45% 8% 15% 10% 2	4261
	21st to end	Day	21% 42% 7% 14% 15% 1	4837
June	1st to 10th	Day	11% 65% 4 12% 7% 1	2660
	11th to 20th	Day	17% 66% 4 8% 5%	2660
	21st to end	Day	14% 65% 6% 9% 6%	2660
July	1st to 10th	Day	32% 36% 9% 14% 8% 1	4371
	11th to 20th	Day	13% 36% 12% 24% 14% 1	4365
	21st to end	Day	20% 37% 11% 17% 15% 1	4662
August	1st to 10th	Day	24% 38% 8% 18% 11%	4259
	11th to 20th	Day	23% 38% 9% 19% 11%	4083
	21st to end	Day	24% 38% 10% 18% 9%	4187
September	1st to 10th	Day	17% 62% 7% 10% 4	2280
	11th to 20th	Day	12% 61% 5% 12% 9% 1	2098
	21st to end	Day	17% 61% 6% 12% 4	2090
October	1st to 10th	Day	19% 61% 4 11% 4	2090
	11th to 20th	Day	24% 60% 6% 8% 3	1812
	21st to end	Day	27% 60% 5% 6% 3	1881
November	1st to 10th	Day	27% 59% 4 6% 3	1681
	11th to 20th	Day	28% 61% 5% 5% 2	1710
	21st to end	Day	31% 61% 4 3 2	1658
December	1st to 10th	Day	33% 60% 3 2 1	1520
	11th to 20th	Day	40% 50% 7% 2	1915
	21st to end	Day	50% 39% 5% 5% 1	2783
January	1st to 10th	Night	52% 39% 5% 4	4428
	11th to 20th	Night	57% 38% 2 1 1	4440
	21st to end	Night	52% 42% 4 2	4884
February	1st to 10th	Night	26% 65% 2 4 3	2499
	11th to 20th	Night	23% 65% 4 6% 2	2219
	21st to end	Night	23% 66% 4 6% 2	1884
March	1st to 10th	Night	29% 43% 9% 15% 4 1	3733
	11th to 20th	Night	27% 42% 8% 17% 6%	3640
	21st to end	Night	36% 43% 4 11% 4 1	3607
April	1st to 10th	Night	21% 65% 3 7% 5%	1900
	11th to 20th	Night	20% 65% 3 6% 4 2	1838
	21st to end	Night	18% 65% 3 6% 6% 1	1710
May	1st to 10th	Night	25% 43% 9% 10% 9% 3	2840
	11th to 20th	Night	24% 43% 7% 17% 7%	2641
	21st to end	Night	28% 41% 5% 11% 8% 6%	2751
June	1st to 10th	Night	12% 66% 5% 10% 6% 1	1520
	11th to 20th	Night	16% 65% 4 8% 6% 1	1520
	21st to end	Night	13% 65% 6% 9% 6% 1	1520
July	1st to 10th	Night	32% 36% 7% 14% 5% 5%	2490
	11th to 20th	Night	15% 37% 9% 26% 12% 2	2482
	21st to end	Night	21% 37% 10% 11% 19% 1	2662
August	1st to 10th	Night	25% 38% 8% 17% 12%	2648
	11th to 20th	Night	24% 38% 6% 21% 11%	2812
	21st to end	Night	24% 38% 8% 14% 14% 2	3466
September	1st to 10th	Night	14% 62% 4 12% 7% 1	1900
	11th to 20th	Night	12% 61% 5% 13% 8% 2	2062
	21st to end	Night	17% 61% 5% 10% 6%	2090
October	1st to 10th	Night	19% 60% 4 11% 5% 1	2090
	11th to 20th	Night	23% 61% 5% 9% 3	2366
	21st to end	Night	27% 60% 4 6% 3	2717
November	1st to 10th	Night	27% 59% 4 6% 4	2420
	11th to 20th	Night	27% 61% 3 6% 3	2470
	21st to end	Night	29% 60% 5% 3 2 1	2517
December	1st to 10th	Night	31% 61% 3 3 1	2660
	11th to 20th	Night	40% 51% 5% 2 2	3281
	21st to end	Night	49% 39% 7% 4 1	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	19% 22% 32% 19% 7% 1	270
	11th to 20th	Day	23% 17% 41% 16% 3	270
	21st to end	Day	26% 18% 29% 24% 3	297
February	1st to 10th	Day	19% 29% 31% 15% 5% 2	270
	11th to 20th	Day	20% 29% 33% 16% 1	270
	21st to end	Day	20% 30% 39% 11%	225
March	1st to 10th	Day	18% 26% 40% 13% 3	270
	11th to 20th	Day	21% 18% 30% 22% 8% 1	365
	21st to end	Day	27% 16% 30% 20% 7% 1	506
April	1st to 10th	Day	23% 15% 37% 22% 3 1	460
	11th to 20th	Day	26% 21% 26% 17% 9% 1	452
	21st to end	Day	20% 15% 29% 25% 8% 2	460
May	1st to 10th	Day	21% 14% 35% 21% 7% 2	463
	11th to 20th	Day	18% 10% 31% 28% 12% 2	585
	21st to end	Day	14% 8% 30% 30% 14% 3	734
June	1st to 10th	Day	13% 7% 33% 32% 13% 2	680
	11th to 20th	Day	16% 7% 31% 31% 13% 3	680
	21st to end	Day	15% 8% 28% 33% 12% 4	680
July	1st to 10th	Day	8% 6% 25% 36% 20% 5%	671
	11th to 20th	Day	9% 6% 25% 37% 18% 5%	668
	21st to end	Day	8% 3 27% 38% 17% 5%	739
August	1st to 10th	Day	9% 5% 24% 33% 23% 6%	592
	11th to 20th	Day	13% 4 18% 31% 24% 10%	479
	21st to end	Day	15% 7% 21% 30% 21% 5%	539
September	1st to 10th	Day	16% 8% 22% 31% 18% 6%	490
	11th to 20th	Day	11% 6% 21% 31% 24% 7%	490
	21st to end	Day	16% 12% 23% 26% 17% 6%	490
October	1st to 10th	Day	18% 14% 27% 21% 16% 3	490
	11th to 20th	Day	29% 14% 32% 21% 4	333
	21st to end	Day	34% 17% 31% 14% 3 1	330
November	1st to 10th	Day	23% 19% 30% 19% 8% 1	273
	11th to 20th	Day	20% 30% 33% 13% 4	270
	21st to end	Day	29% 23% 33% 14% 1	270
December	1st to 10th	Day	25% 27% 28% 17% 3	270
	11th to 20th	Day	28% 26% 30% 11% 4 1	270
	21st to end	Day	29% 29% 28% 11% 3	297
January	1st to 10th	Night	23% 19% 33% 19% 6% 1	950
	11th to 20th	Night	26% 18% 32% 18% 5% 1	950
	21st to end	Night	21% 14% 36% 22% 6%	1045
February	1st to 10th	Night	20% 17% 34% 24% 4 1	869
	11th to 20th	Night	21% 18% 32% 23% 6%	743
	21st to end	Night	23% 17% 35% 21% 3	628
March	1st to 10th	Night	18% 14% 32% 26% 9% 1	760
	11th to 20th	Night	16% 15% 33% 27% 8% 1	760
	21st to end	Night	22% 11% 26% 32% 8% 1	716
April	1st to 10th	Night	21% 14% 31% 27% 6% 1	570
	11th to 20th	Night	24% 12% 27% 27% 9% 1	563
	21st to end	Night	22% 8% 29% 29% 12% 1	570
May	1st to 10th	Night	18% 6% 30% 34% 11% 1	570
	11th to 20th	Night	17% 5% 24% 35% 17% 1	561
	21st to end	Night	16% 5% 21% 37% 18% 3	617
June	1st to 10th	Night	13% 6% 22% 41% 16% 2	570
	11th to 20th	Night	15% 4 24% 35% 19% 3	570
	21st to end	Night	12% 4 20% 41% 21% 2	570
July	1st to 10th	Night	10% 1 16% 41% 27% 5%	555
	11th to 20th	Night	10% 3 20% 35% 28% 4	552
	21st to end	Night	8% 4 18% 39% 28% 3	624
August	1st to 10th	Night	10% 3 16% 41% 27% 4	567
	11th to 20th	Night	11% 2 16% 35% 29% 7%	564
	21st to end	Night	13% 4 17% 40% 23% 3	627
September	1st to 10th	Night	13% 6% 21% 35% 20% 6%	570
	11th to 20th	Night	12% 7% 18% 36% 23% 5%	732
	21st to end	Night	18% 9% 21% 28% 21% 3	760
October	1st to 10th	Night	20% 10% 23% 29% 16% 2	760
	11th to 20th	Night	29% 11% 26% 24% 8% 1	760
	21st to end	Night	31% 14% 28% 21% 6%	836
November	1st to 10th	Night	24% 15% 30% 23% 7% 1	745
	11th to 20th	Night	27% 21% 28% 19% 5%	760
	21st to end	Night	31% 16% 29% 20% 4	807
December	1st to 10th	Night	29% 22% 30% 16% 3	950
	11th to 20th	Night	28% 20% 31% 17% 4 1	950
	21st to end	Night	32% 17% 31% 18% 2	1045

Page generated at 2024-10-30 01:23:00. Version ac07

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