Los Gatos B&B
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Los Gatos B&B clear sky chart from 2005-11-06 to 2025-02-06.

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% 10% 4 10% 6% 5% 5% 4 6% 7% 29%	108631
	Night	14% 11% 4 10% 6% 5% 5% 4 6% 7% 29%	109608
Transparency	Day	50% 8% 12% 19% 9% 1	112235
	Night	51% 8% 13% 18% 9% 1	114168
Seeing	Day	21% 16% 30% 20% 10% 3	14856
	Night	20% 16% 30% 24% 9% 1	24272

By Month

Percentage Cloud Cover NE (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% 6% 18% 9% 6% 5% 3 4 4 15%	3597
	11th to 20th	Day	11% 18% 8% 18% 9% 7% 5% 3 5% 4 13%	3680
	21st to end	Day	12% 14% 8% 13% 10% 7% 6% 4 5% 5% 16%	4466
February	1st to 10th	Day	15% 17% 5% 13% 9% 5% 5% 4 5% 4 18%	1755
	11th to 20th	Day	10% 17% 7% 16% 8% 6% 5% 4 4 4 19%	1663
	21st to end	Day	17% 14% 4 13% 8% 5% 4 3 4 5% 22%	1560
March	1st to 10th	Day	19% 13% 5% 10% 6% 4 3 3 4 6% 28%	3290
	11th to 20th	Day	9% 16% 5% 10% 6% 4 5% 3 6% 6% 30%	3480
	21st to end	Day	13% 11% 5% 13% 6% 5% 4 3 5% 6% 29%	3927
April	1st to 10th	Day	15% 14% 4 8% 6% 5% 4 3 6% 6% 29%	2280
	11th to 20th	Day	17% 11% 4 8% 5% 4 4 4 5% 5% 34%	2254
	21st to end	Day	18% 11% 4 8% 5% 5% 4 3 5% 6% 32%	2356
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 3 5% 6% 34%	4264
	11th to 20th	Day	15% 9% 3 9% 6% 5% 5% 5% 6% 8% 29%	4398
	21st to end	Day	10% 6% 2 7% 5% 5% 6% 5% 5% 8% 42%	4837
June	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 5% 6% 8% 34%	2660
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 5% 7% 8% 36%	2660
	21st to end	Day	11% 6% 2 7% 5% 6% 6% 5% 7% 9% 37%	2660
July	1st to 10th	Day	10% 5% 2 6% 5% 6% 6% 5% 9% 11% 37%	4440
	11th to 20th	Day	7% 5% 2 6% 5% 5% 6% 6% 10% 11% 36%	4440
	21st to end	Day	8% 5% 3 7% 6% 6% 7% 5% 8% 9% 36%	4721
August	1st to 10th	Day	16% 6% 3 7% 5% 5% 5% 4 6% 8% 34%	4104
	11th to 20th	Day	12% 8% 2 8% 6% 7% 7% 5% 8% 9% 29%	3994
	21st to end	Day	10% 6% 3 8% 6% 5% 5% 4 6% 9% 37%	4180
September	1st to 10th	Day	14% 6% 2 6% 4 5% 5% 4 6% 8% 39%	2280
	11th to 20th	Day	12% 6% 3 6% 4 5% 4 3 6% 7% 45%	2280
	21st to end	Day	17% 7% 2 7% 6% 4 6% 4 6% 6% 33%	2001
October	1st to 10th	Day	17% 7% 3 8% 4 4 4 3 7% 7% 34%	1900
	11th to 20th	Day	18% 9% 3 8% 5% 4 5% 4 6% 6% 30%	1900
	21st to end	Day	21% 12% 4 8% 4 5% 5% 3 5% 6% 25%	2062
November	1st to 10th	Day	11% 12% 3 9% 6% 6% 5% 4 4 6% 34%	1761
	11th to 20th	Day	11% 14% 4 10% 6% 6% 5% 4 6% 7% 26%	1635
	21st to end	Day	16% 14% 4 11% 6% 5% 5% 4 5% 6% 22%	1600
December	1st to 10th	Day	15% 19% 6% 14% 7% 5% 5% 5% 6% 5% 13%	2600
	11th to 20th	Day	17% 13% 6% 14% 7% 5% 4 3 5% 5% 21%	2986
	21st to end	Day	17% 17% 5% 14% 8% 6% 5% 3 5% 6% 13%	3960
January	1st to 10th	Night	13% 14% 6% 17% 9% 6% 5% 4 4 5% 17%	6349
	11th to 20th	Night	8% 17% 7% 16% 9% 6% 5% 4 6% 6% 15%	6202
	21st to end	Night	14% 14% 5% 13% 8% 6% 6% 3 5% 5% 19%	6490
February	1st to 10th	Night	13% 17% 6% 12% 6% 5% 5% 4 6% 4 21%	2536
	11th to 20th	Night	11% 13% 6% 14% 8% 7% 6% 4 5% 5% 21%	2403
	21st to end	Night	15% 11% 4 13% 6% 5% 6% 4 6% 6% 23%	1893
March	1st to 10th	Night	17% 11% 4 9% 5% 5% 4 4 5% 6% 29%	3546
	11th to 20th	Night	12% 17% 6% 10% 6% 5% 5% 4 4 7% 25%	3479
	21st to end	Night	15% 11% 4 9% 6% 5% 5% 3 5% 6% 31%	3704
April	1st to 10th	Night	17% 11% 4 7% 5% 4 5% 4 5% 7% 31%	1900
	11th to 20th	Night	17% 11% 3 8% 4 5% 3 3 5% 6% 35%	1875
	21st to end	Night	16% 8% 3 7% 5% 4 4 4 6% 8% 36%	1838
May	1st to 10th	Night	20% 9% 3 8% 5% 5% 5% 4 5% 7% 30%	2674
	11th to 20th	Night	14% 9% 3 7% 5% 4 5% 4 7% 8% 35%	2495
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 7% 9% 43%	2738
June	1st to 10th	Night	14% 6% 3 7% 4 4 6% 3 6% 9% 38%	1520
	11th to 20th	Night	9% 6% 3 7% 5% 4 5% 4 6% 8% 43%	1520
	21st to end	Night	9% 6% 2 6% 5% 4 5% 5% 6% 9% 42%	1520
July	1st to 10th	Night	6% 8% 2 7% 6% 5% 5% 4 6% 10% 41%	2520
	11th to 20th	Night	8% 4 2 5% 4 4 5% 5% 6% 9% 48%	2520
	21st to end	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 42%	2827
August	1st to 10th	Night	14% 6% 3 7% 4 5% 4 4 7% 7% 39%	2825
	11th to 20th	Night	14% 6% 2 7% 5% 4 5% 4 5% 7% 40%	2803
	21st to end	Night	7% 4 2 6% 5% 4 5% 4 7% 9% 45%	3476
September	1st to 10th	Night	12% 6% 2 5% 4 4 5% 4 4 8% 45%	1900
	11th to 20th	Night	12% 4 3 7% 4 4 5% 3 5% 6% 46%	1900
	21st to end	Night	14% 8% 2 5% 5% 5% 5% 4 6% 7% 37%	2176
October	1st to 10th	Night	15% 9% 3 8% 5% 4 5% 3 6% 6% 37%	2280
	11th to 20th	Night	17% 9% 3 6% 5% 4 4 3 6% 8% 35%	2280
	21st to end	Night	23% 10% 3 8% 5% 5% 4 3 5% 6% 28%	2535
November	1st to 10th	Night	13% 11% 3 7% 6% 4 5% 4 5% 6% 37%	2537
	11th to 20th	Night	15% 11% 4 8% 5% 5% 5% 4 6% 7% 30%	2763
	21st to end	Night	14% 13% 4 9% 6% 6% 5% 4 6% 7% 24%	2800
December	1st to 10th	Night	11% 15% 6% 15% 8% 7% 6% 4 6% 7% 16%	4580
	11th to 20th	Night	16% 15% 5% 11% 6% 5% 5% 3 5% 5% 23%	5208
	21st to end	Night	20% 18% 5% 11% 6% 5% 4 3 5% 5% 16%	6996

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	70% 7% 8% 12% 3	3598
	11th to 20th	Day	70% 7% 8% 9% 5% 1	3710
	21st to end	Day	67% 7% 11% 11% 4	4466
February	1st to 10th	Day	69% 6% 10% 11% 4	1755
	11th to 20th	Day	68% 5% 7% 15% 4	1672
	21st to end	Day	64% 5% 10% 14% 6% 1	1560
March	1st to 10th	Day	58% 5% 10% 21% 6%	3293
	11th to 20th	Day	52% 8% 15% 16% 8% 1	3480
	21st to end	Day	54% 7% 8% 23% 7% 1	3927
April	1st to 10th	Day	55% 5% 10% 19% 9% 2	2280
	11th to 20th	Day	51% 7% 10% 17% 13% 1	2254
	21st to end	Day	52% 5% 8% 19% 13% 2	2356
May	1st to 10th	Day	50% 7% 10% 18% 13% 2	4276
	11th to 20th	Day	50% 10% 13% 19% 7% 1	4402
	21st to end	Day	37% 10% 11% 25% 14% 2	4837
June	1st to 10th	Day	45% 8% 11% 19% 15% 1	2660
	11th to 20th	Day	41% 9% 15% 23% 11% 1	2660
	21st to end	Day	41% 9% 14% 22% 13% 1	2660
July	1st to 10th	Day	37% 9% 15% 27% 11% 1	4370
	11th to 20th	Day	33% 11% 18% 24% 13%	4365
	21st to end	Day	39% 12% 15% 22% 12% 1	4571
August	1st to 10th	Day	45% 8% 14% 21% 11% 1	4091
	11th to 20th	Day	45% 10% 15% 24% 5%	4033
	21st to end	Day	41% 7% 12% 32% 7% 1	4180
September	1st to 10th	Day	41% 8% 12% 25% 12% 1	2280
	11th to 20th	Day	38% 6% 13% 26% 16% 1	2280
	21st to end	Day	48% 8% 12% 20% 11% 1	2001
October	1st to 10th	Day	38% 7% 14% 26% 14% 1	3160
	11th to 20th	Day	45% 7% 13% 20% 15%	3140
	21st to end	Day	43% 6% 15% 26% 8% 1	3376
November	1st to 10th	Day	50% 8% 13% 17% 10% 2	1761
	11th to 20th	Day	54% 8% 13% 16% 7% 1	1635
	21st to end	Day	61% 7% 15% 15% 3	1600
December	1st to 10th	Day	68% 9% 11% 10% 2	2600
	11th to 20th	Day	63% 7% 13% 11% 6%	2986
	21st to end	Day	69% 8% 12% 9% 2	3960
January	1st to 10th	Night	65% 9% 10% 11% 5%	6349
	11th to 20th	Night	64% 8% 11% 11% 5% 1	6247
	21st to end	Night	63% 7% 9% 10% 9% 1	6490
February	1st to 10th	Night	62% 7% 12% 13% 5%	2536
	11th to 20th	Night	63% 6% 12% 14% 5% 1	2405
	21st to end	Night	59% 8% 12% 13% 7% 1	1893
March	1st to 10th	Night	54% 7% 13% 19% 6%	3556
	11th to 20th	Night	57% 9% 13% 16% 6%	3480
	21st to end	Night	50% 7% 11% 21% 10% 1	3704
April	1st to 10th	Night	52% 6% 12% 19% 9% 1	1900
	11th to 20th	Night	50% 7% 11% 18% 14% 1	1875
	21st to end	Night	46% 7% 12% 20% 13% 3	1838
May	1st to 10th	Night	52% 8% 12% 17% 8% 3	2681
	11th to 20th	Night	45% 11% 16% 20% 8% 1	2496
	21st to end	Night	33% 11% 16% 20% 18% 2	2739
June	1st to 10th	Night	41% 7% 12% 25% 14% 1	1520
	11th to 20th	Night	35% 10% 15% 24% 13% 3	1520
	21st to end	Night	36% 10% 13% 26% 14% 1	1520
July	1st to 10th	Night	37% 9% 15% 23% 14% 2	2480
	11th to 20th	Night	29% 10% 16% 30% 14% 1	2472
	21st to end	Night	36% 9% 13% 24% 16% 2	2737
August	1st to 10th	Night	40% 9% 14% 26% 10% 1	2814
	11th to 20th	Night	41% 8% 15% 27% 8%	2830
	21st to end	Night	32% 9% 15% 32% 12% 1	3476
September	1st to 10th	Night	36% 9% 16% 25% 13% 2	1900
	11th to 20th	Night	35% 7% 13% 27% 16% 1	1900
	21st to end	Night	44% 8% 14% 21% 12% 1	2176
October	1st to 10th	Night	42% 8% 12% 25% 13%	3800
	11th to 20th	Night	41% 7% 14% 22% 13% 3	3779
	21st to end	Night	42% 6% 15% 27% 9% 1	4171
November	1st to 10th	Night	46% 8% 12% 22% 11% 2	2537
	11th to 20th	Night	51% 7% 14% 18% 8% 2	2763
	21st to end	Night	57% 9% 16% 15% 4	2800
December	1st to 10th	Night	65% 9% 14% 11% 2	4580
	11th to 20th	Night	61% 6% 10% 13% 8%	5208
	21st to end	Night	68% 8% 8% 11% 4	6996

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	27% 24% 35% 11% 5%	200
	11th to 20th	Day	30% 26% 35% 8% 1	223
	21st to end	Day	23% 27% 37% 10% 2	330
February	1st to 10th	Day	32% 29% 29% 8% 1	285
	11th to 20th	Day	33% 27% 34% 6%	270
	21st to end	Day	33% 23% 30% 14% 1	372
March	1st to 10th	Day	25% 24% 30% 16% 3	460
	11th to 20th	Day	25% 25% 32% 13% 4	460
	21st to end	Day	30% 20% 31% 12% 5% 1	506
April	1st to 10th	Day	27% 23% 30% 15% 4 1	460
	11th to 20th	Day	27% 22% 28% 13% 8% 2	452
	21st to end	Day	28% 17% 29% 18% 7% 1	460
May	1st to 10th	Day	24% 20% 29% 16% 9% 2	463
	11th to 20th	Day	17% 14% 33% 24% 10% 2	487
	21st to end	Day	15% 11% 30% 25% 15% 4	529
June	1st to 10th	Day	18% 14% 31% 24% 11% 3	490
	11th to 20th	Day	12% 12% 29% 31% 12% 3	490
	21st to end	Day	13% 14% 34% 26% 9% 3	490
July	1st to 10th	Day	10% 8% 27% 34% 16% 5%	485
	11th to 20th	Day	11% 7% 25% 31% 21% 5%	484
	21st to end	Day	11% 7% 32% 33% 14% 3	532
August	1st to 10th	Day	11% 7% 25% 30% 20% 8%	486
	11th to 20th	Day	13% 7% 29% 25% 16% 8%	479
	21st to end	Day	12% 10% 27% 26% 15% 10%	539
September	1st to 10th	Day	18% 10% 24% 23% 16% 9%	490
	11th to 20th	Day	10% 8% 23% 26% 21% 12%	490
	21st to end	Day	20% 13% 27% 21% 15% 4	490
October	1st to 10th	Day	20% 11% 31% 19% 13% 6%	490
	11th to 20th	Day	24% 16% 29% 21% 7% 2	490
	21st to end	Day	28% 19% 31% 19% 4	524
November	1st to 10th	Day	20% 21% 31% 18% 9% 1	395
	11th to 20th	Day	24% 25% 31% 17% 3 1	235
	21st to end	Day	28% 30% 31% 12% 1	200
December	1st to 10th	Day	31% 18% 35% 12% 3 1	200
	11th to 20th	Day	33% 26% 30% 11% 1 1	200
	21st to end	Day	29% 20% 36% 13% 1	220
January	1st to 10th	Night	23% 27% 33% 15% 2	800
	11th to 20th	Night	23% 23% 33% 18% 3 1	800
	21st to end	Night	20% 23% 37% 18% 3	880
February	1st to 10th	Night	25% 23% 32% 19% 1	781
	11th to 20th	Night	21% 25% 37% 16% 2	743
	21st to end	Night	26% 23% 32% 16% 3	628
March	1st to 10th	Night	23% 20% 34% 19% 3	760
	11th to 20th	Night	25% 22% 30% 20% 3	760
	21st to end	Night	24% 19% 31% 20% 6%	836
April	1st to 10th	Night	24% 19% 32% 22% 3	760
	11th to 20th	Night	23% 15% 32% 21% 7% 1	751
	21st to end	Night	19% 14% 32% 26% 9%	698
May	1st to 10th	Night	20% 11% 24% 32% 11% 1	476
	11th to 20th	Night	14% 9% 33% 34% 9% 1	374
	21st to end	Night	11% 7% 30% 33% 18%	411
June	1st to 10th	Night	16% 6% 30% 31% 17% 1	380
	11th to 20th	Night	10% 10% 25% 39% 15%	380
	21st to end	Night	11% 9% 26% 42% 11% 1	380
July	1st to 10th	Night	8% 4 21% 45% 21% 2	370
	11th to 20th	Night	10% 1 24% 41% 23% 1	368
	21st to end	Night	11% 4 23% 43% 17% 2	468
August	1st to 10th	Night	10% 3 23% 38% 22% 3	567
	11th to 20th	Night	11% 5% 20% 35% 25% 4	569
	21st to end	Night	10% 6% 22% 36% 23% 2	836
September	1st to 10th	Night	13% 9% 23% 32% 19% 3	760
	11th to 20th	Night	13% 7% 20% 28% 26% 5%	760
	21st to end	Night	17% 10% 26% 26% 18% 3	760
October	1st to 10th	Night	18% 12% 29% 21% 17% 3	760
	11th to 20th	Night	21% 16% 29% 26% 8% 1	760
	21st to end	Night	30% 13% 33% 21% 3	836
November	1st to 10th	Night	22% 16% 31% 24% 8%	780
	11th to 20th	Night	24% 19% 32% 19% 5% 2	800
	21st to end	Night	22% 22% 29% 22% 4 1	800
December	1st to 10th	Night	27% 22% 32% 16% 3	800
	11th to 20th	Night	25% 22% 33% 17% 3	800
	21st to end	Night	27% 21% 34% 16% 2	880

Page generated at 2025-02-03 03:05:56. Version ac07

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