LVAAS South Mountain Campus
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LVAAS South Mountain Campus clear sky chart from 2005-11-06 to 2024-11-04.

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	16% 7% 2 6% 4 4 4 4 6% 7% 39%	101350
	Night	17% 7% 2 6% 4 4 4 4 5% 7% 41%	97667
Transparency	Day	42% 6% 12% 23% 15% 2	104897
	Night	42% 5% 11% 23% 16% 2	102208
Seeing	Day	23% 13% 28% 21% 12% 4	14933
	Night	20% 11% 29% 28% 11% 1	24179

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	15% 8% 2 5% 5% 3 4 3 5% 5% 45%	2517
	11th to 20th	Day	14% 11% 4 11% 5% 5% 4 4 5% 6% 32%	2566
	21st to end	Day	20% 10% 4 7% 5% 4 4 3 4 5% 34%	3124
February	1st to 10th	Day	16% 8% 3 5% 5% 5% 4 3 6% 7% 37%	1710
	11th to 20th	Day	14% 9% 3 7% 5% 4 4 4 6% 6% 38%	1781
	21st to end	Day	19% 10% 3 7% 5% 3 3 3 6% 5% 36%	1570
March	1st to 10th	Day	25% 9% 3 5% 4 4 3 3 5% 5% 35%	3138
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 4 5% 7% 44%	3480
	21st to end	Day	21% 8% 2 5% 3 3 3 2 4 6% 43%	4029
April	1st to 10th	Day	16% 8% 2 7% 5% 4 4 4 5% 6% 37%	2280
	11th to 20th	Day	17% 7% 2 5% 4 4 3 4 5% 8% 40%	2254
	21st to end	Day	17% 5% 3 7% 4 4 4 4 7% 6% 39%	2280
May	1st to 10th	Day	28% 7% 2 6% 4 4 4 4 5% 7% 30%	4122
	11th to 20th	Day	25% 8% 3 7% 5% 5% 4 4 5% 6% 28%	4398
	21st to end	Day	13% 5% 2 5% 4 4 4 4 7% 9% 44%	4837
June	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 4 7% 9% 37%	2660
	11th to 20th	Day	13% 6% 2 6% 5% 6% 5% 5% 8% 8% 37%	2660
	21st to end	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	2660
July	1st to 10th	Day	7% 5% 2 7% 6% 7% 6% 5% 8% 11% 36%	4440
	11th to 20th	Day	10% 5% 2 5% 5% 4 6% 5% 7% 11% 41%	4440
	21st to end	Day	12% 9% 3 8% 6% 5% 5% 5% 6% 8% 34%	4755
August	1st to 10th	Day	21% 5% 2 6% 4 5% 5% 4 6% 8% 32%	4104
	11th to 20th	Day	13% 6% 2 5% 4 4 5% 4 6% 8% 42%	3769
	21st to end	Day	13% 5% 2 5% 3 4 4 4 6% 9% 46%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 5% 4 3 5% 7% 43%	2280
	11th to 20th	Day	13% 5% 2 4 3 3 4 3 5% 7% 51%	2259
	21st to end	Day	19% 6% 2 6% 5% 4 4 4 5% 5% 40%	2075
October	1st to 10th	Day	18% 6% 2 5% 4 4 4 3 6% 6% 42%	1900
	11th to 20th	Day	15% 6% 2 5% 4 5% 4 3 4 6% 47%	1900
	21st to end	Day	20% 5% 2 6% 3 4 4 3 5% 6% 42%	2023
November	1st to 10th	Day	13% 8% 2 5% 3 2 2 3 4 6% 51%	1698
	11th to 20th	Day	17% 6% 2 4 4 4 4 4 5% 6% 46%	1710
	21st to end	Day	16% 7% 2 5% 3 3 4 4 5% 8% 42%	1553
December	1st to 10th	Day	17% 9% 3 7% 5% 3 5% 4 6% 6% 35%	1520
	11th to 20th	Day	21% 7% 3 5% 3 3 4 3 5% 6% 40%	1906
	21st to end	Day	18% 8% 3 9% 6% 5% 5% 4 5% 6% 31%	2772
January	1st to 10th	Night	16% 7% 2 6% 4 4 4 3 5% 7% 43%	4429
	11th to 20th	Night	16% 9% 3 7% 4 4 4 3 5% 7% 39%	4377
	21st to end	Night	24% 9% 2 5% 4 4 3 3 4 6% 35%	4532
February	1st to 10th	Night	16% 9% 3 6% 4 4 4 4 5% 7% 40%	2470
	11th to 20th	Night	16% 9% 3 7% 4 4 4 4 4 5% 40%	2284
	21st to end	Night	19% 8% 2 5% 4 3 3 4 5% 7% 41%	1884
March	1st to 10th	Night	22% 10% 3 6% 4 3 4 3 4 5% 37%	3699
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 5% 6% 49%	3479
	21st to end	Night	17% 9% 3 6% 4 3 3 3 4 5% 44%	3601
April	1st to 10th	Night	17% 7% 2 6% 4 4 5% 3 5% 7% 39%	1900
	11th to 20th	Night	15% 7% 2 7% 4 4 4 4 5% 7% 41%	1875
	21st to end	Night	20% 5% 2 4 3 3 4 3 5% 7% 45%	1900
May	1st to 10th	Night	26% 9% 2 5% 4 3 5% 3 5% 7% 30%	2844
	11th to 20th	Night	26% 8% 3 8% 5% 4 4 4 5% 5% 29%	2495
	21st to end	Night	12% 6% 3 7% 4 4 4 4 6% 9% 42%	2738
June	1st to 10th	Night	15% 7% 2 6% 4 3 3 3 6% 7% 43%	1520
	11th to 20th	Night	13% 5% 2 6% 4 4 5% 4 7% 9% 41%	1520
	21st to end	Night	11% 4 2 5% 4 5% 5% 3 7% 10% 44%	1520
July	1st to 10th	Night	9% 6% 2 7% 6% 6% 6% 6% 6% 9% 38%	2520
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 5% 8% 10% 38%	2520
	21st to end	Night	15% 7% 2 6% 4 4 5% 5% 7% 7% 38%	2794
August	1st to 10th	Night	21% 6% 2 8% 4 4 5% 5% 6% 8% 32%	2825
	11th to 20th	Night	14% 7% 3 6% 4 5% 5% 4 5% 6% 42%	3028
	21st to end	Night	12% 5% 2 5% 4 3 4 3 6% 8% 48%	3476
September	1st to 10th	Night	15% 6% 2 5% 5% 4 3 3 4 6% 48%	1900
	11th to 20th	Night	12% 5% 2 4 4 3 3 3 5% 6% 53%	1920
	21st to end	Night	18% 6% 3 6% 3 4 4 3 4 6% 44%	2102
October	1st to 10th	Night	19% 7% 2 5% 4 3 3 3 4 6% 43%	2280
	11th to 20th	Night	15% 6% 2 4 3 4 3 3 5% 7% 49%	2280
	21st to end	Night	20% 6% 2 4 2 3 3 3 4 5% 47%	2574
November	1st to 10th	Night	12% 6% 2 5% 3 4 3 4 4 6% 52%	2453
	11th to 20th	Night	16% 7% 2 5% 4 4 3 3 4 6% 46%	2470
	21st to end	Night	14% 6% 2 5% 5% 3 5% 4 6% 6% 43%	2626
December	1st to 10th	Night	19% 7% 3 6% 4 5% 5% 4 5% 6% 37%	2660
	11th to 20th	Night	18% 7% 2 5% 5% 4 5% 3 6% 6% 38%	3288
	21st to end	Night	19% 9% 3 7% 4 4 4 3 5% 5% 37%	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	40% 3 16% 27% 11% 3	2518
	11th to 20th	Day	51% 5% 11% 19% 12% 2	2566
	21st to end	Day	52% 6% 11% 21% 9% 1	3124
February	1st to 10th	Day	46% 5% 14% 23% 12% 1	1710
	11th to 20th	Day	46% 5% 9% 24% 14% 2	1790
	21st to end	Day	50% 4 10% 23% 11% 4	1570
March	1st to 10th	Day	50% 5% 9% 27% 8% 2	3141
	11th to 20th	Day	36% 7% 11% 29% 15% 2	3480
	21st to end	Day	44% 4 10% 18% 21% 3	4029
April	1st to 10th	Day	45% 5% 9% 21% 14% 5%	2280
	11th to 20th	Day	41% 6% 11% 22% 16% 4	2254
	21st to end	Day	43% 6% 10% 21% 16% 4	2280
May	1st to 10th	Day	53% 6% 11% 18% 10% 2	4135
	11th to 20th	Day	55% 7% 11% 17% 8% 1	4402
	21st to end	Day	35% 7% 13% 26% 17% 2	4837
June	1st to 10th	Day	41% 8% 13% 23% 14% 1	2660
	11th to 20th	Day	41% 8% 15% 23% 10% 2	2660
	21st to end	Day	38% 8% 14% 25% 14% 1	2660
July	1st to 10th	Day	40% 9% 14% 21% 14% 2	4370
	11th to 20th	Day	37% 7% 17% 26% 13% 1	4365
	21st to end	Day	47% 7% 10% 19% 16% 2	4603
August	1st to 10th	Day	48% 8% 13% 22% 10%	4091
	11th to 20th	Day	38% 6% 12% 30% 13% 1	3806
	21st to end	Day	34% 6% 11% 29% 18% 2	4180
September	1st to 10th	Day	40% 6% 11% 20% 20% 2	2280
	11th to 20th	Day	32% 5% 10% 24% 24% 3	2259
	21st to end	Day	47% 4 9% 18% 20% 2	2075
October	1st to 10th	Day	38% 5% 9% 20% 24% 5%	3160
	11th to 20th	Day	28% 4 11% 29% 24% 5%	3140
	21st to end	Day	28% 3 14% 24% 27% 4	3313
November	1st to 10th	Day	35% 4 14% 24% 20% 3	1698
	11th to 20th	Day	39% 5% 9% 25% 19% 2	1710
	21st to end	Day	39% 5% 13% 30% 10% 2	1553
December	1st to 10th	Day	48% 7% 14% 20% 11% 1	1520
	11th to 20th	Day	46% 4 16% 24% 10% 1	1906
	21st to end	Day	51% 7% 12% 22% 8%	2772
January	1st to 10th	Night	41% 5% 11% 29% 11% 3	4429
	11th to 20th	Night	45% 4 13% 25% 11% 2	4377
	21st to end	Night	50% 5% 9% 25% 10% 2	4532
February	1st to 10th	Night	44% 5% 13% 25% 10% 2	2470
	11th to 20th	Night	46% 4 9% 19% 18% 3	2286
	21st to end	Night	43% 5% 9% 23% 17% 4	1884
March	1st to 10th	Night	50% 5% 8% 23% 12% 2	3709
	11th to 20th	Night	34% 7% 13% 27% 17% 2	3480
	21st to end	Night	44% 4 7% 17% 23% 5%	3601
April	1st to 10th	Night	44% 5% 11% 21% 15% 4	1900
	11th to 20th	Night	43% 6% 9% 21% 19% 2	1875
	21st to end	Night	40% 5% 10% 22% 19% 5%	1900
May	1st to 10th	Night	53% 7% 9% 20% 10% 1	2850
	11th to 20th	Night	54% 8% 13% 13% 10% 2	2496
	21st to end	Night	38% 8% 15% 23% 14% 3	2739
June	1st to 10th	Night	41% 6% 10% 22% 19% 2	1520
	11th to 20th	Night	37% 8% 16% 25% 13% 1	1520
	21st to end	Night	35% 8% 14% 28% 14% 1	1520
July	1st to 10th	Night	42% 9% 16% 17% 15% 2	2480
	11th to 20th	Night	40% 7% 16% 24% 12% 1	2472
	21st to end	Night	42% 8% 14% 17% 18% 1	2705
August	1st to 10th	Night	48% 8% 17% 16% 10% 1	2814
	11th to 20th	Night	42% 6% 12% 24% 15% 1	3057
	21st to end	Night	33% 5% 10% 30% 19% 1	3476
September	1st to 10th	Night	39% 5% 10% 21% 22% 2	1900
	11th to 20th	Night	32% 6% 10% 23% 26% 4	1920
	21st to end	Night	42% 5% 8% 22% 22% 1	2102
October	1st to 10th	Night	43% 4 10% 21% 20% 2	3800
	11th to 20th	Night	27% 4 9% 30% 26% 5%	3779
	21st to end	Night	28% 3 12% 32% 22% 3	4234
November	1st to 10th	Night	34% 5% 12% 25% 20% 4	2453
	11th to 20th	Night	40% 4 9% 24% 18% 4	2470
	21st to end	Night	39% 5% 12% 28% 14% 2	2626
December	1st to 10th	Night	47% 5% 13% 21% 13% 1	2660
	11th to 20th	Night	44% 6% 13% 20% 15% 3	3288
	21st to end	Night	48% 5% 13% 23% 10% 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	30% 23% 26% 17% 2 2	180
	11th to 20th	Day	34% 24% 28% 12% 1 1	195
	21st to end	Day	26% 27% 31% 11% 4 1	297
February	1st to 10th	Day	26% 28% 31% 10% 3 1	270
	11th to 20th	Day	30% 22% 35% 11% 1	389
	21st to end	Day	36% 16% 29% 16% 3	382
March	1st to 10th	Day	33% 17% 28% 18% 5%	460
	11th to 20th	Day	26% 25% 29% 14% 4 1	460
	21st to end	Day	30% 22% 29% 12% 6% 1	506
April	1st to 10th	Day	27% 22% 30% 15% 6% 1	460
	11th to 20th	Day	27% 19% 28% 15% 8% 3	452
	21st to end	Day	30% 14% 32% 16% 4 3	460
May	1st to 10th	Day	32% 16% 26% 16% 7% 3	463
	11th to 20th	Day	26% 11% 30% 20% 11% 2	487
	21st to end	Day	21% 7% 27% 22% 19% 5%	529
June	1st to 10th	Day	18% 12% 30% 21% 16% 3	490
	11th to 20th	Day	20% 8% 27% 25% 16% 4	490
	21st to end	Day	16% 10% 32% 25% 14% 4	490
July	1st to 10th	Day	11% 3 24% 32% 24% 7%	485
	11th to 20th	Day	10% 3 25% 32% 23% 6%	484
	21st to end	Day	15% 5% 29% 31% 14% 5%	532
August	1st to 10th	Day	14% 5% 22% 30% 20% 9%	486
	11th to 20th	Day	16% 4 20% 32% 20% 8%	479
	21st to end	Day	16% 4 24% 27% 18% 10%	539
September	1st to 10th	Day	20% 8% 21% 24% 19% 8%	490
	11th to 20th	Day	15% 5% 23% 28% 18% 11%	490
	21st to end	Day	26% 10% 25% 21% 14% 5%	490
October	1st to 10th	Day	27% 6% 25% 21% 14% 7%	490
	11th to 20th	Day	20% 14% 29% 23% 12% 3	490
	21st to end	Day	24% 12% 34% 18% 10% 2	503
November	1st to 10th	Day	20% 11% 29% 24% 13% 3	374
	11th to 20th	Day	24% 19% 29% 22% 5% 1	370
	21st to end	Day	23% 23% 32% 16% 4 1	213
December	1st to 10th	Day	28% 27% 28% 9% 7% 1	180
	11th to 20th	Day	34% 23% 27% 11% 5%	180
	21st to end	Day	30% 19% 29% 13% 7% 2	198
January	1st to 10th	Night	21% 19% 36% 20% 4	760
	11th to 20th	Night	25% 16% 33% 22% 4	760
	21st to end	Night	19% 19% 37% 22% 3	836
February	1st to 10th	Night	22% 17% 35% 24% 3	760
	11th to 20th	Night	24% 23% 35% 16% 2	743
	21st to end	Night	25% 17% 37% 19% 3	628
March	1st to 10th	Night	23% 18% 31% 23% 4	760
	11th to 20th	Night	24% 18% 33% 19% 6%	760
	21st to end	Night	22% 15% 37% 20% 6%	836
April	1st to 10th	Night	23% 18% 34% 20% 5%	760
	11th to 20th	Night	21% 13% 36% 24% 6%	751
	21st to end	Night	24% 10% 33% 26% 7%	760
May	1st to 10th	Night	26% 9% 31% 26% 8%	580
	11th to 20th	Night	21% 6% 34% 28% 10%	374
	21st to end	Night	17% 6% 21% 40% 15% 1	411
June	1st to 10th	Night	18% 5% 26% 34% 17%	380
	11th to 20th	Night	13% 5% 25% 44% 12%	380
	21st to end	Night	13% 3 25% 46% 13%	380
July	1st to 10th	Night	12% 4 16% 45% 22% 2	370
	11th to 20th	Night	10% 1 23% 37% 27% 2	368
	21st to end	Night	14% 3 22% 38% 22% 2	447
August	1st to 10th	Night	13% 1 14% 45% 25% 3	567
	11th to 20th	Night	16% 3 14% 38% 27% 2	705
	21st to end	Night	15% 2 15% 39% 26% 2	836
September	1st to 10th	Night	18% 3 22% 35% 19% 2	760
	11th to 20th	Night	15% 4 16% 37% 25% 4	760
	21st to end	Night	22% 5% 21% 32% 17% 2	760
October	1st to 10th	Night	23% 5% 22% 29% 17% 3	760
	11th to 20th	Night	17% 10% 28% 33% 12%	760
	21st to end	Night	23% 11% 29% 28% 9%	836
November	1st to 10th	Night	16% 10% 33% 28% 12% 1	755
	11th to 20th	Night	21% 14% 28% 28% 8%	760
	21st to end	Night	18% 16% 33% 26% 7%	760
December	1st to 10th	Night	25% 16% 32% 22% 6% 1	760
	11th to 20th	Night	22% 15% 33% 25% 5%	760
	21st to end	Night	22% 15% 34% 26% 3	836

Page generated at 2024-11-01 22:47:47. Version ac07

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