Camp Onas
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Camp Onas clear sky chart from 2005-11-06 to 2024-01-12.

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% 6% 3 5% 5% 3 5% 5% 5% 7% 40%	74734
	Night	16% 6% 3 5% 5% 3 4 4 5% 7% 43%	74972
Transparency	Day	43% 4 11% 23% 15% 2	74440
	Night	42% 4 11% 24% 16% 3	74800
Seeing	Day	21% 17% 29% 20% 10% 3	13822
	Night	20% 15% 30% 25% 9% 1	23183

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	13% 7% 4 6% 6% 4 4 5% 5% 7% 40%	1517
	11th to 20th	Day	14% 8% 3 8% 7% 4 6% 5% 5% 5% 36%	1466
	21st to end	Day	14% 8% 4 6% 6% 3 5% 4 5% 7% 39%	1782
February	1st to 10th	Day	18% 7% 3 5% 6% 3 4 5% 5% 7% 36%	1620
	11th to 20th	Day	16% 8% 3 7% 6% 3 4 4 5% 5% 39%	1703
	21st to end	Day	20% 9% 3 6% 5% 3 5% 4 4 5% 37%	1480
March	1st to 10th	Day	13% 7% 3 6% 5% 3 4 4 5% 6% 45%	1797
	11th to 20th	Day	17% 7% 3 6% 6% 3 5% 5% 5% 6% 38%	1968
	21st to end	Day	21% 7% 4 5% 4 2 4 4 5% 6% 39%	2308
April	1st to 10th	Day	17% 7% 3 6% 6% 3 4 4 4 6% 40%	2160
	11th to 20th	Day	17% 6% 2 4 5% 3 4 4 5% 8% 41%	2134
	21st to end	Day	17% 5% 3 6% 6% 4 4 5% 6% 6% 39%	2160
May	1st to 10th	Day	20% 7% 3 6% 5% 3 5% 5% 5% 7% 34%	2334
	11th to 20th	Day	20% 7% 2 5% 5% 2 4 5% 6% 8% 36%	2478
	21st to end	Day	15% 7% 3 5% 5% 3 4 5% 6% 8% 39%	2725
June	1st to 10th	Day	15% 6% 2 5% 5% 3 5% 6% 6% 10% 38%	2520
	11th to 20th	Day	14% 6% 3 5% 6% 4 6% 5% 6% 9% 36%	2520
	21st to end	Day	13% 5% 2 5% 6% 4 5% 5% 6% 9% 41%	2520
July	1st to 10th	Day	11% 5% 3 6% 7% 4 6% 6% 6% 9% 38%	2520
	11th to 20th	Day	8% 5% 3 4 4 3 6% 6% 8% 11% 43%	2520
	21st to end	Day	11% 5% 3 7% 6% 4 6% 6% 6% 8% 37%	2730
August	1st to 10th	Day	11% 5% 2 5% 6% 3 6% 8% 7% 9% 37%	2327
	11th to 20th	Day	13% 5% 2 5% 6% 4 6% 5% 6% 10% 39%	2135
	21st to end	Day	15% 6% 3 5% 4 3 5% 5% 6% 8% 41%	2376
September	1st to 10th	Day	14% 6% 2 5% 5% 3 4 5% 5% 7% 42%	2160
	11th to 20th	Day	14% 4 2 3 4 2 3 4 5% 9% 50%	2128
	21st to end	Day	17% 6% 2 6% 6% 3 5% 4 5% 6% 40%	1980
October	1st to 10th	Day	20% 6% 2 4 4 3 5% 4 4 7% 42%	1808
	11th to 20th	Day	15% 6% 2 4 5% 3 4 4 5% 6% 46%	1800
	21st to end	Day	21% 7% 2 4 4 3 4 4 4 6% 42%	1902
November	1st to 10th	Day	14% 6% 2 5% 3 2 3 3 4 6% 51%	1671
	11th to 20th	Day	17% 4 3 3 4 3 4 5% 5% 6% 46%	1710
	21st to end	Day	15% 6% 2 5% 4 3 4 4 6% 7% 45%	1577
December	1st to 10th	Day	18% 8% 2 7% 5% 2 4 4 5% 8% 37%	1520
	11th to 20th	Day	20% 8% 2 5% 4 3 3 4 3 6% 41%	1906
	21st to end	Day	18% 7% 3 7% 7% 4 5% 6% 5% 6% 32%	2772
January	1st to 10th	Night	14% 7% 3 5% 4 3 4 4 4 7% 45%	2649
	11th to 20th	Night	18% 8% 2 6% 5% 3 4 4 5% 6% 39%	2517
	21st to end	Night	14% 8% 2 5% 5% 2 4 5% 5% 6% 44%	2574
February	1st to 10th	Night	17% 9% 3 5% 5% 3 3 5% 5% 6% 40%	2340
	11th to 20th	Night	18% 8% 3 6% 5% 3 4 4 4 5% 41%	2142
	21st to end	Night	19% 7% 2 4 5% 2 4 5% 5% 6% 41%	1776
March	1st to 10th	Night	16% 5% 2 4 4 3 5% 4 5% 7% 46%	2150
	11th to 20th	Night	17% 7% 3 5% 4 3 4 4 3 5% 44%	1988
	21st to end	Night	19% 6% 2 5% 5% 3 4 3 5% 6% 42%	2047
April	1st to 10th	Night	18% 6% 3 5% 4 3 5% 5% 6% 7% 40%	1800
	11th to 20th	Night	16% 6% 2 6% 5% 3 4 5% 5% 7% 40%	1775
	21st to end	Night	20% 6% 2 4 4 2 3 4 5% 7% 43%	1800
May	1st to 10th	Night	20% 8% 4 5% 5% 2 4 5% 5% 5% 35%	1642
	11th to 20th	Night	19% 7% 3 4 5% 3 5% 4 5% 7% 39%	1415
	21st to end	Night	16% 6% 2 5% 5% 4 4 3 6% 8% 41%	1550
June	1st to 10th	Night	16% 6% 2 5% 4 2 4 5% 4 7% 43%	1440
	11th to 20th	Night	13% 5% 2 5% 6% 3 6% 6% 7% 8% 40%	1440
	21st to end	Night	11% 4 2 4 5% 4 5% 5% 6% 9% 44%	1440
July	1st to 10th	Night	11% 5% 2 6% 6% 4 6% 6% 7% 9% 39%	1440
	11th to 20th	Night	8% 5% 3 5% 5% 4 6% 6% 7% 10% 43%	1440
	21st to end	Night	9% 5% 2 5% 4 4 4 6% 8% 10% 43%	1584
August	1st to 10th	Night	11% 6% 2 5% 5% 3 6% 6% 7% 8% 42%	1611
	11th to 20th	Night	12% 6% 2 6% 6% 4 5% 7% 7% 7% 37%	1748
	21st to end	Night	14% 6% 3 4 6% 3 5% 4 7% 9% 40%	1980
September	1st to 10th	Night	15% 6% 3 5% 4 3 5% 4 4 6% 46%	1800
	11th to 20th	Night	13% 5% 2 4 4 2 3 4 4 7% 52%	1831
	21st to end	Night	17% 6% 2 5% 4 3 3 4 5% 6% 44%	1980
October	1st to 10th	Night	19% 6% 3 5% 4 3 4 3 4 6% 43%	2150
	11th to 20th	Night	16% 4 2 4 4 3 3 4 5% 5% 49%	2160
	21st to end	Night	21% 6% 3 4 4 2 3 4 4 6% 45%	2452
November	1st to 10th	Night	13% 4 2 4 4 2 3 4 4 6% 53%	2407
	11th to 20th	Night	18% 5% 3 4 4 2 4 5% 3 4 48%	2470
	21st to end	Night	14% 5% 3 5% 4 3 4 4 6% 8% 44%	2602
December	1st to 10th	Night	20% 6% 3 4 4 3 4 4 5% 6% 39%	2660
	11th to 20th	Night	18% 6% 3 5% 5% 3 4 5% 6% 6% 40%	3288
	21st to end	Night	19% 8% 3 6% 5% 3 4 4 4 6% 38%	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	44% 3 11% 25% 13% 4	1518
	11th to 20th	Day	49% 4 13% 21% 11% 3	1466
	21st to end	Day	46% 3 10% 24% 15% 2	1782
February	1st to 10th	Day	47% 4 13% 23% 11% 2	1620
	11th to 20th	Day	48% 3 8% 24% 14% 3	1712
	21st to end	Day	51% 3 8% 23% 12% 4	1480
March	1st to 10th	Day	41% 4 10% 28% 14% 3	1800
	11th to 20th	Day	47% 4 10% 21% 15% 3	1968
	21st to end	Day	47% 3 8% 20% 17% 4	2308
April	1st to 10th	Day	46% 4 9% 21% 15% 5%	2160
	11th to 20th	Day	41% 4 11% 22% 18% 4	2134
	21st to end	Day	44% 4 9% 21% 16% 5%	2160
May	1st to 10th	Day	49% 5% 9% 17% 16% 3	2334
	11th to 20th	Day	46% 5% 10% 21% 15% 2	2482
	21st to end	Day	42% 6% 14% 22% 15% 2	2725
June	1st to 10th	Day	42% 7% 13% 23% 14% 1	2520
	11th to 20th	Day	45% 5% 14% 22% 11% 2	2520
	21st to end	Day	39% 6% 15% 26% 14% 1	2520
July	1st to 10th	Day	42% 5% 13% 24% 15% 1	2450
	11th to 20th	Day	33% 6% 14% 29% 15% 2	2445
	21st to end	Day	42% 6% 11% 22% 17% 2	2577
August	1st to 10th	Day	39% 7% 13% 25% 15%	2314
	11th to 20th	Day	40% 5% 15% 24% 15% 2	2135
	21st to end	Day	40% 5% 11% 22% 19% 3	2376
September	1st to 10th	Day	40% 6% 12% 21% 19% 3	2160
	11th to 20th	Day	33% 4 10% 25% 24% 3	2128
	21st to end	Day	46% 4 8% 20% 21% 2	1980
October	1st to 10th	Day	43% 5% 11% 23% 17% 2	1808
	11th to 20th	Day	40% 4 10% 25% 20% 1	1800
	21st to end	Day	44% 3 8% 25% 17% 2	1902
November	1st to 10th	Day	36% 3 12% 25% 20% 3	1671
	11th to 20th	Day	39% 4 9% 26% 20% 2	1710
	21st to end	Day	39% 3 13% 30% 12% 2	1577
December	1st to 10th	Day	48% 3 16% 21% 12% 1	1520
	11th to 20th	Day	46% 3 15% 24% 10% 2	1906
	21st to end	Day	52% 3 11% 24% 9%	2772
January	1st to 10th	Night	41% 3 11% 25% 16% 4	2649
	11th to 20th	Night	47% 3 14% 23% 10% 2	2517
	21st to end	Night	41% 4 10% 27% 17% 3	2574
February	1st to 10th	Night	46% 3 13% 25% 11% 2	2340
	11th to 20th	Night	46% 4 9% 21% 17% 4	2144
	21st to end	Night	44% 4 7% 24% 18% 3	1776
March	1st to 10th	Night	39% 2 12% 26% 17% 4	2160
	11th to 20th	Night	43% 4 9% 22% 18% 3	1989
	21st to end	Night	44% 3 8% 19% 20% 5%	2047
April	1st to 10th	Night	44% 4 11% 22% 16% 4	1800
	11th to 20th	Night	43% 4 9% 22% 20% 2	1775
	21st to end	Night	41% 5% 9% 21% 19% 5%	1800
May	1st to 10th	Night	50% 4 10% 17% 17% 2	1642
	11th to 20th	Night	45% 5% 12% 17% 19% 3	1416
	21st to end	Night	41% 7% 17% 19% 14% 3	1551
June	1st to 10th	Night	40% 7% 11% 22% 19% 1	1440
	11th to 20th	Night	39% 7% 14% 24% 13% 1	1440
	21st to end	Night	36% 6% 14% 29% 15% 1	1440
July	1st to 10th	Night	41% 7% 15% 21% 15% 2	1400
	11th to 20th	Night	35% 7% 14% 28% 14% 2	1392
	21st to end	Night	34% 8% 17% 23% 16% 3	1496
August	1st to 10th	Night	37% 6% 17% 23% 16% 1	1600
	11th to 20th	Night	43% 6% 14% 20% 15% 2	1748
	21st to end	Night	40% 5% 13% 20% 20% 3	1980
September	1st to 10th	Night	40% 5% 10% 21% 20% 2	1800
	11th to 20th	Night	33% 4 10% 23% 26% 4	1831
	21st to end	Night	41% 3 8% 23% 24% 1	1980
October	1st to 10th	Night	43% 4 10% 25% 15% 2	2150
	11th to 20th	Night	37% 3 12% 28% 17% 2	2160
	21st to end	Night	42% 3 9% 27% 17% 2	2452
November	1st to 10th	Night	34% 4 12% 25% 21% 4	2407
	11th to 20th	Night	40% 3 9% 24% 20% 4	2470
	21st to end	Night	39% 3 12% 28% 15% 2	2602
December	1st to 10th	Night	47% 3 12% 23% 14% 1	2660
	11th to 20th	Night	43% 4 13% 21% 16% 3	3288
	21st to end	Night	49% 3 12% 26% 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	24% 31% 29% 14% 1 1	180
	11th to 20th	Day	28% 33% 28% 9% 2	170
	21st to end	Day	21% 35% 29% 11% 4	264
February	1st to 10th	Day	31% 32% 28% 6% 3	240
	11th to 20th	Day	29% 29% 32% 9% 1	371
	21st to end	Day	34% 24% 28% 12% 2	346
March	1st to 10th	Day	25% 25% 31% 15% 3	420
	11th to 20th	Day	23% 29% 31% 13% 2 1	420
	21st to end	Day	28% 26% 30% 10% 5% 1	462
April	1st to 10th	Day	24% 28% 29% 13% 5% 1	420
	11th to 20th	Day	23% 25% 30% 13% 7% 3	412
	21st to end	Day	28% 19% 34% 14% 4 1	420
May	1st to 10th	Day	30% 21% 28% 13% 6% 2	423
	11th to 20th	Day	23% 16% 33% 20% 6% 1	447
	21st to end	Day	20% 9% 27% 27% 15% 2	485
June	1st to 10th	Day	16% 14% 31% 25% 11% 2	450
	11th to 20th	Day	18% 16% 26% 27% 11% 3	450
	21st to end	Day	16% 11% 33% 26% 12% 3	450
July	1st to 10th	Day	11% 8% 22% 31% 20% 7%	445
	11th to 20th	Day	10% 5% 27% 32% 22% 5%	444
	21st to end	Day	14% 7% 32% 31% 13% 4	488
August	1st to 10th	Day	10% 8% 27% 30% 19% 7%	446
	11th to 20th	Day	14% 6% 21% 33% 19% 6%	439
	21st to end	Day	13% 4 30% 29% 15% 9%	495
September	1st to 10th	Day	20% 9% 23% 26% 14% 8%	450
	11th to 20th	Day	16% 5% 29% 25% 16% 9%	450
	21st to end	Day	21% 14% 25% 24% 11% 5%	450
October	1st to 10th	Day	26% 9% 26% 21% 12% 6%	450
	11th to 20th	Day	18% 17% 30% 26% 8% 2	450
	21st to end	Day	24% 17% 35% 14% 9% 1	455
November	1st to 10th	Day	20% 13% 30% 22% 12% 2	365
	11th to 20th	Day	22% 23% 31% 19% 5% 1	370
	21st to end	Day	20% 25% 36% 14% 4	237
December	1st to 10th	Day	26% 30% 29% 9% 6%	180
	11th to 20th	Day	31% 28% 24% 12% 4	180
	21st to end	Day	28% 23% 30% 13% 5% 1	198
January	1st to 10th	Night	19% 27% 35% 16% 2	760
	11th to 20th	Night	26% 20% 31% 20% 3	725
	21st to end	Night	19% 25% 35% 20% 1	792
February	1st to 10th	Night	23% 21% 35% 20% 1	720
	11th to 20th	Night	24% 28% 34% 12% 1	703
	21st to end	Night	26% 26% 32% 16% 1	592
March	1st to 10th	Night	23% 25% 31% 19% 3	720
	11th to 20th	Night	24% 24% 32% 16% 4 1	720
	21st to end	Night	22% 20% 37% 16% 5%	792
April	1st to 10th	Night	21% 24% 33% 17% 4	720
	11th to 20th	Night	21% 16% 36% 20% 6%	711
	21st to end	Night	24% 15% 33% 23% 4	720
May	1st to 10th	Night	26% 13% 31% 23% 7%	562
	11th to 20th	Night	21% 10% 37% 22% 10%	354
	21st to end	Night	17% 6% 24% 39% 12% 2	389
June	1st to 10th	Night	17% 7% 28% 35% 13%	360
	11th to 20th	Night	14% 6% 29% 39% 11% 1	360
	21st to end	Night	11% 4 26% 48% 11% 1	360
July	1st to 10th	Night	12% 4 25% 39% 18% 2	350
	11th to 20th	Night	8% 3 27% 41% 20% 1	348
	21st to end	Night	11% 5% 24% 38% 21% 2	404
August	1st to 10th	Night	12% 2 17% 43% 23% 2	537
	11th to 20th	Night	15% 3 16% 38% 25% 2	684
	21st to end	Night	15% 4 18% 39% 22% 2	792
September	1st to 10th	Night	18% 3 26% 34% 17% 2	720
	11th to 20th	Night	15% 5% 23% 32% 20% 4	720
	21st to end	Night	19% 7% 23% 31% 17% 1	720
October	1st to 10th	Night	22% 9% 25% 24% 16% 3	720
	11th to 20th	Night	18% 13% 28% 30% 11%	720
	21st to end	Night	24% 15% 31% 21% 8%	792
November	1st to 10th	Night	16% 14% 33% 26% 10% 1	740
	11th to 20th	Night	21% 19% 28% 24% 7%	760
	21st to end	Night	17% 20% 34% 23% 6% 1	760
December	1st to 10th	Night	26% 20% 30% 18% 5% 1	760
	11th to 20th	Night	20% 20% 35% 20% 4	760
	21st to end	Night	22% 20% 33% 22% 3	836

Page generated at 2024-01-08 22:31:22. Version ac07

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