Caxambas Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caxambas Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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	6% 5% 2 5% 6% 4 6% 7% 8% 11% 41%	78702
	Night	6% 5% 2 5% 6% 4 5% 6% 7% 10% 42%	80268
Transparency	Day	23% 41% 12% 14% 8% 2	78425
	Night	24% 39% 12% 13% 9% 2	80064
Seeing	Day	6% 3 14% 27% 31% 18%	14674
	Night	7% 3 15% 31% 32% 13%	24839

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% 8% 3 5% 4 3 4 5% 6% 10% 42%	2836
	11th to 20th	Day	15% 8% 3 6% 6% 4 5% 5% 6% 8% 33%	2840
	21st to end	Day	7% 6% 2 6% 6% 4 5% 6% 6% 9% 43%	3416
February	1st to 10th	Day	8% 5% 3 4 4 2 4 6% 6% 8% 50%	1890
	11th to 20th	Day	5% 4 1 3 3 2 4 4 5% 9% 62%	1748
	21st to end	Day	4 3 1 4 4 3 4 5% 5% 9% 58%	1619
March	1st to 10th	Day	2 2 2 3 3 3 4 4 6% 8% 63%	1980
	11th to 20th	Day	4 3 1 4 3 2 4 6% 6% 10% 57%	1980
	21st to end	Day	3 3 2 3 4 2 3 4 7% 8% 62%	2178
April	1st to 10th	Day	3 2 1 3 3 3 4 4 6% 11% 60%	1980
	11th to 20th	Day	4 3 2 3 5% 3 5% 4 6% 9% 56%	1956
	21st to end	Day	4 3 1 3 5% 2 3 5% 5% 11% 58%	2135
May	1st to 10th	Day	3 1 1 2 3 2 4 4 5% 11% 65%	2174
	11th to 20th	Day	6% 5% 2 5% 4 4 5% 6% 8% 10% 43%	2301
	21st to end	Day	8% 4 2 5% 5% 4 6% 6% 8% 10% 42%	2531
June	1st to 10th	Day	11% 7% 3 6% 7% 4 6% 7% 10% 12% 26%	2340
	11th to 20th	Day	6% 5% 3 5% 7% 4 8% 8% 10% 15% 29%	2340
	21st to end	Day	5% 6% 3 6% 8% 5% 8% 9% 11% 13% 27%	2340
July	1st to 10th	Day	6% 5% 2 7% 8% 5% 10% 9% 11% 14% 24%	2340
	11th to 20th	Day	5% 5% 2 7% 8% 7% 9% 11% 11% 13% 23%	2340
	21st to end	Day	5% 4 2 6% 8% 6% 10% 10% 11% 14% 23%	2547
August	1st to 10th	Day	4 4 2 7% 7% 6% 9% 10% 10% 14% 27%	2318
	11th to 20th	Day	4 4 3 6% 8% 5% 10% 11% 12% 13% 24%	2018
	21st to end	Day	6% 5% 3 8% 9% 5% 9% 10% 11% 10% 23%	2178
September	1st to 10th	Day	5% 4 2 7% 9% 6% 8% 9% 8% 13% 28%	1980
	11th to 20th	Day	6% 6% 3 7% 7% 5% 8% 8% 10% 13% 28%	1980
	21st to end	Day	9% 6% 3 7% 8% 5% 9% 8% 10% 10% 24%	1980
October	1st to 10th	Day	5% 6% 3 7% 7% 5% 6% 6% 8% 11% 36%	1980
	11th to 20th	Day	7% 5% 2 7% 6% 4 6% 6% 6% 11% 40%	1813
	21st to end	Day	7% 5% 2 5% 6% 3 4 5% 6% 9% 47%	1980
November	1st to 10th	Day	5% 4 2 5% 5% 3 5% 4 5% 8% 52%	1857
	11th to 20th	Day	8% 3 2 5% 5% 4 5% 5% 8% 8% 47%	1900
	21st to end	Day	5% 3 1 4 5% 3 5% 6% 8% 9% 51%	1900
December	1st to 10th	Day	7% 5% 2 4 4 3 3 5% 6% 9% 53%	1730
	11th to 20th	Day	7% 4 3 4 5% 2 4 5% 6% 10% 50%	2153
	21st to end	Day	9% 6% 2 5% 5% 4 6% 7% 7% 10% 39%	3124
January	1st to 10th	Night	6% 6% 3 6% 7% 5% 6% 5% 8% 11% 39%	4109
	11th to 20th	Night	14% 10% 4 8% 8% 4 6% 5% 6% 8% 29%	4120
	21st to end	Night	6% 6% 3 7% 6% 4 5% 6% 8% 9% 42%	4237
February	1st to 10th	Night	8% 6% 3 5% 4 3 4 5% 5% 8% 49%	2275
	11th to 20th	Night	6% 4 3 4 4 3 4 4 5% 8% 57%	2098
	21st to end	Night	3 3 2 4 4 2 3 4 5% 9% 60%	1635
March	1st to 10th	Night	3 2 1 4 4 2 3 4 5% 9% 63%	1980
	11th to 20th	Night	6% 4 1 3 4 3 4 4 5% 9% 56%	1980
	21st to end	Night	3 3 1 4 4 2 5% 5% 5% 8% 60%	2178
April	1st to 10th	Night	4 3 1 3 4 2 4 5% 7% 10% 57%	1980
	11th to 20th	Night	4 3 2 5% 4 3 5% 5% 6% 10% 54%	1953
	21st to end	Night	5% 4 2 4 3 3 4 5% 6% 10% 55%	1823
May	1st to 10th	Night	3 2 1 2 3 3 4 5% 6% 10% 62%	1798
	11th to 20th	Night	7% 4 2 5% 6% 3 5% 6% 8% 11% 44%	1592
	21st to end	Night	7% 5% 2 4 6% 3 5% 6% 8% 10% 44%	1744
June	1st to 10th	Night	12% 8% 3 7% 7% 4 6% 7% 9% 11% 27%	1620
	11th to 20th	Night	6% 6% 3 6% 6% 5% 6% 6% 10% 13% 33%	1620
	21st to end	Night	5% 5% 3 8% 8% 4 8% 7% 8% 14% 30%	1620
July	1st to 10th	Night	4 5% 3 6% 8% 5% 8% 7% 9% 13% 31%	1620
	11th to 20th	Night	5% 4 3 6% 7% 5% 7% 9% 12% 13% 30%	1620
	21st to end	Night	3 3 2 5% 7% 5% 8% 9% 12% 15% 31%	1771
August	1st to 10th	Night	4 5% 3 7% 7% 5% 7% 7% 11% 14% 30%	1615
	11th to 20th	Night	5% 4 2 6% 6% 5% 7% 8% 11% 15% 31%	1860
	21st to end	Night	6% 7% 3 8% 7% 4 7% 8% 10% 13% 26%	2178
September	1st to 10th	Night	4 4 3 6% 6% 4 8% 9% 11% 15% 30%	1980
	11th to 20th	Night	6% 6% 4 7% 8% 5% 8% 7% 8% 12% 29%	1980
	21st to end	Night	8% 7% 3 8% 8% 6% 7% 8% 8% 11% 26%	1980
October	1st to 10th	Night	6% 6% 3 7% 6% 4 6% 7% 7% 11% 37%	1980
	11th to 20th	Night	6% 5% 2 5% 6% 3 5% 7% 6% 9% 45%	2146
	21st to end	Night	9% 6% 3 6% 6% 3 5% 5% 7% 10% 42%	2376
November	1st to 10th	Night	7% 4 2 5% 5% 3 4 5% 5% 8% 52%	2221
	11th to 20th	Night	6% 6% 3 5% 5% 3 5% 4 5% 9% 49%	2280
	21st to end	Night	7% 5% 2 3 5% 4 6% 5% 7% 9% 47%	2280
December	1st to 10th	Night	6% 4 2 4 4 3 4 5% 7% 9% 51%	2445
	11th to 20th	Night	9% 5% 2 4 5% 3 4 4 5% 8% 50%	3042
	21st to end	Night	8% 8% 3 6% 6% 4 5% 6% 7% 11% 37%	4532

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	29% 29% 11% 18% 11% 3	2837
	11th to 20th	Day	38% 31% 10% 11% 6% 3	2840
	21st to end	Day	28% 26% 9% 19% 13% 4	3416
February	1st to 10th	Day	23% 36% 7% 15% 15% 4	1890
	11th to 20th	Day	14% 38% 11% 21% 11% 5%	1758
	21st to end	Day	13% 37% 8% 16% 21% 5%	1619
March	1st to 10th	Day	10% 39% 8% 21% 19% 4	1980
	11th to 20th	Day	14% 38% 11% 19% 15% 3	1980
	21st to end	Day	10% 38% 11% 24% 14% 4	2178
April	1st to 10th	Day	12% 39% 17% 19% 11% 3	1980
	11th to 20th	Day	14% 38% 14% 22% 11% 2	1956
	21st to end	Day	13% 39% 12% 17% 16% 2	2135
May	1st to 10th	Day	7% 37% 13% 26% 16% 1	2174
	11th to 20th	Day	20% 41% 13% 16% 9%	2305
	21st to end	Day	22% 43% 13% 16% 6% 1	2531
June	1st to 10th	Day	27% 45% 16% 9% 2	2340
	11th to 20th	Day	24% 44% 19% 11% 2	2340
	21st to end	Day	31% 47% 14% 7% 1	2340
July	1st to 10th	Day	30% 49% 16% 6%	2275
	11th to 20th	Day	32% 48% 15% 5%	2271
	21st to end	Day	26% 51% 16% 6%	2405
August	1st to 10th	Day	27% 49% 18% 6% 1	2305
	11th to 20th	Day	28% 49% 16% 7%	2018
	21st to end	Day	33% 47% 14% 5% 1	2178
September	1st to 10th	Day	25% 49% 19% 7%	1980
	11th to 20th	Day	29% 47% 13% 10% 1	1980
	21st to end	Day	32% 44% 13% 7% 3 1	1980
October	1st to 10th	Day	23% 43% 13% 9% 8% 3	1980
	11th to 20th	Day	23% 42% 12% 13% 8% 2	1813
	21st to end	Day	21% 40% 8% 15% 14% 2	1980
November	1st to 10th	Day	18% 42% 6% 11% 14% 9%	1857
	11th to 20th	Day	19% 41% 7% 16% 11% 5%	1900
	21st to end	Day	16% 42% 10% 17% 12% 3	1900
December	1st to 10th	Day	16% 42% 11% 16% 12% 3	1730
	11th to 20th	Day	21% 36% 10% 15% 12% 6%	2150
	21st to end	Day	29% 30% 11% 14% 12% 3	3124
January	1st to 10th	Night	28% 30% 11% 15% 13% 2	4109
	11th to 20th	Night	44% 31% 8% 10% 5% 2	4120
	21st to end	Night	28% 27% 9% 18% 16% 3	4237
February	1st to 10th	Night	23% 36% 7% 14% 15% 5%	2275
	11th to 20th	Night	20% 38% 10% 17% 11% 4	2099
	21st to end	Night	13% 37% 8% 17% 19% 6%	1635
March	1st to 10th	Night	13% 37% 9% 22% 16% 4	1980
	11th to 20th	Night	15% 38% 10% 21% 14% 3	1980
	21st to end	Night	13% 38% 9% 21% 16% 3	2178
April	1st to 10th	Night	14% 39% 14% 20% 11% 3	1980
	11th to 20th	Night	16% 37% 12% 18% 14% 2	1953
	21st to end	Night	14% 39% 11% 19% 15% 2	1823
May	1st to 10th	Night	9% 40% 11% 25% 15%	1798
	11th to 20th	Night	20% 41% 14% 15% 9%	1593
	21st to end	Night	22% 42% 14% 15% 8%	1745
June	1st to 10th	Night	32% 42% 13% 12% 1	1620
	11th to 20th	Night	25% 42% 19% 12% 3	1620
	21st to end	Night	31% 45% 17% 5% 2	1620
July	1st to 10th	Night	29% 47% 16% 6% 1	1575
	11th to 20th	Night	29% 47% 17% 5% 1	1566
	21st to end	Night	23% 49% 19% 10%	1672
August	1st to 10th	Night	25% 48% 18% 8%	1604
	11th to 20th	Night	28% 48% 18% 5% 1	1860
	21st to end	Night	31% 46% 17% 5%	2178
September	1st to 10th	Night	25% 49% 19% 6% 1	1980
	11th to 20th	Night	30% 46% 14% 8% 1	1980
	21st to end	Night	34% 45% 12% 7% 2	1980
October	1st to 10th	Night	26% 42% 13% 10% 7% 3	1980
	11th to 20th	Night	24% 42% 12% 12% 8% 2	2146
	21st to end	Night	24% 39% 9% 13% 12% 3	2376
November	1st to 10th	Night	19% 42% 7% 11% 15% 8%	2221
	11th to 20th	Night	18% 41% 7% 17% 13% 4	2280
	21st to end	Night	20% 41% 10% 14% 13% 2	2280
December	1st to 10th	Night	17% 42% 12% 15% 11% 3	2445
	11th to 20th	Night	22% 35% 7% 17% 11% 7%	3044
	21st to end	Night	29% 31% 15% 11% 12% 2	4532

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	9% 6% 31% 35% 16% 3	270
	11th to 20th	Day	10% 10% 29% 30% 18% 3	270
	21st to end	Day	11% 8% 34% 35% 10% 1	297
February	1st to 10th	Day	6% 7% 22% 41% 20% 3	267
	11th to 20th	Day	4 3 24% 41% 23% 6%	240
	21st to end	Day	4 4 21% 42% 27% 3	337
March	1st to 10th	Day	3 5% 28% 44% 19% 2	420
	11th to 20th	Day	4 5% 25% 36% 27% 2	420
	21st to end	Day	3 2 24% 43% 24% 4	462
April	1st to 10th	Day	4 5% 29% 40% 19% 4	420
	11th to 20th	Day	4 6% 25% 36% 26% 2	412
	21st to end	Day	5% 2 20% 42% 28% 4	420
May	1st to 10th	Day	3 1 14% 42% 32% 8%	423
	11th to 20th	Day	9% 2 15% 33% 29% 12%	447
	21st to end	Day	9% 1 8% 25% 38% 20%	485
June	1st to 10th	Day	14% 3 8% 22% 36% 18%	450
	11th to 20th	Day	8% 1 6% 20% 35% 30%	450
	21st to end	Day	4 1 3 12% 36% 44%	450
July	1st to 10th	Day	4 1 2 7% 38% 49%	445
	11th to 20th	Day	6% 3 8% 37% 46%	444
	21st to end	Day	6% 1 4 13% 40% 37%	488
August	1st to 10th	Day	4 1 2 9% 43% 41%	446
	11th to 20th	Day	5% 1 3 7% 42% 43%	439
	21st to end	Day	9% 1 7% 16% 33% 34%	495
September	1st to 10th	Day	7% 1 4 12% 36% 40%	450
	11th to 20th	Day	5% 2 4 14% 38% 37%	450
	21st to end	Day	9% 2 4 15% 37% 33%	450
October	1st to 10th	Day	9% 1 9% 29% 40% 13%	450
	11th to 20th	Day	9% 3 9% 29% 36% 14%	450
	21st to end	Day	9% 4 13% 33% 31% 10%	495
November	1st to 10th	Day	6% 4 17% 29% 33% 10%	455
	11th to 20th	Day	10% 3 22% 33% 25% 7%	460
	21st to end	Day	4 2 22% 37% 31% 5%	460
December	1st to 10th	Day	9% 3 21% 34% 26% 7%	290
	11th to 20th	Day	7% 7% 23% 31% 26% 6%	270
	21st to end	Day	6% 5% 23% 32% 27% 7%	297
January	1st to 10th	Night	7% 5% 23% 39% 24% 2	760
	11th to 20th	Night	10% 6% 24% 38% 21% 1	760
	21st to end	Night	8% 6% 29% 40% 17% 1	836
February	1st to 10th	Night	9% 4 25% 41% 19% 1	759
	11th to 20th	Night	8% 4 21% 41% 24% 2	703
	21st to end	Night	6% 2 17% 45% 30% 1	592
March	1st to 10th	Night	4 5% 26% 42% 23% 1	720
	11th to 20th	Night	8% 2 21% 40% 28% 1	720
	21st to end	Night	5% 3 22% 45% 24% 2	792
April	1st to 10th	Night	5% 4 19% 40% 30% 2	720
	11th to 20th	Night	6% 3 21% 45% 23% 2	711
	21st to end	Night	7% 2 18% 43% 28% 2	720
May	1st to 10th	Night	3 1 13% 44% 34% 5%	718
	11th to 20th	Night	8% 2 12% 35% 37% 6%	531
	21st to end	Night	8% 1 8% 30% 42% 11%	584
June	1st to 10th	Night	16% 1 7% 16% 46% 14%	540
	11th to 20th	Night	6% 2 4 14% 43% 30%	540
	21st to end	Night	6% 3 11% 39% 42%	540
July	1st to 10th	Night	5% 1 2 8% 40% 44%	525
	11th to 20th	Night	5% 2 8% 38% 46%	522
	21st to end	Night	4 3 7% 40% 46%	591
August	1st to 10th	Night	6% 3 8% 45% 38%	537
	11th to 20th	Night	6% 2 6% 39% 46%	618
	21st to end	Night	11% 1 6% 15% 39% 28%	792
September	1st to 10th	Night	6% 1 4 11% 44% 34%	720
	11th to 20th	Night	9% 1 4 16% 40% 31%	720
	21st to end	Night	11% 1 7% 19% 37% 24%	720
October	1st to 10th	Night	9% 2 9% 35% 34% 11%	720
	11th to 20th	Night	7% 3 11% 32% 37% 11%	720
	21st to end	Night	12% 2 14% 36% 29% 7%	792
November	1st to 10th	Night	8% 3 22% 35% 28% 4	740
	11th to 20th	Night	8% 3 20% 37% 29% 4	760
	21st to end	Night	8% 3 20% 39% 28% 2	760
December	1st to 10th	Night	7% 3 17% 39% 31% 3	760
	11th to 20th	Night	9% 4 20% 35% 29% 3	760
	21st to end	Night	7% 4 21% 37% 28% 3	836

Page generated at 2024-02-07 06:11:56. Version ac07

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