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 2025-03-12.

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	6% 4 2 6% 5% 5% 6% 5% 8% 11% 42%	109064
	Night	6% 6% 2 7% 5% 5% 5% 5% 7% 10% 42%	109950
Transparency	Day	19% 47% 13% 14% 6% 2	112839
	Night	21% 46% 11% 13% 7% 2	114314
Seeing	Day	6% 3 15% 28% 30% 17%	16165
	Night	7% 3 15% 31% 31% 12%	26325

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	7% 6% 2 5% 3 3 4 3 7% 10% 50%	4056
	11th to 20th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 34%	4060
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 4 6% 9% 44%	4898
February	1st to 10th	Day	7% 5% 2 5% 3 4 4 4 6% 8% 51%	2000
	11th to 20th	Day	5% 4 1 3 2 3 3 4 5% 9% 61%	1948
	21st to end	Day	4 3 1 4 3 4 4 4 6% 8% 58%	1805
March	1st to 10th	Day	4 3 2 6% 5% 5% 6% 5% 9% 11% 44%	3545
	11th to 20th	Day	3 2 1 3 3 3 4 4 7% 11% 59%	3491
	21st to end	Day	8% 3 1 3 3 3 4 3 6% 8% 58%	3815
April	1st to 10th	Day	2 2 1 3 3 3 3 3 6% 11% 61%	2090
	11th to 20th	Day	4 3 2 4 4 4 4 3 6% 9% 56%	2066
	21st to end	Day	4 3 1 4 4 3 3 4 6% 11% 57%	2254
May	1st to 10th	Day	2 1 1 2 2 2 3 3 5% 10% 69%	3793
	11th to 20th	Day	4 4 2 5% 3 4 4 5% 8% 12% 50%	4081
	21st to end	Day	5% 3 1 4 4 3 4 3 6% 8% 59%	4476
June	1st to 10th	Day	11% 7% 3 7% 6% 6% 7% 6% 10% 11% 26%	2470
	11th to 20th	Day	7% 6% 3 6% 6% 5% 8% 6% 10% 15% 28%	2470
	21st to end	Day	5% 6% 3 7% 7% 7% 8% 8% 11% 13% 26%	2470
July	1st to 10th	Day	5% 4 2 8% 8% 7% 9% 7% 11% 13% 26%	4120
	11th to 20th	Day	3 4 2 8% 7% 9% 9% 8% 12% 14% 23%	4120
	21st to end	Day	3 3 1 7% 7% 7% 9% 7% 12% 14% 30%	4466
August	1st to 10th	Day	4 5% 3 11% 8% 8% 9% 7% 10% 12% 25%	4081
	11th to 20th	Day	3 3 2 7% 6% 8% 10% 8% 11% 13% 28%	3538
	21st to end	Day	4 4 2 9% 7% 8% 9% 7% 10% 12% 28%	3828
September	1st to 10th	Day	5% 4 2 8% 7% 8% 8% 7% 9% 14% 27%	2090
	11th to 20th	Day	5% 6% 3 8% 6% 8% 8% 6% 10% 13% 28%	2090
	21st to end	Day	9% 6% 3 9% 7% 7% 9% 6% 10% 11% 24%	2090
October	1st to 10th	Day	6% 6% 3 8% 6% 6% 6% 5% 8% 11% 35%	2090
	11th to 20th	Day	7% 5% 3 7% 6% 5% 7% 5% 7% 11% 38%	1913
	21st to end	Day	7% 5% 2 6% 4 5% 4 4 6% 9% 47%	2090
November	1st to 10th	Day	5% 4 2 6% 4 4 5% 4 6% 8% 51%	1957
	11th to 20th	Day	8% 4 2 5% 5% 5% 5% 4 8% 8% 47%	2000
	21st to end	Day	5% 3 1 4 5% 4 5% 4 7% 8% 53%	2000
December	1st to 10th	Day	5% 3 1 3 2 2 3 3 6% 7% 65%	2964
	11th to 20th	Day	6% 5% 2 6% 5% 4 5% 4 7% 10% 48%	3373
	21st to end	Day	9% 6% 3 7% 5% 6% 6% 5% 8% 10% 36%	4466
January	1st to 10th	Night	5% 5% 2 6% 5% 5% 5% 4 7% 10% 46%	5889
	11th to 20th	Night	14% 9% 4 9% 6% 5% 5% 4 5% 7% 31%	5900
	21st to end	Night	10% 6% 2 6% 4 3 4 4 7% 8% 45%	6055
February	1st to 10th	Night	8% 7% 2 6% 4 4 4 3 5% 8% 48%	2400
	11th to 20th	Night	6% 5% 2 4 3 4 4 3 6% 8% 56%	2338
	21st to end	Night	3 3 2 5% 3 3 3 3 6% 8% 61%	1823
March	1st to 10th	Night	5% 5% 3 7% 6% 5% 6% 5% 7% 8% 43%	3528
	11th to 20th	Night	5% 3 1 4 3 4 4 4 7% 10% 55%	3498
	21st to end	Night	6% 4 2 5% 3 4 5% 4 5% 8% 53%	3817
April	1st to 10th	Night	4 4 1 4 4 2 4 4 8% 10% 56%	2090
	11th to 20th	Night	4 3 2 5% 3 4 4 4 6% 10% 54%	2063
	21st to end	Night	5% 4 2 4 3 4 4 4 6% 9% 55%	1924
May	1st to 10th	Night	5% 3 1 5% 3 4 4 4 5% 9% 56%	3114
	11th to 20th	Night	4 3 2 4 3 4 4 4 7% 10% 56%	2812
	21st to end	Night	5% 4 1 4 4 3 4 4 6% 8% 58%	3079
June	1st to 10th	Night	11% 9% 3 8% 5% 5% 6% 5% 9% 11% 28%	1710
	11th to 20th	Night	6% 8% 2 7% 5% 6% 6% 5% 9% 13% 32%	1710
	21st to end	Night	5% 5% 2 9% 8% 6% 8% 6% 9% 14% 29%	1710
July	1st to 10th	Night	3 5% 3 9% 8% 8% 9% 7% 10% 11% 27%	2840
	11th to 20th	Night	4 5% 3 9% 8% 8% 8% 8% 12% 12% 24%	2840
	21st to end	Night	3 4 2 8% 8% 8% 8% 8% 12% 14% 25%	3087
August	1st to 10th	Night	4 5% 3 9% 7% 7% 7% 7% 11% 13% 27%	2843
	11th to 20th	Night	5% 6% 3 9% 7% 8% 8% 7% 10% 14% 25%	3254
	21st to end	Night	5% 6% 2 9% 6% 7% 7% 7% 11% 14% 24%	3828
September	1st to 10th	Night	4 5% 2 7% 5% 6% 8% 7% 11% 15% 29%	2090
	11th to 20th	Night	6% 6% 3 8% 7% 7% 7% 6% 8% 13% 29%	2090
	21st to end	Night	8% 8% 3 9% 7% 7% 6% 7% 8% 11% 27%	2090
October	1st to 10th	Night	7% 6% 3 8% 6% 6% 6% 6% 8% 10% 36%	2090
	11th to 20th	Night	7% 6% 2 6% 5% 5% 5% 5% 6% 9% 43%	2266
	21st to end	Night	9% 6% 3 7% 5% 4 5% 4 6% 10% 43%	2508
November	1st to 10th	Night	6% 5% 2 5% 4 5% 4 4 6% 8% 52%	2341
	11th to 20th	Night	6% 6% 3 5% 5% 4 4 4 6% 9% 48%	2400
	21st to end	Night	6% 6% 1 4 5% 5% 5% 4 7% 9% 48%	2400
December	1st to 10th	Night	4 4 1 3 3 2 3 3 6% 8% 62%	4211
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 6% 8% 50%	4822
	21st to end	Night	8% 9% 3 8% 5% 6% 5% 5% 7% 10% 33%	6490

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	21% 28% 9% 24% 12% 5%	4057
	11th to 20th	Day	37% 31% 10% 16% 5%	4060
	21st to end	Day	27% 30% 5% 22% 14% 1	4898
February	1st to 10th	Day	8% 63% 8% 12% 6% 3	2000
	11th to 20th	Day	6% 61% 4 12% 12% 5%	1958
	21st to end	Day	9% 63% 7% 8% 10% 2	1805
March	1st to 10th	Day	22% 47% 12% 11% 6% 1	3545
	11th to 20th	Day	8% 45% 18% 21% 6% 2	3491
	21st to end	Day	16% 42% 7% 20% 9% 6%	3815
April	1st to 10th	Day	6% 65% 6% 16% 6% 2	2090
	11th to 20th	Day	9% 67% 8% 8% 7% 2	2066
	21st to end	Day	7% 65% 6% 11% 9% 1	2254
May	1st to 10th	Day	5% 42% 12% 24% 15% 3	3828
	11th to 20th	Day	10% 44% 14% 27% 4	4085
	21st to end	Day	8% 41% 11% 29% 10%	4489
June	1st to 10th	Day	17% 69% 8% 7%	2470
	11th to 20th	Day	17% 70% 9% 4	2470
	21st to end	Day	12% 69% 14% 5%	2470
July	1st to 10th	Day	25% 44% 23% 7% 1	4055
	11th to 20th	Day	27% 45% 24% 5%	4051
	21st to end	Day	23% 45% 24% 8%	4324
August	1st to 10th	Day	31% 44% 18% 6% 1	4068
	11th to 20th	Day	24% 45% 23% 9%	3574
	21st to end	Day	24% 44% 27% 4 1	3828
September	1st to 10th	Day	16% 66% 11% 6%	2090
	11th to 20th	Day	15% 65% 12% 7% 2	2090
	21st to end	Day	18% 64% 10% 5% 2	2090
October	1st to 10th	Day	34% 40% 13% 10% 2	3480
	11th to 20th	Day	22% 41% 14% 14% 7% 1	3153
	21st to end	Day	17% 38% 7% 22% 12% 3	3428
November	1st to 10th	Day	11% 59% 9% 13% 7% 2	1957
	11th to 20th	Day	16% 58% 7% 9% 6% 3	2000
	21st to end	Day	11% 58% 6% 10% 10% 4	2000
December	1st to 10th	Day	9% 37% 10% 21% 15% 8%	2964
	11th to 20th	Day	18% 37% 10% 16% 14% 5%	3370
	21st to end	Day	34% 31% 14% 15% 6%	4466
January	1st to 10th	Night	23% 30% 8% 19% 17% 2	5889
	11th to 20th	Night	41% 30% 11% 12% 5% 1	5900
	21st to end	Night	26% 30% 5% 21% 15% 2	6055
February	1st to 10th	Night	12% 63% 6% 12% 6% 1	2400
	11th to 20th	Night	8% 61% 4 10% 11% 6%	2339
	21st to end	Night	9% 62% 6% 9% 11% 3	1823
March	1st to 10th	Night	25% 47% 9% 11% 6% 2	3528
	11th to 20th	Night	12% 44% 17% 17% 8% 1	3498
	21st to end	Night	17% 44% 8% 15% 12% 5%	3817
April	1st to 10th	Night	8% 65% 5% 15% 6% 2	2090
	11th to 20th	Night	8% 67% 8% 8% 7% 2	2063
	21st to end	Night	8% 66% 6% 11% 7% 1	1924
May	1st to 10th	Night	12% 47% 13% 21% 5% 2	3144
	11th to 20th	Night	9% 42% 14% 30% 5%	2813
	21st to end	Night	7% 44% 10% 26% 13% 1	3087
June	1st to 10th	Night	15% 69% 9% 7% 1	1710
	11th to 20th	Night	15% 69% 10% 5%	1710
	21st to end	Night	12% 69% 13% 5% 1	1710
July	1st to 10th	Night	29% 43% 22% 6%	2795
	11th to 20th	Night	29% 45% 22% 4	2786
	21st to end	Night	30% 44% 19% 6%	2988
August	1st to 10th	Night	28% 44% 19% 8% 2	2832
	11th to 20th	Night	29% 46% 19% 5%	3284
	21st to end	Night	25% 48% 24% 2	3828
September	1st to 10th	Night	15% 66% 13% 6%	2090
	11th to 20th	Night	15% 65% 13% 6% 2	2090
	21st to end	Night	16% 67% 7% 7% 2	2090
October	1st to 10th	Night	36% 43% 13% 7% 2	3480
	11th to 20th	Night	26% 41% 13% 12% 8% 1	3765
	21st to end	Night	21% 38% 7% 19% 11% 3	4120
November	1st to 10th	Night	10% 59% 9% 13% 8% 1	2341
	11th to 20th	Night	16% 59% 6% 9% 7% 3	2400
	21st to end	Night	14% 59% 5% 7% 11% 4	2400
December	1st to 10th	Night	11% 37% 7% 27% 9% 9%	4211
	11th to 20th	Night	20% 34% 8% 18% 15% 5%	4824
	21st to end	Night	35% 33% 14% 11% 6%	6490

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	8% 7% 35% 33% 15% 3	300
	11th to 20th	Day	10% 11% 30% 29% 16% 3	300
	21st to end	Day	12% 8% 35% 35% 9% 1	330
February	1st to 10th	Day	5% 7% 22% 41% 20% 4	300
	11th to 20th	Day	5% 5% 29% 38% 18% 5%	300
	21st to end	Day	3 5% 25% 40% 25% 3	404
March	1st to 10th	Day	4 6% 30% 42% 16% 1	500
	11th to 20th	Day	4 6% 25% 38% 25% 2	464
	21st to end	Day	4 3 25% 42% 22% 4	506
April	1st to 10th	Day	3 6% 30% 40% 18% 3	460
	11th to 20th	Day	4 6% 27% 36% 24% 2	452
	21st to end	Day	5% 2 20% 43% 27% 4	460
May	1st to 10th	Day	3 1 15% 42% 32% 8%	463
	11th to 20th	Day	8% 2 17% 34% 28% 11%	487
	21st to end	Day	8% 1 8% 27% 37% 19%	529
June	1st to 10th	Day	13% 3 7% 23% 37% 17%	490
	11th to 20th	Day	10% 2 8% 21% 32% 28%	490
	21st to end	Day	4 1 3 13% 36% 42%	490
July	1st to 10th	Day	4 1 2 9% 38% 46%	485
	11th to 20th	Day	6% 3 8% 36% 46%	484
	21st to end	Day	6% 1 4 13% 41% 36%	532
August	1st to 10th	Day	4 1 4 11% 42% 38%	486
	11th to 20th	Day	4 1 3 9% 41% 42%	479
	21st to end	Day	8% 1 7% 17% 34% 33%	539
September	1st to 10th	Day	6% 1 5% 12% 38% 38%	490
	11th to 20th	Day	4 1 4 16% 39% 35%	490
	21st to end	Day	9% 2 5% 17% 36% 32%	490
October	1st to 10th	Day	10% 2 9% 29% 38% 13%	490
	11th to 20th	Day	9% 4 10% 30% 34% 13%	490
	21st to end	Day	9% 5% 15% 34% 29% 9%	539
November	1st to 10th	Day	6% 4 18% 31% 32% 9%	495
	11th to 20th	Day	10% 3 21% 33% 27% 6%	500
	21st to end	Day	4 2 23% 37% 30% 4	500
December	1st to 10th	Day	8% 5% 22% 35% 24% 7%	321
	11th to 20th	Day	6% 6% 25% 32% 24% 6%	300
	21st to end	Day	7% 5% 25% 32% 25% 6%	330
January	1st to 10th	Night	7% 6% 25% 37% 23% 2	800
	11th to 20th	Night	10% 6% 25% 37% 21% 1	800
	21st to end	Night	9% 6% 28% 40% 16% 1	880
February	1st to 10th	Night	10% 5% 25% 40% 19% 2	800
	11th to 20th	Night	8% 5% 22% 41% 22% 2	783
	21st to end	Night	6% 2 19% 45% 28% 1	660
March	1st to 10th	Night	4 5% 26% 43% 21% 1	800
	11th to 20th	Night	8% 3 21% 40% 27% 1	767
	21st to end	Night	5% 4 23% 44% 23% 2	836
April	1st to 10th	Night	5% 4 20% 41% 29% 2	760
	11th to 20th	Night	6% 3 21% 45% 23% 2	751
	21st to end	Night	7% 2 19% 43% 27% 2	760
May	1st to 10th	Night	3 1 13% 44% 34% 5%	757
	11th to 20th	Night	8% 2 14% 35% 36% 5%	561
	21st to end	Night	8% 1 8% 31% 42% 11%	617
June	1st to 10th	Night	15% 1 8% 17% 46% 13%	570
	11th to 20th	Night	7% 2 6% 15% 41% 29%	570
	21st to end	Night	6% 3 11% 39% 41%	570
July	1st to 10th	Night	4 1 2 9% 41% 43%	555
	11th to 20th	Night	5% 3 8% 39% 45%	552
	21st to end	Night	4 1 3 8% 40% 45%	624
August	1st to 10th	Night	6% 3 10% 44% 37%	567
	11th to 20th	Night	6% 1 2 7% 40% 45%	653
	21st to end	Night	10% 1 6% 16% 40% 27%	836
September	1st to 10th	Night	6% 1 4 12% 45% 32%	760
	11th to 20th	Night	9% 1 4 16% 40% 30%	760
	21st to end	Night	10% 2 8% 19% 36% 24%	760
October	1st to 10th	Night	10% 3 9% 34% 34% 10%	760
	11th to 20th	Night	8% 3 11% 32% 36% 11%	760
	21st to end	Night	12% 2 16% 36% 28% 6%	836
November	1st to 10th	Night	8% 3 22% 37% 27% 4	780
	11th to 20th	Night	8% 3 20% 37% 29% 4	800
	21st to end	Night	8% 3 20% 39% 28% 2	800
December	1st to 10th	Night	7% 4 18% 38% 31% 3	800
	11th to 20th	Night	8% 4 21% 35% 28% 3	800
	21st to end	Night	7% 5% 21% 36% 27% 3	880

Page generated at 2025-03-09 08:08:47. Version ac07

Copyright © 2025 Attilla Danko.