Canary Rise Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canary Rise Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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 9% 5% 5% 5% 4 5% 7% 33%	101938
	Night	12% 12% 4 10% 6% 5% 5% 4 5% 6% 30%	97341
Transparency	Day	51% 3 14% 23% 8%	105383
	Night	54% 3 13% 22% 8%	101988
Seeing	Day	19% 14% 34% 22% 8% 2	16250
	Night	19% 11% 32% 27% 11% 1	26148

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	6% 15% 8% 15% 7% 8% 6% 4 6% 6% 19%	2218
	11th to 20th	Day	5% 11% 5% 16% 10% 9% 11% 7% 7% 6% 14%	2220
	21st to end	Day	8% 19% 8% 19% 7% 6% 6% 4 6% 5% 12%	2739
February	1st to 10th	Day	7% 14% 7% 11% 7% 5% 8% 6% 7% 7% 20%	1710
	11th to 20th	Day	8% 11% 5% 12% 7% 7% 6% 5% 5% 7% 28%	1664
	21st to end	Day	6% 13% 5% 13% 8% 6% 5% 6% 6% 6% 26%	1413
March	1st to 10th	Day	9% 12% 4 10% 8% 5% 4 4 5% 6% 34%	3298
	11th to 20th	Day	8% 9% 5% 16% 10% 5% 4 3 5% 6% 28%	3480
	21st to end	Day	12% 16% 5% 9% 5% 4 4 3 4 5% 32%	3860
April	1st to 10th	Day	14% 12% 4 8% 4 4 4 3 5% 6% 36%	2280
	11th to 20th	Day	14% 12% 4 7% 5% 4 5% 4 5% 7% 33%	2404
	21st to end	Day	16% 11% 3 7% 5% 5% 4 3 5% 6% 35%	2484
May	1st to 10th	Day	17% 10% 3 6% 4 4 5% 3 5% 8% 35%	4428
	11th to 20th	Day	17% 9% 3 8% 5% 4 4 4 5% 6% 34%	4399
	21st to end	Day	22% 9% 2 6% 4 4 3 3 4 6% 38%	5068
June	1st to 10th	Day	15% 7% 2 7% 5% 5% 5% 4 7% 8% 36%	2850
	11th to 20th	Day	17% 7% 2 7% 6% 4 5% 4 6% 7% 36%	2850
	21st to end	Day	15% 6% 3 7% 5% 5% 6% 4 8% 9% 31%	2850
July	1st to 10th	Day	10% 5% 2 6% 5% 4 6% 5% 7% 10% 41%	4750
	11th to 20th	Day	11% 4 2 5% 3 4 4 3 6% 9% 50%	4750
	21st to end	Day	14% 6% 2 6% 4 4 5% 4 5% 8% 42%	5029
August	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	4306
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 6% 10% 45%	4041
	21st to end	Day	17% 6% 2 6% 4 4 4 4 5% 8% 40%	4504
September	1st to 10th	Day	13% 6% 2 7% 3 4 5% 3 6% 9% 41%	2280
	11th to 20th	Day	16% 8% 3 8% 5% 4 4 4 6% 8% 34%	2226
	21st to end	Day	20% 8% 3 6% 5% 4 3 3 4 6% 39%	2019
October	1st to 10th	Day	19% 15% 4 9% 5% 4 4 3 5% 6% 27%	1900
	11th to 20th	Day	20% 15% 4 7% 4 4 5% 4 4 6% 26%	1900
	21st to end	Day	19% 19% 6% 11% 5% 5% 3 3 4 4 22%	1901
November	1st to 10th	Day	16% 18% 7% 12% 5% 5% 4 3 3 5% 23%	1543
	11th to 20th	Day	13% 20% 6% 17% 8% 5% 4 2 3 4 17%	1520
	21st to end	Day	13% 17% 6% 16% 9% 4 6% 4 5% 4 16%	1520
December	1st to 10th	Day	10% 15% 5% 18% 11% 8% 7% 4 4 5% 12%	1413
	11th to 20th	Day	9% 20% 9% 12% 7% 6% 5% 3 5% 5% 20%	1679
	21st to end	Day	17% 15% 8% 13% 6% 6% 5% 3 5% 5% 17%	2442
January	1st to 10th	Night	5% 15% 6% 15% 10% 7% 7% 4 6% 5% 19%	4737
	11th to 20th	Night	7% 11% 5% 15% 13% 12% 8% 6% 6% 4 13%	4750
	21st to end	Night	10% 20% 9% 16% 7% 5% 5% 4 5% 4 14%	4926
February	1st to 10th	Night	7% 13% 5% 12% 8% 6% 7% 5% 7% 6% 24%	2470
	11th to 20th	Night	8% 12% 4 9% 6% 5% 6% 5% 6% 6% 34%	2403
	21st to end	Night	6% 13% 6% 12% 7% 7% 7% 5% 7% 6% 25%	2041
March	1st to 10th	Night	12% 12% 4 10% 5% 5% 5% 3 5% 6% 32%	3574
	11th to 20th	Night	6% 13% 4 10% 9% 6% 5% 3 5% 7% 31%	3479
	21st to end	Night	17% 14% 4 8% 5% 3 3 3 4 5% 33%	3771
April	1st to 10th	Night	15% 9% 3 8% 4 4 4 4 5% 6% 37%	1900
	11th to 20th	Night	15% 12% 4 7% 4 3 3 3 5% 7% 36%	1723
	21st to end	Night	14% 9% 5% 8% 5% 5% 4 4 5% 7% 33%	1695
May	1st to 10th	Night	19% 9% 2 6% 4 5% 4 3 5% 6% 37%	2523
	11th to 20th	Night	16% 8% 3 6% 4 5% 4 4 6% 8% 36%	2506
	21st to end	Night	22% 8% 3 5% 4 3 4 4 4 6% 36%	2517
June	1st to 10th	Night	17% 7% 2 7% 4 4 4 3 7% 8% 38%	1330
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 6% 7% 42%	1330
	21st to end	Night	15% 6% 3 5% 3 5% 5% 4 5% 8% 42%	1330
July	1st to 10th	Night	11% 4 1 4 3 4 5% 4 7% 10% 47%	2220
	11th to 20th	Night	6% 4 1 4 3 3 4 4 6% 11% 53%	2220
	21st to end	Night	10% 4 2 5% 3 3 4 3 6% 7% 52%	2535
August	1st to 10th	Night	9% 5% 2 6% 4 5% 6% 3 7% 7% 46%	2632
	11th to 20th	Night	11% 5% 2 5% 3 4 4 4 6% 8% 49%	2798
	21st to end	Night	14% 5% 2 6% 4 3 4 3 5% 8% 44%	3161
September	1st to 10th	Night	13% 5% 3 5% 4 4 4 3 4 6% 49%	1900
	11th to 20th	Night	17% 6% 2 7% 4 4 3 3 4 8% 42%	1952
	21st to end	Night	21% 8% 2 6% 4 3 4 3 5% 6% 40%	2142
October	1st to 10th	Night	16% 11% 3 7% 5% 5% 4 4 5% 7% 34%	2280
	11th to 20th	Night	19% 13% 4 7% 5% 5% 4 4 4 6% 30%	2280
	21st to end	Night	19% 14% 4 10% 5% 6% 5% 4 4 5% 24%	2693
November	1st to 10th	Night	15% 18% 5% 12% 6% 6% 4 2 5% 5% 23%	2696
	11th to 20th	Night	14% 16% 6% 18% 7% 5% 4 3 4 5% 17%	2660
	21st to end	Night	14% 17% 7% 15% 9% 6% 4 3 4 5% 18%	2660
December	1st to 10th	Night	7% 16% 6% 18% 11% 8% 7% 4 4 5% 14%	2764
	11th to 20th	Night	10% 16% 5% 14% 8% 7% 6% 4 5% 6% 18%	3518
	21st to end	Night	13% 17% 7% 15% 10% 6% 5% 5% 4 3 15%	5225

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	66% 2 9% 16% 6%	2219
	11th to 20th	Day	70% 2 10% 15% 3	2220
	21st to end	Day	74% 2 8% 12% 4	2739
February	1st to 10th	Day	61% 3 10% 14% 9% 1	1710
	11th to 20th	Day	55% 3 10% 22% 8% 1	1673
	21st to end	Day	58% 4 9% 16% 12% 1	1413
March	1st to 10th	Day	53% 2 11% 19% 14% 1	3300
	11th to 20th	Day	58% 2 12% 20% 8%	3480
	21st to end	Day	56% 2 8% 23% 11% 1	3860
April	1st to 10th	Day	49% 3 8% 24% 15% 2	2280
	11th to 20th	Day	50% 3 10% 22% 14% 1	2404
	21st to end	Day	51% 2 11% 24% 11% 1	2484
May	1st to 10th	Day	50% 2 10% 26% 11% 1	4440
	11th to 20th	Day	51% 3 11% 21% 13% 1	4403
	21st to end	Day	51% 2 9% 27% 11% 1	5068
June	1st to 10th	Day	46% 4 14% 23% 13% 1	2850
	11th to 20th	Day	47% 3 14% 24% 11%	2850
	21st to end	Day	47% 5% 18% 23% 7%	2850
July	1st to 10th	Day	38% 4 22% 29% 7%	4676
	11th to 20th	Day	31% 3 21% 37% 7%	4669
	21st to end	Day	42% 3 16% 33% 6%	4870
August	1st to 10th	Day	43% 3 16% 27% 12% 1	4291
	11th to 20th	Day	36% 3 27% 28% 5%	4080
	21st to end	Day	43% 3 20% 28% 5%	4503
September	1st to 10th	Day	41% 3 17% 31% 8%	2280
	11th to 20th	Day	48% 4 20% 23% 4	2226
	21st to end	Day	49% 3 14% 28% 6%	2019
October	1st to 10th	Day	50% 2 15% 26% 7%	3160
	11th to 20th	Day	51% 2 14% 19% 13%	3140
	21st to end	Day	59% 2 17% 19% 3	3108
November	1st to 10th	Day	67% 3 13% 12% 5% 1	1543
	11th to 20th	Day	73% 2 9% 11% 4	1520
	21st to end	Day	71% 4 12% 10% 3	1520
December	1st to 10th	Day	75% 4 8% 10% 3	1413
	11th to 20th	Day	68% 3 11% 16% 3	1680
	21st to end	Day	70% 2 7% 16% 5%	2442
January	1st to 10th	Night	67% 2 12% 16% 4	4737
	11th to 20th	Night	73% 3 8% 14% 3	4750
	21st to end	Night	73% 2 10% 11% 3	4926
February	1st to 10th	Night	58% 4 12% 17% 8% 1	2470
	11th to 20th	Night	50% 3 14% 22% 10%	2404
	21st to end	Night	57% 3 11% 19% 9%	2041
March	1st to 10th	Night	53% 2 11% 20% 12% 1	3585
	11th to 20th	Night	55% 2 14% 20% 8% 1	3480
	21st to end	Night	56% 2 7% 21% 13% 1	3771
April	1st to 10th	Night	48% 4 6% 22% 18% 2	1900
	11th to 20th	Night	49% 2 9% 22% 16% 3	1723
	21st to end	Night	51% 3 7% 24% 14% 1	1695
May	1st to 10th	Night	50% 1 6% 27% 16% 1	2530
	11th to 20th	Night	47% 2 13% 24% 12% 1	2507
	21st to end	Night	50% 2 11% 25% 11% 1	2518
June	1st to 10th	Night	44% 3 15% 23% 14%	1330
	11th to 20th	Night	41% 4 11% 28% 15% 1	1330
	21st to end	Night	41% 6% 17% 26% 10% 1	1330
July	1st to 10th	Night	34% 4 26% 27% 8% 1	2185
	11th to 20th	Night	26% 3 21% 41% 9%	2178
	21st to end	Night	32% 4 16% 40% 8% 1	2454
August	1st to 10th	Night	37% 2 16% 34% 10% 1	2623
	11th to 20th	Night	34% 3 24% 34% 6%	2825
	21st to end	Night	40% 2 22% 28% 7%	3161
September	1st to 10th	Night	37% 3 16% 31% 11%	1900
	11th to 20th	Night	43% 3 20% 27% 7%	1952
	21st to end	Night	46% 3 14% 31% 6%	2142
October	1st to 10th	Night	43% 3 14% 31% 9%	3800
	11th to 20th	Night	49% 3 15% 26% 7%	3779
	21st to end	Night	57% 2 14% 21% 6%	4441
November	1st to 10th	Night	63% 3 13% 15% 4	2696
	11th to 20th	Night	71% 4 9% 11% 4	2660
	21st to end	Night	71% 4 13% 9% 3	2660
December	1st to 10th	Night	73% 4 11% 9% 3	2764
	11th to 20th	Night	67% 3 12% 13% 5%	3516
	21st to end	Night	75% 2 6% 13% 4	5225

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	14% 14% 39% 22% 9% 1	270
	11th to 20th	Day	17% 10% 41% 25% 7%	270
	21st to end	Day	18% 12% 37% 24% 7% 2	297
February	1st to 10th	Day	16% 17% 44% 17% 5% 1	270
	11th to 20th	Day	15% 22% 34% 20% 6% 3	270
	21st to end	Day	18% 27% 35% 14% 6%	225
March	1st to 10th	Day	17% 16% 42% 18% 8%	270
	11th to 20th	Day	15% 22% 36% 20% 6% 1	270
	21st to end	Day	18% 18% 40% 16% 7% 1	318
April	1st to 10th	Day	23% 14% 32% 22% 7% 1	460
	11th to 20th	Day	25% 15% 32% 21% 6% 1	602
	21st to end	Day	21% 15% 34% 22% 8% 1	650
May	1st to 10th	Day	25% 17% 34% 17% 6% 2	653
	11th to 20th	Day	21% 14% 35% 19% 8% 2	675
	21st to end	Day	23% 13% 34% 23% 6% 1	734
June	1st to 10th	Day	19% 16% 32% 22% 9% 3	680
	11th to 20th	Day	19% 17% 39% 16% 7% 2	680
	21st to end	Day	18% 9% 33% 25% 12% 3	680
July	1st to 10th	Day	12% 9% 34% 26% 15% 5%	671
	11th to 20th	Day	15% 12% 28% 28% 13% 5%	668
	21st to end	Day	12% 10% 32% 28% 14% 4	739
August	1st to 10th	Day	12% 11% 31% 31% 12% 3	676
	11th to 20th	Day	13% 8% 29% 28% 17% 5%	665
	21st to end	Day	18% 10% 31% 28% 11% 2	733
September	1st to 10th	Day	17% 11% 33% 27% 10% 2	490
	11th to 20th	Day	21% 15% 36% 22% 7% 1	436
	21st to end	Day	26% 21% 28% 20% 5%	300
October	1st to 10th	Day	31% 12% 31% 21% 6%	300
	11th to 20th	Day	22% 19% 36% 19% 3	300
	21st to end	Day	32% 18% 32% 13% 4	330
November	1st to 10th	Day	23% 18% 39% 14% 5% 1	291
	11th to 20th	Day	28% 20% 33% 15% 4	270
	21st to end	Day	30% 19% 39% 10% 2	270
December	1st to 10th	Day	20% 13% 37% 23% 4 2	270
	11th to 20th	Day	23% 18% 37% 19% 2	270
	21st to end	Day	21% 13% 38% 19% 7% 2	297
January	1st to 10th	Night	14% 15% 34% 24% 11% 2	950
	11th to 20th	Night	19% 10% 38% 25% 7% 1	950
	21st to end	Night	17% 12% 36% 27% 6% 1	1045
February	1st to 10th	Night	15% 12% 32% 32% 8% 1	950
	11th to 20th	Night	14% 13% 33% 26% 11% 3	929
	21st to end	Night	13% 13% 39% 22% 11% 3	785
March	1st to 10th	Night	15% 15% 34% 24% 11% 1	679
	11th to 20th	Night	15% 15% 38% 24% 8% 1	570
	21st to end	Night	22% 11% 30% 23% 12% 2	627
April	1st to 10th	Night	19% 11% 31% 28% 9% 1	570
	11th to 20th	Night	23% 10% 30% 26% 10% 1	563
	21st to end	Night	19% 10% 31% 29% 10%	570
May	1st to 10th	Night	23% 12% 29% 29% 8% 1	570
	11th to 20th	Night	19% 9% 34% 25% 11% 1	561
	21st to end	Night	21% 9% 29% 30% 11%	617
June	1st to 10th	Night	20% 8% 28% 29% 14% 1	570
	11th to 20th	Night	18% 9% 29% 30% 13% 1	570
	21st to end	Night	16% 6% 24% 34% 18% 2	570
July	1st to 10th	Night	10% 4 28% 36% 20% 2	555
	11th to 20th	Night	12% 6% 28% 32% 20% 2	552
	21st to end	Night	9% 4 27% 36% 22% 2	624
August	1st to 10th	Night	10% 5% 26% 38% 19% 1	567
	11th to 20th	Night	13% 7% 22% 33% 21% 4	564
	21st to end	Night	17% 6% 26% 33% 17% 2	627
September	1st to 10th	Night	16% 7% 28% 33% 15% 1	570
	11th to 20th	Night	21% 9% 29% 26% 14% 1	570
	21st to end	Night	24% 10% 27% 27% 10% 1	622
October	1st to 10th	Night	22% 14% 30% 28% 6% 1	760
	11th to 20th	Night	27% 10% 32% 23% 8% 1	760
	21st to end	Night	27% 13% 33% 22% 5% 1	923
November	1st to 10th	Night	23% 13% 33% 22% 8% 1	963
	11th to 20th	Night	24% 12% 32% 24% 7% 1	950
	21st to end	Night	24% 17% 36% 19% 4	950
December	1st to 10th	Night	15% 13% 36% 25% 9% 1	950
	11th to 20th	Night	20% 15% 35% 23% 6% 1	950
	21st to end	Night	22% 11% 33% 25% 7% 1	1045

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