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 2025-11-18.

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% 34%	127468
	Night	12% 12% 5% 11% 6% 5% 5% 4 5% 6% 29%	123193
Transparency	Day	51% 3 13% 23% 9% 1	130890
	Night	56% 3 12% 21% 9% 1	127862
Seeing	Day	19% 14% 34% 22% 8% 2	17686
	Night	19% 11% 32% 27% 10% 1	27575

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	5% 15% 8% 15% 7% 8% 7% 4 5% 5% 21%	3178
	11th to 20th	Day	4 13% 6% 18% 8% 7% 8% 8% 10% 5% 12%	3152
	21st to end	Day	5% 18% 10% 19% 7% 5% 6% 4 6% 6% 14%	3943
February	1st to 10th	Day	7% 14% 6% 11% 8% 6% 8% 6% 7% 7% 19%	1800
	11th to 20th	Day	7% 10% 4 12% 7% 7% 6% 6% 6% 7% 28%	1754
	21st to end	Day	6% 13% 5% 13% 8% 6% 5% 6% 6% 6% 27%	1485
March	1st to 10th	Day	7% 12% 4 10% 7% 4 4 3 5% 6% 38%	4743
	11th to 20th	Day	11% 9% 5% 14% 8% 5% 4 3 5% 6% 30%	4980
	21st to end	Day	13% 14% 5% 10% 6% 4 4 3 5% 5% 32%	5524
April	1st to 10th	Day	14% 12% 4 9% 4 4 4 3 5% 6% 35%	2400
	11th to 20th	Day	14% 12% 4 7% 5% 4 5% 4 6% 7% 33%	2532
	21st to end	Day	17% 11% 3 7% 5% 5% 4 3 5% 6% 34%	2615
May	1st to 10th	Day	15% 8% 2 5% 3 3 4 3 5% 7% 45%	6348
	11th to 20th	Day	15% 9% 3 7% 5% 5% 4 4 6% 8% 36%	6319
	21st to end	Day	16% 7% 2 5% 3 3 3 3 4 7% 47%	7271
June	1st to 10th	Day	14% 7% 2 7% 5% 5% 5% 4 7% 8% 37%	3000
	11th to 20th	Day	16% 7% 2 6% 6% 4 5% 4 6% 8% 36%	3000
	21st to end	Day	15% 6% 3 7% 5% 5% 6% 4 8% 10% 31%	3000
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 43%	6799
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 6% 9% 45%	6800
	21st to end	Day	15% 6% 2 6% 5% 4 5% 4 6% 8% 40%	7232
August	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	4442
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 6% 10% 44%	4171
	21st to end	Day	16% 6% 2 6% 4 4 4 4 5% 8% 40%	4646
September	1st to 10th	Day	13% 6% 3 7% 3 5% 5% 4 6% 9% 41%	2400
	11th to 20th	Day	17% 8% 3 8% 5% 4 4 4 6% 8% 34%	2343
	21st to end	Day	19% 8% 2 6% 4 4 3 3 4 6% 40%	2125
October	1st to 10th	Day	18% 14% 4 9% 5% 4 5% 3 5% 6% 28%	2000
	11th to 20th	Day	20% 15% 4 8% 4 4 5% 4 4 6% 26%	2000
	21st to end	Day	19% 19% 6% 11% 5% 5% 3 3 4 5% 22%	2001
November	1st to 10th	Day	16% 18% 6% 12% 6% 5% 3 3 3 6% 23%	1647
	11th to 20th	Day	14% 19% 6% 16% 8% 5% 4 2 3 4 19%	1656
	21st to end	Day	13% 18% 7% 16% 9% 4 6% 3 5% 4 15%	1600
December	1st to 10th	Day	12% 17% 5% 20% 13% 8% 5% 3 3 4 9%	2425
	11th to 20th	Day	10% 18% 8% 13% 6% 6% 5% 4 6% 5% 20%	2639
	21st to end	Day	13% 18% 9% 19% 7% 5% 4 3 4 4 13%	3498
January	1st to 10th	Night	4 15% 6% 17% 9% 7% 7% 5% 5% 6% 19%	6787
	11th to 20th	Night	7% 11% 5% 14% 11% 12% 8% 8% 8% 4 12%	6753
	21st to end	Night	9% 19% 10% 16% 7% 5% 6% 4 6% 5% 13%	7033
February	1st to 10th	Night	7% 13% 5% 11% 9% 7% 7% 6% 7% 6% 23%	2600
	11th to 20th	Night	7% 11% 4 9% 7% 5% 7% 6% 7% 6% 33%	2533
	21st to end	Night	7% 13% 6% 12% 7% 7% 7% 5% 6% 6% 25%	2145
March	1st to 10th	Night	9% 12% 5% 11% 6% 6% 5% 3 5% 6% 31%	5144
	11th to 20th	Night	7% 13% 4 11% 8% 7% 5% 4 6% 7% 27%	4979
	21st to end	Night	18% 14% 4 9% 5% 3 3 3 4 5% 32%	5407
April	1st to 10th	Night	15% 9% 3 8% 4 4 4 4 5% 6% 38%	2000
	11th to 20th	Night	15% 12% 4 7% 4 3 3 3 5% 7% 36%	1815
	21st to end	Night	14% 9% 5% 8% 5% 5% 4 4 5% 7% 33%	1784
May	1st to 10th	Night	15% 9% 2 5% 3 3 3 3 4 5% 48%	3613
	11th to 20th	Night	16% 8% 3 6% 4 4 4 4 6% 7% 38%	3596
	21st to end	Night	16% 6% 2 5% 4 3 5% 4 5% 7% 43%	3612
June	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 6% 8% 39%	1400
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 6% 8% 42%	1400
	21st to end	Night	15% 6% 3 5% 3 5% 5% 4 6% 8% 41%	1400
July	1st to 10th	Night	12% 5% 1 5% 3 4 5% 4 6% 9% 48%	3180
	11th to 20th	Night	10% 4 1 4 3 4 4 4 6% 11% 48%	3180
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 47%	3642
August	1st to 10th	Night	9% 5% 2 6% 4 5% 6% 3 6% 7% 46%	2716
	11th to 20th	Night	11% 5% 2 5% 4 4 3 4 6% 8% 49%	2888
	21st to end	Night	14% 5% 2 6% 4 4 4 3 6% 8% 44%	3261
September	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 4 7% 49%	2000
	11th to 20th	Night	17% 6% 2 7% 4 3 3 3 4 9% 42%	2055
	21st to end	Night	20% 8% 2 6% 4 3 3 3 5% 6% 41%	2255
October	1st to 10th	Night	16% 11% 3 7% 5% 5% 4 4 5% 7% 34%	2400
	11th to 20th	Night	19% 14% 4 7% 5% 5% 4 4 3 6% 30%	2400
	21st to end	Night	20% 14% 4 10% 5% 6% 5% 4 4 5% 24%	2835
November	1st to 10th	Night	14% 18% 5% 12% 6% 5% 4 3 5% 5% 24%	2871
	11th to 20th	Night	14% 16% 6% 17% 7% 5% 4 3 4 5% 17%	2899
	21st to end	Night	13% 17% 7% 16% 9% 6% 4 2 4 4 17%	2800
December	1st to 10th	Night	9% 22% 9% 21% 9% 6% 5% 3 3 3 10%	4762
	11th to 20th	Night	11% 15% 5% 13% 8% 7% 6% 6% 5% 6% 17%	5568
	21st to end	Night	12% 17% 7% 19% 9% 6% 5% 4 4 3 13%	7480

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 7% 15% 8% 2	3179
	11th to 20th	Day	69% 2 7% 19% 3	3180
	21st to end	Day	72% 2 7% 14% 5%	3943
February	1st to 10th	Day	63% 3 10% 14% 9% 1	1800
	11th to 20th	Day	55% 3 11% 22% 8% 1	1763
	21st to end	Day	58% 4 9% 16% 12% 1	1485
March	1st to 10th	Day	49% 2 13% 16% 13% 6%	4745
	11th to 20th	Day	57% 2 11% 20% 10%	4980
	21st to end	Day	55% 2 6% 22% 13% 1	5524
April	1st to 10th	Day	50% 3 8% 24% 14% 2	2400
	11th to 20th	Day	51% 3 11% 21% 14% 1	2532
	21st to end	Day	51% 2 10% 24% 11% 1	2615
May	1st to 10th	Day	42% 2 11% 27% 17% 1	6357
	11th to 20th	Day	47% 3 10% 22% 17% 1	6323
	21st to end	Day	40% 2 7% 30% 18% 3	7271
June	1st to 10th	Day	46% 4 14% 24% 13% 1	3000
	11th to 20th	Day	46% 4 14% 26% 11%	3000
	21st to end	Day	48% 4 18% 23% 8%	3000
July	1st to 10th	Day	37% 3 21% 30% 8%	6726
	11th to 20th	Day	38% 2 20% 34% 5%	6719
	21st to end	Day	44% 3 16% 31% 6%	7024
August	1st to 10th	Day	43% 3 16% 27% 12% 1	4427
	11th to 20th	Day	36% 3 27% 28% 5%	4210
	21st to end	Day	43% 3 21% 28% 5%	4645
September	1st to 10th	Day	42% 3 17% 31% 8%	2400
	11th to 20th	Day	49% 4 20% 22% 4	2343
	21st to end	Day	47% 3 15% 29% 6%	2125
October	1st to 10th	Day	50% 2 15% 26% 7%	3260
	11th to 20th	Day	51% 2 14% 19% 13%	3240
	21st to end	Day	59% 2 17% 19% 3	3208
November	1st to 10th	Day	66% 3 13% 13% 5% 1	1647
	11th to 20th	Day	71% 2 10% 12% 4	1656
	21st to end	Day	73% 4 11% 9% 2	1600
December	1st to 10th	Day	81% 3 8% 6% 2	2425
	11th to 20th	Day	66% 3 9% 14% 9%	2640
	21st to end	Day	77% 2 5% 13% 3	3498
January	1st to 10th	Night	67% 2 8% 13% 9% 1	6787
	11th to 20th	Night	72% 2 7% 15% 4	6800
	21st to end	Night	74% 2 8% 12% 4	7033
February	1st to 10th	Night	59% 4 12% 16% 8% 1	2600
	11th to 20th	Night	50% 3 14% 23% 10%	2534
	21st to end	Night	58% 3 11% 19% 8%	2145
March	1st to 10th	Night	54% 2 11% 16% 13% 4	5155
	11th to 20th	Night	58% 2 13% 18% 9%	4980
	21st to end	Night	57% 1 6% 20% 14% 1	5407
April	1st to 10th	Night	48% 4 6% 23% 18% 2	2000
	11th to 20th	Night	49% 2 9% 22% 16% 3	1815
	21st to end	Night	51% 3 7% 24% 14% 1	1784
May	1st to 10th	Night	41% 1 7% 30% 20% 1	3620
	11th to 20th	Night	46% 2 12% 23% 16% 1	3597
	21st to end	Night	42% 2 9% 27% 17% 4	3613
June	1st to 10th	Night	43% 3 16% 23% 14%	1400
	11th to 20th	Night	40% 4 12% 29% 15% 1	1400
	21st to end	Night	41% 5% 17% 26% 10% 1	1400
July	1st to 10th	Night	35% 3 22% 30% 9% 1	3145
	11th to 20th	Night	32% 3 23% 35% 7%	3138
	21st to end	Night	36% 3 18% 33% 8%	3536
August	1st to 10th	Night	37% 2 16% 34% 10% 1	2707
	11th to 20th	Night	34% 3 24% 34% 5%	2915
	21st to end	Night	40% 2 22% 28% 7%	3261
September	1st to 10th	Night	38% 3 17% 31% 11%	2000
	11th to 20th	Night	43% 3 20% 27% 7%	2055
	21st to end	Night	45% 3 14% 31% 7%	2255
October	1st to 10th	Night	44% 3 14% 31% 9%	3920
	11th to 20th	Night	50% 3 15% 26% 7%	3899
	21st to end	Night	57% 2 14% 21% 6%	4583
November	1st to 10th	Night	63% 3 13% 16% 5% 1	2871
	11th to 20th	Night	70% 4 10% 12% 4	2899
	21st to end	Night	72% 3 13% 9% 3	2800
December	1st to 10th	Night	82% 3 8% 6% 2	4762
	11th to 20th	Night	68% 3 10% 11% 8%	5566
	21st to end	Night	77% 2 5% 13% 3	7480

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% 38% 23% 9% 2	300
	11th to 20th	Day	16% 11% 40% 26% 7%	300
	21st to end	Day	18% 13% 37% 22% 7% 2	330
February	1st to 10th	Day	17% 16% 44% 17% 5% 1	300
	11th to 20th	Day	13% 20% 35% 22% 6% 4	300
	21st to end	Day	18% 27% 35% 14% 6%	249
March	1st to 10th	Day	17% 16% 42% 17% 7%	300
	11th to 20th	Day	15% 22% 37% 20% 5% 1	300
	21st to end	Day	18% 18% 41% 16% 7% 1	352
April	1st to 10th	Day	23% 14% 33% 22% 7% 1	500
	11th to 20th	Day	25% 15% 32% 21% 6% 1	650
	21st to end	Day	22% 15% 32% 23% 7% 1	700
May	1st to 10th	Day	24% 17% 34% 18% 6% 2	703
	11th to 20th	Day	21% 15% 36% 18% 8% 2	725
	21st to end	Day	22% 13% 34% 23% 7% 1	789
June	1st to 10th	Day	18% 16% 33% 22% 8% 3	730
	11th to 20th	Day	18% 16% 39% 17% 7% 2	730
	21st to end	Day	19% 9% 33% 25% 11% 3	730
July	1st to 10th	Day	11% 9% 34% 26% 14% 5%	721
	11th to 20th	Day	16% 12% 29% 26% 12% 5%	718
	21st to end	Day	12% 9% 33% 28% 13% 4	794
August	1st to 10th	Day	12% 11% 30% 32% 12% 4	726
	11th to 20th	Day	14% 8% 30% 27% 17% 5%	715
	21st to end	Day	18% 10% 31% 28% 11% 2	787
September	1st to 10th	Day	17% 11% 33% 26% 11% 2	530
	11th to 20th	Day	21% 14% 36% 22% 7% 1	473
	21st to end	Day	25% 20% 28% 21% 5% 2	330
October	1st to 10th	Day	29% 12% 33% 20% 6%	330
	11th to 20th	Day	24% 21% 34% 19% 3	330
	21st to end	Day	32% 17% 32% 14% 4	363
November	1st to 10th	Day	25% 18% 38% 14% 5% 1	330
	11th to 20th	Day	30% 18% 34% 14% 4	321
	21st to end	Day	29% 18% 38% 11% 2 1	300
December	1st to 10th	Day	22% 13% 37% 24% 4 2	300
	11th to 20th	Day	23% 17% 39% 20% 2	300
	21st to end	Day	21% 12% 37% 20% 8% 3	330
January	1st to 10th	Night	13% 15% 34% 25% 11% 2	1000
	11th to 20th	Night	18% 10% 37% 26% 7% 1	1000
	21st to end	Night	17% 13% 36% 26% 6% 1	1100
February	1st to 10th	Night	15% 12% 32% 32% 7% 1	1000
	11th to 20th	Night	13% 12% 34% 27% 11% 3	979
	21st to end	Night	14% 13% 39% 23% 10% 2	825
March	1st to 10th	Night	15% 15% 35% 24% 10% 1	714
	11th to 20th	Night	14% 15% 39% 24% 7% 1	600
	21st to end	Night	22% 11% 30% 23% 12% 2	660
April	1st to 10th	Night	20% 11% 31% 28% 9% 1	600
	11th to 20th	Night	23% 10% 30% 27% 10% 1	593
	21st to end	Night	20% 11% 30% 29% 10%	600
May	1st to 10th	Night	22% 11% 30% 29% 8% 1	600
	11th to 20th	Night	20% 9% 34% 25% 10% 1	591
	21st to end	Night	20% 9% 28% 31% 11%	650
June	1st to 10th	Night	20% 8% 29% 30% 13% 1	600
	11th to 20th	Night	17% 9% 29% 31% 12% 1	600
	21st to end	Night	17% 6% 25% 34% 17% 2	600
July	1st to 10th	Night	10% 4 29% 36% 20% 2	585
	11th to 20th	Night	12% 6% 28% 32% 19% 2	582
	21st to end	Night	9% 4 26% 37% 22% 2	657
August	1st to 10th	Night	10% 5% 26% 37% 20% 2	597
	11th to 20th	Night	14% 7% 22% 33% 21% 4	594
	21st to end	Night	16% 6% 26% 33% 17% 2	660
September	1st to 10th	Night	16% 7% 28% 33% 15% 2	600
	11th to 20th	Night	21% 9% 29% 26% 14% 1	600
	21st to end	Night	24% 11% 27% 27% 11% 1	655
October	1st to 10th	Night	22% 14% 31% 28% 6% 1	800
	11th to 20th	Night	27% 10% 31% 23% 8% 1	800
	21st to end	Night	28% 13% 32% 22% 5% 1	972
November	1st to 10th	Night	24% 14% 32% 21% 7% 1	1025
	11th to 20th	Night	24% 13% 32% 24% 7% 1	1036
	21st to end	Night	23% 17% 36% 20% 4 1	1000
December	1st to 10th	Night	16% 13% 35% 25% 9% 1	1000
	11th to 20th	Night	21% 14% 35% 23% 6% 1	1000
	21st to end	Night	22% 11% 32% 25% 8% 1	1100

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