Renaissance Academy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Renaissance Academy clear sky chart from 2005-11-06 to 2025-12-18.

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	12% 6% 2 6% 4 4 5% 4 6% 8% 41%	126711
	Night	13% 7% 2 6% 4 4 4 3 5% 7% 43%	124296
Transparency	Day	38% 8% 13% 22% 16% 3	130302
	Night	38% 7% 11% 22% 18% 4	128774
Seeing	Day	16% 10% 26% 26% 16% 5%	16736
	Night	16% 8% 27% 31% 15% 2	26331

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	14% 5% 1 4 3 3 3 3 4 5% 55%	3799
	11th to 20th	Day	12% 6% 2 6% 4 3 3 3 4 5% 53%	4060
	21st to end	Day	10% 9% 3 8% 4 4 5% 3 4 5% 44%	4466
February	1st to 10th	Day	13% 8% 2 8% 3 4 5% 4 5% 6% 41%	1800
	11th to 20th	Day	20% 6% 2 6% 4 3 4 2 4 5% 43%	1928
	21st to end	Day	15% 8% 2 6% 4 3 3 4 6% 8% 40%	1650
March	1st to 10th	Day	19% 9% 2 6% 4 4 4 3 4 6% 40%	4727
	11th to 20th	Day	10% 7% 2 5% 3 3 3 3 5% 6% 52%	4980
	21st to end	Day	13% 7% 2 5% 4 4 5% 3 5% 6% 47%	5648
April	1st to 10th	Day	12% 6% 2 5% 4 4 4 3 6% 7% 49%	2400
	11th to 20th	Day	10% 6% 2 5% 4 4 4 3 6% 7% 49%	2374
	21st to end	Day	13% 6% 2 5% 4 4 4 4 7% 7% 44%	2400
May	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 5% 7% 9% 34%	5405
	11th to 20th	Day	17% 8% 3 7% 5% 5% 5% 4 6% 8% 31%	6045
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 9% 42%	6934
June	1st to 10th	Day	9% 5% 2 5% 5% 4 5% 5% 8% 11% 40%	2800
	11th to 20th	Day	11% 6% 2 6% 3 5% 5% 4 7% 10% 41%	2800
	21st to end	Day	6% 5% 2 5% 5% 5% 6% 5% 8% 11% 41%	2800
July	1st to 10th	Day	7% 5% 2 6% 4 5% 6% 7% 9% 13% 35%	6360
	11th to 20th	Day	9% 7% 3 8% 6% 6% 7% 6% 9% 11% 28%	6050
	21st to end	Day	6% 5% 2 7% 6% 6% 7% 5% 9% 12% 35%	6424
August	1st to 10th	Day	15% 9% 3 8% 7% 6% 6% 5% 8% 10% 22%	4175
	11th to 20th	Day	9% 6% 2 8% 6% 6% 6% 5% 7% 9% 35%	3850
	21st to end	Day	8% 5% 2 5% 4 5% 5% 6% 7% 11% 42%	4312
September	1st to 10th	Day	14% 5% 2 6% 4 5% 4 4 7% 10% 39%	2400
	11th to 20th	Day	15% 7% 3 8% 4 4 5% 3 5% 8% 39%	2400
	21st to end	Day	20% 7% 3 6% 4 5% 4 4 5% 8% 35%	2150
October	1st to 10th	Day	16% 6% 2 4 4 4 5% 3 5% 6% 45%	2000
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 5% 5% 49%	2000
	21st to end	Day	13% 5% 2 6% 3 4 4 3 4 6% 51%	2200
November	1st to 10th	Day	15% 5% 3 4 3 3 4 3 4 6% 49%	1946
	11th to 20th	Day	14% 7% 2 4 3 3 4 3 4 7% 48%	1890
	21st to end	Day	13% 4 2 5% 5% 4 4 3 5% 6% 49%	1852
December	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 5% 6% 51%	2680
	11th to 20th	Day	15% 7% 3 7% 4 3 4 3 4 5% 44%	3046
	21st to end	Day	13% 5% 2 5% 3 3 4 3 5% 9% 48%	3960
January	1st to 10th	Night	12% 7% 3 5% 3 3 3 3 4 5% 52%	6142
	11th to 20th	Night	14% 6% 2 5% 4 3 3 2 4 5% 51%	5900
	21st to end	Night	13% 7% 2 7% 4 3 3 3 4 7% 45%	6490
February	1st to 10th	Night	17% 7% 2 6% 4 4 4 4 5% 5% 42%	2600
	11th to 20th	Night	21% 8% 2 6% 3 3 3 3 5% 5% 40%	2357
	21st to end	Night	15% 7% 3 5% 4 4 4 3 4 6% 46%	1980
March	1st to 10th	Night	18% 7% 2 6% 4 4 4 3 5% 5% 42%	5108
	11th to 20th	Night	13% 6% 3 6% 4 4 4 3 4 6% 47%	4980
	21st to end	Night	16% 8% 2 5% 4 3 4 3 4 5% 47%	5269
April	1st to 10th	Night	13% 7% 2 6% 5% 4 5% 4 6% 7% 43%	2000
	11th to 20th	Night	11% 7% 2 5% 4 3 3 3 6% 7% 49%	1975
	21st to end	Night	13% 6% 2 5% 3 4 4 3 6% 7% 46%	2000
May	1st to 10th	Night	12% 8% 3 8% 5% 5% 5% 5% 6% 9% 33%	4490
	11th to 20th	Night	19% 9% 3 8% 5% 5% 5% 3 5% 8% 32%	3874
	21st to end	Night	13% 9% 3 8% 5% 5% 5% 4 5% 9% 35%	3920
June	1st to 10th	Night	10% 6% 2 5% 5% 5% 5% 4 8% 10% 40%	1600
	11th to 20th	Night	7% 5% 2 7% 6% 6% 5% 6% 6% 10% 40%	1600
	21st to end	Night	6% 5% 2 6% 5% 5% 4 5% 7% 10% 45%	1600
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 6% 4 10% 14% 35%	3598
	11th to 20th	Night	8% 7% 3 8% 5% 5% 6% 5% 8% 13% 32%	3889
	21st to end	Night	10% 7% 3 8% 6% 6% 5% 4 7% 10% 35%	4427
August	1st to 10th	Night	15% 9% 3 8% 6% 5% 5% 4 6% 10% 29%	2943
	11th to 20th	Night	9% 7% 3 8% 5% 6% 5% 4 6% 9% 39%	3197
	21st to end	Night	9% 5% 2 6% 4 4 5% 5% 7% 10% 44%	3586
September	1st to 10th	Night	10% 6% 3 6% 4 4 5% 4 5% 8% 45%	2000
	11th to 20th	Night	13% 7% 2 8% 4 4 4 3 4 7% 43%	2000
	21st to end	Night	18% 8% 3 8% 5% 4 5% 3 5% 7% 34%	2245
October	1st to 10th	Night	14% 5% 2 6% 4 3 4 4 4 5% 48%	2400
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 4 5% 50%	2400
	21st to end	Night	13% 5% 2 5% 3 4 3 3 5% 5% 51%	2640
November	1st to 10th	Night	14% 6% 3 5% 4 3 4 3 5% 6% 47%	2571
	11th to 20th	Night	14% 8% 3 6% 3 3 3 4 5% 7% 45%	2730
	21st to end	Night	12% 5% 1 5% 4 4 4 4 5% 7% 50%	2765
December	1st to 10th	Night	9% 6% 2 6% 4 3 4 3 4 6% 53%	4720
	11th to 20th	Night	16% 7% 3 7% 5% 5% 5% 3 5% 6% 38%	5304
	21st to end	Night	11% 6% 2 6% 4 4 4 4 5% 7% 48%	6996

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	31% 4 7% 26% 20% 12%	3800
	11th to 20th	Day	34% 4 6% 19% 31% 6%	4060
	21st to end	Day	41% 5% 9% 25% 17% 2	4466
February	1st to 10th	Day	42% 5% 13% 24% 13% 3	1800
	11th to 20th	Day	44% 4 10% 18% 18% 5%	1937
	21st to end	Day	41% 6% 11% 20% 17% 5%	1650
March	1st to 10th	Day	44% 5% 9% 20% 16% 7%	4727
	11th to 20th	Day	32% 6% 9% 18% 25% 9%	4980
	21st to end	Day	37% 7% 13% 19% 19% 5%	5648
April	1st to 10th	Day	34% 6% 13% 21% 21% 5%	2400
	11th to 20th	Day	34% 6% 11% 24% 20% 5%	2374
	21st to end	Day	37% 7% 13% 23% 17% 4	2400
May	1st to 10th	Day	43% 11% 17% 18% 10% 1	5437
	11th to 20th	Day	47% 10% 15% 19% 9% 1	6049
	21st to end	Day	37% 9% 16% 24% 13% 2	6949
June	1st to 10th	Day	33% 10% 16% 25% 14% 1	2800
	11th to 20th	Day	35% 10% 17% 23% 14% 1	2800
	21st to end	Day	33% 11% 17% 26% 13% 1	2800
July	1st to 10th	Day	34% 13% 19% 23% 10% 2	6290
	11th to 20th	Day	45% 13% 23% 15% 3	5977
	21st to end	Day	37% 12% 14% 25% 12%	6240
August	1st to 10th	Day	53% 10% 17% 16% 4	4162
	11th to 20th	Day	40% 11% 15% 22% 12%	3886
	21st to end	Day	33% 9% 15% 26% 15% 2	4312
September	1st to 10th	Day	39% 9% 15% 18% 16% 3	2400
	11th to 20th	Day	44% 6% 11% 21% 16% 2	2400
	21st to end	Day	47% 8% 10% 19% 13% 2	2150
October	1st to 10th	Day	31% 6% 10% 26% 25% 3	3260
	11th to 20th	Day	27% 3 7% 21% 33% 9%	3240
	21st to end	Day	23% 4 9% 28% 27% 9%	3538
November	1st to 10th	Day	37% 5% 11% 25% 19% 3	1946
	11th to 20th	Day	36% 5% 13% 21% 20% 5%	1890
	21st to end	Day	36% 5% 9% 27% 21% 3	1852
December	1st to 10th	Day	34% 5% 9% 28% 21% 3	2680
	11th to 20th	Day	43% 5% 13% 19% 15% 4	3042
	21st to end	Day	34% 6% 14% 30% 16% 1	3960
January	1st to 10th	Night	33% 5% 7% 22% 25% 9%	6142
	11th to 20th	Night	35% 4 6% 21% 29% 5%	5900
	21st to end	Night	39% 5% 8% 25% 19% 4	6490
February	1st to 10th	Night	42% 6% 10% 23% 16% 3	2600
	11th to 20th	Night	46% 4 8% 21% 16% 5%	2359
	21st to end	Night	40% 4 9% 21% 18% 7%	1980
March	1st to 10th	Night	43% 5% 9% 19% 17% 8%	5108
	11th to 20th	Night	38% 6% 8% 16% 22% 10%	4980
	21st to end	Night	40% 5% 9% 24% 16% 6%	5269
April	1st to 10th	Night	39% 7% 12% 17% 21% 4	2000
	11th to 20th	Night	34% 6% 12% 23% 19% 6%	1975
	21st to end	Night	36% 7% 12% 23% 18% 4	2000
May	1st to 10th	Night	44% 11% 17% 18% 9% 1	4520
	11th to 20th	Night	50% 8% 12% 21% 8% 1	3875
	21st to end	Night	43% 10% 15% 22% 10% 1	3927
June	1st to 10th	Night	37% 8% 16% 24% 14% 1	1600
	11th to 20th	Night	36% 11% 18% 19% 14% 1	1600
	21st to end	Night	33% 10% 17% 25% 14% 2	1600
July	1st to 10th	Night	35% 13% 19% 22% 9% 2	3560
	11th to 20th	Night	41% 14% 24% 17% 4	3842
	21st to end	Night	41% 11% 13% 22% 13%	4297
August	1st to 10th	Night	49% 9% 18% 19% 4	2932
	11th to 20th	Night	41% 9% 14% 23% 12%	3227
	21st to end	Night	34% 8% 11% 27% 19% 2	3586
September	1st to 10th	Night	35% 9% 17% 21% 15% 3	2000
	11th to 20th	Night	42% 6% 11% 21% 18% 2	2000
	21st to end	Night	48% 8% 11% 18% 14% 2	2245
October	1st to 10th	Night	36% 5% 9% 24% 23% 2	3920
	11th to 20th	Night	29% 4 6% 19% 32% 10%	3899
	21st to end	Night	22% 4 7% 29% 27% 11%	4252
November	1st to 10th	Night	37% 6% 9% 22% 23% 3	2571
	11th to 20th	Night	39% 6% 10% 20% 18% 7%	2730
	21st to end	Night	33% 6% 10% 26% 22% 4	2765
December	1st to 10th	Night	33% 5% 8% 25% 25% 4	4720
	11th to 20th	Night	46% 6% 11% 17% 15% 5%	5307
	21st to end	Night	34% 7% 15% 27% 15% 1	6996

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	19% 23% 37% 16% 5%	243
	11th to 20th	Day	18% 24% 38% 18% 2	300
	21st to end	Day	19% 16% 41% 20% 3 1	330
February	1st to 10th	Day	19% 19% 38% 18% 5%	300
	11th to 20th	Day	27% 18% 38% 13% 3	476
	21st to end	Day	18% 19% 38% 22% 3 1	414
March	1st to 10th	Day	18% 19% 37% 20% 5% 1	500
	11th to 20th	Day	19% 20% 35% 20% 5% 2	500
	21st to end	Day	16% 15% 40% 22% 6% 1	550
April	1st to 10th	Day	16% 18% 39% 21% 6% 1	500
	11th to 20th	Day	12% 13% 33% 29% 10% 2	492
	21st to end	Day	18% 10% 32% 28% 11% 2	500
May	1st to 10th	Day	17% 10% 34% 25% 11% 2	503
	11th to 20th	Day	19% 6% 28% 31% 13% 3	527
	21st to end	Day	19% 5% 21% 29% 19% 7%	573
June	1st to 10th	Day	12% 4 22% 32% 25% 6%	530
	11th to 20th	Day	15% 7% 16% 30% 23% 8%	530
	21st to end	Day	9% 2 17% 39% 25% 7%	530
July	1st to 10th	Day	10% 1 10% 35% 34% 10%	525
	11th to 20th	Day	9% 3 7% 30% 37% 13%	524
	21st to end	Day	8% 2 16% 32% 32% 9%	576
August	1st to 10th	Day	16% 3 13% 34% 26% 8%	526
	11th to 20th	Day	9% 3 13% 31% 30% 14%	519
	21st to end	Day	12% 3 16% 28% 29% 12%	583
September	1st to 10th	Day	15% 3 20% 27% 22% 13%	530
	11th to 20th	Day	19% 5% 14% 29% 24% 8%	530
	21st to end	Day	25% 7% 19% 23% 20% 5%	530
October	1st to 10th	Day	20% 5% 19% 26% 21% 8%	530
	11th to 20th	Day	19% 12% 23% 25% 18% 3	530
	21st to end	Day	16% 10% 30% 25% 14% 5%	583
November	1st to 10th	Day	17% 10% 29% 26% 14% 4	476
	11th to 20th	Day	17% 15% 33% 25% 8% 2	430
	21st to end	Day	14% 17% 30% 25% 12% 2	392
December	1st to 10th	Day	22% 15% 41% 15% 5% 1	220
	11th to 20th	Day	16% 17% 37% 21% 7% 1	214
	21st to end	Day	21% 15% 30% 21% 10% 1	220
January	1st to 10th	Night	18% 18% 35% 23% 6%	800
	11th to 20th	Night	21% 15% 32% 26% 6%	800
	21st to end	Night	18% 14% 41% 24% 3	880
February	1st to 10th	Night	21% 11% 38% 26% 4	800
	11th to 20th	Night	24% 17% 39% 18% 2	783
	21st to end	Night	19% 13% 37% 25% 5%	660
March	1st to 10th	Night	18% 11% 37% 28% 6%	800
	11th to 20th	Night	20% 11% 39% 24% 7% 1	800
	21st to end	Night	20% 12% 35% 27% 6%	880
April	1st to 10th	Night	18% 11% 40% 24% 7%	800
	11th to 20th	Night	14% 11% 33% 31% 10%	791
	21st to end	Night	17% 5% 32% 37% 8% 1	800
May	1st to 10th	Night	17% 9% 32% 34% 9% 1	800
	11th to 20th	Night	16% 4 25% 40% 13% 1	537
	21st to end	Night	16% 4 14% 40% 24% 3	433
June	1st to 10th	Night	12% 3 18% 43% 21% 4	400
	11th to 20th	Night	8% 3 16% 43% 28% 3	400
	21st to end	Night	8% 1 14% 48% 27% 2	400
July	1st to 10th	Night	7% 2 10% 43% 35% 2	390
	11th to 20th	Night	7% 1 8% 40% 38% 6%	509
	21st to end	Night	9% 2 12% 42% 31% 4	657
August	1st to 10th	Night	10% 2 11% 40% 32% 4	612
	11th to 20th	Night	11% 2 12% 37% 33% 5%	790
	21st to end	Night	11% 2 12% 33% 36% 6%	880
September	1st to 10th	Night	13% 2 14% 35% 28% 8%	800
	11th to 20th	Night	17% 3 14% 33% 28% 6%	800
	21st to end	Night	22% 5% 16% 33% 23% 2	800
October	1st to 10th	Night	17% 5% 17% 30% 26% 6%	800
	11th to 20th	Night	19% 8% 22% 32% 17% 2	800
	21st to end	Night	16% 8% 25% 31% 17% 3	880
November	1st to 10th	Night	17% 8% 26% 30% 15% 3	820
	11th to 20th	Night	18% 11% 32% 27% 11% 1	840
	21st to end	Night	14% 11% 29% 31% 14% 1	840
December	1st to 10th	Night	19% 13% 33% 26% 8%	840
	11th to 20th	Night	17% 10% 36% 30% 7%	829
	21st to end	Night	18% 10% 31% 34% 7%	880

Page generated at 2025-12-15 01:13:54. Version ac07

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