Renaissance Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Renaissance Observatory clear sky chart from 2005-11-06 to 2025-02-25.

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	14% 7% 3 7% 5% 4 4 3 5% 7% 40%	108598
	Night	15% 8% 3 6% 4 4 4 3 5% 6% 42%	110206
Transparency	Day	41% 6% 11% 24% 16% 2	112274
	Night	40% 5% 10% 23% 18% 3	114670
Seeing	Day	15% 8% 22% 25% 20% 10%	15766
	Night	17% 7% 24% 32% 18% 2	25694

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	15% 11% 7% 11% 5% 6% 5% 3 4 5% 27%	3617
	11th to 20th	Day	14% 9% 4 11% 7% 7% 5% 2 4 5% 31%	3620
	21st to end	Day	21% 11% 7% 6% 4 4 4 3 4 5% 32%	4555
February	1st to 10th	Day	19% 11% 4 7% 5% 3 4 3 4 6% 35%	2000
	11th to 20th	Day	18% 10% 4 7% 5% 4 4 3 5% 6% 34%	1948
	21st to end	Day	17% 9% 4 9% 4 4 5% 5% 4 5% 34%	1610
March	1st to 10th	Day	25% 11% 3 7% 4 3 3 3 3 5% 33%	3120
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 5% 7% 47%	3287
	21st to end	Day	14% 8% 3 7% 5% 4 4 4 4 6% 41%	4094
April	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 4 5% 8% 42%	2280
	11th to 20th	Day	15% 7% 3 6% 5% 3 4 4 5% 6% 41%	2254
	21st to end	Day	17% 7% 3 6% 4 3 4 3 6% 6% 41%	2337
May	1st to 10th	Day	18% 7% 3 7% 5% 5% 5% 4 7% 9% 31%	4082
	11th to 20th	Day	20% 6% 2 6% 4 4 4 4 5% 6% 38%	4081
	21st to end	Day	13% 4 2 7% 5% 5% 5% 4 7% 8% 40%	4496
June	1st to 10th	Day	11% 4 2 6% 4 4 4 4 6% 8% 47%	2660
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 5% 6% 9% 47%	2660
	21st to end	Day	7% 4 2 4 5% 4 7% 4 8% 10% 45%	2660
July	1st to 10th	Day	12% 6% 2 6% 4 4 5% 5% 7% 8% 40%	4440
	11th to 20th	Day	6% 4 2 5% 4 5% 6% 4 8% 10% 48%	4440
	21st to end	Day	10% 8% 4 11% 7% 7% 6% 5% 6% 9% 28%	4630
August	1st to 10th	Day	6% 3 2 4 4 3 4 4 6% 10% 53%	3978
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 43%	3729
	21st to end	Day	6% 4 1 4 4 4 4 3 6% 9% 56%	4180
September	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 5% 8% 46%	2280
	11th to 20th	Day	9% 5% 2 6% 5% 3 5% 4 6% 8% 48%	2090
	21st to end	Day	12% 4 2 6% 4 4 4 3 5% 5% 50%	2090
October	1st to 10th	Day	10% 4 2 5% 3 3 3 3 4 6% 57%	2090
	11th to 20th	Day	12% 5% 2 5% 5% 2 5% 3 5% 6% 50%	1986
	21st to end	Day	19% 7% 2 6% 3 3 3 2 4 5% 46%	1886
November	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 5% 5% 53%	1762
	11th to 20th	Day	16% 8% 2 6% 4 4 3 3 4 6% 45%	1800
	21st to end	Day	19% 8% 3 6% 3 3 3 3 5% 6% 40%	1800
December	1st to 10th	Day	17% 10% 3 6% 4 3 3 2 4 5% 44%	2930
	11th to 20th	Day	16% 11% 5% 10% 5% 4 5% 2 5% 6% 31%	3144
	21st to end	Day	23% 15% 5% 9% 5% 4 4 3 5% 6% 23%	3982
January	1st to 10th	Night	18% 14% 4 8% 4 4 4 4 5% 5% 31%	6348
	11th to 20th	Night	17% 14% 4 8% 4 5% 5% 2 3 4 34%	6360
	21st to end	Night	20% 11% 4 5% 3 3 3 2 4 6% 38%	6405
February	1st to 10th	Night	22% 10% 4 7% 5% 4 4 3 5% 5% 31%	2400
	11th to 20th	Night	20% 9% 3 8% 4 4 4 3 3 5% 37%	2338
	21st to end	Night	21% 9% 2 6% 5% 4 3 3 5% 5% 36%	1939
March	1st to 10th	Night	24% 11% 2 6% 4 3 4 3 4 5% 35%	3733
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 5% 48%	3672
	21st to end	Night	16% 7% 3 7% 5% 4 4 3 5% 6% 40%	3565
April	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	1900
	11th to 20th	Night	17% 6% 2 5% 4 4 4 3 4 6% 45%	1875
	21st to end	Night	17% 7% 3 6% 6% 4 3 4 5% 8% 38%	1840
May	1st to 10th	Night	19% 7% 2 6% 5% 4 4 3 6% 8% 36%	2813
	11th to 20th	Night	16% 6% 2 6% 4 4 4 3 6% 7% 43%	2812
	21st to end	Night	8% 4 2 7% 5% 4 5% 4 7% 10% 43%	3056
June	1st to 10th	Night	9% 5% 2 6% 4 4 3 5% 6% 9% 48%	1520
	11th to 20th	Night	6% 4 2 3 4 5% 4 4 6% 9% 52%	1520
	21st to end	Night	5% 3 1 3 4 5% 5% 5% 8% 11% 51%	1520
July	1st to 10th	Night	8% 6% 2 5% 5% 4 4 4 6% 9% 48%	2530
	11th to 20th	Night	6% 4 2 5% 3 4 3 4 6% 8% 56%	2530
	21st to end	Night	10% 7% 4 8% 5% 6% 6% 5% 7% 9% 32%	2924
August	1st to 10th	Night	5% 3 1 4 3 3 4 3 5% 7% 61%	2947
	11th to 20th	Night	6% 3 2 5% 4 4 4 4 6% 9% 52%	3100
	21st to end	Night	4 3 1 4 3 3 4 4 6% 8% 60%	3476
September	1st to 10th	Night	11% 5% 2 4 4 4 3 3 5% 6% 53%	1900
	11th to 20th	Night	8% 5% 1 5% 5% 4 4 4 6% 7% 51%	2069
	21st to end	Night	13% 5% 1 4 3 3 2 3 4 7% 54%	2090
October	1st to 10th	Night	8% 4 2 4 3 3 4 2 5% 5% 60%	2090
	11th to 20th	Night	15% 5% 2 4 3 4 4 2 3 5% 53%	2190
	21st to end	Night	18% 7% 2 6% 3 3 3 3 4 5% 47%	2709
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 4 6% 53%	2536
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 4 6% 48%	2600
	21st to end	Night	19% 7% 3 5% 4 3 3 2 4 5% 44%	2600
December	1st to 10th	Night	18% 9% 3 7% 4 3 3 3 4 4 43%	4250
	11th to 20th	Night	19% 10% 3 6% 4 4 4 3 4 6% 38%	5053
	21st to end	Night	26% 14% 4 8% 5% 4 4 3 4 4 24%	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	59% 5% 11% 17% 7% 1	3618
	11th to 20th	Day	54% 4 7% 21% 11% 1	3620
	21st to end	Day	54% 5% 9% 18% 11% 3	4555
February	1st to 10th	Day	52% 3 10% 22% 11% 2	2000
	11th to 20th	Day	51% 4 10% 20% 12% 3	1958
	21st to end	Day	51% 6% 10% 17% 13% 4	1610
March	1st to 10th	Day	54% 4 7% 18% 13% 4	3120
	11th to 20th	Day	37% 5% 11% 27% 16% 3	3287
	21st to end	Day	42% 7% 12% 23% 15% 1	4094
April	1st to 10th	Day	39% 7% 14% 23% 16% 1	2280
	11th to 20th	Day	43% 5% 9% 23% 17% 3	2254
	21st to end	Day	43% 6% 11% 27% 11% 2	2337
May	1st to 10th	Day	46% 11% 14% 20% 9% 1	4120
	11th to 20th	Day	45% 8% 10% 24% 12%	4085
	21st to end	Day	38% 9% 13% 18% 20% 2	4509
June	1st to 10th	Day	34% 8% 12% 24% 20% 3	2660
	11th to 20th	Day	30% 9% 13% 25% 20% 3	2660
	21st to end	Day	32% 9% 15% 22% 17% 5%	2660
July	1st to 10th	Day	40% 6% 13% 26% 14% 2	4371
	11th to 20th	Day	29% 7% 13% 35% 14% 2	4365
	21st to end	Day	52% 7% 15% 18% 8% 1	4483
August	1st to 10th	Day	26% 7% 15% 34% 19% 1	3965
	11th to 20th	Day	35% 6% 13% 27% 17% 1	3765
	21st to end	Day	25% 6% 12% 37% 17% 3	4179
September	1st to 10th	Day	36% 7% 10% 24% 19% 5%	2280
	11th to 20th	Day	33% 7% 11% 24% 22% 3	2090
	21st to end	Day	36% 4 8% 24% 23% 4	2090
October	1st to 10th	Day	19% 3 5% 22% 45% 6%	3480
	11th to 20th	Day	24% 3 9% 26% 33% 6%	3278
	21st to end	Day	31% 3 7% 27% 26% 7%	3086
November	1st to 10th	Day	34% 4 10% 27% 20% 5%	1762
	11th to 20th	Day	41% 4 8% 24% 19% 5%	1800
	21st to end	Day	45% 4 9% 23% 17% 2	1800
December	1st to 10th	Day	44% 3 9% 26% 16% 1	2930
	11th to 20th	Day	55% 3 10% 20% 11% 1	3141
	21st to end	Day	62% 4 13% 15% 6%	3982
January	1st to 10th	Night	54% 4 11% 22% 9% 1	6348
	11th to 20th	Night	54% 5% 6% 19% 14% 2	6360
	21st to end	Night	49% 3 8% 20% 19% 2	6405
February	1st to 10th	Night	54% 4 11% 19% 10% 1	2400
	11th to 20th	Night	50% 4 7% 21% 15% 2	2339
	21st to end	Night	49% 5% 10% 19% 13% 4	1939
March	1st to 10th	Night	51% 6% 9% 16% 16% 3	3733
	11th to 20th	Night	36% 7% 12% 23% 15% 7%	3672
	21st to end	Night	43% 5% 13% 23% 14% 1	3565
April	1st to 10th	Night	38% 5% 10% 26% 18% 3	1900
	11th to 20th	Night	40% 5% 10% 19% 20% 6%	1875
	21st to end	Night	44% 6% 10% 21% 16% 3	1840
May	1st to 10th	Night	45% 8% 14% 23% 9% 1	2840
	11th to 20th	Night	40% 7% 13% 25% 14%	2813
	21st to end	Night	31% 10% 17% 22% 17% 2	3064
June	1st to 10th	Night	31% 7% 12% 24% 21% 4	1520
	11th to 20th	Night	25% 8% 17% 21% 25% 4	1520
	21st to end	Night	23% 10% 17% 26% 17% 7%	1520
July	1st to 10th	Night	33% 6% 11% 29% 18% 3	2490
	11th to 20th	Night	25% 5% 14% 35% 18% 3	2482
	21st to end	Night	48% 7% 15% 19% 10% 1	2831
August	1st to 10th	Night	22% 6% 14% 40% 18% 1	2936
	11th to 20th	Night	27% 6% 16% 29% 21% 1	3130
	21st to end	Night	21% 5% 12% 35% 24% 3	3476
September	1st to 10th	Night	31% 7% 9% 24% 23% 6%	1900
	11th to 20th	Night	30% 6% 10% 24% 24% 5%	2069
	21st to end	Night	31% 4 10% 23% 25% 6%	2090
October	1st to 10th	Night	19% 3 6% 15% 51% 7%	3480
	11th to 20th	Night	22% 3 6% 25% 39% 6%	3637
	21st to end	Night	31% 2 7% 22% 28% 8%	4459
November	1st to 10th	Night	34% 4 9% 24% 24% 5%	2536
	11th to 20th	Night	38% 4 7% 22% 21% 8%	2600
	21st to end	Night	43% 4 9% 24% 18% 3	2600
December	1st to 10th	Night	46% 4 10% 23% 17% 1	4250
	11th to 20th	Night	48% 4 11% 21% 16% 1	5055
	21st to end	Night	62% 5% 8% 17% 6% 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	25% 13% 30% 22% 8% 1	300
	11th to 20th	Day	21% 17% 40% 18% 3 1	300
	21st to end	Day	22% 17% 39% 15% 6%	330
February	1st to 10th	Day	26% 15% 36% 19% 4 1	300
	11th to 20th	Day	28% 13% 40% 15% 2 1	300
	21st to end	Day	27% 15% 32% 22% 5%	237
March	1st to 10th	Day	23% 16% 37% 18% 5% 1	270
	11th to 20th	Day	24% 12% 38% 18% 6% 1	345
	21st to end	Day	24% 18% 30% 19% 9% 1	506
April	1st to 10th	Day	17% 15% 29% 27% 10% 2	460
	11th to 20th	Day	19% 13% 25% 25% 15% 3	452
	21st to end	Day	19% 10% 31% 24% 11% 4	460
May	1st to 10th	Day	17% 12% 25% 30% 12% 4	463
	11th to 20th	Day	19% 5% 20% 28% 19% 9%	487
	21st to end	Day	11% 5% 19% 28% 23% 14%	536
June	1st to 10th	Day	10% 6% 16% 25% 30% 14%	680
	11th to 20th	Day	5% 3 16% 31% 30% 15%	680
	21st to end	Day	7% 3 19% 31% 25% 15%	680
July	1st to 10th	Day	12% 2 10% 22% 28% 26%	671
	11th to 20th	Day	7% 3 10% 27% 33% 20%	668
	21st to end	Day	9% 2 11% 25% 33% 20%	631
August	1st to 10th	Day	9% 3 8% 24% 33% 22%	486
	11th to 20th	Day	13% 2 11% 30% 30% 14%	479
	21st to end	Day	11% 1 8% 21% 34% 24%	539
September	1st to 10th	Day	10% 3 10% 21% 37% 18%	490
	11th to 20th	Day	10% 1 8% 23% 38% 20%	490
	21st to end	Day	16% 5% 18% 21% 28% 12%	490
October	1st to 10th	Day	9% 4 15% 32% 30% 10%	490
	11th to 20th	Day	11% 12% 29% 29% 11% 8%	386
	21st to end	Day	24% 10% 27% 24% 12% 2	330
November	1st to 10th	Day	14% 7% 30% 31% 13% 5%	300
	11th to 20th	Day	18% 15% 29% 24% 12% 2	300
	21st to end	Day	22% 10% 32% 23% 12% 1	300
December	1st to 10th	Day	18% 18% 31% 22% 9% 3	300
	11th to 20th	Day	23% 14% 28% 23% 11%	300
	21st to end	Day	27% 17% 31% 21% 4 1	330
January	1st to 10th	Night	23% 13% 32% 28% 5%	1000
	11th to 20th	Night	26% 13% 34% 23% 4	1000
	21st to end	Night	23% 9% 37% 27% 3	996
February	1st to 10th	Night	26% 9% 34% 27% 3	800
	11th to 20th	Night	25% 13% 36% 24% 2	783
	21st to end	Night	26% 11% 37% 24% 2	647
March	1st to 10th	Night	21% 11% 32% 30% 6%	760
	11th to 20th	Night	22% 9% 33% 28% 7% 1	760
	21st to end	Night	23% 8% 28% 33% 8% 1	687
April	1st to 10th	Night	16% 9% 32% 32% 11%	570
	11th to 20th	Night	19% 7% 29% 31% 12% 2	563
	21st to end	Night	20% 7% 27% 34% 11% 1	570
May	1st to 10th	Night	18% 5% 26% 34% 16% 1	570
	11th to 20th	Night	13% 4 20% 36% 25% 2	561
	21st to end	Night	5% 2 18% 39% 31% 5%	617
June	1st to 10th	Night	11% 2 15% 40% 29% 2	570
	11th to 20th	Night	7% 2 12% 44% 33% 3	570
	21st to end	Night	5% 1 12% 41% 37% 4	570
July	1st to 10th	Night	8% 3 10% 26% 43% 10%	555
	11th to 20th	Night	6% 2 8% 32% 46% 6%	552
	21st to end	Night	9% 2 9% 36% 37% 7%	624
August	1st to 10th	Night	7% 1 6% 31% 49% 5%	567
	11th to 20th	Night	7% 1 7% 38% 41% 6%	564
	21st to end	Night	7% 1 6% 30% 48% 8%	627
September	1st to 10th	Night	12% 2 9% 32% 38% 7%	570
	11th to 20th	Night	9% 2 10% 32% 41% 6%	739
	21st to end	Night	14% 3 18% 30% 29% 5%	760
October	1st to 10th	Night	10% 4 15% 36% 31% 5%	760
	11th to 20th	Night	16% 7% 23% 34% 19% 2	760
	21st to end	Night	21% 6% 29% 30% 13% 1	836
November	1st to 10th	Night	15% 6% 25% 38% 15% 2	780
	11th to 20th	Night	18% 8% 30% 33% 12%	800
	21st to end	Night	22% 8% 26% 32% 12%	800
December	1st to 10th	Night	23% 8% 30% 31% 7%	800
	11th to 20th	Night	24% 8% 31% 29% 7% 1	906
	21st to end	Night	27% 12% 29% 28% 4	1100

Page generated at 2025-02-22 05:51:34. Version ac07

Copyright © 2025 Attilla Danko.