Suwannee Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Suwannee Skies Observatory clear sky chart from 2005-11-06 to 2025-03-27.

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	9% 5% 2 6% 5% 5% 5% 5% 7% 9% 40%	109432
	Night	10% 6% 2 6% 4 4 5% 4 6% 9% 44%	109902
Transparency	Day	36% 9% 15% 18% 16% 6%	113249
	Night	35% 8% 15% 19% 16% 7%	114224
Seeing	Day	11% 7% 21% 25% 22% 14%	15732
	Night	11% 6% 21% 32% 24% 6%	25852

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	12% 6% 2 4 2 2 3 3 4 7% 56%	4056
	11th to 20th	Day	19% 9% 3 7% 4 3 3 3 5% 6% 37%	4060
	21st to end	Day	10% 5% 2 6% 4 3 4 3 7% 10% 48%	4810
February	1st to 10th	Day	16% 7% 2 6% 4 4 3 3 5% 7% 45%	2000
	11th to 20th	Day	14% 5% 2 5% 4 3 3 3 5% 5% 51%	1948
	21st to end	Day	12% 6% 2 5% 4 4 4 3 5% 6% 50%	1650
March	1st to 10th	Day	13% 8% 3 6% 4 4 5% 4 6% 9% 37%	3528
	11th to 20th	Day	8% 5% 2 5% 3 4 4 4 8% 8% 50%	3590
	21st to end	Day	13% 4 2 4 3 4 4 4 5% 8% 50%	3881
April	1st to 10th	Day	8% 5% 2 5% 4 5% 4 3 7% 9% 49%	2090
	11th to 20th	Day	11% 5% 2 6% 5% 3 5% 5% 5% 7% 46%	2066
	21st to end	Day	5% 3 1 4 3 4 4 5% 7% 8% 55%	2408
May	1st to 10th	Day	5% 3 1 4 4 4 5% 5% 7% 11% 52%	4082
	11th to 20th	Day	9% 6% 2 7% 5% 6% 5% 5% 7% 9% 39%	4081
	21st to end	Day	5% 3 1 4 4 4 4 4 6% 11% 53%	4476
June	1st to 10th	Day	10% 6% 3 7% 6% 7% 7% 6% 8% 10% 30%	2470
	11th to 20th	Day	5% 5% 3 7% 7% 7% 8% 7% 9% 11% 30%	2470
	21st to end	Day	8% 5% 2 8% 7% 7% 8% 7% 9% 10% 29%	2470
July	1st to 10th	Day	5% 5% 3 8% 7% 8% 9% 8% 11% 14% 22%	4120
	11th to 20th	Day	5% 4 2 9% 8% 8% 10% 7% 11% 12% 24%	4120
	21st to end	Day	4 5% 2 9% 8% 9% 10% 8% 11% 14% 20%	4466
August	1st to 10th	Day	11% 4 2 7% 6% 7% 7% 6% 10% 13% 27%	4082
	11th to 20th	Day	6% 5% 2 8% 6% 7% 7% 6% 10% 12% 31%	3729
	21st to end	Day	9% 6% 2 9% 7% 7% 8% 6% 8% 11% 27%	3941
September	1st to 10th	Day	11% 8% 3 10% 8% 8% 8% 6% 8% 9% 21%	2090
	11th to 20th	Day	10% 7% 3 10% 7% 7% 7% 6% 7% 9% 27%	2090
	21st to end	Day	9% 7% 3 9% 6% 5% 5% 5% 7% 7% 39%	2090
October	1st to 10th	Day	13% 6% 2 7% 5% 5% 6% 3 6% 8% 39%	2090
	11th to 20th	Day	5% 4 2 5% 4 3 3 4 5% 8% 57%	1962
	21st to end	Day	7% 4 2 6% 4 5% 5% 3 6% 7% 51%	2090
November	1st to 10th	Day	8% 5% 2 5% 4 4 5% 3 6% 8% 51%	1957
	11th to 20th	Day	9% 6% 2 6% 4 4 5% 3 5% 7% 49%	1900
	21st to end	Day	10% 6% 2 5% 4 4 4 3 5% 8% 49%	1800
December	1st to 10th	Day	5% 4 1 5% 4 4 5% 3 5% 6% 57%	2930
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 6% 8% 47%	3373
	21st to end	Day	16% 8% 3 6% 4 4 4 3 5% 6% 42%	4466
January	1st to 10th	Night	10% 6% 2 4 3 2 3 3 4 7% 56%	5889
	11th to 20th	Night	17% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	5900
	21st to end	Night	15% 7% 3 6% 3 3 4 4 5% 8% 43%	6142
February	1st to 10th	Night	12% 6% 2 7% 5% 3 4 4 5% 6% 46%	2400
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 5% 6% 48%	2338
	21st to end	Night	12% 7% 2 6% 3 3 3 3 5% 6% 50%	1980
March	1st to 10th	Night	16% 9% 3 7% 5% 4 4 4 5% 6% 37%	3543
	11th to 20th	Night	8% 6% 2 5% 4 5% 4 4 6% 9% 46%	3590
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 7% 49%	3890
April	1st to 10th	Night	10% 6% 2 5% 4 3 5% 3 6% 7% 49%	2090
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 4 6% 7% 50%	2063
	21st to end	Night	5% 4 2 4 3 4 3 3 6% 8% 59%	1784
May	1st to 10th	Night	6% 3 1 4 4 4 3 3 6% 9% 57%	2813
	11th to 20th	Night	9% 6% 2 6% 4 4 5% 3 6% 9% 45%	2812
	21st to end	Night	3 3 1 3 3 3 4 3 5% 10% 62%	3079
June	1st to 10th	Night	9% 6% 2 7% 6% 5% 5% 5% 7% 10% 37%	1710
	11th to 20th	Night	4 4 2 6% 5% 5% 6% 5% 10% 15% 38%	1710
	21st to end	Night	6% 5% 3 5% 5% 5% 5% 5% 9% 12% 38%	1710
July	1st to 10th	Night	5% 6% 3 8% 8% 7% 8% 7% 11% 14% 24%	2840
	11th to 20th	Night	2 3 2 7% 5% 5% 6% 6% 10% 15% 39%	2840
	21st to end	Night	4 6% 2 9% 7% 6% 9% 7% 10% 14% 26%	3087
August	1st to 10th	Night	8% 4 2 7% 6% 6% 7% 6% 10% 13% 31%	2842
	11th to 20th	Night	3 3 1 5% 4 4 5% 5% 9% 16% 46%	3100
	21st to end	Night	7% 7% 3 9% 7% 6% 6% 6% 9% 11% 29%	3668
September	1st to 10th	Night	8% 7% 3 10% 7% 7% 6% 6% 8% 11% 27%	2090
	11th to 20th	Night	11% 7% 4 8% 5% 6% 7% 5% 8% 10% 30%	2090
	21st to end	Night	10% 6% 3 6% 5% 4 5% 4 7% 9% 42%	2090
October	1st to 10th	Night	11% 7% 3 7% 4 5% 5% 3 6% 7% 44%	2090
	11th to 20th	Night	6% 4 2 5% 4 3 4 3 5% 6% 58%	2216
	21st to end	Night	7% 4 2 6% 5% 3 4 3 6% 7% 53%	2508
November	1st to 10th	Night	8% 4 1 5% 4 4 4 4 6% 8% 51%	2341
	11th to 20th	Night	9% 6% 2 6% 4 3 4 3 5% 6% 51%	2495
	21st to end	Night	10% 7% 2 5% 4 3 5% 3 5% 6% 49%	2600
December	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 6% 55%	4250
	11th to 20th	Night	12% 8% 2 6% 4 3 3 3 5% 6% 47%	4822
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 6% 41%	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	29% 3 8% 16% 28% 16%	4057
	11th to 20th	Day	48% 4 5% 12% 20% 11%	4060
	21st to end	Day	31% 6% 13% 22% 17% 11%	4810
February	1st to 10th	Day	40% 4 9% 14% 20% 12%	2000
	11th to 20th	Day	35% 4 8% 17% 24% 12%	1958
	21st to end	Day	35% 5% 9% 16% 22% 13%	1650
March	1st to 10th	Day	40% 8% 11% 18% 15% 7%	3528
	11th to 20th	Day	29% 7% 15% 17% 22% 10%	3590
	21st to end	Day	31% 6% 11% 28% 16% 9%	3881
April	1st to 10th	Day	31% 6% 15% 18% 19% 12%	2090
	11th to 20th	Day	36% 6% 9% 21% 19% 9%	2066
	21st to end	Day	25% 7% 13% 23% 23% 10%	2408
May	1st to 10th	Day	21% 10% 19% 27% 17% 5%	4120
	11th to 20th	Day	38% 9% 15% 22% 13% 2	4085
	21st to end	Day	23% 8% 18% 31% 18% 1	4489
June	1st to 10th	Day	43% 12% 19% 18% 7% 1	2470
	11th to 20th	Day	40% 15% 20% 20% 6%	2470
	21st to end	Day	42% 16% 20% 15% 6% 1	2470
July	1st to 10th	Day	42% 17% 31% 9% 1	4055
	11th to 20th	Day	43% 18% 31% 7% 1	4051
	21st to end	Day	44% 18% 28% 8% 1	4324
August	1st to 10th	Day	41% 13% 26% 15% 4	4069
	11th to 20th	Day	37% 15% 25% 15% 8%	3765
	21st to end	Day	45% 12% 22% 17% 3	3941
September	1st to 10th	Day	54% 13% 16% 11% 6% 1	2090
	11th to 20th	Day	50% 11% 18% 13% 7% 1	2090
	21st to end	Day	41% 8% 13% 19% 15% 5%	2090
October	1st to 10th	Day	50% 8% 9% 13% 13% 8%	3480
	11th to 20th	Day	18% 4 5% 18% 39% 16%	3241
	21st to end	Day	20% 5% 7% 22% 35% 10%	3428
November	1st to 10th	Day	30% 5% 12% 19% 20% 14%	1957
	11th to 20th	Day	34% 6% 8% 18% 24% 11%	1900
	21st to end	Day	34% 4 9% 21% 23% 8%	1800
December	1st to 10th	Day	28% 5% 12% 19% 25% 12%	2930
	11th to 20th	Day	34% 6% 10% 21% 21% 8%	3370
	21st to end	Day	42% 5% 7% 18% 22% 5%	4466
January	1st to 10th	Night	29% 3 7% 15% 31% 15%	5889
	11th to 20th	Night	50% 4 6% 16% 18% 6%	5900
	21st to end	Night	39% 6% 10% 18% 18% 10%	6142
February	1st to 10th	Night	38% 5% 9% 16% 21% 12%	2400
	11th to 20th	Night	37% 5% 8% 18% 20% 12%	2339
	21st to end	Night	35% 5% 11% 17% 21% 11%	1980
March	1st to 10th	Night	46% 8% 10% 16% 13% 7%	3543
	11th to 20th	Night	32% 7% 15% 20% 17% 10%	3590
	21st to end	Night	33% 7% 10% 22% 19% 9%	3890
April	1st to 10th	Night	34% 6% 13% 18% 18% 11%	2090
	11th to 20th	Night	30% 7% 10% 24% 20% 8%	2063
	21st to end	Night	23% 5% 12% 29% 22% 8%	1784
May	1st to 10th	Night	20% 10% 18% 31% 15% 5%	2840
	11th to 20th	Night	33% 10% 19% 24% 11% 2	2813
	21st to end	Night	17% 7% 18% 37% 20% 1	3087
June	1st to 10th	Night	38% 9% 20% 26% 6%	1710
	11th to 20th	Night	29% 15% 27% 23% 5%	1710
	21st to end	Night	35% 12% 26% 20% 6% 1	1710
July	1st to 10th	Night	44% 18% 28% 8% 2	2795
	11th to 20th	Night	30% 15% 43% 10% 1	2786
	21st to end	Night	41% 17% 32% 9% 2	2988
August	1st to 10th	Night	39% 14% 32% 13% 3	2831
	11th to 20th	Night	23% 13% 34% 24% 7%	3130
	21st to end	Night	44% 14% 24% 14% 4	3668
September	1st to 10th	Night	46% 15% 21% 13% 5% 1	2090
	11th to 20th	Night	45% 13% 20% 15% 6% 1	2090
	21st to end	Night	36% 10% 16% 19% 15% 4	2090
October	1st to 10th	Night	51% 8% 10% 12% 11% 7%	3480
	11th to 20th	Night	20% 4 7% 21% 32% 16%	3676
	21st to end	Night	21% 5% 8% 22% 34% 11%	4120
November	1st to 10th	Night	30% 5% 11% 22% 19% 13%	2341
	11th to 20th	Night	34% 4 8% 18% 22% 14%	2495
	21st to end	Night	35% 5% 10% 19% 21% 11%	2600
December	1st to 10th	Night	31% 4 10% 20% 19% 17%	4250
	11th to 20th	Night	37% 5% 11% 19% 18% 10%	4824
	21st to end	Night	42% 5% 9% 19% 19% 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	12% 16% 50% 16% 5% 1	300
	11th to 20th	Day	12% 19% 40% 18% 9% 1	300
	21st to end	Day	18% 20% 42% 15% 4	330
February	1st to 10th	Day	15% 13% 37% 25% 8% 2	300
	11th to 20th	Day	19% 16% 36% 22% 7% 1	300
	21st to end	Day	13% 13% 46% 19% 8% 1	249
March	1st to 10th	Day	12% 17% 33% 25% 12% 1	483
	11th to 20th	Day	14% 13% 33% 24% 13% 2	500
	21st to end	Day	10% 14% 33% 28% 14% 2	530
April	1st to 10th	Day	12% 14% 32% 24% 17% 1	460
	11th to 20th	Day	13% 10% 29% 29% 17% 2	452
	21st to end	Day	6% 6% 27% 35% 20% 7%	460
May	1st to 10th	Day	7% 8% 22% 31% 21% 12%	463
	11th to 20th	Day	7% 4 17% 33% 24% 15%	487
	21st to end	Day	8% 3 11% 26% 32% 20%	529
June	1st to 10th	Day	12% 2 10% 26% 31% 20%	490
	11th to 20th	Day	7% 4 13% 21% 30% 25%	490
	21st to end	Day	7% 1 5% 24% 31% 31%	490
July	1st to 10th	Day	7% 2 7% 16% 29% 39%	485
	11th to 20th	Day	7% 1 2 15% 34% 42%	484
	21st to end	Day	7% 2 5% 20% 36% 31%	532
August	1st to 10th	Day	12% 2 6% 17% 32% 31%	486
	11th to 20th	Day	10% 2 3 15% 34% 37%	479
	21st to end	Day	10% 3 4 22% 34% 27%	539
September	1st to 10th	Day	12% 3 8% 22% 29% 26%	490
	11th to 20th	Day	11% 4 9% 29% 30% 17%	490
	21st to end	Day	11% 3 10% 27% 32% 18%	490
October	1st to 10th	Day	13% 5% 23% 31% 20% 8%	490
	11th to 20th	Day	7% 5% 22% 34% 27% 7%	490
	21st to end	Day	9% 5% 24% 39% 19% 5%	539
November	1st to 10th	Day	13% 4 23% 36% 19% 4	495
	11th to 20th	Day	14% 8% 32% 30% 14% 3	400
	21st to end	Day	10% 9% 41% 28% 11% 1	300
December	1st to 10th	Day	8% 15% 37% 22% 15% 3	300
	11th to 20th	Day	15% 13% 36% 26% 9% 1	300
	21st to end	Day	16% 12% 33% 28% 11% 1	330
January	1st to 10th	Night	16% 13% 32% 30% 9% 1	800
	11th to 20th	Night	12% 9% 29% 36% 14% 1	800
	21st to end	Night	18% 11% 35% 30% 6%	880
February	1st to 10th	Night	15% 8% 30% 34% 12%	800
	11th to 20th	Night	15% 10% 33% 32% 9% 1	783
	21st to end	Night	15% 8% 32% 40% 5%	660
March	1st to 10th	Night	13% 9% 34% 36% 9%	800
	11th to 20th	Night	12% 8% 31% 34% 15%	800
	21st to end	Night	10% 8% 31% 37% 13% 1	863
April	1st to 10th	Night	12% 8% 29% 35% 16% 1	760
	11th to 20th	Night	10% 8% 31% 36% 15% 1	751
	21st to end	Night	6% 4 26% 39% 23% 2	598
May	1st to 10th	Night	6% 2 20% 47% 23% 3	570
	11th to 20th	Night	7% 2 18% 39% 30% 4	561
	21st to end	Night	5% 1 10% 36% 39% 8%	617
June	1st to 10th	Night	11% 2 9% 34% 37% 8%	570
	11th to 20th	Night	6% 2 8% 28% 39% 18%	570
	21st to end	Night	8% 2 5% 20% 46% 19%	570
July	1st to 10th	Night	6% 2 5% 17% 43% 28%	555
	11th to 20th	Night	5% 1 12% 53% 29%	552
	21st to end	Night	4 1 3 15% 55% 21%	624
August	1st to 10th	Night	8% 2 4 17% 50% 20%	567
	11th to 20th	Night	7% 1 2 13% 52% 26%	564
	21st to end	Night	9% 2 5% 24% 42% 18%	741
September	1st to 10th	Night	10% 3 8% 23% 42% 15%	760
	11th to 20th	Night	13% 4 9% 31% 34% 10%	760
	21st to end	Night	13% 3 12% 29% 36% 7%	760
October	1st to 10th	Night	13% 4 20% 37% 23% 3	760
	11th to 20th	Night	7% 4 22% 38% 27% 2	760
	21st to end	Night	9% 3 25% 39% 23% 2	836
November	1st to 10th	Night	10% 4 28% 38% 19% 1	780
	11th to 20th	Night	12% 7% 27% 38% 15% 2	800
	21st to end	Night	12% 7% 28% 38% 13% 1	800
December	1st to 10th	Night	13% 7% 27% 34% 18% 1	800
	11th to 20th	Night	13% 11% 26% 34% 15%	800
	21st to end	Night	15% 7% 30% 34% 13%	880

Page generated at 2025-03-24 09:04:27. Version ac07

Copyright © 2025 Attilla Danko.