Carbondale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carbondale clear sky chart from 2005-11-06 to 2026-06-16.

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	11% 7% 3 7% 4 4 4 4 6% 8% 42%	137373
	Night	13% 8% 3 7% 4 4 4 3 5% 7% 44%	134880
Transparency	Day	39% 6% 11% 25% 17% 3	140976
	Night	39% 5% 11% 24% 18% 3	139358
Seeing	Day	15% 12% 26% 25% 16% 6%	17680
	Night	16% 10% 28% 29% 15% 2	27515

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% 11% 4 10% 5% 5% 4 3 4 6% 35%	4691
	11th to 20th	Day	9% 7% 3 7% 4 4 4 3 5% 7% 47%	4950
	21st to end	Day	17% 10% 4 7% 5% 4 4 3 4 5% 36%	5812
February	1st to 10th	Day	13% 13% 5% 8% 4 3 5% 3 4 6% 37%	1998
	11th to 20th	Day	15% 10% 3 9% 5% 4 3 3 4 6% 37%	2048
	21st to end	Day	14% 10% 3 7% 5% 5% 4 4 6% 5% 37%	1730
March	1st to 10th	Day	15% 12% 3 6% 3 3 4 3 4 5% 42%	4580
	11th to 20th	Day	10% 8% 2 5% 3 3 3 3 5% 6% 51%	4942
	21st to end	Day	11% 8% 3 8% 5% 5% 4 4 5% 7% 40%	6039
April	1st to 10th	Day	11% 7% 2 7% 4 4 4 4 6% 8% 44%	2520
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 3 5% 6% 41%	2494
	21st to end	Day	16% 6% 2 6% 4 4 4 4 5% 8% 39%	2520
May	1st to 10th	Day	14% 7% 3 8% 5% 5% 5% 5% 7% 9% 33%	7373
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	7644
	21st to end	Day	17% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	9047
June	1st to 10th	Day	9% 4 2 6% 4 4 5% 5% 6% 9% 46%	2940
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 6% 10% 49%	2871
	21st to end	Day	5% 4 2 5% 5% 5% 5% 5% 7% 11% 46%	2800
July	1st to 10th	Day	9% 4 2 6% 4 4 5% 4 6% 10% 46%	6360
	11th to 20th	Day	5% 4 2 6% 4 5% 6% 5% 8% 13% 42%	6360
	21st to end	Day	5% 5% 2 7% 5% 5% 6% 6% 8% 11% 38%	6728
August	1st to 10th	Day	6% 4 2 5% 3 4 4 4 6% 9% 53%	4013
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 5% 7% 9% 44%	3849
	21st to end	Day	6% 4 1 4 3 4 4 4 6% 9% 55%	4312
September	1st to 10th	Day	11% 6% 1 5% 4 4 4 3 6% 7% 48%	2400
	11th to 20th	Day	8% 6% 2 6% 4 4 5% 4 5% 8% 48%	2310
	21st to end	Day	11% 4 2 5% 4 4 3 3 4 7% 54%	2200
October	1st to 10th	Day	9% 3 1 4 2 2 4 3 5% 6% 60%	2110
	11th to 20th	Day	11% 5% 2 5% 3 3 3 3 5% 6% 54%	2000
	21st to end	Day	19% 7% 2 6% 2 3 3 2 4 5% 46%	2120
November	1st to 10th	Day	10% 6% 2 5% 5% 4 3 3 5% 6% 52%	1852
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 6% 47%	1890
	21st to end	Day	17% 11% 3 5% 4 3 4 3 4 5% 41%	1890
December	1st to 10th	Day	9% 9% 2 7% 3 3 3 2 4 6% 50%	2822
	11th to 20th	Day	12% 11% 5% 8% 5% 4 4 3 5% 6% 38%	3088
	21st to end	Day	21% 16% 5% 10% 5% 4 3 3 4 5% 25%	4070
January	1st to 10th	Night	15% 10% 4 9% 5% 4 4 3 4 5% 38%	8232
	11th to 20th	Night	11% 9% 4 9% 5% 4 4 3 4 5% 44%	8022
	21st to end	Night	17% 10% 4 7% 4 4 3 3 5% 5% 38%	8402
February	1st to 10th	Night	16% 13% 4 9% 5% 4 4 3 3 5% 35%	2620
	11th to 20th	Night	17% 8% 3 8% 4 4 4 3 5% 5% 40%	2458
	21st to end	Night	17% 9% 4 6% 5% 3 4 3 4 5% 41%	2076
March	1st to 10th	Night	16% 11% 3 6% 5% 4 4 4 4 5% 38%	5493
	11th to 20th	Night	11% 7% 2 6% 4 4 4 3 5% 5% 49%	5282
	21st to end	Night	13% 8% 2 8% 5% 5% 4 4 5% 7% 38%	5130
April	1st to 10th	Night	12% 5% 3 5% 4 3 4 3 6% 7% 47%	2100
	11th to 20th	Night	15% 5% 2 6% 3 4 4 3 5% 8% 44%	2075
	21st to end	Night	18% 7% 2 7% 5% 4 4 4 4 6% 40%	2100
May	1st to 10th	Night	15% 8% 3 7% 5% 4 5% 4 7% 9% 34%	5479
	11th to 20th	Night	12% 7% 2 7% 5% 4 5% 4 5% 8% 40%	5200
	21st to end	Night	15% 9% 3 8% 6% 5% 5% 4 6% 8% 32%	5139
June	1st to 10th	Night	10% 4 2 5% 4 5% 5% 4 6% 8% 47%	1680
	11th to 20th	Night	5% 4 2 4 4 4 4 4 5% 11% 53%	1640
	21st to end	Night	4 3 1 3 4 4 4 5% 8% 11% 53%	1600
July	1st to 10th	Night	9% 5% 2 6% 3 4 4 3 6% 8% 51%	3618
	11th to 20th	Night	5% 4 2 5% 4 5% 5% 5% 7% 10% 48%	3617
	21st to end	Night	5% 5% 2 6% 4 4 5% 5% 8% 13% 42%	4125
August	1st to 10th	Night	5% 3 1 4 3 3 4 4 5% 10% 58%	3139
	11th to 20th	Night	8% 5% 2 6% 3 4 4 3 5% 9% 51%	3200
	21st to end	Night	4 3 1 4 3 4 4 3 6% 9% 60%	3586
September	1st to 10th	Night	10% 6% 2 6% 4 4 4 2 5% 5% 53%	2000
	11th to 20th	Night	8% 5% 1 5% 4 4 3 3 6% 8% 52%	2070
	21st to end	Night	13% 4 2 4 3 3 3 4 5% 8% 52%	2200
October	1st to 10th	Night	6% 4 2 5% 3 3 3 2 4 6% 61%	2285
	11th to 20th	Night	12% 5% 2 5% 3 3 3 2 4 5% 56%	2400
	21st to end	Night	19% 8% 2 5% 2 3 2 2 4 5% 47%	2717
November	1st to 10th	Night	10% 5% 2 5% 3 2 3 3 5% 7% 55%	2666
	11th to 20th	Night	12% 6% 2 6% 3 3 3 4 4 7% 51%	2730
	21st to end	Night	17% 8% 2 6% 4 3 3 2 3 5% 46%	2730
December	1st to 10th	Night	14% 9% 4 7% 3 3 3 3 4 5% 46%	4580
	11th to 20th	Night	13% 9% 3 7% 4 4 4 3 4 5% 44%	5339
	21st to end	Night	22% 13% 4 9% 5% 5% 4 3 4 4 27%	7150

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	51% 3 12% 25% 7% 1	4692
	11th to 20th	Day	37% 4 7% 31% 18% 3	4950
	21st to end	Day	50% 3 10% 18% 12% 6%	5812
February	1st to 10th	Day	49% 4 12% 22% 11% 1	1998
	11th to 20th	Day	49% 4 9% 20% 14% 4	2058
	21st to end	Day	47% 5% 8% 22% 13% 5%	1730
March	1st to 10th	Day	46% 4 5% 20% 20% 5%	4580
	11th to 20th	Day	34% 4 9% 28% 20% 5%	4942
	21st to end	Day	42% 5% 13% 27% 12%	6041
April	1st to 10th	Day	38% 6% 12% 25% 18% 1	2520
	11th to 20th	Day	43% 5% 11% 22% 15% 4	2494
	21st to end	Day	43% 7% 11% 26% 12% 1	2520
May	1st to 10th	Day	46% 8% 11% 24% 11% 1	7408
	11th to 20th	Day	43% 7% 11% 22% 16% 1	7648
	21st to end	Day	51% 6% 9% 17% 15% 2	9061
June	1st to 10th	Day	34% 8% 13% 25% 19% 2	2940
	11th to 20th	Day	29% 8% 11% 27% 22% 3	2871
	21st to end	Day	30% 8% 17% 23% 17% 5%	2800
July	1st to 10th	Day	34% 6% 12% 27% 19% 2	6291
	11th to 20th	Day	31% 8% 17% 30% 12% 1	6285
	21st to end	Day	36% 8% 19% 28% 9% 1	6536
August	1st to 10th	Day	26% 7% 13% 33% 20% 1	3999
	11th to 20th	Day	34% 7% 13% 27% 17% 2	3885
	21st to end	Day	25% 5% 13% 35% 19% 3	4311
September	1st to 10th	Day	35% 5% 10% 26% 20% 5%	2400
	11th to 20th	Day	32% 7% 10% 24% 25% 2	2310
	21st to end	Day	31% 5% 9% 25% 27% 4	2200
October	1st to 10th	Day	15% 3 6% 23% 45% 8%	3435
	11th to 20th	Day	22% 4 8% 23% 36% 7%	3240
	21st to end	Day	32% 4 5% 26% 28% 5%	3410
November	1st to 10th	Day	33% 5% 10% 28% 19% 6%	1852
	11th to 20th	Day	39% 4 8% 22% 21% 5%	1890
	21st to end	Day	45% 5% 8% 24% 16% 2	1890
December	1st to 10th	Day	37% 3 11% 33% 16% 1	2822
	11th to 20th	Day	48% 4 9% 24% 14% 2	3085
	21st to end	Day	63% 4 11% 14% 7% 1	4070
January	1st to 10th	Night	49% 3 14% 25% 9% 1	8233
	11th to 20th	Night	43% 4 5% 25% 20% 3	8022
	21st to end	Night	48% 3 11% 21% 15% 2	8402
February	1st to 10th	Night	53% 3 9% 21% 12% 2	2620
	11th to 20th	Night	46% 4 8% 23% 16% 3	2459
	21st to end	Night	47% 4 8% 22% 15% 4	2076
March	1st to 10th	Night	49% 4 6% 19% 18% 4	5493
	11th to 20th	Night	36% 5% 10% 21% 19% 8%	5282
	21st to end	Night	44% 5% 13% 25% 11% 1	5130
April	1st to 10th	Night	35% 5% 13% 27% 17% 3	2100
	11th to 20th	Night	39% 4 11% 23% 19% 4	2075
	21st to end	Night	45% 6% 9% 24% 14% 3	2100
May	1st to 10th	Night	46% 7% 15% 23% 9% 1	5509
	11th to 20th	Night	41% 6% 14% 22% 15% 2	5201
	21st to end	Night	49% 6% 11% 20% 11% 2	5149
June	1st to 10th	Night	34% 7% 12% 25% 20% 3	1680
	11th to 20th	Night	25% 7% 12% 26% 25% 6%	1640
	21st to end	Night	22% 9% 16% 27% 18% 8%	1600
July	1st to 10th	Night	32% 6% 10% 25% 23% 3	3580
	11th to 20th	Night	30% 8% 16% 30% 14% 2	3572
	21st to end	Night	30% 7% 23% 27% 13%	4007
August	1st to 10th	Night	21% 7% 18% 34% 19% 1	3129
	11th to 20th	Night	31% 5% 15% 26% 20% 3	3230
	21st to end	Night	21% 5% 12% 36% 22% 3	3586
September	1st to 10th	Night	34% 4 7% 28% 21% 6%	2000
	11th to 20th	Night	30% 5% 9% 28% 24% 4	2070
	21st to end	Night	31% 6% 9% 21% 27% 6%	2200
October	1st to 10th	Night	15% 4 5% 16% 48% 11%	3740
	11th to 20th	Night	22% 2 5% 21% 42% 7%	3899
	21st to end	Night	32% 3 5% 24% 27% 8%	4377
November	1st to 10th	Night	30% 5% 10% 27% 23% 5%	2666
	11th to 20th	Night	34% 4 8% 25% 23% 6%	2730
	21st to end	Night	43% 3 8% 25% 20% 2	2730
December	1st to 10th	Night	42% 4 9% 28% 17% 1	4580
	11th to 20th	Night	43% 4 12% 22% 19% 1	5341
	21st to end	Night	60% 4 10% 17% 7% 1	7150

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	23% 21% 31% 22% 3 1	330
	11th to 20th	Day	23% 26% 37% 11% 2	330
	21st to end	Day	20% 25% 38% 15% 2	363
February	1st to 10th	Day	21% 23% 39% 15% 3	330
	11th to 20th	Day	26% 27% 35% 10% 2 1	330
	21st to end	Day	28% 24% 33% 13% 3	273
March	1st to 10th	Day	21% 23% 37% 15% 4 1	330
	11th to 20th	Day	27% 21% 37% 13% 2 1	330
	21st to end	Day	23% 21% 34% 16% 5%	560
April	1st to 10th	Day	20% 20% 32% 22% 6% 1	540
	11th to 20th	Day	21% 21% 27% 24% 7% 1	532
	21st to end	Day	19% 15% 34% 22% 8% 1	540
May	1st to 10th	Day	18% 16% 32% 24% 8% 2	543
	11th to 20th	Day	19% 10% 29% 22% 16% 4	572
	21st to end	Day	13% 7% 29% 30% 15% 6%	844
June	1st to 10th	Day	11% 5% 21% 28% 23% 11%	780
	11th to 20th	Day	7% 4 23% 38% 21% 8%	756
	21st to end	Day	6% 5% 25% 35% 21% 8%	730
July	1st to 10th	Day	10% 3 15% 29% 26% 18%	721
	11th to 20th	Day	7% 3 16% 34% 30% 11%	718
	21st to end	Day	7% 3 15% 33% 31% 12%	794
August	1st to 10th	Day	8% 2 13% 34% 31% 12%	596
	11th to 20th	Day	11% 3 16% 27% 32% 11%	519
	21st to end	Day	9% 2 11% 30% 32% 15%	583
September	1st to 10th	Day	10% 2 15% 32% 30% 10%	530
	11th to 20th	Day	7% 2 13% 29% 34% 15%	530
	21st to end	Day	15% 7% 21% 27% 22% 9%	530
October	1st to 10th	Day	8% 5% 23% 37% 18% 8%	440
	11th to 20th	Day	15% 13% 33% 24% 12% 3	330
	21st to end	Day	27% 15% 32% 21% 5%	363
November	1st to 10th	Day	14% 13% 35% 26% 9% 3	330
	11th to 20th	Day	15% 22% 31% 24% 8% 1	330
	21st to end	Day	25% 19% 27% 20% 8% 1	330
December	1st to 10th	Day	14% 24% 39% 13% 8% 2	330
	11th to 20th	Day	24% 20% 32% 18% 6%	330
	21st to end	Day	24% 23% 36% 14% 3	363
January	1st to 10th	Night	21% 19% 32% 24% 3	1050
	11th to 20th	Night	21% 22% 36% 17% 3	1050
	21st to end	Night	19% 17% 40% 22% 1	1155
February	1st to 10th	Night	23% 17% 37% 21% 2	940
	11th to 20th	Night	23% 20% 33% 23% 1	823
	21st to end	Night	24% 16% 37% 22% 1	692
March	1st to 10th	Night	21% 17% 37% 23% 3	840
	11th to 20th	Night	21% 15% 36% 23% 5%	718
	21st to end	Night	23% 14% 31% 25% 7%	693
April	1st to 10th	Night	16% 13% 36% 28% 6%	630
	11th to 20th	Night	17% 15% 29% 29% 10% 1	623
	21st to end	Night	21% 10% 33% 28% 8% 1	630
May	1st to 10th	Night	17% 7% 31% 35% 10% 1	630
	11th to 20th	Night	17% 7% 27% 32% 16% 2	621
	21st to end	Night	11% 5% 21% 39% 22% 2	683
June	1st to 10th	Night	12% 3 20% 37% 27% 2	630
	11th to 20th	Night	6% 2 18% 49% 24% 1	615
	21st to end	Night	5% 2 16% 45% 31% 2	600
July	1st to 10th	Night	8% 2 11% 32% 38% 9%	585
	11th to 20th	Night	4 3 10% 42% 36% 5%	582
	21st to end	Night	9% 2 11% 35% 38% 5%	657
August	1st to 10th	Night	7% 2 10% 37% 37% 6%	597
	11th to 20th	Night	9% 1 11% 37% 37% 5%	594
	21st to end	Night	5% 2 10% 36% 41% 6%	660
September	1st to 10th	Night	12% 2 13% 31% 36% 6%	600
	11th to 20th	Night	10% 2 12% 32% 38% 6%	670
	21st to end	Night	14% 5% 19% 32% 26% 5%	800
October	1st to 10th	Night	8% 6% 20% 39% 24% 5%	800
	11th to 20th	Night	15% 8% 29% 29% 17% 2	800
	21st to end	Night	24% 9% 32% 26% 8% 1	880
November	1st to 10th	Night	12% 10% 35% 32% 11% 1	820
	11th to 20th	Night	15% 13% 33% 30% 10%	840
	21st to end	Night	23% 13% 31% 26% 8%	840
December	1st to 10th	Night	21% 13% 33% 28% 4	962
	11th to 20th	Night	21% 12% 35% 27% 5%	1050
	21st to end	Night	24% 16% 37% 20% 3	1155

Page generated at 2026-06-13 01:31:45. Version ac07

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