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 2025-02-21.

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% 7% 3 6% 4 4 4 4 6% 7% 43%	108542
	Night	13% 7% 3 6% 4 4 4 3 5% 6% 44%	110192
Transparency	Day	38% 6% 11% 25% 17% 3	112187
	Night	39% 5% 10% 24% 19% 3	114689
Seeing	Day	15% 11% 25% 26% 17% 6%	15855
	Night	16% 10% 28% 29% 15% 2	25812

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% 11% 5% 11% 5% 5% 4 3 4 5% 33%	3617
	11th to 20th	Day	11% 8% 3 8% 4 4 4 3 5% 7% 43%	3804
	21st to end	Day	18% 11% 4 7% 4 4 3 3 4 6% 36%	4488
February	1st to 10th	Day	13% 13% 5% 7% 4 3 4 3 4 6% 37%	1903
	11th to 20th	Day	15% 10% 3 8% 6% 4 3 3 4 6% 36%	1948
	21st to end	Day	15% 11% 3 7% 5% 5% 4 4 6% 6% 36%	1570
March	1st to 10th	Day	19% 14% 3 6% 3 3 4 3 4 5% 35%	3120
	11th to 20th	Day	13% 7% 2 5% 4 3 3 3 5% 5% 49%	3377
	21st to end	Day	12% 8% 3 8% 5% 5% 4 4 6% 7% 39%	4121
April	1st to 10th	Day	10% 7% 2 7% 4 4 4 4 6% 8% 45%	2280
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 3 5% 6% 42%	2254
	21st to end	Day	17% 6% 2 7% 4 4 4 4 5% 7% 39%	2280
May	1st to 10th	Day	14% 6% 3 7% 5% 5% 5% 5% 8% 10% 33%	3951
	11th to 20th	Day	17% 7% 3 6% 4 4 4 4 5% 9% 36%	4099
	21st to end	Day	9% 7% 3 6% 5% 5% 5% 5% 6% 8% 42%	4824
June	1st to 10th	Day	9% 4 2 6% 4 4 5% 4 6% 9% 46%	2660
	11th to 20th	Day	6% 4 2 4 4 4 5% 4 6% 10% 51%	2660
	21st to end	Day	5% 4 1 5% 5% 5% 6% 5% 7% 11% 46%	2660
July	1st to 10th	Day	11% 4 2 5% 5% 5% 5% 4 6% 11% 42%	4440
	11th to 20th	Day	5% 3 1 5% 4 5% 5% 4 7% 12% 49%	4440
	21st to end	Day	6% 6% 3 8% 6% 6% 7% 6% 8% 9% 34%	4673
August	1st to 10th	Day	6% 4 2 5% 4 4 4 4 7% 9% 53%	3890
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 5% 7% 10% 43%	3729
	21st to end	Day	6% 4 1 4 3 3 4 4 6% 9% 55%	4180
September	1st to 10th	Day	12% 6% 1 5% 3 4 4 3 6% 7% 48%	2280
	11th to 20th	Day	8% 6% 2 6% 5% 4 5% 4 5% 8% 47%	2195
	21st to end	Day	11% 4 2 4 4 4 3 3 4 7% 54%	2090
October	1st to 10th	Day	9% 4 1 4 2 2 4 3 4 6% 60%	2005
	11th to 20th	Day	12% 5% 2 5% 3 3 3 3 5% 6% 53%	1900
	21st to end	Day	18% 7% 2 6% 2 3 3 2 4 5% 46%	2014
November	1st to 10th	Day	10% 6% 2 6% 4 4 3 3 5% 5% 53%	1762
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 6% 47%	1800
	21st to end	Day	16% 10% 3 5% 4 3 4 3 5% 6% 41%	1800
December	1st to 10th	Day	10% 9% 2 6% 3 4 3 2 4 6% 50%	2738
	11th to 20th	Day	12% 11% 5% 8% 5% 4 4 3 5% 6% 37%	3008
	21st to end	Day	22% 16% 5% 10% 5% 4 3 3 3 4 25%	3982
January	1st to 10th	Night	16% 10% 5% 10% 5% 4 4 3 4 5% 34%	6348
	11th to 20th	Night	13% 9% 4 10% 5% 4 5% 3 3 5% 39%	6158
	21st to end	Night	19% 10% 4 6% 4 4 3 3 5% 4 39%	6490
February	1st to 10th	Night	17% 14% 5% 9% 4 4 3 3 3 5% 34%	2495
	11th to 20th	Night	16% 8% 3 9% 4 4 4 3 4 5% 40%	2338
	21st to end	Night	18% 9% 5% 6% 5% 3 4 3 4 5% 38%	1885
March	1st to 10th	Night	21% 10% 2 6% 4 3 3 3 4 4 38%	3733
	11th to 20th	Night	13% 6% 2 5% 3 4 4 3 5% 6% 49%	3612
	21st to end	Night	15% 8% 2 7% 5% 5% 4 4 5% 7% 39%	3508
April	1st to 10th	Night	12% 6% 3 5% 5% 3 4 3 6% 7% 48%	1900
	11th to 20th	Night	16% 5% 2 6% 3 4 4 3 5% 7% 44%	1875
	21st to end	Night	19% 6% 2 6% 5% 4 3 4 4 6% 40%	1900
May	1st to 10th	Night	16% 7% 2 6% 4 4 4 3 6% 8% 39%	2943
	11th to 20th	Night	15% 7% 2 5% 4 4 5% 3 4 6% 45%	2791
	21st to end	Night	8% 5% 3 7% 5% 5% 5% 4 7% 9% 42%	2743
June	1st to 10th	Night	10% 4 2 5% 3 5% 5% 4 6% 8% 48%	1520
	11th to 20th	Night	5% 4 2 3 4 4 4 4 6% 11% 55%	1520
	21st to end	Night	4 3 1 3 4 4 4 5% 8% 11% 52%	1520
July	1st to 10th	Night	10% 5% 2 5% 3 4 4 4 6% 8% 49%	2530
	11th to 20th	Night	5% 3 1 4 4 4 4 4 5% 9% 57%	2530
	21st to end	Night	7% 7% 3 8% 5% 5% 5% 6% 8% 10% 38%	2872
August	1st to 10th	Night	5% 3 1 4 3 3 4 4 5% 10% 59%	3042
	11th to 20th	Night	8% 5% 2 6% 3 4 4 3 5% 9% 51%	3100
	21st to end	Night	4 3 1 4 3 4 4 3 6% 9% 60%	3476
September	1st to 10th	Night	10% 6% 2 6% 4 4 3 2 4 5% 54%	1900
	11th to 20th	Night	9% 5% 2 6% 4 4 3 3 5% 8% 51%	1966
	21st to end	Night	12% 4 2 4 3 3 3 4 5% 8% 52%	2090
October	1st to 10th	Night	6% 4 2 5% 3 3 3 2 5% 6% 61%	2171
	11th to 20th	Night	13% 5% 2 6% 3 3 3 2 4 5% 55%	2280
	21st to end	Night	18% 8% 2 6% 2 3 2 2 4 5% 48%	2581
November	1st to 10th	Night	11% 5% 2 5% 3 2 3 3 4 6% 56%	2536
	11th to 20th	Night	12% 6% 2 6% 3 3 3 4 4 7% 50%	2600
	21st to end	Night	17% 8% 2 6% 4 3 3 2 3 5% 47%	2600
December	1st to 10th	Night	14% 9% 3 7% 3 3 3 3 4 5% 46%	4444
	11th to 20th	Night	14% 9% 3 6% 4 4 4 3 4 5% 44%	5199
	21st to end	Night	22% 14% 4 9% 5% 5% 4 3 4 4 27%	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	54% 4 10% 22% 9% 2	3618
	11th to 20th	Day	40% 4 8% 28% 17% 3	3804
	21st to end	Day	50% 4 10% 16% 15% 6%	4488
February	1st to 10th	Day	49% 4 12% 22% 11% 1	1903
	11th to 20th	Day	49% 4 9% 19% 14% 4	1958
	21st to end	Day	48% 5% 9% 21% 13% 5%	1570
March	1st to 10th	Day	52% 5% 6% 19% 13% 6%	3120
	11th to 20th	Day	37% 5% 10% 28% 15% 5%	3377
	21st to end	Day	43% 6% 15% 22% 13% 1	4121
April	1st to 10th	Day	36% 6% 12% 27% 18% 1	2280
	11th to 20th	Day	43% 5% 10% 22% 15% 4	2254
	21st to end	Day	44% 7% 11% 24% 12% 2	2280
May	1st to 10th	Day	43% 11% 13% 23% 10% 1	3986
	11th to 20th	Day	44% 9% 10% 26% 11% 1	4103
	21st to end	Day	39% 8% 10% 19% 23% 1	4837
June	1st to 10th	Day	33% 8% 13% 26% 19% 2	2660
	11th to 20th	Day	28% 8% 11% 27% 22% 3	2660
	21st to end	Day	30% 8% 17% 23% 17% 5%	2660
July	1st to 10th	Day	35% 7% 13% 25% 16% 3	4371
	11th to 20th	Day	26% 8% 13% 35% 17% 2	4365
	21st to end	Day	42% 9% 14% 25% 9% 1	4526
August	1st to 10th	Day	26% 7% 13% 33% 20% 1	3876
	11th to 20th	Day	34% 7% 12% 26% 18% 2	3765
	21st to end	Day	25% 5% 13% 35% 19% 3	4179
September	1st to 10th	Day	35% 5% 10% 26% 20% 5%	2280
	11th to 20th	Day	33% 7% 9% 24% 25% 2	2195
	21st to end	Day	31% 5% 9% 26% 26% 4	2090
October	1st to 10th	Day	15% 3 6% 23% 45% 8%	3330
	11th to 20th	Day	23% 4 8% 23% 36% 7%	3140
	21st to end	Day	32% 4 5% 27% 29% 5%	3304
November	1st to 10th	Day	33% 5% 10% 27% 19% 6%	1762
	11th to 20th	Day	39% 4 8% 22% 21% 6%	1800
	21st to end	Day	44% 5% 8% 25% 17% 2	1800
December	1st to 10th	Day	36% 3 11% 33% 16% 1	2738
	11th to 20th	Day	49% 4 8% 24% 13% 2	3005
	21st to end	Day	63% 4 11% 14% 7% 1	3982
January	1st to 10th	Night	52% 3 10% 24% 10% 1	6348
	11th to 20th	Night	48% 4 6% 24% 15% 3	6158
	21st to end	Night	48% 4 9% 20% 17% 2	6490
February	1st to 10th	Night	54% 3 9% 20% 12% 2	2495
	11th to 20th	Night	47% 4 8% 21% 16% 3	2339
	21st to end	Night	49% 4 9% 19% 15% 4	1885
March	1st to 10th	Night	50% 5% 7% 19% 16% 4	3733
	11th to 20th	Night	35% 6% 12% 22% 18% 7%	3612
	21st to end	Night	44% 6% 12% 27% 10% 1	3508
April	1st to 10th	Night	36% 5% 11% 27% 18% 3	1900
	11th to 20th	Night	39% 4 9% 23% 19% 5%	1875
	21st to end	Night	44% 6% 9% 24% 14% 3	1900
May	1st to 10th	Night	41% 9% 16% 24% 10% 1	2973
	11th to 20th	Night	40% 7% 13% 23% 16% 1	2792
	21st to end	Night	36% 8% 12% 24% 18% 2	2751
June	1st to 10th	Night	33% 7% 12% 24% 21% 3	1520
	11th to 20th	Night	23% 7% 11% 27% 25% 6%	1520
	21st to end	Night	22% 9% 17% 27% 18% 8%	1520
July	1st to 10th	Night	33% 6% 11% 28% 18% 4	2490
	11th to 20th	Night	23% 6% 12% 37% 19% 4	2482
	21st to end	Night	38% 7% 19% 23% 13% 1	2781
August	1st to 10th	Night	20% 7% 18% 34% 19% 1	3032
	11th to 20th	Night	32% 5% 14% 26% 20% 3	3130
	21st to end	Night	21% 5% 12% 37% 21% 3	3476
September	1st to 10th	Night	34% 4 6% 29% 20% 7%	1900
	11th to 20th	Night	31% 5% 8% 27% 24% 4	1966
	21st to end	Night	31% 6% 9% 22% 25% 6%	2090
October	1st to 10th	Night	15% 3 5% 16% 49% 11%	3626
	11th to 20th	Night	23% 2 5% 20% 42% 7%	3779
	21st to end	Night	31% 3 6% 24% 27% 9%	4241
November	1st to 10th	Night	30% 5% 10% 27% 24% 6%	2536
	11th to 20th	Night	34% 4 8% 24% 23% 6%	2600
	21st to end	Night	42% 3 8% 25% 21% 2	2600
December	1st to 10th	Night	41% 4 9% 28% 17% 1	4444
	11th to 20th	Night	43% 4 12% 22% 19% 1	5201
	21st to end	Night	60% 4 10% 17% 7% 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	24% 21% 30% 22% 3 1	300
	11th to 20th	Day	24% 25% 37% 12% 3	300
	21st to end	Day	19% 25% 37% 15% 2	330
February	1st to 10th	Day	22% 23% 38% 14% 2	300
	11th to 20th	Day	28% 27% 33% 10% 2 1	300
	21st to end	Day	30% 26% 30% 12% 2	225
March	1st to 10th	Day	20% 24% 38% 16% 3	270
	11th to 20th	Day	27% 21% 35% 14% 2	270
	21st to end	Day	25% 20% 32% 17% 5%	475
April	1st to 10th	Day	18% 22% 32% 22% 6% 1	460
	11th to 20th	Day	21% 21% 25% 25% 7% 1	452
	21st to end	Day	20% 16% 33% 21% 8% 2	460
May	1st to 10th	Day	19% 17% 29% 24% 10% 2	463
	11th to 20th	Day	18% 10% 28% 23% 17% 4	492
	21st to end	Day	10% 6% 30% 30% 16% 7%	734
June	1st to 10th	Day	11% 5% 21% 27% 25% 11%	680
	11th to 20th	Day	6% 3 22% 39% 22% 8%	680
	21st to end	Day	7% 5% 27% 34% 20% 8%	680
July	1st to 10th	Day	10% 3 14% 30% 25% 18%	671
	11th to 20th	Day	7% 3 16% 33% 30% 11%	668
	21st to end	Day	8% 3 16% 34% 29% 11%	739
August	1st to 10th	Day	8% 2 12% 33% 32% 12%	553
	11th to 20th	Day	12% 4 17% 28% 30% 9%	479
	21st to end	Day	10% 2 11% 29% 33% 16%	539
September	1st to 10th	Day	11% 2 15% 31% 31% 11%	490
	11th to 20th	Day	8% 2 13% 29% 33% 14%	490
	21st to end	Day	14% 8% 21% 27% 21% 9%	490
October	1st to 10th	Day	8% 6% 25% 37% 16% 9%	405
	11th to 20th	Day	16% 14% 35% 22% 10% 3	300
	21st to end	Day	25% 15% 31% 22% 5%	330
November	1st to 10th	Day	13% 13% 34% 26% 10% 3	300
	11th to 20th	Day	15% 23% 30% 24% 8% 1	300
	21st to end	Day	25% 19% 27% 20% 8% 1	300
December	1st to 10th	Day	14% 24% 38% 13% 9% 2	300
	11th to 20th	Day	25% 20% 30% 19% 6%	300
	21st to end	Day	25% 25% 35% 13% 3	330
January	1st to 10th	Night	21% 19% 33% 23% 4	1000
	11th to 20th	Night	22% 22% 36% 17% 3	1000
	21st to end	Night	20% 16% 40% 23% 1	1100
February	1st to 10th	Night	24% 17% 36% 20% 2	895
	11th to 20th	Night	23% 20% 33% 22% 1	783
	21st to end	Night	25% 17% 36% 21% 1	629
March	1st to 10th	Night	21% 17% 37% 23% 3	760
	11th to 20th	Night	22% 14% 36% 24% 5%	650
	21st to end	Night	24% 13% 31% 25% 7%	627
April	1st to 10th	Night	16% 14% 36% 27% 7%	570
	11th to 20th	Night	17% 14% 28% 29% 11% 1	563
	21st to end	Night	21% 10% 34% 27% 7% 1	570
May	1st to 10th	Night	16% 7% 31% 35% 10% 1	570
	11th to 20th	Night	17% 6% 26% 32% 17% 2	561
	21st to end	Night	9% 5% 21% 40% 23% 3	617
June	1st to 10th	Night	12% 3 19% 36% 28% 2	570
	11th to 20th	Night	5% 2 18% 50% 24% 2	570
	21st to end	Night	4 2 17% 45% 29% 2	570
July	1st to 10th	Night	8% 2 12% 33% 37% 9%	555
	11th to 20th	Night	5% 3 10% 43% 35% 5%	552
	21st to end	Night	9% 2 12% 37% 36% 4	624
August	1st to 10th	Night	7% 2 11% 37% 38% 6%	567
	11th to 20th	Night	9% 1 12% 38% 36% 4	564
	21st to end	Night	6% 1 10% 35% 42% 7%	627
September	1st to 10th	Night	12% 2 14% 30% 36% 6%	570
	11th to 20th	Night	10% 2 13% 32% 37% 6%	636
	21st to end	Night	13% 5% 19% 32% 26% 4	760
October	1st to 10th	Night	8% 6% 21% 38% 23% 5%	760
	11th to 20th	Night	16% 8% 29% 28% 16% 2	760
	21st to end	Night	23% 9% 32% 26% 9% 1	836
November	1st to 10th	Night	13% 9% 35% 32% 11% 1	780
	11th to 20th	Night	15% 13% 32% 30% 10%	800
	21st to end	Night	22% 13% 31% 26% 9%	800
December	1st to 10th	Night	21% 13% 34% 28% 4	916
	11th to 20th	Night	21% 12% 34% 27% 5%	1000
	21st to end	Night	24% 17% 36% 20% 3	1100

Page generated at 2025-02-18 02:26:29. Version ac07

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