Coleman
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coleman clear sky chart from 2005-11-06 to 2024-07-08.

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	13% 9% 3 7% 5% 5% 5% 4 6% 7% 37%	89587
	Night	13% 10% 3 8% 5% 4 4 3 5% 6% 38%	89780
Transparency	Day	45% 6% 13% 24% 12% 1	89339
	Night	46% 5% 12% 24% 12% 1	89634
Seeing	Day	16% 8% 28% 29% 15% 5%	15525
	Night	17% 6% 30% 34% 12% 1	25458

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% 5% 10% 6% 5% 5% 4 6% 5% 30%	2527
	11th to 20th	Day	13% 12% 4 10% 6% 6% 7% 5% 5% 6% 26%	2530
	21st to end	Day	16% 14% 6% 11% 5% 4 4 3 5% 5% 25%	2783
February	1st to 10th	Day	10% 10% 4 9% 5% 5% 4 4 5% 6% 37%	1648
	11th to 20th	Day	10% 11% 4 7% 5% 5% 6% 4 5% 6% 37%	1805
	21st to end	Day	12% 12% 4 8% 5% 4 4 4 6% 8% 33%	1570
March	1st to 10th	Day	11% 9% 2 6% 3 3 4 4 5% 6% 47%	3120
	11th to 20th	Day	8% 9% 4 8% 5% 5% 5% 4 5% 7% 40%	3266
	21st to end	Day	20% 12% 3 9% 5% 5% 4 3 5% 5% 28%	4165
April	1st to 10th	Day	15% 12% 4 9% 5% 5% 4 5% 5% 6% 30%	2280
	11th to 20th	Day	20% 9% 2 6% 4 5% 4 4 5% 6% 33%	2254
	21st to end	Day	17% 9% 3 8% 5% 4 5% 4 5% 7% 34%	2456
May	1st to 10th	Day	14% 7% 3 8% 5% 4 5% 4 6% 7% 39%	4206
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 6% 7% 45%	4399
	21st to end	Day	12% 7% 2 8% 4 4 5% 4 6% 8% 39%	4824
June	1st to 10th	Day	11% 6% 2 5% 5% 5% 4 5% 6% 8% 43%	2660
	11th to 20th	Day	12% 7% 3 6% 5% 4 5% 4 6% 8% 39%	2660
	21st to end	Day	11% 6% 3 6% 5% 5% 5% 4 7% 9% 41%	2660
July	1st to 10th	Day	8% 3 1 4 5% 4 5% 5% 8% 10% 46%	2621
	11th to 20th	Day	8% 4 2 6% 5% 4 4 4 8% 11% 45%	2520
	21st to end	Day	7% 5% 1 6% 5% 5% 4 5% 6% 7% 47%	2743
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 9% 42%	2507
	11th to 20th	Day	11% 4 2 5% 5% 4 5% 4 7% 8% 45%	2284
	21st to end	Day	11% 6% 2 5% 4 5% 4 4 5% 8% 45%	2376
September	1st to 10th	Day	12% 7% 2 6% 5% 4 5% 3 5% 8% 43%	2160
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 7% 9% 44%	2057
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 5% 7% 9% 37%	1980
October	1st to 10th	Day	14% 7% 3 7% 4 3 4 3 5% 8% 40%	1902
	11th to 20th	Day	20% 9% 3 7% 6% 5% 4 4 5% 7% 30%	1738
	21st to end	Day	19% 9% 3 8% 5% 5% 5% 3 5% 6% 31%	1782
November	1st to 10th	Day	13% 7% 2 7% 5% 5% 6% 4 5% 7% 40%	1672
	11th to 20th	Day	13% 11% 4 9% 6% 6% 5% 4 5% 7% 29%	1691
	21st to end	Day	15% 10% 3 7% 5% 5% 5% 3 5% 7% 35%	1520
December	1st to 10th	Day	12% 11% 5% 7% 5% 4 4 4 6% 6% 35%	1520
	11th to 20th	Day	15% 14% 4 9% 5% 5% 5% 4 6% 6% 28%	1918
	21st to end	Day	19% 18% 6% 12% 6% 4 4 2 4 5% 19%	2783
January	1st to 10th	Night	13% 14% 6% 9% 5% 4 3 3 3 5% 35%	4428
	11th to 20th	Night	12% 14% 6% 11% 7% 6% 4 4 6% 5% 26%	4440
	21st to end	Night	13% 18% 6% 12% 6% 4 4 3 4 5% 26%	4884
February	1st to 10th	Night	8% 14% 4 10% 7% 6% 4 3 4 6% 34%	2530
	11th to 20th	Night	10% 10% 4 9% 5% 5% 5% 4 5% 7% 38%	2261
	21st to end	Night	14% 12% 4 8% 5% 4 5% 3 5% 5% 34%	1884
March	1st to 10th	Night	12% 9% 3 6% 4 4 3 3 4 7% 46%	3733
	11th to 20th	Night	10% 9% 3 7% 5% 4 5% 4 6% 7% 40%	3722
	21st to end	Night	18% 9% 3 9% 6% 5% 5% 4 5% 6% 30%	3466
April	1st to 10th	Night	18% 10% 3 7% 6% 4 4 3 5% 6% 34%	1900
	11th to 20th	Night	20% 7% 3 6% 4 4 4 3 5% 6% 38%	1875
	21st to end	Night	17% 8% 2 7% 6% 3 4 4 5% 6% 37%	1724
May	1st to 10th	Night	15% 8% 3 7% 4 4 5% 3 5% 7% 39%	2689
	11th to 20th	Night	12% 7% 2 8% 4 5% 4 4 6% 6% 42%	2506
	21st to end	Night	16% 7% 2 7% 5% 5% 4 3 5% 7% 40%	2743
June	1st to 10th	Night	9% 6% 2 6% 5% 4 4 3 6% 8% 46%	1520
	11th to 20th	Night	13% 6% 3 7% 4 6% 4 4 6% 8% 40%	1520
	21st to end	Night	9% 6% 2 5% 4 4 5% 4 6% 9% 45%	1520
July	1st to 10th	Night	8% 3 1 4 4 4 5% 4 6% 8% 54%	1504
	11th to 20th	Night	9% 5% 2 5% 3 3 4 4 6% 9% 50%	1440
	21st to end	Night	6% 5% 2 4 5% 4 4 3 6% 9% 52%	1575
August	1st to 10th	Night	7% 4 1 5% 5% 5% 4 5% 8% 10% 44%	1432
	11th to 20th	Night	8% 4 2 5% 4 4 5% 4 6% 9% 50%	1614
	21st to end	Night	10% 5% 2 6% 4 3 4 4 5% 6% 52%	1980
September	1st to 10th	Night	8% 5% 2 6% 3 3 3 3 6% 7% 52%	1800
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 5% 6% 53%	1885
	21st to end	Night	13% 7% 2 6% 4 5% 4 3 6% 8% 44%	1980
October	1st to 10th	Night	14% 7% 2 5% 4 4 4 4 5% 6% 46%	2056
	11th to 20th	Night	16% 8% 3 7% 5% 5% 5% 3 6% 6% 36%	2222
	21st to end	Night	18% 10% 3 8% 5% 4 4 3 5% 6% 33%	2574
November	1st to 10th	Night	14% 9% 3 5% 4 4 4 3 5% 6% 42%	2406
	11th to 20th	Night	13% 11% 3 7% 6% 5% 4 4 5% 6% 36%	2484
	21st to end	Night	15% 11% 3 8% 5% 4 4 3 6% 6% 35%	2660
December	1st to 10th	Night	13% 13% 4 8% 5% 5% 3 3 5% 6% 34%	2660
	11th to 20th	Night	13% 15% 5% 9% 5% 5% 4 3 5% 5% 32%	3279
	21st to end	Night	23% 18% 5% 8% 5% 4 3 3 4 4 23%	4884

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% 6% 14% 19% 7% 1	2528
	11th to 20th	Day	58% 4 14% 17% 6% 1	2530
	21st to end	Day	61% 3 15% 15% 5% 1	2783
February	1st to 10th	Day	46% 5% 13% 23% 12% 1	1648
	11th to 20th	Day	46% 5% 13% 22% 12% 2	1815
	21st to end	Day	48% 6% 12% 23% 10% 2	1570
March	1st to 10th	Day	37% 5% 14% 23% 19% 2	3120
	11th to 20th	Day	40% 8% 13% 25% 12% 2	3266
	21st to end	Day	56% 5% 9% 19% 9% 1	4165
April	1st to 10th	Day	53% 5% 11% 20% 10% 1	2280
	11th to 20th	Day	50% 6% 8% 23% 13% 2	2254
	21st to end	Day	48% 6% 9% 21% 14% 2	2456
May	1st to 10th	Day	42% 6% 10% 24% 16% 1	4244
	11th to 20th	Day	37% 5% 11% 31% 14% 1	4403
	21st to end	Day	41% 7% 11% 22% 17% 3	4837
June	1st to 10th	Day	37% 6% 13% 27% 15% 2	2660
	11th to 20th	Day	41% 6% 13% 23% 15% 2	2660
	21st to end	Day	39% 5% 15% 26% 13% 2	2660
July	1st to 10th	Day	30% 6% 14% 31% 17% 2	2552
	11th to 20th	Day	31% 7% 14% 29% 15% 3	2445
	21st to end	Day	33% 7% 13% 28% 18% 2	2591
August	1st to 10th	Day	35% 7% 15% 30% 11% 2	2492
	11th to 20th	Day	35% 6% 15% 29% 15% 1	2284
	21st to end	Day	36% 6% 15% 26% 16% 1	2376
September	1st to 10th	Day	40% 5% 13% 28% 14%	2160
	11th to 20th	Day	36% 5% 19% 31% 9%	2057
	21st to end	Day	42% 6% 15% 28% 9%	1980
October	1st to 10th	Day	42% 6% 14% 30% 8%	1902
	11th to 20th	Day	53% 5% 11% 23% 7% 1	1738
	21st to end	Day	53% 5% 13% 20% 8%	1782
November	1st to 10th	Day	44% 5% 12% 26% 13%	1672
	11th to 20th	Day	53% 5% 14% 19% 9%	1691
	21st to end	Day	48% 6% 18% 22% 6% 1	1520
December	1st to 10th	Day	48% 7% 12% 25% 7%	1520
	11th to 20th	Day	55% 4 14% 14% 9% 3	1915
	21st to end	Day	69% 4 8% 15% 5%	2783
January	1st to 10th	Night	54% 3 12% 21% 10% 1	4428
	11th to 20th	Night	60% 4 10% 19% 5%	4440
	21st to end	Night	62% 4 12% 16% 6% 1	4884
February	1st to 10th	Night	51% 3 9% 22% 12% 2	2530
	11th to 20th	Night	46% 5% 12% 24% 11% 2	2262
	21st to end	Night	51% 4 11% 22% 10% 2	1884
March	1st to 10th	Night	40% 4 16% 27% 12% 2	3733
	11th to 20th	Night	41% 6% 10% 28% 14% 1	3722
	21st to end	Night	54% 5% 10% 20% 10% 1	3466
April	1st to 10th	Night	51% 5% 7% 19% 16% 2	1900
	11th to 20th	Night	46% 4 9% 23% 14% 4	1875
	21st to end	Night	47% 4 11% 23% 14% 1	1724
May	1st to 10th	Night	44% 4 14% 21% 15% 1	2716
	11th to 20th	Night	39% 7% 12% 27% 14% 2	2507
	21st to end	Night	45% 4 13% 19% 14% 5%	2751
June	1st to 10th	Night	34% 6% 13% 30% 15% 2	1520
	11th to 20th	Night	42% 4 12% 24% 18% 1	1520
	21st to end	Night	33% 7% 15% 30% 13% 2	1520
July	1st to 10th	Night	27% 5% 12% 35% 17% 3	1464
	11th to 20th	Night	30% 5% 16% 29% 16% 4	1392
	21st to end	Night	28% 5% 17% 30% 17% 3	1487
August	1st to 10th	Night	32% 6% 14% 30% 15% 2	1423
	11th to 20th	Night	30% 6% 16% 30% 15% 2	1614
	21st to end	Night	33% 5% 12% 28% 20% 2	1980
September	1st to 10th	Night	30% 5% 13% 32% 19% 1	1800
	11th to 20th	Night	32% 4 15% 36% 13% 1	1885
	21st to end	Night	39% 4 16% 29% 10% 1	1980
October	1st to 10th	Night	38% 5% 12% 30% 13% 1	2056
	11th to 20th	Night	47% 5% 14% 23% 10% 1	2222
	21st to end	Night	51% 5% 12% 21% 10%	2574
November	1st to 10th	Night	42% 4 12% 27% 14% 1	2406
	11th to 20th	Night	49% 5% 13% 20% 13% 1	2484
	21st to end	Night	49% 4 14% 25% 7% 1	2660
December	1st to 10th	Night	50% 4 15% 22% 7%	2660
	11th to 20th	Night	54% 4 13% 19% 8% 1	3281
	21st to end	Night	65% 5% 10% 15% 5%	4884

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	16% 8% 29% 30% 14% 3	270
	11th to 20th	Day	23% 7% 32% 26% 10% 2	270
	21st to end	Day	22% 6% 30% 32% 9% 1	297
February	1st to 10th	Day	14% 7% 43% 26% 7% 3	270
	11th to 20th	Day	12% 11% 44% 23% 9%	270
	21st to end	Day	19% 12% 41% 22% 5%	225
March	1st to 10th	Day	15% 10% 43% 25% 6%	270
	11th to 20th	Day	17% 11% 30% 28% 10% 3	296
	21st to end	Day	23% 8% 28% 28% 10% 2	506
April	1st to 10th	Day	20% 11% 32% 28% 8% 1	460
	11th to 20th	Day	25% 13% 25% 24% 10% 3	452
	21st to end	Day	22% 9% 27% 24% 15% 3	460
May	1st to 10th	Day	20% 8% 32% 28% 9% 3	535
	11th to 20th	Day	16% 9% 32% 29% 10% 4	675
	21st to end	Day	15% 7% 28% 27% 16% 6%	734
June	1st to 10th	Day	13% 6% 30% 29% 17% 5%	680
	11th to 20th	Day	15% 8% 26% 31% 16% 4	680
	21st to end	Day	14% 6% 25% 34% 16% 5%	680
July	1st to 10th	Day	9% 3 21% 33% 25% 8%	658
	11th to 20th	Day	9% 5% 25% 32% 21% 8%	618
	21st to end	Day	7% 2 21% 38% 22% 9%	684
August	1st to 10th	Day	10% 3 18% 36% 23% 10%	626
	11th to 20th	Day	11% 4 15% 30% 27% 13%	478
	21st to end	Day	13% 7% 18% 28% 23% 11%	495
September	1st to 10th	Day	17% 5% 21% 31% 18% 8%	450
	11th to 20th	Day	13% 4 17% 32% 28% 7%	450
	21st to end	Day	15% 8% 26% 26% 20% 6%	450
October	1st to 10th	Day	17% 10% 26% 24% 18% 5%	372
	11th to 20th	Day	20% 14% 35% 23% 7%	270
	21st to end	Day	25% 10% 36% 22% 6% 1	297
November	1st to 10th	Day	13% 10% 35% 26% 13% 3	270
	11th to 20th	Day	16% 15% 35% 24% 9% 3	270
	21st to end	Day	20% 10% 37% 24% 9% 1	270
December	1st to 10th	Day	17% 8% 39% 25% 10% 1	270
	11th to 20th	Day	23% 10% 37% 22% 7% 2	270
	21st to end	Day	25% 11% 35% 21% 8%	297
January	1st to 10th	Night	18% 7% 37% 30% 8%	950
	11th to 20th	Night	19% 7% 36% 27% 9% 1	950
	21st to end	Night	18% 5% 33% 34% 9% 1	1045
February	1st to 10th	Night	14% 7% 37% 33% 8% 1	950
	11th to 20th	Night	15% 8% 38% 31% 9%	786
	21st to end	Night	20% 8% 35% 32% 5%	628
March	1st to 10th	Night	16% 5% 33% 36% 9% 1	760
	11th to 20th	Night	16% 6% 38% 31% 8%	748
	21st to end	Night	22% 4 30% 34% 9% 1	627
April	1st to 10th	Night	21% 6% 35% 31% 5% 1	570
	11th to 20th	Night	24% 6% 30% 30% 10%	563
	21st to end	Night	21% 5% 30% 33% 10% 1	570
May	1st to 10th	Night	20% 4 30% 36% 10%	570
	11th to 20th	Night	18% 5% 32% 36% 9% 1	561
	21st to end	Night	14% 5% 22% 39% 18% 1	617
June	1st to 10th	Night	11% 5% 26% 42% 15% 1	570
	11th to 20th	Night	15% 4 25% 41% 13% 2	570
	21st to end	Night	12% 3 20% 44% 19% 1	570
July	1st to 10th	Night	8% 2 17% 45% 26% 1	549
	11th to 20th	Night	10% 3 19% 40% 26% 1	522
	21st to end	Night	8% 3 19% 47% 20% 3	591
August	1st to 10th	Night	9% 1 18% 45% 25% 2	537
	11th to 20th	Night	9% 2 14% 42% 30% 4	534
	21st to end	Night	11% 2 19% 42% 25% 2	594
September	1st to 10th	Night	9% 3 24% 35% 24% 4	540
	11th to 20th	Night	13% 4 23% 33% 22% 4	625
	21st to end	Night	15% 7% 24% 33% 20% 2	720
October	1st to 10th	Night	17% 7% 24% 33% 18% 1	720
	11th to 20th	Night	19% 9% 30% 33% 9%	720
	21st to end	Night	24% 6% 30% 29% 10% 1	792
November	1st to 10th	Night	18% 8% 34% 31% 8% 1	740
	11th to 20th	Night	17% 12% 35% 28% 7% 1	774
	21st to end	Night	19% 9% 35% 29% 8%	950
December	1st to 10th	Night	19% 9% 38% 26% 7% 1	950
	11th to 20th	Night	21% 7% 34% 28% 8% 2	950
	21st to end	Night	25% 7% 33% 30% 5%	1045

Page generated at 2024-07-05 10:05:39. Version ac07

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