Dedication Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dedication Point clear sky chart from 2005-11-06 to 2025-11-18.

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	5% 5% 2 5% 4 4 4 3 5% 7% 56%	135481
	Night	7% 7% 2 6% 4 4 4 3 5% 6% 51%	132233
Transparency	Day	27% 5% 11% 21% 21% 15%	130275
	Night	32% 6% 11% 21% 18% 12%	128434
Seeing	Day	7% 9% 26% 30% 21% 8%	15820
	Night	8% 6% 23% 37% 22% 3	25122

By Month

Percentage Cloud Cover SW (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	11% 14% 4 10% 7% 6% 6% 4 6% 8% 24%	3639
	11th to 20th	Day	8% 11% 4 10% 5% 5% 5% 4 6% 7% 34%	3640
	21st to end	Day	11% 9% 4 10% 5% 3 4 3 4 6% 42%	4004
February	1st to 10th	Day	8% 8% 5% 10% 6% 4 6% 5% 5% 7% 35%	1788
	11th to 20th	Day	8% 12% 3 8% 5% 4 5% 4 6% 8% 37%	1950
	21st to end	Day	6% 10% 3 8% 6% 5% 5% 5% 7% 8% 38%	1650
March	1st to 10th	Day	5% 9% 4 9% 6% 6% 5% 5% 7% 8% 36%	4518
	11th to 20th	Day	5% 8% 3 7% 4 4 4 4 5% 7% 49%	4796
	21st to end	Day	7% 9% 3 8% 6% 6% 6% 5% 7% 9% 34%	5762
April	1st to 10th	Day	9% 7% 2 5% 5% 5% 4 4 7% 10% 42%	2400
	11th to 20th	Day	5% 6% 3 7% 5% 4 4 4 6% 7% 48%	2399
	21st to end	Day	7% 5% 2 6% 4 3 5% 4 6% 7% 51%	2600
May	1st to 10th	Day	5% 5% 2 4 3 4 4 3 5% 6% 60%	5880
	11th to 20th	Day	6% 4 1 4 3 3 3 3 5% 6% 61%	6012
	21st to end	Day	4 3 1 4 3 3 3 3 5% 7% 64%	6902
June	1st to 10th	Day	6% 5% 2 5% 4 4 4 5% 7% 8% 49%	2800
	11th to 20th	Day	6% 4 1 4 3 3 3 3 5% 8% 61%	2800
	21st to end	Day	2 2 1 2 2 2 3 3 5% 5% 73%	2800
July	1st to 10th	Day	1 1 1 2 2 2 3 2 3 3 80%	6319
	11th to 20th	Day	1 1 1 2 1 2 2 2 3 3 83%	6320
	21st to end	Day	2 2 1 2 2 2 3 3 5% 7% 69%	6880
August	1st to 10th	Day	2 3 1 3 2 3 4 3 5% 7% 68%	5962
	11th to 20th	Day	1 1 1 2 2 1 2 2 3 4 82%	5764
	21st to end	Day	4 4 2 4 2 3 3 3 4 4 69%	5984
September	1st to 10th	Day	1 2 1 3 2 2 3 2 4 5% 75%	2400
	11th to 20th	Day	4 3 2 4 3 2 2 2 5% 7% 66%	2221
	21st to end	Day	5% 3 1 4 2 3 3 3 4 5% 68%	2200
October	1st to 10th	Day	4 3 1 3 3 3 3 3 3 4 70%	3600
	11th to 20th	Day	6% 5% 2 4 3 3 3 3 6% 7% 58%	3147
	21st to end	Day	5% 5% 2 6% 4 4 4 4 6% 8% 51%	3200
November	1st to 10th	Day	9% 8% 2 6% 5% 5% 4 4 5% 9% 43%	1854
	11th to 20th	Day	11% 7% 2 7% 6% 5% 5% 4 7% 9% 38%	1863
	21st to end	Day	9% 7% 2 8% 6% 5% 6% 5% 6% 9% 37%	1775
December	1st to 10th	Day	7% 6% 2 8% 5% 5% 5% 4 5% 8% 45%	2620
	11th to 20th	Day	14% 11% 4 10% 7% 5% 6% 4 6% 7% 26%	3028
	21st to end	Day	13% 10% 4 11% 8% 6% 6% 4 6% 7% 25%	4004
January	1st to 10th	Night	12% 14% 5% 11% 7% 6% 6% 4 6% 6% 23%	6306
	11th to 20th	Night	11% 11% 3 9% 5% 5% 6% 4 5% 6% 35%	6320
	21st to end	Night	11% 9% 4 9% 4 4 4 3 4 5% 43%	6952
February	1st to 10th	Night	11% 10% 3 7% 4 6% 5% 4 6% 6% 37%	2605
	11th to 20th	Night	9% 8% 3 7% 5% 5% 4 5% 6% 10% 39%	2338
	21st to end	Night	8% 11% 3 7% 6% 5% 5% 5% 8% 6% 37%	1980
March	1st to 10th	Night	8% 10% 3 7% 4 4 4 4 7% 8% 42%	5376
	11th to 20th	Night	7% 11% 3 6% 4 4 4 3 5% 6% 47%	5203
	21st to end	Night	9% 9% 2 7% 5% 5% 6% 4 6% 8% 38%	5209
April	1st to 10th	Night	8% 7% 2 6% 5% 5% 5% 4 6% 6% 46%	2000
	11th to 20th	Night	7% 5% 2 6% 4 5% 5% 3 5% 7% 50%	1948
	21st to end	Night	7% 5% 2 5% 4 4 4 4 6% 7% 53%	1800
May	1st to 10th	Night	7% 4 2 4 2 3 3 3 5% 7% 60%	4100
	11th to 20th	Night	5% 4 2 5% 4 4 5% 3 4 5% 58%	3891
	21st to end	Night	4 3 2 4 3 3 3 2 4 5% 67%	3972
June	1st to 10th	Night	8% 5% 2 5% 4 5% 4 4 6% 8% 50%	1600
	11th to 20th	Night	5% 4 2 3 3 3 3 3 6% 6% 63%	1600
	21st to end	Night	3 2 3 3 3 3 3 5% 6% 69%	1600
July	1st to 10th	Night	2 1 1 2 2 2 2 2 3 4 79%	3640
	11th to 20th	Night	1 2 1 2 3 2 3 3 83%	3640
	21st to end	Night	1 2 1 5% 4 4 4 4 6% 8% 61%	3970
August	1st to 10th	Night	3 3 1 3 3 3 3 4 5% 7% 65%	3841
	11th to 20th	Night	1 1 2 1 2 2 2 3 5% 81%	4084
	21st to end	Night	5% 3 1 3 2 3 3 3 4 5% 69%	5015
September	1st to 10th	Night	3 3 1 3 2 2 3 2 4 5% 73%	2000
	11th to 20th	Night	4 3 2 3 3 2 4 2 5% 6% 66%	2178
	21st to end	Night	6% 3 1 3 2 3 3 2 4 5% 69%	2200
October	1st to 10th	Night	4 2 1 3 2 2 3 2 4 5% 71%	3600
	11th to 20th	Night	5% 4 1 4 3 3 3 3 4 6% 64%	4001
	21st to end	Night	8% 6% 2 5% 4 4 5% 4 6% 7% 50%	4600
November	1st to 10th	Night	10% 8% 2 7% 4 4 4 4 4 8% 45%	2665
	11th to 20th	Night	13% 7% 2 6% 4 5% 5% 4 7% 8% 39%	2691
	21st to end	Night	10% 8% 3 6% 4 4 4 4 5% 8% 43%	2620
December	1st to 10th	Night	7% 7% 2 5% 4 5% 4 3 5% 9% 47%	4560
	11th to 20th	Night	16% 11% 4 9% 6% 6% 6% 5% 6% 7% 23%	5176
	21st to end	Night	13% 11% 3 11% 6% 6% 6% 4 6% 7% 27%	6952

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% 10% 18% 15% 3	3639
	11th to 20th	Day	45% 10% 19% 22% 4	3640
	21st to end	Day	42% 7% 16% 23% 10% 1	4004
February	1st to 10th	Day	45% 9% 19% 20% 6% 1	1788
	11th to 20th	Day	42% 8% 18% 22% 9% 1	1960
	21st to end	Day	40% 7% 18% 22% 12% 1	1650
March	1st to 10th	Day	41% 8% 13% 25% 12% 2	4518
	11th to 20th	Day	32% 6% 11% 35% 15% 1	4796
	21st to end	Day	39% 9% 20% 21% 9% 2	5762
April	1st to 10th	Day	36% 6% 15% 23% 16% 3	2400
	11th to 20th	Day	32% 6% 14% 25% 19% 5%	2402
	21st to end	Day	30% 6% 12% 28% 20% 4	2600
May	1st to 10th	Day	23% 4 8% 24% 35% 6%	5880
	11th to 20th	Day	22% 4 8% 25% 31% 11%	6015
	21st to end	Day	18% 5% 10% 28% 30% 9%	6904
June	1st to 10th	Day	30% 7% 12% 25% 22% 4	2800
	11th to 20th	Day	21% 5% 9% 23% 31% 12%	2800
	21st to end	Day	13% 3 6% 19% 35% 24%	2800
July	1st to 10th	Day	10% 2 4 9% 22% 53%	6251
	11th to 20th	Day	8% 2 2 5% 22% 61%	6245
	21st to end	Day	14% 3 4 13% 34% 32%	6681
August	1st to 10th	Day	19% 3 5% 11% 26% 36%	4342
	11th to 20th	Day	9% 2 4 14% 36% 36%	4175
	21st to end	Day	14% 2 4 14% 36% 30%	4311
September	1st to 10th	Day	12% 2 5% 16% 31% 33%	2400
	11th to 20th	Day	19% 4 8% 25% 28% 17%	2221
	21st to end	Day	20% 3 7% 23% 35% 13%	2200
October	1st to 10th	Day	19% 3 7% 18% 41% 13%	3600
	11th to 20th	Day	26% 3 12% 30% 25% 4	3147
	21st to end	Day	28% 4 13% 32% 21% 2	3200
November	1st to 10th	Day	38% 6% 15% 28% 13%	1854
	11th to 20th	Day	39% 9% 21% 25% 6% 1	1863
	21st to end	Day	40% 9% 21% 25% 5%	1775
December	1st to 10th	Day	34% 8% 24% 29% 5%	2620
	11th to 20th	Day	53% 6% 24% 14% 2	3028
	21st to end	Day	51% 9% 17% 18% 4	4004
January	1st to 10th	Night	55% 9% 18% 14% 3	6306
	11th to 20th	Night	45% 10% 16% 21% 8%	6320
	21st to end	Night	41% 8% 14% 23% 12% 2	6952
February	1st to 10th	Night	43% 9% 20% 22% 4	2605
	11th to 20th	Night	38% 8% 18% 24% 11% 1	2339
	21st to end	Night	40% 8% 15% 22% 13% 1	1980
March	1st to 10th	Night	35% 7% 12% 29% 15% 2	5376
	11th to 20th	Night	36% 4 8% 30% 20% 2	5203
	21st to end	Night	38% 9% 16% 27% 10% 1	5209
April	1st to 10th	Night	36% 6% 11% 26% 17% 3	2000
	11th to 20th	Night	31% 5% 10% 28% 22% 4	1948
	21st to end	Night	28% 5% 11% 29% 23% 3	1800
May	1st to 10th	Night	22% 4 8% 21% 35% 9%	4097
	11th to 20th	Night	26% 4 8% 21% 33% 8%	3891
	21st to end	Night	20% 4 9% 25% 33% 10%	3972
June	1st to 10th	Night	31% 7% 13% 22% 24% 4	1600
	11th to 20th	Night	22% 4 8% 21% 34% 11%	1600
	21st to end	Night	15% 3 6% 18% 32% 28%	1600
July	1st to 10th	Night	11% 2 3 9% 19% 57%	3600
	11th to 20th	Night	8% 1 2 5% 20% 64%	3592
	21st to end	Night	19% 3 5% 12% 31% 31%	3857
August	1st to 10th	Night	19% 3 4 10% 24% 39%	2788
	11th to 20th	Night	10% 2 3 10% 27% 47%	2948
	21st to end	Night	14% 2 3 11% 33% 36%	3608
September	1st to 10th	Night	14% 3 4 12% 30% 38%	2000
	11th to 20th	Night	18% 4 6% 20% 26% 26%	2178
	21st to end	Night	19% 3 5% 19% 34% 21%	2200
October	1st to 10th	Night	17% 3 6% 16% 33% 26%	3600
	11th to 20th	Night	22% 3 6% 30% 33% 6%	4001
	21st to end	Night	31% 5% 10% 29% 22% 3	4600
November	1st to 10th	Night	36% 6% 12% 26% 17% 2	2665
	11th to 20th	Night	40% 7% 14% 29% 11%	2691
	21st to end	Night	37% 6% 18% 30% 10%	2620
December	1st to 10th	Night	33% 7% 25% 29% 6%	4560
	11th to 20th	Night	55% 8% 19% 16% 2	5176
	21st to end	Night	51% 9% 17% 16% 6%	6952

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	13% 12% 31% 26% 15% 4	200
	11th to 20th	Day	10% 8% 33% 28% 18% 5%	200
	21st to end	Day	11% 5% 26% 34% 18% 5%	220
February	1st to 10th	Day	8% 17% 34% 21% 17% 4	335
	11th to 20th	Day	13% 13% 30% 27% 13% 4	495
	21st to end	Day	9% 16% 29% 29% 15% 3	414
March	1st to 10th	Day	10% 14% 35% 29% 11% 2	500
	11th to 20th	Day	9% 13% 30% 28% 17% 3	500
	21st to end	Day	11% 15% 32% 26% 13% 3	550
April	1st to 10th	Day	11% 17% 26% 21% 18% 7%	500
	11th to 20th	Day	6% 16% 34% 25% 15% 5%	492
	21st to end	Day	8% 14% 33% 26% 15% 4	500
May	1st to 10th	Day	4 14% 30% 30% 17% 5%	503
	11th to 20th	Day	12% 10% 25% 27% 19% 8%	528
	21st to end	Day	7% 7% 19% 33% 20% 14%	573
June	1st to 10th	Day	6% 6% 27% 28% 22% 11%	530
	11th to 20th	Day	5% 11% 28% 32% 18% 5%	530
	21st to end	Day	3 5% 28% 30% 22% 11%	530
July	1st to 10th	Day	2 3 23% 42% 21% 10%	526
	11th to 20th	Day	1 3 25% 42% 23% 6%	524
	21st to end	Day	2 2 20% 35% 33% 8%	575
August	1st to 10th	Day	3 2 25% 34% 27% 9%	527
	11th to 20th	Day	2 1 20% 37% 28% 13%	517
	21st to end	Day	4 4 19% 31% 27% 15%	583
September	1st to 10th	Day	3 3 15% 29% 32% 17%	530
	11th to 20th	Day	4 5% 19% 30% 29% 13%	530
	21st to end	Day	4 5% 22% 31% 26% 12%	530
October	1st to 10th	Day	7% 7% 21% 25% 25% 15%	530
	11th to 20th	Day	8% 8% 20% 28% 26% 11%	427
	21st to end	Day	9% 9% 23% 31% 21% 7%	363
November	1st to 10th	Day	10% 12% 24% 32% 19% 4	330
	11th to 20th	Day	10% 8% 28% 30% 17% 6%	321
	21st to end	Day	9% 7% 24% 32% 23% 5%	287
December	1st to 10th	Day	13% 8% 23% 27% 19% 13%	200
	11th to 20th	Day	14% 11% 29% 30% 15% 3	200
	21st to end	Day	11% 15% 28% 28% 15% 3	220
January	1st to 10th	Night	12% 7% 28% 32% 17% 4	800
	11th to 20th	Night	10% 6% 28% 34% 20% 3	800
	21st to end	Night	12% 4 21% 35% 24% 3	880
February	1st to 10th	Night	13% 9% 29% 34% 15% 1	800
	11th to 20th	Night	10% 5% 28% 39% 16% 2	784
	21st to end	Night	9% 7% 32% 36% 15% 1	660
March	1st to 10th	Night	11% 9% 31% 34% 14% 2	800
	11th to 20th	Night	11% 9% 26% 36% 16% 3	800
	21st to end	Night	12% 9% 29% 34% 14% 1	880
April	1st to 10th	Night	9% 9% 25% 36% 19% 2	800
	11th to 20th	Night	8% 10% 27% 37% 17% 2	760
	21st to end	Night	7% 8% 28% 39% 15% 3	600
May	1st to 10th	Night	6% 9% 32% 34% 18% 2	600
	11th to 20th	Night	5% 8% 26% 34% 22% 4	513
	21st to end	Night	6% 6% 24% 34% 25% 6%	433
June	1st to 10th	Night	8% 7% 21% 38% 21% 6%	400
	11th to 20th	Night	6% 8% 30% 34% 21% 2	400
	21st to end	Night	2 5% 25% 39% 26% 3	400
July	1st to 10th	Night	2 3 20% 48% 26% 2	390
	11th to 20th	Night	1 2 20% 53% 24%	388
	21st to end	Night	1 2 16% 49% 30% 3	438
August	1st to 10th	Night	5% 3 14% 45% 32% 2	507
	11th to 20th	Night	1 1 13% 51% 31% 2	601
	21st to end	Night	3 3 16% 43% 29% 5%	880
September	1st to 10th	Night	3 1 13% 41% 37% 5%	800
	11th to 20th	Night	5% 3 13% 39% 35% 6%	800
	21st to end	Night	6% 5% 16% 34% 31% 9%	800
October	1st to 10th	Night	8% 5% 19% 36% 28% 5%	800
	11th to 20th	Night	6% 5% 19% 39% 26% 6%	800
	21st to end	Night	7% 6% 21% 38% 23% 4	880
November	1st to 10th	Night	10% 5% 21% 38% 24% 2	820
	11th to 20th	Night	13% 8% 24% 35% 18% 2	828
	21st to end	Night	11% 5% 22% 37% 22% 3	800
December	1st to 10th	Night	11% 6% 24% 37% 19% 4	800
	11th to 20th	Night	15% 7% 22% 38% 17% 2	800
	21st to end	Night	17% 8% 29% 33% 12% 1	880

Page generated at 2025-11-14 22:55:59. Version ac07

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