Damer Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Damer Observing Site clear sky chart from 2005-11-06 to 2026-02-01.

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	14% 9% 4 8% 5% 4 4 4 5% 7% 35%	127193
	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 36%	125021
Transparency	Day	46% 6% 12% 22% 13% 1	130760
	Night	47% 5% 11% 21% 14% 2	129528
Seeing	Day	17% 10% 27% 24% 15% 6%	17342
	Night	19% 10% 29% 29% 12% 1	27274

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% 14% 9% 14% 5% 4 4 4 5% 6% 22%	3697
	11th to 20th	Day	13% 15% 8% 15% 6% 7% 5% 6% 5% 4 17%	3700
	21st to end	Day	21% 17% 6% 11% 5% 4 3 3 4 5% 21%	4084
February	1st to 10th	Day	17% 15% 6% 12% 6% 5% 4 4 4 5% 23%	1970
	11th to 20th	Day	16% 12% 4 10% 6% 6% 4 3 4 5% 28%	1948
	21st to end	Day	15% 15% 6% 10% 5% 3 5% 4 6% 6% 26%	1650
March	1st to 10th	Day	19% 13% 6% 10% 4 3 3 2 3 5% 30%	4480
	11th to 20th	Day	10% 10% 4 7% 4 4 4 4 6% 7% 40%	4786
	21st to end	Day	18% 14% 5% 10% 6% 4 4 4 5% 6% 23%	5755
April	1st to 10th	Day	18% 12% 3 7% 5% 5% 5% 3 5% 7% 31%	2400
	11th to 20th	Day	17% 9% 3 7% 4 5% 4 4 5% 6% 35%	2374
	21st to end	Day	19% 8% 2 7% 5% 5% 4 3 6% 7% 34%	2587
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 4 6% 8% 30%	5862
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 4 6% 8% 37%	5861
	21st to end	Day	14% 6% 3 6% 5% 4 4 4 6% 8% 40%	6799
June	1st to 10th	Day	11% 5% 3 6% 5% 5% 5% 4 6% 8% 43%	2800
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 5% 6% 9% 44%	2800
	21st to end	Day	11% 5% 2 7% 5% 5% 5% 5% 6% 9% 40%	2800
July	1st to 10th	Day	10% 6% 2 7% 4 5% 5% 4 7% 10% 40%	6360
	11th to 20th	Day	9% 5% 2 6% 4 4 6% 5% 8% 11% 41%	6360
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 5% 6% 8% 40%	6889
August	1st to 10th	Day	7% 4 2 6% 5% 4 5% 4 6% 8% 48%	4234
	11th to 20th	Day	10% 4 2 6% 4 4 5% 4 7% 9% 45%	4045
	21st to end	Day	6% 5% 2 5% 4 4 5% 4 6% 10% 49%	4312
September	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 3 6% 8% 47%	2385
	11th to 20th	Day	10% 5% 1 4 4 4 5% 4 6% 8% 49%	2200
	21st to end	Day	13% 6% 2 5% 5% 5% 5% 4 6% 7% 43%	2200
October	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 5% 7% 46%	2200
	11th to 20th	Day	16% 7% 2 6% 5% 4 4 4 6% 7% 39%	1997
	21st to end	Day	19% 10% 3 7% 5% 3 5% 3 6% 6% 32%	1980
November	1st to 10th	Day	11% 8% 2 6% 4 4 4 3 4 6% 46%	1852
	11th to 20th	Day	17% 13% 4 8% 5% 4 3 3 4 6% 33%	1890
	21st to end	Day	19% 13% 4 8% 5% 3 4 4 4 6% 30%	1890
December	1st to 10th	Day	11% 14% 3 8% 6% 4 4 3 5% 7% 36%	2888
	11th to 20th	Day	15% 16% 7% 12% 5% 5% 4 3 5% 6% 23%	3088
	21st to end	Day	28% 19% 7% 13% 5% 4 4 3 3 4 10%	4070
January	1st to 10th	Night	15% 15% 7% 14% 6% 5% 4 3 5% 5% 22%	6488
	11th to 20th	Night	13% 20% 7% 15% 7% 4 5% 3 4 3 19%	6500
	21st to end	Night	19% 14% 6% 10% 4 4 4 3 4 4 27%	7132
February	1st to 10th	Night	18% 14% 5% 10% 5% 5% 3 3 4 5% 28%	2430
	11th to 20th	Night	14% 12% 5% 9% 6% 6% 4 3 4 6% 32%	2338
	21st to end	Night	20% 12% 4 8% 4 4 3 4 5% 5% 31%	1980
March	1st to 10th	Night	17% 11% 4 8% 5% 4 4 3 4 6% 36%	5373
	11th to 20th	Night	13% 7% 2 7% 4 4 4 4 5% 7% 43%	5173
	21st to end	Night	19% 9% 3 8% 4 4 4 4 5% 6% 34%	5204
April	1st to 10th	Night	15% 10% 3 6% 5% 4 4 4 6% 7% 37%	2000
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 4 5% 7% 37%	1975
	21st to end	Night	18% 8% 3 6% 4 4 4 4 5% 7% 36%	1811
May	1st to 10th	Night	20% 11% 2 8% 4 4 4 3 5% 6% 31%	4033
	11th to 20th	Night	15% 8% 2 5% 4 4 4 3 6% 9% 39%	4032
	21st to end	Night	15% 8% 3 6% 5% 4 4 3 5% 7% 40%	4056
June	1st to 10th	Night	10% 5% 2 5% 4 3 4 4 6% 8% 49%	1600
	11th to 20th	Night	9% 6% 2 5% 5% 4 4 3 7% 8% 47%	1600
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 7% 9% 44%	1600
July	1st to 10th	Night	10% 4 2 6% 4 4 5% 4 6% 9% 46%	3618
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 4 7% 10% 47%	3617
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 4 7% 8% 42%	3978
August	1st to 10th	Night	10% 6% 2 5% 3 4 4 4 6% 9% 47%	2915
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 4 6% 7% 51%	3001
	21st to end	Night	9% 5% 2 5% 4 4 4 3 5% 8% 52%	3586
September	1st to 10th	Night	10% 5% 2 5% 3 3 4 4 5% 7% 52%	2000
	11th to 20th	Night	8% 4 1 4 3 3 4 3 5% 7% 58%	2195
	21st to end	Night	13% 6% 2 5% 5% 3 4 2 5% 6% 49%	2200
October	1st to 10th	Night	10% 5% 2 5% 4 4 3 3 5% 6% 52%	2200
	11th to 20th	Night	16% 7% 2 6% 4 3 4 3 4 7% 44%	2400
	21st to end	Night	19% 8% 2 7% 4 4 4 3 5% 6% 38%	2860
November	1st to 10th	Night	13% 9% 3 6% 4 3 4 3 5% 7% 44%	2666
	11th to 20th	Night	15% 10% 2 8% 5% 4 4 4 6% 6% 35%	2730
	21st to end	Night	19% 14% 3 8% 5% 4 4 3 4 5% 31%	2730
December	1st to 10th	Night	13% 11% 3 7% 4 4 4 4 5% 8% 38%	4511
	11th to 20th	Night	16% 15% 7% 11% 6% 5% 4 4 4 5% 23%	5339
	21st to end	Night	26% 18% 7% 10% 5% 5% 4 3 4 5% 13%	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	61% 6% 10% 18% 5%	3698
	11th to 20th	Day	69% 4 9% 8% 7% 2	3700
	21st to end	Day	68% 3 9% 13% 6%	4084
February	1st to 10th	Day	62% 4 12% 13% 7% 1	1970
	11th to 20th	Day	57% 6% 9% 20% 8% 1	1958
	21st to end	Day	57% 6% 12% 17% 7% 1	1650
March	1st to 10th	Day	57% 5% 7% 21% 9% 1	4480
	11th to 20th	Day	41% 6% 10% 33% 9% 1	4786
	21st to end	Day	60% 7% 12% 14% 5% 1	5757
April	1st to 10th	Day	52% 6% 11% 20% 11%	2400
	11th to 20th	Day	48% 6% 10% 22% 10% 3	2374
	21st to end	Day	48% 6% 12% 20% 10% 2	2587
May	1st to 10th	Day	50% 8% 12% 18% 11% 1	5897
	11th to 20th	Day	44% 8% 12% 23% 12% 1	5865
	21st to end	Day	40% 7% 11% 26% 15% 1	6813
June	1st to 10th	Day	37% 8% 11% 25% 16% 3	2800
	11th to 20th	Day	34% 8% 12% 24% 19% 3	2800
	21st to end	Day	38% 9% 15% 19% 15% 3	2800
July	1st to 10th	Day	38% 6% 12% 25% 17% 2	6291
	11th to 20th	Day	35% 8% 15% 27% 14% 1	6285
	21st to end	Day	41% 7% 13% 22% 15% 2	6693
August	1st to 10th	Day	32% 9% 15% 28% 15% 1	4221
	11th to 20th	Day	33% 7% 12% 29% 17% 1	4084
	21st to end	Day	29% 7% 15% 27% 19% 4	4311
September	1st to 10th	Day	35% 7% 13% 24% 18% 3	2385
	11th to 20th	Day	31% 6% 11% 26% 22% 3	2200
	21st to end	Day	38% 7% 11% 22% 20% 2	2200
October	1st to 10th	Day	27% 5% 9% 32% 26% 1	3590
	11th to 20th	Day	36% 5% 10% 22% 26% 1	3226
	21st to end	Day	44% 4 9% 28% 13% 2	3180
November	1st to 10th	Day	39% 5% 12% 26% 16% 2	1852
	11th to 20th	Day	53% 5% 11% 19% 11% 2	1890
	21st to end	Day	55% 5% 11% 21% 7% 1	1890
December	1st to 10th	Day	48% 5% 16% 23% 8%	2888
	11th to 20th	Day	63% 4 11% 17% 4	3085
	21st to end	Day	79% 4 6% 8% 3	4070
January	1st to 10th	Night	63% 6% 9% 16% 6%	6488
	11th to 20th	Night	71% 3 8% 8% 9% 1	6500
	21st to end	Night	62% 4 10% 16% 8%	7132
February	1st to 10th	Night	59% 5% 11% 15% 8% 2	2430
	11th to 20th	Night	53% 5% 11% 20% 10% 1	2339
	21st to end	Night	55% 5% 12% 16% 10% 2	1980
March	1st to 10th	Night	49% 5% 9% 26% 9% 1	5373
	11th to 20th	Night	40% 6% 12% 27% 13% 2	5173
	21st to end	Night	50% 6% 12% 22% 9% 1	5204
April	1st to 10th	Night	45% 6% 13% 21% 14% 2	2000
	11th to 20th	Night	46% 6% 10% 20% 16% 3	1975
	21st to end	Night	46% 7% 10% 22% 13% 2	1811
May	1st to 10th	Night	52% 7% 9% 17% 13% 2	4060
	11th to 20th	Night	41% 7% 11% 25% 13% 1	4033
	21st to end	Night	44% 6% 9% 21% 17% 2	4064
June	1st to 10th	Night	32% 7% 12% 27% 19% 4	1600
	11th to 20th	Night	33% 8% 13% 23% 20% 3	1600
	21st to end	Night	36% 8% 15% 21% 16% 3	1600
July	1st to 10th	Night	35% 6% 12% 28% 15% 4	3580
	11th to 20th	Night	31% 7% 17% 24% 20% 1	3572
	21st to end	Night	38% 7% 15% 20% 17% 3	3863
August	1st to 10th	Night	32% 7% 16% 29% 15% 1	2904
	11th to 20th	Night	31% 6% 13% 30% 18% 1	3028
	21st to end	Night	30% 6% 11% 28% 21% 3	3586
September	1st to 10th	Night	31% 6% 13% 25% 19% 5%	2000
	11th to 20th	Night	26% 6% 8% 28% 29% 3	2195
	21st to end	Night	37% 5% 10% 24% 22% 2	2200
October	1st to 10th	Night	22% 4 9% 33% 31% 1	3590
	11th to 20th	Night	34% 4 8% 23% 29% 1	3910
	21st to end	Night	37% 4 9% 28% 21% 1	4610
November	1st to 10th	Night	40% 5% 11% 24% 18% 2	2666
	11th to 20th	Night	48% 5% 11% 21% 13% 2	2730
	21st to end	Night	56% 4 10% 21% 8%	2730
December	1st to 10th	Night	45% 4 14% 27% 8% 1	4511
	11th to 20th	Night	63% 4 12% 12% 7% 1	5341
	21st to end	Night	73% 5% 8% 9% 3	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% 17% 37% 17% 5% 1	330
	11th to 20th	Day	23% 21% 36% 16% 3 1	330
	21st to end	Day	27% 18% 32% 18% 5%	363
February	1st to 10th	Day	25% 16% 38% 16% 5%	300
	11th to 20th	Day	27% 17% 36% 16% 4	300
	21st to end	Day	21% 23% 40% 13% 3	249
March	1st to 10th	Day	23% 18% 39% 18% 2	300
	11th to 20th	Day	24% 15% 33% 21% 7%	410
	21st to end	Day	30% 13% 32% 18% 6% 1	550
April	1st to 10th	Day	22% 15% 33% 20% 9% 1	500
	11th to 20th	Day	20% 17% 33% 19% 9% 3	492
	21st to end	Day	25% 13% 32% 20% 9% 2	500
May	1st to 10th	Day	22% 14% 31% 19% 10% 3	503
	11th to 20th	Day	18% 9% 31% 24% 14% 5%	527
	21st to end	Day	12% 6% 28% 28% 18% 8%	731
June	1st to 10th	Day	11% 10% 26% 29% 19% 5%	730
	11th to 20th	Day	12% 5% 26% 31% 20% 5%	730
	21st to end	Day	13% 6% 28% 28% 19% 7%	730
July	1st to 10th	Day	11% 4 17% 29% 24% 16%	721
	11th to 20th	Day	8% 4 21% 31% 24% 12%	718
	21st to end	Day	10% 3 17% 32% 27% 10%	784
August	1st to 10th	Day	6% 2 14% 29% 32% 16%	526
	11th to 20th	Day	11% 3 21% 28% 27% 12%	519
	21st to end	Day	8% 3 15% 30% 32% 14%	583
September	1st to 10th	Day	10% 7% 17% 27% 27% 12%	530
	11th to 20th	Day	10% 3 13% 27% 29% 18%	530
	21st to end	Day	14% 9% 24% 23% 22% 8%	530
October	1st to 10th	Day	14% 5% 27% 28% 19% 8%	530
	11th to 20th	Day	18% 16% 25% 30% 9% 2	420
	21st to end	Day	26% 14% 35% 21% 3 1	363
November	1st to 10th	Day	13% 15% 33% 27% 9% 3	330
	11th to 20th	Day	25% 19% 30% 18% 8%	330
	21st to end	Day	28% 17% 34% 16% 5%	330
December	1st to 10th	Day	19% 18% 38% 17% 8%	330
	11th to 20th	Day	21% 17% 38% 18% 5% 1	330
	21st to end	Day	28% 19% 37% 14% 2	363
January	1st to 10th	Night	23% 17% 34% 22% 5%	1050
	11th to 20th	Night	22% 16% 39% 19% 4	1050
	21st to end	Night	22% 14% 35% 24% 5%	1150
February	1st to 10th	Night	26% 11% 37% 23% 3	801
	11th to 20th	Night	21% 14% 38% 23% 3	783
	21st to end	Night	27% 15% 37% 19% 2	660
March	1st to 10th	Night	20% 13% 37% 25% 5% 1	800
	11th to 20th	Night	18% 14% 37% 26% 6%	800
	21st to end	Night	26% 10% 34% 25% 5%	772
April	1st to 10th	Night	19% 12% 39% 23% 6% 1	600
	11th to 20th	Night	23% 10% 33% 26% 7% 1	593
	21st to end	Night	23% 9% 33% 26% 10% 1	600
May	1st to 10th	Night	23% 7% 31% 31% 9% 1	600
	11th to 20th	Night	19% 7% 26% 34% 14% 1	591
	21st to end	Night	12% 5% 24% 40% 18% 1	650
June	1st to 10th	Night	13% 2 24% 45% 16%	600
	11th to 20th	Night	12% 3 26% 40% 19%	600
	21st to end	Night	10% 2 26% 37% 24% 1	600
July	1st to 10th	Night	8% 3 13% 44% 27% 5%	585
	11th to 20th	Night	10% 3 15% 41% 27% 4	582
	21st to end	Night	7% 2 14% 46% 29% 2	657
August	1st to 10th	Night	8% 1 10% 44% 33% 4	597
	11th to 20th	Night	8% 2 13% 43% 29% 4	594
	21st to end	Night	9% 2 14% 35% 37% 4	660
September	1st to 10th	Night	12% 2 17% 37% 29% 4	600
	11th to 20th	Night	9% 4 15% 37% 31% 4	795
	21st to end	Night	15% 5% 22% 32% 24% 2	800
October	1st to 10th	Night	13% 5% 23% 37% 20% 2	800
	11th to 20th	Night	19% 13% 28% 30% 10%	800
	21st to end	Night	24% 12% 32% 25% 7%	880
November	1st to 10th	Night	17% 12% 36% 25% 10%	820
	11th to 20th	Night	21% 16% 32% 23% 6%	840
	21st to end	Night	25% 15% 30% 24% 6%	840
December	1st to 10th	Night	24% 14% 36% 23% 3	919
	11th to 20th	Night	24% 13% 34% 23% 5%	1050
	21st to end	Night	32% 13% 33% 20% 3	1155

Page generated at 2026-01-29 01:21:42. Version ac07

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